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The ecology and evolution of tooth wear in red deer and moose
Abstract
Differences in body size and diet type (browsergrazer continuum) have formed functional traits of ruminants, including tooth design. Grazers and mixed-feeders eat a more fibrous diet than browsers, which arguably increase tooth wear. Tooth wear has also been suggested to increase with body size. Moreover, for species with large distribution ranges, different populations may be exposed to very different ecological factors affecting diet and thus tooth wear rates. Therefore, evolutionary history and contemporary ecological conditions, both operating through diet, may be important for patterns of tooth wear. Here, we compare inter- and intraspecific rates of tooth wear in multiple populations of one large browser (moose Alces alces ) and one mixed-feeder (red deer Cervus elaphus ) covering the main distribution range of each species in Norway. We found that the mixed- feeding red deer wore teeth faster than the larger and browsing moose, suggesting that feeding-type was more important than body size for patterns of wear. There was substantial spatial variation in tooth wear rates, but the inter-specific difference in wear was consistent. Molar wear rates, but not incisors wear rates, in the browser were less variable between populations than in the mixed-feeder. There was no close link between incisor and molar wear rates at the population level. Our findings are consistent with the view that both evolution related to diet type and current ecological conditions (being proxies for within-species variation in diet quality) are important for patterns of tooth wear.
... Tooth wear has been a useful trait to infer (i) diet composition and feeding styles in fossil and extant species (Janis, 1988;Ramdarshan et al., 2016;Veiberg et al., 2007a;Winkler et al., 2013), (ii) dietary seasonal shifts (Merceron et al., 2004), (iii) population, habitat and climate constraints Kaiser and Schulz, 2006;Kubo and Yamada, 2014;Loe et al., 2006;Pérez-Barbería et al., 2015b, 2014bSkogland, 1988;Veiberg et al., 2007c), (iv) as a potential explanatory variable for reproductive fitness (Nussey et al., 2007) and (v) as a proximate mechanism driving patterns of sexual selection in aging (Carranza and Pérez-Barbería, 2007;Kubo et al., 2013;Loe et al., 2003;Loison et al., 2001;Pérez-Barbería et al., 2015b, 2014c. Among https://doi.org/10.1016/j.ecolind.2019.04.065 females of polygynous mammals with low annual offspring production, reproductive evolutionary theory predicts longer live expectancy than males. ...
... In order to assess the contribution of factors that might be driving tooth wear within this framework, it seems obvious that tooth hardness should be considered; however, it has been overlooked in the literature. Studies that have assessed sex, species or habitat differences in tooth wear (Carranza et al., 2004;Kubo and Yamada, 2014;Loe et al., 2003;Loison et al., 2001;Pérez-Barbería et al., 2015a, 2014cVeiberg et al., 2007cVeiberg et al., , 2007aVeiberg et al., , 2007b) make the implicit assumptions that tooth hardness (i) does not differ between these categories, or (ii) if it differs its contribution is negligible in comparison with the contribution of the main effects under study. The aims of this study are (i) to provide evidence to support or rebut these assumptions using records of enamel and dentine hardness in a balanced, by sex and age, sample of lower first molars from a population of Scottish red deer of known age, and (ii) to discuss the implications for using tooth wear as a proxy of senescence and mastication investment in population studies. ...
... The results of this study clearly indicate that (i) enamel hardness was more variable than dentine hardness, (ii) enamel and dentine hardness were positively correlated though the relationship was weak, (iii) there were no sex differences in tooth hardness, and (iv) enamel and dentine hardness were poor predictors of age-related tooth wear. These findings support the use of tooth wear as a proximate mechanism driving patterns of senescence in red deer, as indicated by a number of studies on deer species (Kubo and Yamada, 2014;Loe et al., 2003;Nussey et al., 2007;Pérez-Barbería et al., 2015a, 2014cVeiberg et al., 2007cVeiberg et al., , 2007aVeiberg et al., , 2007b. In particular, the fact that no sex differences were found in tooth hardness supports the implied assumption made in some studies (Pérez-Barbería et al., 2015a, 2015b, 2014c) that observed differences in tooth depletion rates could be driven by sex differences in reproductive life history strategies, and in behaviour, such as mastication patterns, diet composition and food intake (Pérez-Barbería and Gordon, 1998b;Veiberg et al., 2007a) but not by, or at least not totally confounded, by physical or mechanical properties of the dental hard tissues in each sex. ...
... Tooth wear has been a useful trait to infer (i) diet composition and feeding styles in fossil and extant species (Janis, 1988;Ramdarshan et al., 2016;Veiberg et al., 2007a;Winkler et al., 2013), (ii) dietary seasonal shifts (Merceron et al., 2004), (iii) population, habitat and climate constraints Kaiser and Schulz, 2006;Kubo and Yamada, 2014;Loe et al., 2006;Pérez-Barbería et al., 2015b, 2014bSkogland, 1988;Veiberg et al., 2007c), (iv) as a potential explanatory variable for reproductive fitness (Nussey et al., 2007) and (v) as a proximate mechanism driving patterns of sexual selection in aging (Carranza and Pérez-Barbería, 2007;Kubo et al., 2013;Loe et al., 2003;Loison et al., 2001;Pérez-Barbería et al., 2015b, 2014c. Among https://doi.org/10.1016/j.ecolind.2019.04.065 females of polygynous mammals with low annual offspring production, reproductive evolutionary theory predicts longer live expectancy than males. ...
... In order to assess the contribution of factors that might be driving tooth wear within this framework, it seems obvious that tooth hardness should be considered; however, it has been overlooked in the literature. Studies that have assessed sex, species or habitat differences in tooth wear (Carranza et al., 2004;Kubo and Yamada, 2014;Loe et al., 2003;Loison et al., 2001;Pérez-Barbería et al., 2015a, 2014cVeiberg et al., 2007cVeiberg et al., , 2007aVeiberg et al., , 2007b) make the implicit assumptions that tooth hardness (i) does not differ between these categories, or (ii) if it differs its contribution is negligible in comparison with the contribution of the main effects under study. The aims of this study are (i) to provide evidence to support or rebut these assumptions using records of enamel and dentine hardness in a balanced, by sex and age, sample of lower first molars from a population of Scottish red deer of known age, and (ii) to discuss the implications for using tooth wear as a proxy of senescence and mastication investment in population studies. ...
... The results of this study clearly indicate that (i) enamel hardness was more variable than dentine hardness, (ii) enamel and dentine hardness were positively correlated though the relationship was weak, (iii) there were no sex differences in tooth hardness, and (iv) enamel and dentine hardness were poor predictors of age-related tooth wear. These findings support the use of tooth wear as a proximate mechanism driving patterns of senescence in red deer, as indicated by a number of studies on deer species (Kubo and Yamada, 2014;Loe et al., 2003;Nussey et al., 2007;Pérez-Barbería et al., 2015a, 2014cVeiberg et al., 2007cVeiberg et al., , 2007aVeiberg et al., , 2007b. In particular, the fact that no sex differences were found in tooth hardness supports the implied assumption made in some studies (Pérez-Barbería et al., 2015a, 2015b, 2014c) that observed differences in tooth depletion rates could be driven by sex differences in reproductive life history strategies, and in behaviour, such as mastication patterns, diet composition and food intake (Pérez-Barbería and Gordon, 1998b;Veiberg et al., 2007a) but not by, or at least not totally confounded, by physical or mechanical properties of the dental hard tissues in each sex. ...
Teeth of many mammalian species do not grow further after they have emerged, nor are they replaced or repaired if they break or wear. These dental properties have been used to test evolutionary hypotheses on life expectancy relative to actual age (senescence, aging), as the animal is expected to die when all its dental crown tissue has been depleted due to the wearing effect of mastication. Females of polygynous mammals with small litter size are expected to live longer than males of the same species, as female reproductive fitness is maximised by having a long reproductive life. In contrast, maleś reproductive success is limited to the short period when they are in prime condition, as it is in this period that they are most successful in intra-sexual competition for mating opportunities. Consequently, it has been predicted that femaleś teeth should be more durable and so wear more slowly than maleś teeth. However, these predictions are affected by potential sex differences in the hardness of dental tissues, which have not been assessed in depth in the literature. I tested sexual differences in the hardness of enamel and dentine on a balanced, by sex and age, sample of 156 lower first molars of Scottish red deer of known age using Vickers micro-hardness indentation measures as a proxy of the resilience of the tooth to wear. My results clearly indicate that there are no sexual differences in enamel and dentine hardness, and that tooth hardness has a negligible effect on predicting tooth wear, which supports the use of tooth wear relative to body size as a convenient proxy for assessing sexual differences in senescence in polygynous ungulates. I warn on making conclusions from comparisons between populations or species in tooth wear when tooth hardness was controlled for.
... The second factor concerns the wear-inducing properties of the material ingested, which is related to either intrinsic properties of the forage itself (such as the presence of hard silica phytoliths) or to extrinsic material ingested simultaneously (such as soil or dust) (Mayland et al. 1975; van Soest 1994;Williams and Kay 2001;Massey and Hartley 2006;Damuth and Janis 2011;Strömberg 2011;Jardine et al. 2012;Kaiser et al. 2013). While most recent studies concerning the evolution of hypsodonty have tended to focus on the relative importance for tooth wear of intrinsic abrasive silica in grasses versus increased extrinsic abrasive material in more open, drier habitats (Mayland et al. 1975; van Soest 1994;Williams and Kay 2001;Massey and Hartley 2006;Damuth and Janis 2011;Hummel et al. 2011;Strömberg 2011;Jardine et al. 2012;Kaiser et al. 2013), ecological studies of tooth-wear variation in extant ungulates have often emphasised supposed differences in planttissue properties, with the suggestion that increasing fibre content results in increased tooth wear (e.g., Veiberg et al. 2007a). Although fibre itself is not sufficiently hard to directly abrade tooth enamel, it can increase plant-tissue toughness, such that higher occlusal forces and greater mastication time are needed to process forage (Pérez- Gordon 1998a, 1999), potentially increasing attrition and the impact of any abrasive particles present (Damuth and Janis 2011). ...
... A number of studies comparing tooth wear rates between ungulate species with different feeding types have reported higher rates of wear for grazers, followed by mixed feeders, and then browsers (Solounias et al. 1994;van Soest 1994;Veiberg et al. 2007a;Damuth and Janis 2014). Furthermore, several studies have reported significant intraspecific variation in tooth wear between populations in different geographic areas (Skogland 1988;Kojola et al. 1998;Loison et al. 2001;Nussey et al. 2007;Veiberg et al. 2007a;Ozaki et al. 2010;Kubo and Yamada 2014). ...
... A number of studies comparing tooth wear rates between ungulate species with different feeding types have reported higher rates of wear for grazers, followed by mixed feeders, and then browsers (Solounias et al. 1994;van Soest 1994;Veiberg et al. 2007a;Damuth and Janis 2014). Furthermore, several studies have reported significant intraspecific variation in tooth wear between populations in different geographic areas (Skogland 1988;Kojola et al. 1998;Loison et al. 2001;Nussey et al. 2007;Veiberg et al. 2007a;Ozaki et al. 2010;Kubo and Yamada 2014). This has been attributed either to perceived differences in quality of habitat or available forage, or to differences in population density and associated resource competition leading to variation between individuals in access to higher quality forage (Fowler 1987;Freeland and Choquenot 1990). ...
... The effect of environmental conditions on tooth wear may not be equivalent in molars and incisors. Veiberg et al. [20] studied incisor and molar wear in red deer and moose (Alces alces) in several populations in Norway and found that inter-population effects differed between incisors and molars. In supposedly harsher conditions (more arid environment, less available energy density), molars experienced higher wear rates but this was not the case for incisors. ...
... Tooth wear was estimated by measuring, with the aid of a calliper and a magnifying glass, the thickness of the dentine on the sectioned mesial section of M 1 (molar height, MH, ± 0.1 mm) from the top of the cementum of the radicular pad to the middle point of the sectioned crown [7,26]. It has been noted that although crown formation in M 1 is fully complete at the age of 4 months [19,29], the completion of eruption and final positioning of the molar in the mandible does not take place until 3 years of age in red deer [19,20], and teeth also move in the mandible at very old age. Consequently, measuring molar height perpendicular from the mandible bone, labial or buccal, is not a reliable measurement of molar wear, especially in young The actual distribution of red deer within each population is shaded in grey. ...
... But on the other hand, the effect of sex across age on tooth wear appears to be variable among populations. For example, no sex difference was found in the red deer of Rum [39] and Veiberg et al. [20] reported high interpopulational variation in molar and incisor wear for red deer in Norway. Kubo et al. [38] studied two sika deer (Cervus nippon) populations and only found heavier incisor wear in males in comparison with females in the population with stronger wear. ...
Teeth in Cervidae are permanent structures that are not replaceable or repairable; consequently their rate of wear, due to the grinding effect of food and dental attrition, affects their duration and can determine an animal's lifespan. Tooth wear is also a useful indicator of accumulative life energy investment in intake and mastication and their interactions with diet. Little is known regarding how natural and sexual selection operate on dental structures within a species in contrasting environments and how these relate to life history traits to explain differences in population rates of tooth wear and longevity. We hypothesised that populations under harsh environmental conditions should be selected for more hypsodont teeth while sexual selection may maintain similar sex differences within different populations. We investigated the patterns of tooth wear in males and females of Iberian red deer (Cervus elaphus hispanicus) in Southern Spain and Scottish red deer (C. e. scoticus) across Scotland, that occur in very different environments, using 10343 samples from legal hunting activities. We found higher rates of both incisor and molar wear in the Spanish compared to Scottish populations. However, Scottish red deer had larger incisors at emergence than Iberian red deer, whilst molars emerged at a similar size in both populations and sexes. Iberian and Scottish males had earlier tooth depletion than females, in support of a similar sexual selection process in both populations. However, whilst average lifespan for Iberian males was 4 years shorter than that for Iberian females and Scottish males, Scottish males only showed a reduction of 1 year in average lifespan with respect to Scottish females. More worn molars were associated with larger mandibles in both populations, suggesting that higher intake and/or greater investment in food comminution may have favoured increased body growth, before later loss of tooth efficiency due to severe wear. These results illustrate how independent selection in both subspecies, that diverged 11,700 years BP, has resulted in the evolution of different longevity, although sexual selection has maintained a similar pattern of relative sex differences in tooth depletion. This study opens interesting questions on optimal allocation in life history trade-offs and the independent evolution of allopatric populations.
... The second factor concerns the wear-inducing properties of the material ingested, which is related to either intrinsic properties of the forage itself (such as the presence of hard silica phytoliths) or to extrinsic material ingested simultaneously (such as soil or dust) (Mayland et al. 1975; van Soest 1994 Kaiser et al. 2013). While most recent studies concerning the evolution of hypsodonty have tended to focus on the relative importance for tooth wear of intrinsic abrasive silica in grasses versus increased extrinsic abrasive material in more open, drier habitats (Mayland et al. 1975; van Soest 1994 Hummel et al. 2011; Strömberg 2011; Jardine et al. 2012; Kaiser et al. 2013), ecological studies of tooth-wear variation in extant ungulates have often emphasised supposed differences in planttissue properties, with the suggestion that increasing fibre content results in increased tooth wear (e.g., Veiberg et al. 2007a). Although fibre itself is not sufficiently hard to directly abrade tooth enamel, it can increase plant-tissue toughness, such that higher occlusal forces and greater mastication time are needed to process forage ( Gordon 1998a, 1999 ), potentially increasing attrition and the impact of any abrasive particles present (Damuth and Janis 2011). ...
... More open habitats may also tend to promote the probability of ingesting soil and grit, increasing tooth wear (Strömberg 2002Strömberg , 2011; Mendoza and Palmqvist 2008; Damuth and Janis 2011; Jardine et al. 2012; Kaiser et al. 2013). A number of studies comparing tooth wear rates between ungulate species with different feeding types have reported higher rates of wear for grazers, followed by mixed feeders, and then browsers (Solounias et al. 1994; van Soest 1994; Veiberg et al. 2007a; Damuth and Janis 2014). Furthermore, several studies have reported significant intraspecific variation in tooth wear between populations in different geographic areas (Skogland 1988; Kojola et al. 1998; Loison et al. 2001; Nussey et al. 2007; Veiberg et al. 2007a; Ozaki et al. 2010; Kubo and Yamada 2014). ...
... A number of studies comparing tooth wear rates between ungulate species with different feeding types have reported higher rates of wear for grazers, followed by mixed feeders, and then browsers (Solounias et al. 1994; van Soest 1994; Veiberg et al. 2007a; Damuth and Janis 2014). Furthermore, several studies have reported significant intraspecific variation in tooth wear between populations in different geographic areas (Skogland 1988; Kojola et al. 1998; Loison et al. 2001; Nussey et al. 2007; Veiberg et al. 2007a; Ozaki et al. 2010; Kubo and Yamada 2014). This has been attributed either to perceived differences in quality of habitat or available forage , or to differences in population density and associated resource competition leading to variation between individuals in access to higher quality forage (Fowler 1987; Freeland and Choquenot 1990). ...
Body size has profound implications for ecology and life-history traits of mammalian species. Tooth wear is an indicator of food-processing investment and diet properties, with fitness consequences through differences in comminution efficiency, nutrient gain, and senescence. We investigate the relationships between mandible length (a proxy of skeletal body size), molar dentine thickness (a measure of tooth wear), and faecal neutral detergent fibre with residual ash (NDF–ash, a combined proxy of fibre and mineral components in the diet) in 874 male and female red deer (Cervus elaphus L., 1758) from 21 locations in moorland and woodland habitats across Scotland. Significant differences in mandible length occurred between habitats: woodland deer having larger mandibles than moorland deer. Within habitats, larger mandibles were related to higher rates of dentine wear, suggesting increased body size was associated with greater intake and processing of food. Both dentine wear and faecal NDF–ash were higher in moorland deer than in woodland deer, suggesting that fibre and (or) mineral abrasives in the diet may have contributed towards habitat differences in dentine wear. Between habitats, higher dentine wear was not associated with larger mandibles, in contrast to the relationship within habitats, indicating the precedence of additional environmental factors between habitats.
... To get an impression of possible changes in sex ratio between samples we counted the relative numbers of male versus female canines (D'Errico and Vanhaeren 2002) and pelvic fragments (Lie 1973;Greenfield 2006), which were sexed based on their general morphology and use of a modern reference collection. After eruption, the teeth are gradually worn down during an animal's life and molar height should thus indicate an individual's age class (Nussey et al. 2007;Veiberg et al. 2007a). Differences in crown heights may, however, also reflect changes in the amount of abrasives in the diet (Veiberg et al. 2007a). ...
... After eruption, the teeth are gradually worn down during an animal's life and molar height should thus indicate an individual's age class (Nussey et al. 2007;Veiberg et al. 2007a). Differences in crown heights may, however, also reflect changes in the amount of abrasives in the diet (Veiberg et al. 2007a). Thus, in addition to crown heights, we also studied the relative number of fused versus unfused bones and sorted individuals into 4 age classes (older than 0.5, 1, 1.5, or 2.5 years) by using the fusion pattern of the epiphyses of humeri, phalanges, tibias, and metapodials, which fuse at different ages (Mariezkurrena 1983;Carden 2006). ...
... molars relative to their body size (Janis 1990;Pérez-Barberia and Gordon 2001). Relatively larger teeth have been related to greater tooth wear and foraging on fibrous graminoids or in dustier, open environments (Veiberg et al. 2007a;Mendoza and Palmqvist 2008;Hummel et al. 2011). Our results show an opposite pattern with reduced occlusal surface area of the cheek teeth (Table 3; Fig. 2) and a reduction in hypsodonty, especially of the m3 (Fig. 1), indicating that the morphological changes were not an adaptation to foraging in a more open landscape. ...
Large-scale variation in mammalian body size has often been found to be related to environmental conditions. A general finding among large herbivores is that body size increases with decreasing temperature (Bergmann's rule), because animals with larger body size have better heat conservation or fasting tolerance, or because higher quality forage occurs in colder environments. Using a data set on the skeletal morphology of Norwegian red deer (Artiodactyla, Cervidae: Cervus elaphus) spanning the last approximately 7,100 years, we document an inverse relationship between climatic conditions and body size. The size of Norwegian red deer, as estimated from both teeth and weight-bearing bones, was significantly larger during the warmer and wetter middle Holocene than it is today. However, the reduction in body size does not seem to be related to changing climatic conditions. Rather, this decrease happened during a period of large-scale human-mediated habitat fragmentation, increased populations of domestic herbivores, and heavy hunting pressure that reduced population density. The size of teeth was reduced as much as, or even more than, the size of weight-bearing bones, which indicates an evolutionary response rather than phenotypic plasticity to changing forage and environmental conditions. Decreased body size may be a general response in wild ungulates to a more human-dominated landscape, resulting from reduced access to optimal habitats and high adult hunting mortality.
... In this context, describing the tooth wear pattern within a single population (i.e., a wild population with an uniform management regime and experiencing similar climatic/environmental conditions) and checking at which tooth wear level an animal is no longer able to sustain its optimal physical condition (i.e., when it begins to lose body mass till to reach values below the population average) can also facilitate comparisons of the lifehistory parameters of different populations that may live under varying environmental conditions (see [45]), and to understand the differential trends among them. This is especially important for income breeders such as roe deer [46], where females rely on food intake rather than fat reserves for reproduction [47]. ...
... Tooth wear was also estimated using height of the first molar (M 1 ) and the M 1 hypsodonty index, which are the most widely-used indices of wear [1,16,30,31]. In cervids, it has been noted that although crown formation in M 1 is fully completed in the first months of life [64], the completion of eruption and final positioning of the molar in the mandible take place later [45,64], and teeth also move in the mandible at very old age. Consequently, measuring molar height perpendicular from the mandible bone, labial or buccal side, is not necessarily a reliable measurement of molar wear [65]. ...
Background
In many mammalian species, once the permanent teeth have erupted, the only change to dentition is a gradual loss of tooth surface/height through wear. The crown of the teeth cannot be repaired once worn. When dental crown tissue has been depleted due to wear, the animal is expected to have a suboptimal body condition. We evaluated the role of tooth wear in causing a reduction of physical condition in adult roe deer females ( Capreolus capreolus ).
Results
The progressive wearing of the lower cheek teeth was assessed in a Northern Apennines (Italy) population with a new scoring scheme based on objectively described tooth characteristics (morphotypes) being either present or absent. Eviscerated body mass and mandible length, which is a good proxy for body size in roe deer, were related to the tooth wear score by the use of linear regressions. The sum of wear scores for molariform teeth correlated most strongly with body condition (i.e., eviscerated body mass/mandible length), showing the importance of the entire chewing surface for acquiring energy by food comminution, chewing, and digestion. In comparison with individuals of comparable size experiencing minor tooth wear, the body mass of those with the most advanced stage of tooth wear was decreased by 33.7%. This method was compared to the height and the hypsodonty index of the first molar, the most commonly used indices of tooth wear. The sum of molariform wear scoring scheme resulted in a more suitable index to describe the variation in body condition of roe deer.
Conclusions
Describing tooth wear patterns in hunted populations and monitoring at which tooth wear level (and therefore dental morphotype) an animal is no longer able to sustain its physical condition (i.e. when it begins to lose body mass) can be a useful tool for improving the management of the most widespread and abundant deer species in Europe. At the same time, such an approach can clarify the role of tooth wear as a proximate cause of senescence in ungulates.
... Previous research on cervid dentition has focused on the progressive wear of molar teeth and the associated life history consequences (Skogland 1988, Hindelang & Peterson 1994, Bubenik 1997, Kojola et al. 1998, Mysterud 2001, Loe et al. 2003, Carranza et al. 2004, Loe et al. 2006, Veiberg et al. 2007a, Veiberg et al. 2007b, Carranza et al. 2008. A consensus among many of these studies is that tooth condition is suggested to be an important determinant of longevity and senescence (Skogland 1988, Hindelang & Peterson 1994, Loe et al. 2003, Carranza et al. 2004. ...
... In certain regions of Newfoundland and Cape Breton, impaired browse regeneration and limited resources have been documented to result from elevated moose densities (Mercer & McLaren 2002, Bridgland et al. 2007. Previous study of both incisor and molar wearing in moose, suggests that current ecological conditions, such as food quality, are important factors in incisor wearing (Veiberg et al. 2007a). Food resource quality and availability among regions likely, in part, explains some proportion of the tooth integrity variability that we have seen in this study. ...
2010: The spatial variation of extreme tooth breakage in an herbivore and potential age structure effects. — Ann. Zool. Fennici 47: 261–271. Teeth are essential in mammals for the capture, handling and processing of food and self-defense. The rate of deterioration may affect longevity and indicate certain envi-ronmental conditions. The goal of this study was to characterize tooth conditions of moose (Alces alces) from multiple regions and to make inferences of possible causes of variation. An assessment of > 5500 moose incisors, found that the frequency of breakage and rate of decline in incisor integrity, with age, was much higher in Cape Breton and Newfoundland (breakage from 6% to 47%) than in New Brunswick, Ontario, New Hampshire, Vermont, and Yukon (breakage from 1% to 6%). Incisal degradation, among jurisdictions, differed significantly though population age struc-tures did not appear different. The two jurisdictions most affected by incisal deteriora-tion, Cape Breton and Newfoundland, are inhabited by genetically distinct subspecies, at higher densities than other regions; therefore, breakage may be linked to local envi-ronmental conditions.
... Additional support to our interpretation comes from the finding that spatial variation in antler length was higher than temporal variation, despite ample evidence that antler size in red deer shows strong inter-annual variation that is weather and density dependent [35][36][37][38][39] . Moreover, if favourable environmental conditions were the main cause for antlers being larger in HC populations, it would be unlikely that males of these populations would show higher rates of tooth wear, as tooth wear is related to harsh habitat conditions in several species of deer 21,[40][41][42] . ...
Theory predicts that the plastic expression of sex-traits should be modulated not only by their production costs but also by the benefits derived from the presence of rivals and mates, yet there is a paucity of evidence for an adaptive response of sex-trait expression to social environment. We studied antler size, a costly and plastic sex trait, and tooth wear, a trait related to food intake and longevity, in over 4,000 male Iberian red deer (Cervus elaphus hispanicus) from 56 wild populations characterized by two contrasting management practices that affect male age structure and adult sex-ratio. As a consequence, these populations exhibit high and low levels of male-male competition for mating opportunities. We hypothesized that males under conditions of low intra-sexual competition would develop smaller antlers, after controlling for body size and age, than males under conditions of high intra-sexual competition, thus reducing energy demands (i.e. reducing intake and food comminution), and as a consequence, leading to less tooth wear and a concomitant longer potential lifespan. Our results supported these predictions. To reject possible uncontrolled factors that may have occurred in the wild populations, we carried out an experimental design on red deer in captivity, placing males in separate plots with females or with rival males during the period of antler growth. Males living with rivals grew larger antlers than males living in a female environment, which corroborates the results found in the wild populations. As far as we know, these results show, for the first time, the modulation of a sexual trait and its costs on longevity conditional upon the level of intra-sexual competition.
... The outcome of the digestion process is also closely related to food comminution before and after mastication (Jaster & Murphy, 1983;Shaver, Nytes, Satter, & Jorgensen, 1988). An excessively low chewing efficiency can lead to reducing in nutritional and energy input, and thus to undernutrition and death (King et al., 2005;Pahl, 1987;Veiberg et al., 2007). Therefore, chewing efficiency is an important aspect of biological anthropology as it provides information on the quality of dietary environment, the effects of diet on primate digestion as well as how primate adapt to their dietary environment. ...
Objectives:
Chewing efficiency plays an important role in the survival and distribution of primates. Yet, little is known about the intra-specific variation of chewing efficiency. The purpose of this study is to report the pattern of seasonal and regional variation in chewing efficiency among Yakushima Japanese macaques (Macaca fuscata yakui).
Materials and methods:
Fecal samples of Yakushima Japanese macaques were collected from lowland, highland and summit areas in Yakushima between July 2015 and March 2016 (n = 236). Using sieving analysis, we compared fecal particle size (dMEAN) and proportion of finest particles p(0) between different geographical areas and seasons.
Results:
Seasonally, in the lowland zone, there was a non-significant decrease in dMEAN during spring, while p(0) was significantly higher during summer than it was during winter and spring. Regionally, dMEAN was higher in the summit zone than it was in other areas during autumn, while p(0) was also higher in the summit zone.
Conclusions:
While seasonal variation in dMEAN can be explained by the reported difference in the proportions of food categories in diet between seasons, its influence is mitigated, possibly by the selective feeding of less mechanically challenging parts in each category. Regional variation in dMEAN and p(0) may be the results of bamboo consumption in this area. Combining our data with studies that focus on seasonal and regional variations of food properties or gut microbes might provide a better understanding of the relation between diet, chewing and digestion in Yakushima macaques.
... elaphus elaphus). Other studies focused on dental features were developed in cervids, such as the study of dental measurements (Cederlund et al. 1991;Cooper et al. 2013) or dental wear (Veiberg et al. 2007;Azorit, 2011). ...
... Adaptations under the sympatric model may be harder to distinguish from changes in response to general environmental conditions, but developments in quantitative palaeontology have revealed methods to identify dietary specialisations from tooth morphology regardless of taxonomic affiliation (Jernvall et al. 1996, Mendoza andPalmqvist 2008). Usefully, feeding-type may also be unrelated to body size in dictating patterns of tooth wear (Veiberg et al. 2007) and this could provide an independent estimate of diet quality. It follows that cautious prediction of body mass using the craniodental morphology of extinct species could enable reliable estimates of body size independent of phylogeny and non-dietary, ecological adaptations (Mendoza et al. 2006). ...
... As individuals age, survival and reproductive rates decline [25][26][27][28]. Factors such as tooth wear can contribute to senescence in deer [29,30]. Overall, mortality factors that remove prime-aged females potentially exert a stronger influence on population potential of deer than those that primarily remove senescent females. ...
As roads continue to be built and expanded, it is important that managers understand the effects that vehicle-related mortality can have on the population dynamics of wildlife. Our objective was to examine the frequency of mule deer (Odocoileus hemionus) vehicle collisions to determine if different demographic groups showed differential susceptibility to mortality when compared with their proportion in the population. We also compared vehicle collision rates of mule deer, elk (Cervus canadensis), and moose (Alces alces) to determine their relative vulnerability to vehicle collisions. We found that 65% of mule deer involved in vehicle collisions were female; of those, 40% were adult does ≥2 yrs. When we compared the proportion of bucks, does, and fawns killed in vehicle collisions to surveys of live deer, we found that bucks were killed at rate of 2.1–3.0 times their proportion in the population. Additionally, when we compared vehicle collision rates for 2010 and 2011, we found that mule deer were 7.4–8.7 times more likely to be involved in collisions than elk and 1.2–2.0 times more likely than moose. However, we were unable to detect a negative correlation (P=0.55) between mule deer abundance and increasing traffic volume.
... where C is the pre-harvest proportion calves in the population, and M is the annual natural mortality rate for post-recruitment individuals (i.e. ! 4 months; Veiberg et al. 2007, Austrheim et al. 2008b). Likewise, we estimated population growth rate, k, based on the change in harvest over time, i.e. by regressing the log-annual harvest on year within county (for moose) or country as a whole (for red deer and roe deer). ...
... Although the log-transformation of tooth height led to better fits than the linear or quadratic models in only 14 out of 51 case studies, we selected the log-transformation because an exponential decrease has been used in most recent studies (e.g. Veiberg et al., 2007b;Ozaki et al., 2010) and obvious deviations from a linear decrease have been reported in some cases (e.g. Loe et al., 2003;Carranza et al., 2008). ...
We test whether the intensity of tooth wear influences the strength of actuarial senescence across species of large herbivores. We collected from the literature data on tooth wear in the wild (measured as the slope of the regression of log-transformed M1 crown height on age), longevity (measured as the age at which 90% of individuals are dead) and two metrics of actuarial senescence in captive populations (rate of senescence between 6 and 12years of age and Gompertz rate of senescence). Between-species differences and variation in tooth height accounted for most of the observed variation in tooth wear among large herbivores: tooth height and tooth wear were positively correlated. In contrast, tooth wear was little influenced by sex, body mass, or taxonomy. No marked between-sex differences in longevity occurred. Males senesced faster than females when tooth wear was low (for both senescence metrics), while between-sex differences in actuarial senescence when tooth wear was high depended on the metric used to measure actuarial senescence. While longevity was mostly independent of the intensity of tooth wear, we found general support for a positive relationship between both measures of actuarial senescence and tooth wear. These patterns were consistent whether hypsodonty was controlled for or not. Although varying according to sex and to the metric used for assessing actuarial senescence, our findings suggest overall that tooth wear could be positively associated with actuarial senescence among large herbivores. Further longitudinal studies focusing on changes within individuals will be required to test whether a mechanistic link between tooth wear and actuarial senescence occurs in large herbivores.
... On Nakanoshima Island, both food habits and lifehistory traits changed along with irruptive dynamics. Previous studies of both interspecific and intraspecific comparisons have shown that the molar wear rate was more influenced by food habits than body size (Veiberg et al., 2007a;Ozaki et al., 2010). Thus, acceleration of wear rate is considered to be affected by food habit change. ...
Negative effects of density-dependent food limitation on molar wear rate in ungulate populations, as well as unworn molar size and its sex differences in ruminants, have been studied for a long time. However, these studies were based on comparisons of populations from different districts or habitats. If drastic changes in food habits and life history occurred under density-dependent resource limitation, it is of great interest whether this change caused temporal changes in molar wear rate, and whether the degree of hypsodonty changed under this short but intensive selective pressure. We examined the temporal change in molar wear rate using long-term monitoring data of a sika deer (Cervus nipon) population on Nakanoshima Island, Hokkaido, Japan. Corresponding to the change in food habits, the molar wear rate changed mainly because of the amount of soil that was secondarily ingested when deer fed on fallen leaves. Molar wear rate was the fastest level after the first population crash on Nakanoshima Island among extant sika deer populations. Nevertheless, we did not find any evidence of increased hypsodonty in Nakanoshima deer. It is possible that natural selection for increased molar durability (hypsodonty) has been working on Nakanoshima deer, but the adaptive change has not yet appeared at a statistically significant level.
... Med njimi so še zlasti pomembni trdnost oz. mineralizacija zobne sklenine (KIERDORF / BECHER 1997), prehranska strategija vrste (VEIBERG et al. 2007a), spol (VAN DEELEN et al. 2000, LOE et al. 2003, HØYE 2006, CARRANZA / PEREZ-BAR-BERIA 2007, CARRANZA et al. 2008, populacijske gostote pokorny, b., Jerina, K., Jelenko, i.: Zanesljivost makroskopskega (okularnega) ocenjevanja starosti jelenjadi ... (MYSTERUD et al. 2001) in vrsta ter kakovost prehranskih virov (npr. OZAKI et al. 2010, NUSSEY et al. 2007 Zaradi motečih dejavnikov, ki vplivajo na obrabljenost zob, in subjektivne napake ocenjevalcev prihaja pri makroskopskem ocenjevanju starosti živali vedno do napak, ki so lahko tudi zelo velike (npr. ...
To check the reliability of macroscopic (ocular) assessment of the age of red deer (Cervus elaphus L.) obtained by ocular inspection of teeth eruption and wear (done by hunters or hunter commissions), a validation of the precision of these assessments was carried out on a representative sample set, i.e. a total 2008-annual cull of red deer in the entire Slovenia. Test of the reliability of ocular age assessment was performed by cutting/grinding of the first mandibular molar (M1) and counting the incremental layers of dental cementum on 821 samples of adults (aged from two to twenty-two years). The ocular age assessment of adult red deer (regardless of sex) was biased with a large error (maximum deviation between both assessments: nine years). With both methods the same animal age was established in 24.5% of cases, and with the age of the animals the reliability of ocular assessment declined. Ages of hinds and younger stags were both under-assessed and over-assessed; however, ages of older stags were generally over-assessed. Out of 426 analysed stags, 142 (33.3%) were categorized in another age category as found by counting annuli in tooth cementum. This raises doubts about the reliability of the current categorization of adult red deer stags into three age categories (2–4 years old, 5–9 years old, and 10+ years old, respectively); indeed, precise (on a yearly basis) ages of adult stags are impossible to be identified by routine age assessment, such as the inspection of teeth wear.
... We also excluded counties 4, 6, 9, 15 and 16 ( Fig. 1) and the years 1987 and 1988 from both data sets, and also 1989 from the prime stag data set because of low harvesting numbers, leaving a total of 126 017 individuals available for analyses. Age was estimated by tooth wear (Szidnai 1978), a method known to show some variation for older individuals (Mysterud & Østbye 2006) but also variation between (Veiberg et al. 2007) and within populations (Nussey et al. 2007). As the same method was utilized over the full data set, it is unlikely that over-or underestimation of age plays a role for the observed patterns, but we are aware that the ageing method probably adds some noise to the data, particularly for older individuals. ...
Background/Question/Methods
Wild animals have always been an important resource for humans, and we are known to utilize a range of species from different taxa. However, this utilization, and in particular human harvesting, is known to have a large impact on natural populations, and may cause undesirable life history changes over shorter periods of time than expected from natural selection. In wild ungulate populations unrestricted trophy hunting is believed to cause strong selection pressures resulting in evolutionary change towards smaller trophies. However, sufficiently strong directional hunter selection must be present to induce long-term decrease in trophy size, and how harvesting selection varies in space and time has rarely been tested. The key to changes in trophy size is hunter selectivity for specific phenotypic traits. We analyze two unique datasets of harvesting records spanning decadal (1973-2008) and century (1881-2008) scales to identify potential phenotypic trait changes during this time and how harvest selection vary in space and time in red deer (Cervus elaphus).
Results/Conclusions
Our results show that patterns of red deer antler size spanning more than a century were remarkably similar both in space and time. We found a common spatial trend with recent antler sizes being as large as or even larger than earlier peaks in the time series. For the decadal scale data, we found selection patterns to be very dynamic for age-specific trophy size in space and time when comparing foreign and local hunters. This provides evidence that harvesting selection is more variable than earlier assumed. This may contribute to the lack of evidence of a long-term negative trend over more than a century of the largest red deer antlers recorded at trophy exhibitions in Hungary, but unexplained recent increases in antler size suggest other management restrictions and/or environmental factors to play a role for antler size development.
This study highlights that trophy hunting is not necessarily an unsustainable practice that lead to a decline in trophy sizes even over century long time scales. Also, we need to identify the conditions enabling sustainable management in the long term. We also discuss a set of factors that could form the basis for a theory of evolutionary enlightened management of trophy hunting, including factors such as spatial and temporal refuges, compensatory culling, saving stags until prime age culmination and higher prices for larger trophies.
... Common marmosets' preference for less mechanically challenging barks and reports of dental injuries (up to 56% of the population; Valença- Montenegro, 2002;Venturini, 2006) are consistent with a risk-minimization strategy. While marmosets represent an extreme potential for dental injury, more subtle but still important factors such as increased dental wear can also negatively impact feeding ability and fitness (King et al., 2005;Veiberg et al., 2007;Ozaki et al., 2010). This suggests that how animals choose to overcome mechanical defenses can have important evolutionary consequences. ...
Animals must overcome the physical properties protecting foods to obtain nutrition. While animals can experience selection for traits that facilitate resource exploitation, specific feeding behaviors may entail multiple, different mechanical challenges with each potentially eliciting distinct selection pressures. Tree gouging by common marmosets (Primates: Callithrix jacchus) provides an illustrative case for studying these distinct mechanical challenges and their correlated behaviors and morphologies. We test the hypothesis that marmosets respond differently to three sequential mechanical stages of bark removal: (1) indentation; (2) crack initiation; (3) crack propagation. By surveying trees gouged by free-ranging marmosets in Pernambuco, Brazil, we found that mechanical variables related to crack initiation (fracture toughness, critical strain energy release rate and elastic modulus) were inversely correlated with measures of gouging intensity, with less mechanically challenging trees being gouged more intensely. Because crack initiation is likely the most mechanically challenging aspect of tree gouging, behavioral preference for less challenging resources likely allows marmosets to reduce costs and potential risks associated with accessing exudates. Variables related to bark indentation (hardness and friction) showed no relationship to the intensity of gouging behavior. Contrary to our prediction, trees with greater mechanical challenges for crack propagation (work to peel) were gouged more intensely. We attribute this pattern of gouging trees requiring greater effort in crack propagation to an inverse correlation between work to peel and fracture toughness in our tree sample. Importantly, marmosets exhibit morphological specializations of the feeding apparatus that facilitate indentation and crack propagation, potentially mitigating the need for behavioral choice. Here we show that extracting a single food resource can exert a series of distinct, potentially competing, selective forces during resource acquisition. This study illustrates how animals combine behaviors and morphological specializations to competently overcome distinct mechanical challenges, emphasizing the need for holistic approaches in understanding feeding adaptations.
... Many methods of age determination have been used to date (Morris, 1972;Spinage, 1973;King, 1991;Fortelius and Solounias, 2000;Monakhov, 2004;Roulichová and Andera, 2007;Kaiser et al., 2009). In most of them, the age classification is based on biological characteristics that show the transition of one growth stage to another, such as deposition of cementum layers on canines (Grue and Jensen, 1979;Saez-Royuela et al., 1989;Maffei and Becerra, 2000;Nakanishi et al., 2009); sequence of tooth eruption (Ancrenaz and Delhomme, 1997) and wear (Stander, 1997;Veiberg et al., 2007;Ozaki et al., 2010); or cranial suture fusion (Landon et al., 1998). ...
... The county, date of kill and information on whether the hunter was local or a foreign trophy stalker are also available for all individuals (). Age is estimated by tooth wear (Szidnai 1978), a method known to show some variation for older individuals (Mysterud and Østbye 2006) but also variation between (Veiberg et al. 2007) and within populations (Nussey et al. 2007). However, since the same method is utilized over the full data set, it is unlikely that over-or underestimation of age play a role for the observed patterns, but we are aware that the ageing method probably adds some confusion to the data, particularly for older individuals (Rivrud et al., 2013). ...
Wildlife management should be based on data and management decisions which require adequate information. In case of red deer population sizes, the level of hunting pressure, and the effects of harvesting on the male population are debated in many form. Several relationships and effects of management and hunting cannot be well understood without the collection and use of long- term data. Since 1970 it is compulsory in Hungary to present antlers of harvested red deer for a trophy evaluation (scoring) by Trophy Scoring Committees authorized by the state authorities. This paper presents some of the uses of trophy scoring data on the basis of Somogy county. Population reconstruction, comparison of mortality patterns of different cohorts, and spatio-temporal differences in age composition of shot males are discussed.
... Adaptations under the sympatric model may be harder to distinguish from changes in response to general environmental conditions, but developments in quantitative palaeontology have revealed methods to identify dietary specialisations from tooth morphology regardless of taxonomic affiliation (Jernvall et al. 1996, Mendoza andPalmqvist 2008). Usefully, feeding-type may also be unrelated to body size in dictating patterns of tooth wear (Veiberg et al. 2007) and this could provide an independent estimate of diet quality. It follows that cautious prediction of body mass using the craniodental morphology of extinct species could enable reliable estimates of body size independent of phylogeny and non-dietary, ecological adaptations (Mendoza et al. 2006). ...
The main radiation of large mammalian herbivores in Africa took place in the Pliocene–Pleistocene, when a long-term trend towards aridification promoted grasslands and the diversification of ruminant grazers. Traditional models of this evolution identify habitat fragmentation in response to climate change as the primary cause of speciation and diversification. However, with their adaptation to poorer and drier diets, these animals incurred a cost: an increase in water requirements to aid digestion and to thermoregulate their larger body size. Water requirements are included in the current model, relating this foremost physiological need to an environmental resource: habitat fragments would have contained sources of drinking water for the persistence of water-dependent species. However, the location of drinking water and its influences are subsumed within the extent of those fragments; their roles in habitat fragmentation and the subsequent evolutionary processes are less clear. The current model neglects to consider the interaction of water dependency with the location of drinking water; increased aridification would not only have involved shifts in the spatial distribution and species composition of forage resources, but it would also have increased the patchiness of surface water distributions. Animal foraging distributions would have been constrained within species-specific distances of their drinking water over an evolutionary timescale, distances that were not necessarily in accord with the extent of their potential habitat as solely defined by forage distributions, particularly as animals became more dependent on water with the increase in grazing and its associated traits. Drinking-water location exerts a dominant influence on animal survival and reproduction, suggesting that these roles of drinking-water location need to be incorporated into existing models of large mammalian herbivore evolution in Africa.
... We also excluded counties 4, 6, 9, 15 and 16 ( Fig. 1) and the years 1987 and 1988 from both data sets, and also 1989 from the prime stag data set because of low harvesting numbers, leaving a total of 126 017 individuals available for analyses. Age was estimated by tooth wear (Szidnai 1978), a method known to show some variation for older individuals (Mysterud & Østbye 2006) but also variation between (Veiberg et al. 2007) and within populations (Nussey et al. 2007). As the same method was utilized over the full data set, it is unlikely that over-or underestimation of age plays a role for the observed patterns, but we are aware that the ageing method probably adds some noise to the data, particularly for older individuals. ...
1. Human harvesting has a large impact on natural populations and may cause undesirable life-history changes. In wild ungulate populations, unrestricted trophy hunting may cause strong selection pressures resulting in evolutionary change towards smaller trophies. It has rarely been tested how harvesting selection varies in space and time, and whether directional hunter selection is sufficiently strong to induce long-term decreases in trophy size in century- scale data.
2. We analysed two unique data sets of harvesting records spanning decade (1973–2008) and century scales (1881–2008) to identify changes in trophy size and how harvesting selection varies in space and time in red deer Cervus elaphus. We contrasted predictions from the trophy-hunting depletion, the restricted trophy hunting and the hunting pressure hypotheses. 3. Foreign hunters selected older and larger males than local hunters, but selection patterns for age-specific trophy size between counties and over time were dynamic. Patterns of red deer trophy size development from exhibitions (representing the ‘upper tail’ of antler sizes) were remarkably similar across Hungary from 1881 to 2008. A weak decline in trophy size between 1881 and 1958 was followed by a strong increase in trophy size between 1958 and 1974, culminating in a period of stable antler tine numbers and a weak decline in beam length until 2008.
4. We rejected the trophy hunting depletion hypothesis due to the increase in trophy size after a period of decline; patterns were most consistent with the hunting pressure hypothe- sis. Large increases in trophy size during 1958–1974 were likely due to a relief in hunting pressure due to implementation of strict management regulations allowing stags to grow old after the massive overharvesting during World War II, but we cannot exclude impacts from environmental factors, and that data from trophy exhibitions may underestimate trends.
5. Synthesis and applications. Trophy hunting does not necessarily lead to a non-reversible decline in trophy size, even over century-long time-scales. To ensure sustainable trophy hunting management, we need to consider factors such as spatial and temporal refuges, compensatory culling, saving stags until prime-age culmination and higher prices for larger trophies.
... The browsing roe deer Capreolus capreolus had a slower molar wear rate than the intermediate feeders and grazers, although this was confounded with the body size effect, so that the potential effect of feeding type on molar wear rate remained unclear. Recently, Veiberg et al. (2007a) showed that the large browsing moose Alces alces had a slower molar wear rate than the mixed-feeding red deer Cervus elaphus, suggesting that feeding type was more important than body size. Our intraspecific data also support this interpretation. ...
Functionality of cheek teeth is essential for ruminants to masticate plant materials thoroughly and promote microbial degradation in their rumens. Thus, an excessive rate of tooth wear is expected to lead to premature loss of tooth functionality, and hence to reduced longevity. So far, however, the relationships between food habits, molar wear and longevity have not been investigated. We first compared molar wear rates among nine sika deer Cervus nippon populations with different food habits. We then investigated correlations between molar wear rate and two ecological factors, percentage of graminoids in diet and annual precipitation, relating to intrinsic and extrinsic abrasiveness of the ingested food, respectively. Secondly, we estimated ‘retained molar durability’ (molar height at a given age divided by wear rate) at successive ages for each population, and tested for correlation between molar durability and life expectancy among populations. The M1 and M3 wear rates differed among the populations and showed a positive correlation with graminoid consumption and a negative correlation with precipitation, suggesting that both ecological factors influence molar wear rates in the Japanese sika deer. M3 durability had a stronger correlation with life expectancy than M1 durability, especially at the older age stages. This implies that the influence of M3 durability on life expectancy becomes stronger at the time when the M1 is severely worn and loses its functionality, and is therefore more important for life span elongation than the M1. These results are concordant with the fact that the M3 is the most hypsodont molar in many ungulates. In the Japanese sika deer, microevolutionary acquisition of hypsodonty appears to be the case in a northern population (the Kinkazan Island), whose molar wear rates are extremely rapid due to their food habits.
... The optimal scaling model implicitly assumes that any departure from the reference state results in a degradation of the state of the major ecosystem related to the indicator. This is useful for indicators such as the moose, Alces alces, which might experience a strong decline because of hunting but whose large populations have on the other side a detrimental effect on the vegetation because of an unsustainable grazing pressure [27,28]. We use the ''minimal'' scaling model (Figure 1b) when the reference state refers to a low, precautionary level, as found in marine management of small pelagic fish [29]: ...
The magnitude and urgency of the biodiversity crisis is widely recognized within scientific and political organizations. However, a lack of integrated measures for biodiversity has greatly constrained the national and international response to the biodiversity crisis. Thus, integrated biodiversity indexes will greatly facilitate information transfer from science toward other areas of human society. The Nature Index framework samples scientific information on biodiversity from a variety of sources, synthesizes this information, and then transmits it in a simplified form to environmental managers, policymakers, and the public. The Nature Index optimizes information use by incorporating expert judgment, monitoring-based estimates, and model-based estimates. The index relies on a network of scientific experts, each of whom is responsible for one or more biodiversity indicators. The resulting set of indicators is supposed to represent the best available knowledge on the state of biodiversity and ecosystems in any given area. The value of each indicator is scaled relative to a reference state, i.e., a predicted value assessed by each expert for a hypothetical undisturbed or sustainably managed ecosystem. Scaled indicator values can be aggregated or disaggregated over different axes representing spatiotemporal dimensions or thematic groups. A range of scaling models can be applied to allow for different ways of interpreting the reference states, e.g., optimal situations or minimum sustainable levels. Statistical testing for differences in space or time can be implemented using Monte-Carlo simulations. This study presents the Nature Index framework and details its implementation in Norway. The results suggest that the framework is a functional, efficient, and pragmatic approach for gathering and synthesizing scientific knowledge on the state of biodiversity in any marine or terrestrial ecosystem and has general applicability worldwide.
... Although Solounias et al. (1994) showed a positive correlation, they speculated that this was an artefact of the fact that the single browser was the smallest animal in the sample, while the largest ones were all grazers. This speculation was supported by the study of Veiberg et al. (2007), who showed that mixed-feeding red deer (Cervus elaphus) had wear rates twice that of the larger, browsing moose (Alces alces). Ozaki et al. (2010) also show that body size has no influence on the rate of tooth wear in Japanese sika deer (Cervus nippon). ...
High-crowned (hypsodont) teeth are widely found among both extant and extinct mammalian herbivores. Extant grazing ungulates (hoofed mammals) have hypsodont teeth (a derived condition), and so extinct hypsodont forms have usually been presumed to have been grazers. Thus, hypsodonty among ungulates has, over the past 150 years, formed the basis of widespread palaeoecological interpretations, and has figured prominently in the evolutionary study of the spread of grasslands in the mid Cenozoic. However, perceived inconsistencies between levels of hypsodonty and dental wear patterns in both extant and extinct ungulates have caused some workers to reject hypsodonty as a useful predictive tool in palaeobiology, a view that we consider both misguided and premature.
Dental enamel is the hardest tissue of the mammalian body, consisting of 96–98% inorganic compound. As the dentition is functionally adapted to diet and feeding behaviour, relative differences in enamel thickness can reflect dietary adaptations. We hypothesize that differences in enamel thickness are related to adaptation for diet associated with habitat quality dwelling of European roe deer Capreolus capreolus. To test this hypothesis, 49 first permanent left lower molars were extracted from the mandible of roe deer (from Lithuania – 28 and Poland – 21 molars) inhabiting two type of habitats: field and forest. The linear thickness of total enamel (mean value of enamel thickness measured at three different points) was found to differ between the roe deer from the field and forest habitats, irrespective of age, with the animals of field ecotype tend to have thinner enamel (F(1,26) = 6.845, P = 0.025). This suggests that there is an adaptation in enamel thickness to various types of diet in the field and forest habitat. On the other hand, roe deer from the field habitat can be also more exposed to stress, due to the lower possibility to hide or are more vulnerable to potential threats. More frequent exposure to stress can significantly disrupt ameloblasts secretion and thus affect the thickness of the enamel.
In Denmark, red deer (Cervus elaphus) are legal quarry (subject to no quotas) throughout the hunting season (1 September – 31 January) for anyone holding a valid license to hunt on their own land (more than 1 hectare) or on rented ground (larger than 5 hectares). As a consequence, in most parts of Denmark, multiple land owners and hunters on rented ground compete for the same individuals without any overall plan or coordination of the culling of local populations. The disadvantages of such a lack of management (for instance, the apparent deficit of mature stags because of high hunting pressure before reaching maturity) have been debated for decades. To contribute factual information to this debate, the demographic composition of two Danish red deer populations with contrasting land owner structure and hunting regimes were analysed and compared, from Djursland (hunting seasons 2008/9-2012/13) and Oksbøl red deer reserve (1985/86-2012/13). Djursland (1417 km2, the easternmost tip of Jutland) represents a ‘typical’ Danish landscape, comprising multiple owners of small or larger estates each of which run their own hunting practices. In this area, 1-year old males were protected in an effort to increase the proportion of mature stags in the population. During a five-year period, hunters on Djursland voluntarily delivered jaws from hunted red deer for age determination and morphometric information. The population on the Oksbøl red deer reserve (163 km2, south western Jutland) is managed by the Danish Nature Agency, with the aim of maintaining a stable red deer population with a high proportion of mature stags through a deliberate harvesting policy. On Oksbøl, the age of all harvested and deer found dead had been estimated on the basis of teeth wear (although the validity of this locally developed age estimation method had never been tested on independent data).
The aims of this analysis were (i) to test and calibrate the wear-based age es-timation method used on Oksbøl against independent data, (ii) to describe the demographic composition of the two populations from age at death dis-tributions, and (iii) to establish population models from this information. Since data was also available on the number of points on antlers, weight, pregnancy and lactation rates, relationships between these variables and age, population density and date were also calculated.
In summary, the results are as follows:
1. From a reference material of 37 individuals of known age (marked before 2 years old), true age correlated closely (R2 = 97%) and accurately (no bias) with age estimated from the number of incremental lines in teeth ce-mentum layers (‘method 1’), although with a precision of ±2 years for any given individual. Age estimation based on dentin layers can thus be con-sidered as a reliable method to estimate age of Danish red deer.
2. Age estimated from tooth wear in 15 red deer from Oksbøl correlated closely with age estimated from dental lines (R2 = 92 %). However, the age estimated from the number of dentin lines was on average 49.5 % higher (p< 0.0001) than that estimated from tooth wear, suggesting that the locally developed wear based age determination method systematically underestimated the age of dead red deer. A deer estimated to be 10 years old on the basis of the tooth wear method would, on average, be estimated to be 15 years old from counts of dentin lines.
3. The demographic composition of the Oksbøl population was constructed based on life tables established from 4278 aged females and 2896 males which died between 1990/91 and 2012/13. Females had an estimated annual mortality (based on adjusted age distribution from method 2 cal-culated at the start of the hunting season) of 33% as calves and 15-20% for all older age classes. This was equivalent to a spring population of females which consisted of 19% yearlings/calves from the preceding summer, 13% 2-year olds, 11% 3-year olds and 55% 4+ year olds. Males had an estimated annual mortality of 45% for calves, 35% for 1-3 year olds, and 20% for stags from 4 years of age, equivalent to an male age composition of 26% yearlings, 17% 2-years olds, 11% 3-years olds, 26% 4-7 year olds and 21% of 8 years of age or older. At the start of the rutting season, the population consisted of 2.6 hinds (i.e. females aged 1½ years old or older) for every stag aged 2½ years or more and 5.7 hinds for every stag aged 5½ year or more.
4. The demographic composition of the Djursland population was con-structed based on life tables established from 895 aged females and 622 males which died between 2008/09 and 2012/13. Seventy-four unsexed calves where assumed to represent an even sex distribution and were di-vided equally within the male and female life tables. Females had an es-timated annual mortality (calculated from the start of the hunting season) of 23% as calves and 20% as 1-7 year olds, and 34 of 8 years of age or older. This was equivalent to a spring female population of 22% yearlings/calves from the preceding summer, 18% 2-year olds, 15% 3-year olds and 45% 4+ year olds. Males had an estimated annual mortality of 24% for calves, 4% for yearlings, 26% for 2-year olds, and about 50% for 3-7 years of age. An apparent reduction in annual mortality after 8 years of age (24%) may be an artefact caused by a few old stags escaped from captivity. The estimated age distribution of males in spring thus consisted of 29% yearlings, 28% 2-year olds, 21% 3-year olds, 11% 4 year olds and 11% of 5 years of age or older. At the start of the rutting season, the population consisted of 1.8 hinds for every stag aged 2½ year or more, and 8.1 hinds for every stag aged 5½ year or more.
5. The population effect of protecting 1-year old males from hunting on Djursland could not be estimated rigorously because of the lack of refer-ence material (because protection was implemented throughout the sam-pling period) but could be cautiously estimated as a difference in mortality between yearlings and calves and 2-year old stags of about 20%. Ac-cordingly, without the protection of yearling males from hunting, the number of all older age groups of males would probably be 20% lower than observed.
6. Male body weight increased with age until the 5th year on Djursland and 10th year at Oksbøl. In both populations, female body weights increased with age until their 3rd year. Females from Djursland weighed on average 12% more than females from Oksbøl (methodological differences pre-cluded comparisons of stags between populations). In both populations, calf weights increased by 6-7 kg for both sexes during the first 2 months of the hunting season. During the same period the weight of adult stags decreased because of rutting activities. Calves from the Oksbøl population weighed 8-9% less in those years (mid 1990s) when population density peaked at almost twice the size as in the 1980s and after 2000. In 1- and 2-year old males, there was a 12% difference in body weight between cohorts born during the highest and lowest population densities.
7. The number of antler points increased until 8-15 years of age, reaching an average of 11 but with considerable (±3) individual variation. In both populations 2/3 of all males had at least 10 points at 5 years of age and 80-90% had at least 10 points at 8 years of age. The proportion of stags with 14 points or more peaked at c.25% during 12-15 years of age.
8. In both population more females than males were reported amongst the grown individuals (Djursland: 60% females, Oksbøl: 58% females) even though the sex ratio amongst calves was close to unity. In Oksbøl, the female: male ratio varied from 50:50 for individuals from cohorts born during lowest population densities to 65:35 for cohorts born during greatest densities. Since the sex-ratio of (dead) calves did not vary signifi-cantly as a function of population density, the female biases sex ratio of adults is likely to reflect increased emigration of stags under dense popu-lation conditions. On Djursland, the apparent female-biased sex ratio in the population may be the result of a campaign aimed at ceasing the growth of the population by targeting hinds and/or lower reporting fre-quencies for stags than for hinds.
9. Data on pregnancy and lactation rates were available from Djursland only. Here, 88% of all hinds on Djursland were pregnant, divided between 64% amongst 1-year old and 91% of older hinds. At the start of the hunting season 79% of all hinds were lactating (i.e. being with calf), based on 57% of the 2-old and 82% of older hinds.
10. On the basis of estimated age specific mortalities for each population and observed fecundity on Djursland (extrapolated to Oksbøl), population growth rates were estimated to be =1.02 at Oksbøl and 1.00 at Djursland. Since the population at Oksbøl remained about the same from the 1980ies to 2012/13, the predicted positive growth rate for the Oksbøl population might be the result of the substituted fecundity rates in the model (taken from the Djursland population) exceeding the true rates of the Oksbøl population. A population model incorporating a fecundity rate estimated from Djursland and no hunting mortality (99% annual survival until 8th years of age, 80% annual survival after that age), predicted an annual population growth rate of =1.21, which is equal to a doubling of the population size in four years. Estimates are given for population growth rates under different combinations of female age specific annual survival.
11. The estimated population patterns for the Oksbøl and Djursland popula-tions are discussed in relation to five dominant (but partly opposing) population objectives to: (i) maximise the number of harvested individuals relative to the population size (‘game ranch model’), (ii) maximise the number of harvested mature stags relative to the size of the population (‘trophy model’), (iii) maintain a ‘high’ proportion of mature stags in the living population, (iv) attain a ‘sustainable’ harvesting (several defini-tions), and (v) sustain an intended ‘natural’ demographic composition.
12. In terms of number of harvested individuals relative to the size of the winter population, the populations at Oksbøl and Djursland resulted in a yield of 37 and 32 harvested individuals/ 100 individuals in the winter population. This was 55-60% of the maximum possible number of har-vested individuals in a population managed for that purpose (game ranch model: 62/100), about the same number as harvested in a population managed to maintain an intended natural demographic composition (34/100) and half the number harvested in a population managed to maximize the number of harvested stags of at least 8 years of age.
13. On Djursland, 0.4 mature stags (defined as at least 8 years of age) were harvested per 100 individuals in the spring population. This constitutes 4% of the harvest from a population managed to maximize the harvest of mature stags (trophy model: 8.7/100), 15% of the harvest from a popula-tion with an intended natural demographic composition (2.6/100) and one third the number of mature stags harvested at Oksbøl (1.2/100) or in a population managed in order to optimize meat harvest (game ranch model). Without protection of 1-year old males, the yield of mature stags would probably have been 20% lower than observed. In addition to providing hunters with a very low yield of mature stags, in an evolution-ary perspective, the low average longevity of stags on Djursland creates a real risk of selecting for earlier maturity and smaller body size.
14. Even though the harvest policy on Oksbøl resulted in a three times higher harvest of mature stags relative to the population size than on Djursland and a less biased ratio between the numbers of hinds and mature stags, a change in age-specific culling towards a higher harvest of calves and individuals older than 8 years compared to present would double the harvest of mature stags as well as their proportion of the live population. This would also be in line with the general mortality pattern observed in naturally regulated ungulate populations elsewhere.
15. If managers aim to increase the number of mature stags in the population as well as in the overall hunting yield, the most efficient tool would be to protect all immature stags from hunting until they have reached the re-quired size for harvest and mating.
Population dynamics of animals in their natural environment are influenced by a combination of extrinsic perturbations like climatic forcing, and intrinsic density-dependent processes, which are molded by individual characteristics like age, sex, or life history. While the empirical evidence of direct effects of density on life history traits is growing, less is known about how such responses may be molded by environmental or individual characteristics. This thesis aims to investigate how population density influences life history of reindeer Rangifer tarandus by focusing on some potentially important traits and ecological interactions that previously have attracted less focus. These are early (including prenatal) development, tooth wear and parasite-host relations. The empirical basis for the analyses is a spatially extensive, quasi-experimental study design involving 18 reindeer herds. These herds formed 9 replicate pairs of neighboring herds with persistent, long-term contrasts in densities and offered, in the context of studies on large mammals, a rare opportunity to obtain robust estimates of the density-dependent effects. Density dependence was pervasive in all traits subject to analysis. Fetal size was significantly affected already at an early prenatal stage and was mediated by lower female body mass in high-density herds. The influence of density on body mass was even more pronounced at weaning than prenatally. Teeth wore down rapidly, and high density caused increased tooth wear rates early in life. Tooth height was positively related to body mass and pregnancy rate, in particular among older females, suggesting tooth wear as a proximate mechanism for diminishing performance at high density. Opposite to the overall negative effects of density on life history traits, high density appeared to reduce infestation of reindeer calves of warble fly cysts (Hypoderma tarandi), a major parasitic harasser in reindeer. This relationship was not apparent among yearlings, suggesting the stronger herd affinity among calves to create a parasite swamping effect diluting
the risk of parasitization per se. Susceptibility to warble fly encystations was also shown to be dependent on phenotype, as calves of lighter color had higher parasite burdens than darker ones. While lighter colored calves may be more conspicuous for visual host search, the lack of the pigment-compound melanin may as well make their immune system less competent in preventing establishment of cysts. In conclusion, this thesis suggests that density dependence is a major force shaping life history of reindeer, both directly through resource limitation, and also indirectly mediated by parasitism or by persistent consequences of tooth wear or early development.
Here we review published molar wear rates, measured in terms of tooth height loss per year (mm yr-1) published on natural populations of ungulates (25 species), rodents and lagomorphs (Glires; 14 species) and macropodid marsupials (seven species). Although the data are limited, they nevertheless reveal consistent patterns, and raise new questions. Among ungulates, wear rates are uncorrelated with body mass but are positively correlated with hypsodonty. Browsers show lower wear rates than do mixed feeders or grazers. Percentage of grass in the diet shows a non-linear relationship with wear rates suggesting that levels of dietary abrasives result from a complex interaction among forages, habitat characteristics and feeding behaviours (whether or not grass itself is a significant abrasive agent). Rodents exhibit higher wear rates, and kangaroos lower wear rates, than do ungulates feeding on similar diets. Hypselodont rodents and lagomorphs show rates of molar wear an order of magnitude higher than do grazing ungulates.
The National monitoring program for wild cervids (moose, Alces alces, red deer, Cervus elaphus,
wild reindeer, Rangifer tarandus) in Norway was established in 1991. The program is
funded by the Directorate for nature management (DN), and operated by the Norwegian institute
for nature research (NINA). The data collected during the 21 years of monitoring represent
a unique opportunity to follow the development in population condition (carcass mass, fecundity
and recruitment rates), population density and population structure of representative populations
of moose, red deer and wild reindeer. The monitoring is carried out in 17 monitoring areas
distributed all over Norway (moose: 7, red deer: 3, reindeer: 7). In this report we show the
trends of development during the 21 year period, with main focus on the results from the last
contract period, 2007-2011.
During the period 1991-2011, there was a steady increase in the number of harvested red deer
and a reduction in the number of harvested wild reindeer at a national level, whereas the number
of harvested moose was relatively stable. For moose and red deer, a similar development
is reflected in the number of traffic kills.
On a regional level the population density and harvest of moose increased from Sør-Trøndelag
to Finnmark, while the harvest decreased from Buskerud to Vest-Agder. Further east, as well
as in Oppland, the harvest numbers show less of a linear trend. In the same period there was a
general decrease in calf recruitment rates based on hunter observations (seen moose) in most
counties. This was particularly evident in the counties from Buskerud to Vest-Agder. Despite a
significant reduction in population density in these counties, recruitment rates are still low.
Higher recruitment rates are still found in Østfold and in the counties from Sør-Trøndelag to
Finnmark.
Within monitoring areas, moose densities increased or were relatively stable in Troms, Nordland,
Nord-Trøndelag and Hedmark during the period 1991-2011, and decreased in Oppland,
Vestfold/Telemark and Vest-Agder. In the same period carcass weights and/or recruitment
rates decreased in all areas, apart from Oppland and Troms. The recruitment rates from hunter
observations did not always co-vary with the fertility rates based on ovary analyses, possibly
because of hunting selection and methodological problems.
The decrease in moose carcass weights and recruitment rates was most evident in areas with
the highest moose densities in the early 1990’s, and is likely to be a consequence of density
dependent food limitations. However, a subsequent decrease in moose density in these areas
has not led to an increase in carcass weights or recruitment rates. The lack of response may
be due to the fact that a major part of the reproductive females are individuals born during the
high density years, and/or because the per capita available food is still limited despite a significant
population reduction. A general reduction in food quality following increased summer temperatures
in central and southern Norway may also have had a negative impact on body
weights and recruitment rates.
By the use of cohort analysis and age-at-death data we reconstructed the moose population
development during the period 1991-2011 and show that the reconstructed population closely
correlate with the number of moose seen per hunter day, as well as with the annual moose
harvest. In addition, we found that the reconstructed female age structure was increasing or
relatively stable in most areas. In all areas there was also an increase in the average age of
harvested adult males. This is in accordance with an increasing proportion of males observed
in Norwegian moose populations during the last 15 years.
In the three monitoring areas for red deer, the population during 1991-2011 was characterized
by i) increasing densities, ii) decreasing body weights and iii) reduced fertility among two year
old females. The reduced fertility rates are linked to the reduction in body weights, which in turn
is likely to be a consequence of density-dependent food limitation. During the period 1991-
2011 most sex and age categories showed a 10-15 % reduction in body weights. The strongest
reduction in productivity among two year olds was found in Hordaland (Kvinnherad), a decrease
by 80 %. This represents a significant reduction of the overall population productivity.
The decrease was lower in Sogn og Fjordane and Møre og Romsdal/Sør-Trøndelag, but was
following the same trend. The negative trend is likely to continue unless the population growth
is stopped. The red deer observations from hunters in Kvinnherad indicate that deer density is
currently decreasing, while it seems to be rather stable in the two other monitoring areas.
Following a reduction in the harvest pressure of males, the female-male ratio has become less
female-biased in all monitoring areas during the last 8-9 years. This is probably also the reason
why the mean age of harvested adult stags (> 1 years old) has increased. The change in sex
ratio and male age structure is the result of a systematic shift in harvest pattern following local
management decisions.
The management goal for the wild reindeer herds has been to stabilise population densities at
relatively moderate levels. Monitoring data shows that this is achieved in Snøhetta, Knutshø,
Rondane and Forolhogna, where populations have mostly been fluctuating around the mean
density during the last two decades. In contrast, managers in Setesdal Ryfylke and Hardangervidda
attempted to increase body mass, reproductive performance and quality of winter
rangers by reducing reindeer densities during the 1980’s and 1990’s. Monitoring data suggest
that these populations have responded to reduced densities by an increase in body mass and
calf recruitment. Despite the relatively stable reindeer densities, there has recently been a
marked reduction in body weights and jaw lengths in Forolhogna and Knutshø, and in Knutshø
we also see a pronounced decrease in number of calves per 100 females and yearlings. In the
report we discuss several factors that can explain these rather surprising results.
In the monitoring area on Svalbard, the reindeer population shows erratic fluctuations in density
following large annual variations in recruitment and natural mortality rates. For two decades
(1979-1999) the population fluctuated around a mean of about 450 animals, but then increased
in density after several years with higher than average recruitment. Since year 2000 the population
has been fluctuating around an average of 800 animals.
During the last contract period, 2007-2011, we also examined in a pilot study to what extent
data provided by the national forest inventory can be used for monitoring the variation in food
availability and browsing pressure in forest habitats. The results presented show that browsing
pressure and food availability varies extensively among areas, and that moose carcass weights
and recruitment rates are generally higher in areas with low browsing pressure and a higher
number of available foraging trees. We concluded that the data are able to provide a good reflection
of the moose forage conditions at a regional scale and that they also might be used to
monitor the forage conditions for red deer.
In the next 5-year period NINA will continue the National monitoring program for wild cervids
much as before in all monitoring areas. However, following the increasing distribution of red
deer in eastern Norway, we will establish two new monitoring areas for red deer in this part. In
addition, we will continue the close collaboration with the national forest inventory and integrate
the monitoring of forest food availability and browsing pressure as a part of the monitoring program.
For reindeer, we will start a similar monitoring of the winter grazing conditions at
Hardangervidda.
Body mass – gut fill scaling relationships affect rate of digestion, foraging behavior, niche differentiation, and trophic interactions. On an intraspecific level, the scalar of this relationship has been reported to be both iso-and allometric (,1.0). We hypothesized the scalar of rumen-reticulum fill depends on diet. When the diet has low concentrations of indigestible fiber the scalar should be allometric to fulfill metabolic demands and isometric when the diet has high concentrations of indigestible fiber as both small and large animals have difficulties processing forage. We collected 50 male and 50 female white-tailed deer (Odocoileus virginianus) over a 30 h period from a site in south Texas in Oct. Animals ranged in body mass from 32 to 106 kg. We also recorded collection time, sex, lactation status of females, back fat thickness, and tooth wear. These covariates affected the body mass – rumen-reticulum fill relationship. Acid detergent fiber, our surrogate of indigestible fiber, in the rumen contents of our study animals was lower in concentration than in another study of white-tailed deer that estimated an isometric scalar for rumen-reticulum fill. The estimated scalar between body mass and rumen-reticulum fill in our study was 0.74 and allometric. Rumen-reticulum fill probably was influenced by chemostatic feedback and mechanisms were governed by metabolic demands. Rumen-reticulum fill scalars for white-tailed deer are not static but dynamic.
In the present study, we estimated age at death of extinct deer (Cervus astylodon) excavated from two Late Pleistocene sites in Okinawa Island (the Hananda-Gama Cave and Yamashita-cho Cave I sites) from degree of molar wear. This was done using a regression equation of extant sika deer of known age, and deriving an age estimation equation based on M3 crown height applicable to fossil specimens. We then reconstructed mortality profiles using 45 and 88 individuals of the Hananda-Gama and Yamashita-cho assemblages, respectively, and compared the profiles with those of extant and archaeological (Jomon period) sika deer (C. nippon) populations. The reconstructed age profiles of both sites were strikingly different from the living and hunted Jomon period profiles in relative abundance of old adults. They were more similar to the attritional mortality profiles of the extant sika deer that died by natural causes (i.e. not by human or animal predation), but showed a further shift towards older age. Combined with the fact that there is no fossil evidence of medium- to large-sized carnivores on Okinawa Island during the Late Pleistocene, our results suggest that C. astylodon populations had extended longevity because of low predatory pressure, including that by Paleolithic human hunters.
Chewing efficiency has been associated with fitness in mammals, yet little is known about the behavioral, ecological, and morphological factors that influence chewing efficiency in wild animals. Although research has established that dental wear and food material properties independently affect chewing efficiency, few studies have addressed the interaction among these factors. We examined chewing efficiency, measured as mean fecal particle size, as a function of seasonal shifts in diet (and corresponding changes in food fracture toughness) in a single breeding population of a grazing primate, the gelada monkey, at Guassa, Ethiopia. We also measured dental topographic traits (slope, angularity, and relief index) and relative two- and three-dimensional shearing crest lengths in a cross-sectional wear series of gelada molars. Chewing efficiency decreased during the dry season, a pattern corresponding to the consumption of foods with higher fracture toughness. Older individuals experienced the most pronounced decreases in chewing efficiency between seasons, implicating dental wear as a causal factor. This pattern is consistent with our finding that dental topographic metrics and three-dimensional relative shearing crest lengths were lowest at the last stage of wear. Integrating these lines of behavioral, ecological, and morphological evidence provides some of the first empirical support for the hypothesis that food fracture toughness and dental wear together contribute to chewing efficiency. Geladas have the highest chewing efficiencies measured thus far in primates, and may be analogous to equids in their emphasis on dental design as a means of particle size reduction in the absence of highly specialized digestive physiology. Am J Phys Anthropol, 2014. © 2014 Wiley Periodicals, Inc.
Incisor size is associated with feeding efficiency in herbivorous ungulates and may have been under selection in correspondence with food habits. In the meantime, males of polygynous, dimorphic species have smaller cheek teeth than females, possibly because their reproductive span is much shorter than that of females. Thus, males are not under selection for more durable teeth when there is no reproductive return. Therefore, incisor size is expected to be under natural selection against wear and under the influence of sex‐based differences in reproductive strategy. We first investigated incisor wear in Japanese sika deer (Cervus nippon) and compared wear rates between the sexes and two ecologically contrasting populations on Kinkazan Island and Mt. Goyo. We then compared unworn incisor size to test the hypotheses that female deer have relatively larger incisors than males and a population with faster incisor wear has larger incisors. The Kinkazan deer showed significantly faster wear than those on Mt. Goyo, and Kinkazan males had faster wear than Kinkazan females. Unworn incisor size was relatively larger for females than that for males and was larger for Kinkazan deer than that for Mt. Goyo deer. The sex‐based difference in incisor size was greater in Mt. Goyo deer than that in Kinkazan deer. These findings support the hypothesis that sex‐based differences in reproductive span result in larger incisor size for female sika deer and imply that strong natural selection against rapid tooth wear diminishes sex‐based differences in incisor size in Kinkazan deer. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 384–397.
Izvleček Za ugotavljanje zanesljivosti makroskopskih (okularnih) ocen starosti navadnega jelena/jelenjadi (Cervus elaphus L.) na podlagi pregleda razvojne stopnje in obrabljenosti zob smo na reprezentativnem, tj. celotnem enoletnem (2008) vzorcu odvzema jelenjadi na območju celotne Slovenije opravili preveritev ocen starosti, podanih s strani lovcev oz. kategorizacijskih komisij. Preizkus zanesljivosti smo napravili z metodo rezanja/brušenja prvega meljaka (M 1) in štetjem prirastnih plasti zobnega cementa, in sicer na 821 vzorcih zob odraslih živali (starost: od dveh do dvaindvajset let). Preizkus skladnosti obeh ocen je pokazal, da so z okularnim ocenjevanjem pridobljeni podatki o starosti odraslih živali (ne glede na spol) obremenjeni z veliko napako (največji odklon: devet let). Z obema metodama je bila starost živali na leto natančno enako določena v 24,5 % primerov; s starostjo živali se je zanesljivost okularnega ocenjevanja zmanjševala. Starosti košut in mlajših jelenov so bile z okularnim ocenjevanjem tako podcenjene kot precenjene, starosti starejših jelenov pa so bile praviloma precenjene. Izmed 426 analiziranih jelenov jih je bilo kar 142 (33,3 %) uvrščenih v drugo starostno kategorijo, kot je pokazala metoda štetja letnih prirastnih plasti zobnega cementa, kar zbuja pomisleke o smiselnosti trenutno veljavne kategorizacije odraslih jelenov v tri starostne kategorije, ki jih je z rutinskimi metodami ocenjevanja starosti nemogoče zanesljivo prepoznati. Ključne besede: navadni jelen (Cervus elaphus L.), ocenjevanje starosti, obraba zob, spodnja čeljustnica, (pred)meljaki, plasti zobnega cementa RELIABILITY OF MACROSCOPIC (OCULAR) ASSESSMENT OF THE AGE OF RED DEER (Cervus elaphus L.) IN SLOVENIA: VALIDATION BY COUNTING ANNULI IN TOOTH CEMENTUM Abstract To check the reliability of macroscopic (ocular) assessment of the age of red deer (Cervus elaphus L.) obtained by ocular inspection of teeth eruption and wear (done by hunters or hunter commissions), a validation of the precision of these assessments was carried out on a representative sample set, i.e. a total 2008-annual cull of red deer in the entire Slovenia. The reliability of ocular age assessment test was performed by cutting/grinding of the first mandibular molar (M 1) and counting the incremental layers of dental cementum on 821 samples of adults (aged from two to twenty-two years). The ocular age assessment of adult red deer (regardless of sex) was biased with a large error (maximum deviation between both assessments: nine years). With both methods, the same animal age was established in 24.5% of cases, and with the age of the animals the reliability of ocular assessment declined. Ages of hinds and younger stags were both under-assessed and over-assessed; however, ages of older stags were generally over-assessed. Out of 426 analysed stags, 142 (33.3%) were categorized in another age category as found by counting annuli in tooth cementum. This raises doubts about the reliability of the current categorization of adult red deer stags into three age categories (2–4 years old, 5–9 years old, and 10+ years old, respectively); indeed, precise (on a yearly basis) ages of adult stags are impossible to be identified by routine age assessment, such as the inspection of teeth wear.
During recent decades, rough livestock grazing has decreased markedly on unimproved land (i.e. natural and semi-natural habitats) across most of Europe, whilst the number of wild cervids has increased. However, we still know little about the overall changes in the herbivore pressure and how herbivore regimes vary between biogeographic regions. We have quantified the spatio-temporal variation in herbivore pressure indirectly by estimating the metabolic biomass of large herbivores in mountain, coastal and inland municipalities of Norway every 10th year during 1949-1999. We quantified how much livestock biomass has decreased, whether this corresponded to increasing cervid biomass, and whether the proportion of grazing relative to browsing has changed within the herbivore community. Total metabolic biomass of livestock and cervids (MBA total) decreased from 126 kg/km 2 in 1949 to 107 kg/km 2 in 1999 (∼85% of MBA total in 1949). Changes differed markedly between regions. Herbivore pressure in the coastal region nearly halved from 1949 to 1999, while the decrease was minor in the inland and mountain regions. Livestock grazing more than halved, whereas the metabolic biomass of cervids increased by 276% from 1949 to 1999. Cervids dominated the community of large herbivores on unimproved land in Norway in 1999 (54% of MBA total). Livestock dominated in the mountain (52% of MBA total) and in the coastal region (54% of MBA total) in 1999, while cervids dominated in the inland region (67% of MBA total). Most herbivore foraging consisted of grazing in 1949 (89% at a national scale). This proportion was reduced to 54% by 1999. Percent browsing was especially high (> 90%) in several municipalities in southeastern Norway in 1999. The increase of wild cervids is exceptional in a historical perspective, and managers have to adapt to wild cervids being the major ecosystem engineers in many landscapes.
Intensive moose (Alces alces) browsing pressure has a large impact on ecosystems as well as economics of forestry companies. Moose winter browsing pressure on young Scots pine (Pinus sylvestris) is affected by a range of factors and I modelled effects of such factors across a bio-geographical gradient in Sweden. The tested factors were: density of moose, roe deer (Capreolus capreolus), red deer (Cervus elaphus), and fallow deer (Dama dama), forage availability, height of surveyed tree, thinning, pre-commercial thinning, clear-cutting, dominating forest, tree density, habitat productivity, number of days with snow cover, distance to road, and distance to settlements. The analyses were carried out at three spatial scales – plot, tract, and landscape scale. The data was extracted from a field survey and a digitalized forest stand database of a forestry company.
At the plot scale, in the minimal adequate model, explaining browsing pressure on pine, the factors study area, moose density, dominating forest type and height of surveyed pines were significant. At the tract scale, the factors study area, moose density and dominating forest were significant. At the landscape scale, the proportion of pine in the forest was negatively related to browsing. Nosignificant relationships between browsing pressure and the other factors were found. These finding suggest that dominating type of the forest is the most general factor affecting browsing pressure at all spatial scales. The browsing pressure was nearly significantly higher in the mixed coniferous forest than in the other types of the forest at the tract spatial scale. The moose density is significant at smaller scales, in contrast to the largest scale. This result supports the idea that the browsing pressure at larger scales is affected by other factors than moose density.
Addresses problems of coronal morphogenesis, amelogenesis, food comminution and digestion, amastication, tooth eruption and wear, in order to identify functional intrrelations and developmental constraints in the evolution of cheek tooth morphology. Many aptive features probably or certainly did not arise for their current functions, but are one-time constraints which have become incorporated into functional systems (exaptations rather than adaptations).-from Author
Managing ungulate populations in a sustainable way requires monitoring plans to provide useful information about population status and trend. Our aim is to evaluate the use of hunters to collect information about the status of caribou Rangifer tarandus groenlandicus in Greenland. Caribou have been harvested under a quota system since 1995 in four regions of west Greenland. In each year, hunters were asked to return information on the sex, approximate age and body condition of animals harvested, and lower jawbones were collected from animals shot in 1995. The harvest is strongly sex-biased (90:10) towards males. Jawbone length did not vary among regions. Age-specific tooth wear was, however, most pronounced in the northern region (Sisimiut-Kangerlussuaq), probably due to the nature of the substrate in the area. The condition of animals, based on a rump-fat index, appears to be good over all west Greenland, with some slight but consistent differences between regions. We conclude that information provided by hunters will be useful in monitoring the caribou populations, but validation of their information is required.
In large-herbivore populations, environmental variation and density dependence co-occur and have similar effects on various fitness components. Our review aims to quantify the temporal variability of fitness components and examine how that variability affects changes in population growth rates. Regardless of the source of variation, adult female survival shows little year-to-year variation [coefficient of variation (CV<10%)], fecundity of prime-aged females and yearling survival rates show moderate year-to-year variation (CV<20%), and juvenile survival and fecundity of young females show strong variation (CV>30%). Old females show senescence in both survival and reproduction. These patterns of variation are independent of differences in body mass, taxonomic group, and ecological conditions. Differences in levels of maternal care may fine-tune the temporal variation of early survival. The immature stage, despite a low relative impact on population growth rate compared with the adult stage, may be the critical component of population dynamics of large herbivores. Observed differences in temporal variation may be more important than estimated relative sensitivity or elasticity in determining the relative demographic impact of various fitness components.
Proper management of wildlife relies on metrics of population development. Typically, the best estimation techniques are too expensive for coarse-scale management. In marine fisheries, catch-per-unit effort is commonly used, but problems may arise due to changes in spatial harvest effort or in habitat use as density changes. Managers in Norway are in the early phases of implementing 'seen deer' during harvesting and 'spring counts' on farmland as a means of monitoring red deer Cervus elaphus populations. We provide a first evaluation of how suitable these methods are by comparing the results with population estimates obtained using cohort analysis, and by analysing the within-season variation in number of seen deer. 'Seen deer' predicted annual increases in populations fairly well. Adjusting for harvesting effort provided less good estimates, due to a proportionally larger increase in effort relative to deer population size as population size increased. The number of seen deer per day decreased rapidly at the beginning of the season, and then levelled off or increased slightly during the rut, especially on farmland. The number of seen deer increased both with the number of harvesters and hours harvested, but at a diminishing rate. The current practice of 'spring counts' was not successful in predicting population changes, probably due to a lack of replication. Indeed, date strongly affected the number of deer seen during spring counts. While 'seen deer' seems to be a very promising tool for monitoring population size of red deer, there are some limitations to the practice as implemented for moose Alces alces in Scandinavia due to a more complex relationship with harvesting effort. Our study highlights that the large number of hours harvesters observe wildlife can provide a useful tool for population monitoring. However, the use of such indices may vary between species and according to harvest techniques and should thus be assessed with care before implementation.
To define the food resources of Red Deer ( Cervus elaphus L.) in Europe and to detect the principal sources of variations in their diet, we reviewed field studies based on stomach content analysis. The study areas were classified into three main habitat groups (mixed‐coniferous forest, mixed‐deciduous forest, moorland), the food items into 13 plant categories, and we used five seasonal classes (winter, spring, summer, autumn, hunting season) for analysing the data set. For statistical analyses we used correspondence analysis and analysis of variance.
Red Deer eat a varied diet comprising at least 145 plant species. The main sources of diet variation were due to habitat, leading us to identify three habitat types characterized by the consumption of a few key species. Clear seasonal variation was observed only for the seed and fruit items which were used mainly during the hunting season.
Our results confirm that Red Deer can be classified among the intermediate feeders, with a mixed diet of grass & sedges (29%) and concentrate food items (63%). However, they also show Red Deer to be primarily a concentrate feeder (max. 75%) with no significant seasonal variation between the quantities of grass or sedges and concentrate food in the diet.
In the light of these results, we discuss potential competition with other sympatric ungulates (wild and domestic). We suggest that it may be useful to take into account key food resources in modelling population dynamics and in taking management decisions.
We tested whether the ungulate moose (Alces alces) showed senescence in survival. Senescence, i.e., a progressive deterioration with age, may be obscured by multiple mortality causes in a wild population. Thus, we followed radio-marked individuals of known age to separate different mortality causes in adult moose. The risk of dying of causes not linked to humans increased with age. For females, the increase in natural mortality was first observable after age 10. Tooth wear was significantly related to age for both sexes, but was stronger for males. It suggests that males would experience senescence in survival earlier than females in a non-hunted population. The senescence in mortality observed for female moose may be a result of delayed cost of reproduction acting in concert with tooth wear due to a reduced ability to process food. We also found an increase in hunting mortality with age for both sexes, with males facing a higher risk of dying than females. The age-related hunting mortality may be a result of selectivity by the human predator, or a change in moose behaviour with age.
We explore some of the consequences of harvest on population growth rate, age and sex structure in a Norwegian population of red deer Cervus elaphus, using age-structured demographic models. Survival rates were estimated from individuals marked and monitored annually during 1977-1995, and information about reproduction patterns were obtained from hunting material in the same region. The population had an actual doubling time of 14 years, corresponding to a multiplication rate of 1.051. Harvesting led to a reduction of about 10% of the potential multiplication rate that equalled 1.166. Including stochasticity had only a small effect on the population multiplication rate. Due to a high hunting pressure, males had less than a 10% chance of reaching 4.5 years of age and the male-biased harvest strongly biased the sex ratio. Assuming that when the number of females per male increases above a given threshold some females would not manage to mate, we investigated at which level male harvesting could be maintained without having demographic consequences on the population growth rate. We concluded that the hunting pressure on males could probably be increased further but indirect consequences of a strongly biased sex ratio (e.g. on population genetic structure) remain to be studied. Variation in the multiplication rate mainly resulted from the variation in winter calf survival. In its present form the harvesting regime reduces the growth rate and biases the sex and age structure, but does not seem to threaten the population's viability and productivity.
The structure of the incisor arcade in ruminant ungulates is likely to affect the degree to which animals can be selective in choosing food items. Species of ruminant which feed predominantly on grasses have broader more flattened incisor arcades when compared at the same size with species which browse on woody dicotyledonous plants. This is likely to reflect the differential dispersion of food items on the food plants of these two different groups of ruminants.
1. Density-independent weather effects can have important consequences for the demography of terrestrial herbivores because precipitation, temperature and insolation influence plant phenology, forage quality and biomass production, which in turn affects the habitat carrying capacity. Since forage digestibility influences intake and weight gain, life-history traits of young, growing animals are Likely to reflect variation in the prevailing weather. 2. This paper specifically investigates spatial and temporal variation in age at maturation in female red deer (Cervus elaphus) in Norway in relation to climate variables known to influence primary production. Our findings are corroborated by analysing differences in age at maturation in 21 cohorts of red deer on the Isle of Rum, Scotland. 3. In Norway the majority of females ovulated as yearlings and calved for the first time as 2-year-olds. The proportion calving for the first time at two years varied from 0.23 to 0.67 between regions and fluctuated from 0.
Density-dependence in juvenile survival may be difficult to detect if survival is also affected by density-independent factors. We investigated the relationships among weather parameters, population density, and lamb survival of bighorn sheep with long-term data from a marked population where we manipulated population density. We distinguished neonatal survival and winter survival. Density interacted with weather variables to affect neonatal survival; spring and winter temperatures had a positive effect on neonatal survival only when population density was high. Neonatal survival was positively affected by spring precipitation independently of population density. Winter survival was positively correlated with temperature and precipitation during the previous spring, negatively correlated with density, and independent of winter temperature or snowfall. The effect of weather on lamb winter survival did not vary with density. Bighorn lambs are well adapted to harsh winter weather, but spring weather influ
Several aspects of the life history of reindeer (Rangifer tarandus) are related to the nutritional condition of the animals. Moreover, compensatory growth and fattening in summer decreases
with age. The interaction of tooth wear and the standing crop of lichens on age-related variation in body size and tissue
reserves was examined to evaluate the proximate causes of density-dependent food limitation on life history parameters in
female reindeer. Studies in nine semi-domesticated free-ranging reindeer herds showed that molar height depended on the mean
standing crop of terrestrial lichens in winter habitats. The extent of tooth wear had the strongest effect on body reserves
among the oldest females (11–14 years). This indicates that severe tooth wear limits the animals´ ability to process food
efficiently and, hence, to maintain their body reserves. Both tooth wear and the biomass of lichens influenced body mass in
old females, probably because on heavily exploited winter ranges reindeer had to use higher proportions of lower-ranking coarser
foods, especially dwarf shrubs.
Sex differences in habitat use (termed `habitat segregation') are widespread in sexually dimorphic ungulate species. They
are a puzzling phenomenon, particularly when females use better foraging habitats than males. It has been suggested that males,
owing to their larger body size and higher forage requirements, are inferior in indirect competition to females and are forced
by female grazing pressure into marginal habitats (`indirect-competition hypothesis'). This hypothesis has been widely cited
and has important theoretical and practical implications. However, evidence for it is inconclusive. The present paper presents
the results of the first experimental test of the indirect-competition hypothesis. We manipulated female and male numbers
of red deer (Cervus elaphus L.) on a large scale on the Isle of Rum, Scotland, and tested the influence of this manipulation on deer habitat use. We
predicted that where female numbers were reduced, male use of preferred habitat should increase and sex differences in habitat
use should decrease, while a reduction in male numbers should not have such effects. In contrast, we found that the manipulation
of female and male numbers did not affect habitat use, and conclude that the indirect-competition hypothesis does not explain
habitat segregation on Rum.
The allometric relationships for the fermentation rate of dry matter, the total energy concentration of volatile fatty acids (VFAs), the energy supplied from VFA production and the mass of the digesta contents within the rumen or caecum and proximal colon (hindgut) were used to test whether the digestive strategies of grazing and browsing African ruminants differ. The wet and dry mass of the contents of the rumen and hindgut were allometrically related to body mass (BM). These relationships did not differ between browsing and grazing ruminants. The fermentation rates in the rumen were strongly allometric and the intercepts of the relationships did not differ between browsers and grazers. The fermentation rates in the hindgut were not allometrically related to BM and did not differ between ruminants with different feeding habits. Likewise, the total energy concentration of the VFAs in the rumen and hindgut showed no allometric scaling and did not differ between browsing and grazing ruminants. The energy supplied by VFA production in both the rumen and hindgut of African ruminants scaled at around 0.8 with BM. Only in the case of the energy supplied by VFAs in the rumen were there significantly different intercepts for browsing and grazing ruminants. The energy supplied by VFA production in the rumen was inadequate to meet the energy requirements for maintenance of browsers and small grazers. The retention time of digesta in the alimentary tract was positively related to BM although there was no difference in the allometric relationships for grazers and browsers. The results of these analyses suggest that, after controlling for the effects of body mass, there is little difference in digestive strategy between African ruminants with different morphological adaptations of the gut.
Effective management of ungulates requires regular estimates of population abundance, but these are often expensive and hard to obtain. We therefore examined if change-in-ratio (CIR) estimation methods, in combination with age- and sex-specific data on moose Alces alces observed and killed, could be a cheap alternative for estimating moose abundance in Norway. We used the large number of moose observations reported by moose hunters and estimated pre-harvest adult population size based on annual changes in adult sex ratio. Similarly, we estimated 1) annual recruitment rate based on the proportion of calves observed during the hunting season, 2) the harvest rate, and 3) the natural mortality rate based on variation in recruitment rate and harvest rate. During 1991–2000, annual variation in abundance was correlated with two of three independent indices of moose density, indicating that the CIR methods provide relatively precise estimates of abundance. Similarly, the estimated average natural mortality rate was similar to natural mortality rates of radio-collared moose in Scandinavia, and the estimated abundance was close to what we expected based on the annual harvest. However, large annual variation in estimated rates of natural mortality indicated that over- and underestimation of population abundance occurred for some years. This was likely due to the fact that harvesting occurred during periods of moose observations. Because we had no independent estimates of abundance, we were unable to estimate the bias. Hence, we concluded that variation in CIR abundance is a sensitive index of moose density, but that more studies are needed to determine the accuracy of CIR estimates as measurements of abundance. Future studies should focus on smaller populations with independent estimates on abundance, and base CIR estimation on changes in sex ratio within the hunting season to reduce the number of possible confounding effects.
There are only a few recent studies that have demonstrated senescence in ungulates and nothing is known regarding how patterns of senescence may vary as a:function of density Senescence in general is linked to the cost of reproduction, which probably increases with density in ungulates and may differ between the sexes. Further, senescence in ungulates is also regarded to be a function of tooth wear rates. As density dependence and sexual differences in food choice have been well documented? this ma); lead to different tooth wear rates and! thus, possibly density-dependent and sex-specific patterns of senescence. We therefore investigated the effects of age, sex, density and-their possible interactions on the variability of body weight in 29 047 red deer harvested during 1965-1998 from Norway, out of which 380 males and 1452 females were eight years or older. There was clear evidence that spatio-temporal variation in density correlated negatively with body weights. In addition, there was evidence of senescence in both male and female red deer. Age at onset of senescence in females was after 20 years of age and independent of population density. In males, the onset and rate of senescence increased with increasing population density The onset of senescence for males was at ca. 12 years of age at low density, but decreased to approximately ten years of age at high density The pattern of density-dependent senescence in males, but not that in females, can be explained if (i) the cost of reproduction increases with density more strongly in male than in female red deer, and/or (ii) tooth wear rates are density dependent in males, but not in females. We discuss the ability of these two different, not mutually exclusive hypotheses in explaining the observed pattern of senescence.
■ Abstract In large-herbivore populations, environmental variation and density dependence,co-occur and have similar effects on various fitness components.,Our re- view aims to quantify the temporal variability of fitness components,and examine,how that variability affects changes,in population,growth,rates. Regardless of the source of variation, adult female survival shows little year-to-year variation [coefficient of variation (CV 30%). Old females show,senescence,in both survival and reproduction. These patterns of variation are independent,of differ- ences in body mass, taxonomic group, and ecological conditions. Differences in levels of maternal,care may,fine-tune the temporal,variation of early survival. The imma- ture stage, despite a low relative impact on population growth rate compared with the adult stage, may be the critical component of population dynamics of large herbivores. Observed differences in temporal,variation may,be more,important than estimated rel- ative sensitivity or elasticity in determining,the relative demographic,impact of various
Senescence may result from an optimal balance between current reproductive investment and bodily repair processes required for future reproduction, a theoretical prediction difficult to prove especially in large, long-lived animals. Here we propose that teeth that have fixed dimensions early in life, but that wear during chewing, can be taken as a measure of total lifetime 'repair', and their wear rate as a measure of current expenditure in performance. Our approach also considers the sexual selection process to investigate the advance of senescence in males compared with females, when selection favouring competition over mates reduces the reproductive lifespan of males. We studied carcasses of 2,141 male and 739 female red deer (Cervus elaphus) of different ages, finding that male molariform teeth emerged at a far smaller size than expected from body size dimorphism. This led to higher workload, steeper wear rate and earlier depletion of male teeth than in females, in concordance with sex-specific patterns of lifetime performance and reproduction. These findings provide the empirical support for the disposable-soma hypothesis of senescence, which predicts that investment in bodily repair will decrease when the return from this investment may not be realized as a result of other causes that limit survival or reproduction.
In ungulates, tooth wear is often suggested as a proximate cause of senescence. Tooth wear is expected to be sex-dependent since energetic requirements and food selection varies largely between sexes in sexually dimorphic ungulates. Furthermore, tooth wear may lower mastication efficiency, and we predict a negative correlation between tooth wear and body weight or condition. We tested these predictions on data on tooth wear (estimated as height of first molar) of 1,311 male and 1,348 female red deer ( Cervus elaphus) aged 3-25 years and harvested along the west coast of Norway. The rate of tooth wear decreased with age. Males wear teeth at a higher rate (from 0.61 mm/year in 4-year olds to 0.45 mm/year in 11-year olds) than females (from 0.52 mm/year in 4-year olds to 0.39 mm/year in 11-year olds). Molar height correlated positively with body weight in both sexes, but not after adjusting for body size. Molar height was strongly dependent on body size in 3-year-old individuals (when tooth wear is minimal). Earlier reports in the literature of a positive correlation between tooth height and body weight may therefore be due to initial size differences rather than differences in condition due to tooth wear.
Weighing large animals in the field is often labourious and expensive. Alternative methods which replace direct measurements of body mass are, therefore of practical value. In order to predict body mass in moose Alces alces, an allometric model based on chest circumference, sex, age and population was applied. A model to predict body mass based on chest circumference and a truncated age measurement is suggested. Impact of sex and population was weak. The ability to predict body mass was mostly in fluenced by chest circumference. The proportion of carcass mass to total body mass varied between 45% and 51% among age-classes. In addition, there was a slight effect of sex on this variation, males having a proportionally larger carcass mass than females. The model's predictions of body mass are adequate for describing the distribution of body mass in moose populations and for comparing moose populations.
This chapter discusses the factors that determine the mean retention time (MRT) of fluid and particles in the forestomach of ruminants and camelids. The advantage that forestomach fermenters have over potential monogastric competitors is their superior ability to utilize plant cell walls. The microbial degradation of cell wall constituents is a slow process. To achieve effective cellulose digestion, ruminants and camelids have evolved large fermentation chambers in their stomachs. They retain feed particles substantially longer than fluid in these chambers. This strategy has two consequences: (1) a long MRT of feed particles in the reticulorumen (RR) that improves the utilization of cell-wall constituents and (2) a long MRT restricts feed intake, because the intake of roughage is limited mostly by the capacity of the forestomach. The chapter also explores the many attempts that have been made to predict forage intake in ruminants and to find ways of increasing the intake of roughage.
Populations of feral donkeys, Equus asinus, in northern Australia are limited by density-dependent mortality during the first 6 mo of individuals' lives. A female's ability to raise her offspring successfully increases with age and is dependent on her maintaining high levels of stored mineral nutrients (calcium, phosphorus, and sodium). A low proportion of offspring was successfully raised in a population at carrying capacity where females had low levels of stored mineral nutrients. Females in a growing population that had been reduced to 45% of carrying capacity had high levels of stored minerals and successfully raised a higher proportion of offspring. Females in the population at carrying capacity ingested a species-poor diet (predominantly a grass, Sehima nervosa) containing low levels of nitrogen and mineral nutrients, and high levels of crude fibre. Females in the growing population ingested a more species-rich diet with higher levels of nitrogen and minerals, and less crude fibre. Levels of calcium, phosphorus, and potassium in the faeces of females in the population at carrying capacity were higher than those in the food ingested. The reverse was true for females in the growing population. At the time of sampling (early dry season), 17% of females in the population at carrying capacity and 0% of females in the growing population were eating or had recently eaten clay. Increased salivary secretion and gastrointestinal irritation caused by high-fibre diets (even when lubricated by clay) may be responsible for mineral depletion of females at carrying capacity, and hence population limitation through the inability of females to raise offspring.
A rapid freeze-sectioning technique for demonstrating annuli in tooth cementum of reindeer (Rangifer tarandus) is described. The technique has been applied to a reference material of 37 adult known-age animals and to 1,100 jawbones from two reindeer populations. The known-age material strongly indicates that the annulation is referable to age. The presence of special rut lines in teeth of males from high quality range indicates that rut-line formation might be related to condition.
The rate of wear of ruminant teeth may vary according to diet, habitat, and individual tooth characteristics. This variation may cause error in estimating the age of wild ungulates from patterns of tooth wear. We tested the ability of 10 observers to accurately estimate age from observation of tooth wear in a large sample of jaws of known-age roe deer (Capreolus capreolas) from three populations.. Although the average error was not large (+/-1.02 years), maximum error ranged from -5 to +6 years for jaws of animals between 1 and 7 years old, with observers generally overestimating the age of young animals and underestimating the age of old animals. We found significant differences among observers in estimation error. When a "jaw-board" of known-age reference specimens was provided, this observer effect was largely controlled for, but accuracy was not improved. Error was partly due to variation in tooth wear, both within and among populations. Initial cusp height of the first molar was lower, but tooth wear tended to be slower in one population than in the other two populations,possibly reflecting differences in diet and (or) habitat. Individual variation in tooth wear within populations was observed, possibly reflecting variation in tooth characteristics (e.g., enamel mineralisation), which was a source of error in age estimation from observation. Observers tended to underestimate the age of jaws with a relatively low degree of wear and vice versa. These results show that estimating the age of roe deer from observation of tooth wear produces biased results, severely limiting its application in population studies of this species.
The general aim of the present study was to test whether there are differences in the occlusal design of the ruminant selenodont molar, and by examining correlations between tooth form and diet, improve our understanding of the function of the selenodont molar within the Bovidae. Twenty-six species of bovid ruminants were grouped into the three feeding types established by Hofmann (1968) – i.e. browsers, grazers and intermediate feeders. The characteristics of the shape, number, width and length of the enamel ridges were found to correlate with the hypothesized function of the molar occlusal surface. These follow the principles applied to non-bovid species where adaptation of the occlusal surface has been investigated in some detail. Thirteen characteristics of the occlusal surface were scored. ANOSIM results reject the null hypothesis that there are no differences in the selenodont molar occlusal surface. SIMPER results showed that all the characteristics scored contributed to the differences between groups, and crown height was not explaining the major dissimilarity between feeding groups. Differences in enamel ridge characteristics between feeding types suggest that food is being processed in essentially different ways by the browsers and grazers. Intermediate feeding species cluster within the other feeding types, depending on what the major component of the diet is. The grouping produced by the MDS, based on dental characters, closely agrees with Hofmann's classification based on gut structure.
A review is presented of the chewing effectiveness of herbivorous mammals dealing with the relationship between food comminution (i.e. reduction of particle size), morphological features of teeth, chewing behaviour (i.e. time spent chewing and chewing rate), and the chemical and physical properties of plant tissues. Chewing is the main food processing mechanism in herbivores, increasing the surface/volume ratio of the food, which is a key factor affecting the efficiency of digestion and, therefore, body condition, reproductive success and life history. Chewing effectiveness (CE) is defined as the reduction of a pre-determined amount and particle size of a given food after a known, but not necessarily determined, number of chews. The two main animal-centred factors influencing CE are tooth effectiveness and chewing behaviour. The most frequently used predictors of tooth effectiveness are molar occlusal surface area, molar occlusal contact area (defined as any surface of the upper and lower teeth in or near contact during occlusion) and the length of the enamel cutting edges of the occlusal surface. There is expected to be a direct positive relationship between the predictors of tooth effectiveness and chewing effectiveness. Chewing behaviour has particular importance to food particle reduction in ruminants, because they spend long periods chewing during both initial ingestion and ruminating. The majority of studies find significant unexplained variance when CE is predicted using tooth features or chewing behaviour parameters. There is also little agreement as to what is the key morphological factor determining tooth effectiveness, or what is the relationship between tooth effectiveness and chewing behaviour. The type, maturity stage and physical presentation of the food also contribute to the final particle size after food has been chewed, because of the involvement of the concentration of chemical components of the cell walls (acid detergent and neutral detergent fibres, lignin) and the architectural structure of the plant tissues in particle breakdown. The relationships between body mass and tooth effectiveness, chewing behaviour and CE are also discussed.
Seasonal changes in crude protein content of graminoids and herbs grazed by red deer were monitored from 1 May, or as soon as snow melt exposed the vegetation, until 15 October at five sites along an altitudinal gradient from coast to inland. Crude protein declined exponentially with time at all sites, but declined most rapidly from initially higher values at inland locations at high elevations. As a result crude protein was positively correlated with altitude and distance from the coast in early summer and negatively correlated in autumn. The relationships between protein content, date and altitude were used to estimate the quality of the diet of twelve radio-collared female red deer that migrated to summer ranges in the mountains. Individual differences in body weight were significantly related to the estimated, mean crude protein in vegetation available during the summer. Constraints on the timing of migration to exploit the maximal protein concentrations at higher altitudes and the fitness benefits of adaptive ranging behaviour are discussed.
We evaluated the accuracy of ages assigned by Matson's Laboratory from examination of annuli in the cementum of incisor root tips of 111 known-age Rocky Mountain elk (Cervus elaphus), 108 known-age mule deer (Odocoileus hemionus), and 74 known-age white-tailed deer (Odocoileus virginianus). Accuracy rates were 97.3% for elk through age 14, 92.6% for mule deer through age 14, and 85.1% for white-tailed deer through 9 years old. There was no pattern of error relative to age. Accuracy for a sample of known-age mandibles aged by eruption-wear criteria was lower for mule deer (62.3%) and white-tailed deer (42.9%) than accuracy of ages in subsequent samples determined from cementum analysis of incisors. Accuracy of ages of elk assigned at check stations by eruption-wear criteria was >50% only for age classes 3 and 4, and averaged 16% for elk greater than or equal to 5 years old. Ages assigned by eruption-wear criteria were not reliable for comparing physical measurements and population parameters by age among populations. Further, errors in ages assigned by eruption-wear in one age class were not equally balanced by offsetting errors in assigned ages among other age classes. This resulted in inaccurate estimates of population age structure when ages were assigned by eruption-wear criteria. The accuracy provided by the cementum annuli method is necessary to determine whether various physical and population parameters change significantly with age of the animal.
The study of population regulation has been central to much of the work on the population biology of both animals and plants, as seen in much of the literature (for example, Lack, 1954; Slobodkin, 1961; MacArthur and Connell, 1967; McLaren, 1971; Ricklefs, 1973; Emmel, 1976; Tamarin, 1978). Recent developments in the theoretical aspects of population dynamics have led to a growing union of the concepts of life history analysis with those of population regulation, both in an evolutionary context (for example, Boyce, 1984). Much of the literature dealing with population regulation covers research on fishes and insects, with some work devoted to the study of birds (Nikolskii, 1969; Lack, 1966; Clark et al., 1967; Weatherly, 1972; Varley et al., 1973; Hassel, 1975; Gulland, 1977). Wynne-Edwards (1962) presents information on density dependence for a number of taxonomic categories. Reviews of the literature dealing with density dependence exist for fish (McFadden, 1977) and small mammals (Christian, 1963; Krebs and Myers, 1974). A preliminary review for large mammals was produced by Fowler et al. (1980).
Among small-sized, food-limited females tooth wear was twice as rapid as among well-fed, large females. This effect was caused by overgrazing of winter food resources. With increased tooth wear food-limited females had progressively depleted body reserves (weight and fat deposits) during half of their prime reproductive life-span. An important consequence of this was increased offspring losses and lowered reproductive success. Since energy allocation to growth, fattening, survival and reproduction is dependent on both food availability and effective mastication, tooth wear magnifies the effects of food shortage and counteracts the effects of foraging behaviour to enhance fattening and growth during summer. This result does not support the terminal reproductive effort hypothesis.
Parallel to the large‐scale changes in land‐use patterns over the last century in Europe, many deer species have expanded their range and increased in density, but the role of habitat changes for their population ecology remains poorly documented.
We tested for effects of variability in agricultural (proportion of meadow and density of sheep) and forestry practices (proportion of coniferous and deciduous forest) in 106 municipalities in Norway on body weight of 10 206 female and 15 499 male adult red deer collected over the period 1965–2000.
Long‐term temporal changes in body weights may also be due to delayed density effects, either due to that persistent high density of red deer through grazing and browsing may affect vegetation composition (i.e. an effect of cumulative density after present‐day density is controlled for), or that individuals born at high density start to penetrate the population (cohort‐effects). As these effects may be confounding to variability in forestry or agricultural practice, we also test whether cohort and/or cumulative density may affect body weight of red deer.
There was a strong negative effect of cohort density, but no effect of cumulative density in the previous 10 years once the cohort effect was accounted for.
There was a clear positive effect of proportion of meadow on red deer body weight, while there was no effect of sheep density once the effect of proportion of meadow was adjusted for. Proportion of meadow increased during the study, but most of the variation was between municipalities (i.e. in space).
Neither proportional area of coniferous or deciduous forest consistently affected body weight of red deer in Norway.
Our study emphasizes the multitude of factors over time and space that affects body weight, and hence demography and population dynamics, of large herbivores.
The measurement of passage rate is important for the concept of ruminant diversification. While supporters of Hofmann's 1989 feeding type classification claim that browsing ruminants have faster passage rates than grazing ruminants, other researchers consider the passage rate to depend on body size alone. To date, no convincing comparison of ruminant passage rates has been put forward. For comparative purposes, we suggest the use of the "selectivity factor", which is an expression of how much longer particles of a defined size (<2 mm) are retained in the ruminant digestive tract than fluids. From the limited data available, it seems that grazing ruminants display selectivity factors between 1.56 and 3.80, whereas browsers have a much narrower range of 1.14-1.80. This suggests that browsers are not able to selectively retain particles as long as grazers. Intake of browsers, on the other hand, may not be limited by physical fill of the forestomach to the same degree as in grazers. This result can explain several observations on the digestive physiology of browsers, some of which have been linked to a rumen bypass mechanism. We propose that the ability for selective particle retention is a key factor for understanding the physiological consequences of ruminant diversification.
A review is made of the ruminant digestive system in its morphophysiological variations and adaptations relating to foraging behaviour, digestive physiology, to interactions between plants and ruminants and to geographic and climatic diversity of ruminants' ecological niches. Evidence is provided for evolutionary trends from an extreme selectivity mainly for plant cell contents and dependence upon a fractionated fore- and hindgut fermentation, to an unselective intake of bulk roughage subjected to an efficient plant cell wall fermentation, mainly in the forestomachs. The review is based on detailed comparative morphological studies of all portions of the digestive system of 65 ruminant species from four continents. Their results are related to physiological evidence and to the classification of all extant ruminants into a flexible system of three overlapping morphophysiological feeding types: concentrate selectors (40%), grass and roughage eaters (25%) and intermediate, opportunistic, mixed feeders (35%). Several examples are discussed how ruminants of different feeding types are gaining ecological advantage and it is concluded that ruminants have achieved high levels of digestive efficiency at each evolutionary stage, (including well-documented seasonal adaptations of the digestive system) and that ruminant evolution is still going on. Deductions made from the few domesticated ruminant species may have, in the past, biased scientific evaluation of the free-ranging species' ecology. The main threat to a continuous ruminant evolution and diversity appears to be man's neglect for essential ecological interactions between wild ruminants and their specific habitats, which he alters or destroys.
Summer diet, summer temperature, length of the growth season and animal density appeared to best explain annual and regional
differences in calf and yearling body mass in moose from southeastern Norway. In general animals inhabiting steep, alpine
landscapes had less body mass than animals using flat, low-altitude habitats. Autumn body mass of calves and yearlings decreased
with increasing snow depth during the preceding winter and spring. However, calf body mass was more influenced by the summer
range and less by the winter range than was body mass of yearlings. There was no indication that the effect of snow depth
on autumn body mass was greater in moose living on poor than on good summer ranges. Body mass decreased with increasing competition
for summer forage, while the winter range mainly had an density-independent effect. Habitat quality, expressed as regression
lines between calf and yearling body mass and animal density (hunting yield), differed between regions. On ranges of medium
and high altitude where birch (Betula spp.) rowan (Sorbus aucuparia) and bilberry (Vaccinium myrtillus) dominated moose summer diet, body mass decreased at a rapid rate with increasing animal density. Body mass decreased at
a slower rate at low-altitude ranges and at high-altitude ranges where willow (Salix spp.) and forbs dominated the diet. Body mass of lactating cows decreased with increasing animal density, but animal density
did not affect body mass of non-lactating cows. There was no indication that the decrease in autumn body mass with increasing
moose density over the last 25 years has caused a decrease in animal condition (ability to survive the winter). The results
are discussed in relation to the effect of summer and winter range on population regulation in moose. It is concluded that
a density-dependent effect is apparent on the summer range even at low and intermediate population densities. On the winter
range, on the other hand, density-dependence is likely to occur only at high levels of population density.
We contrast the geochemistry of the Madison drainage, which has high concentrations of geothermal features, with the Lamar
drainage of Yellowstone National Park, USA, and trace the consequences of geochemical differences through abiotic and biotic
linkages in the ecosystem. Waters in the geothermal-dominated drainage contained anomalously high levels of fluoride (F) and
silica (SiO2). Soils, stream sediments, and surface waters that interact or mix with geothermal waters, in turn, had elevated F and SiO2 concentrations compared to similar samples from the Lamar drainage. The geochemical differences were reflected in the chemistry
of forage plants, with some plants from geothermally influenced areas containing four- to eightfold higher concentrations
of F and SiO2 than similar plants in the Lamar drainage. Geothermal heat reduced snowpack, and we found that elk (Cervus elaphus) concentrated in these refugia as snowpack increased each winter. The consequent high dietary intake of F in animals associated
with the geothermal areas was confirmed by the finding that bone samples from elk living in the Madison drainage contained
sixfold higher concentrations of F than samples collected from animals wintering in the Lamar drainage. High F exposure resulted
in compromised dentition due to fluoride toxicosis, which was undoubtedly exacerbated by the abrasive action of silica. The
consequent accelerated and aberrant tooth wear resulted in early onset of senescence, reduced life span, and an abbreviated
age structure. We speculate that these altered demographics, combined with spatial heterogeneity of snowpack, will result
in increased vulnerability of this large herbivore population to wolf predation and less resiliency to compensate demographically
for predation.
Summary1. Recently, contrasting evidence of density-dependent offspring sex ratio variation in red deer (Cervus elaphus L.) has been presented. Kruuk et al. (1999) reported that the proportion of male red deer born on the island of Rum, Scotland, each year declined with increasing population density and with winter rainfall, i.e. as nutritional stress in females increased. In contrast, Post et al. (1999a) reported increasing male-biased offspring sex ratios in Hordaland, Norway, with both rising numbers of hinds and increasing values of the North Atlantic Oscillation (NAO), which they regarded an index of severe winters.2. Compared to Post et al. (1999a), we reanalysed sex ratio variation on a greatly extended data set, including four populations of Norwegian red deer, taking into account a finer population substructure.3. The proportion of male calves shot each autumn declined markedly as density increased in all four populations. The proportion of male calves shot each autumn increased significantly with an increasing NAO index in one of the four populations, but there was no residual effect of the NAO once the effect of snow depth (at low elevation) was controlled for (decreasingly male biased harvest with increasing snow depth).4. At the west coast of Norway, the NAO is positively correlated with temperature and precipitation. However, since temperatures in this region often are around 0 °C during winter, the relationship between the NAO and snow depth may be difficult to predict.5. An analysis of variation in snow depth revealed that snow depth was negatively correlated with the NAO at low altitudes (below 400 m), but this relationship was reversed at high altitudes giving a positive correlation between snow depth and the NAO. We therefore suggest that a high NAO index indicates favourable winter conditions for red deer, as red deer winter at low altitude, and since recent studies show that a high index of the NAO is generally positively correlated with body weight in red deer.6. Female red deer thus reared fewer sons as nutritional stress increased with increasing density and severity of climate in Norway, which is consistent with the birth sex ratios observed on Rum, Scotland.
The gut capacity of mammalian herbivores increases linarly with body weight. This relationship, coupled with the change in basal metabolism with weight, produces an MR/GC ratio (metabolic requirement/gut capacity) that decreases with increasing body size. Since the retention of a food particle within the gut is proportional to this ratio, the extent to which food particles are digested will be related to body size. The fiber fraction of plant material is digested slowly and exclusively by microbial symbiotes. A positive relationship between the fiber content of plant parts and their biomass is used to describe a resource axis on which digestion rate is the scaling variable. In response to this resource axis and metabolic requirements, the fiber content of the diet of herbivores increases with body size. Ruminants are the predominant medium-sized herbivores in East Africa, while nonruminants are mainly small or very large animals. Small herbivores are constrained to rapid passage of ingesta by their high MR/GC ratio and have evolved hindgut fermentation and feed selectively on rapidly digestible (low-fiber) foods. Both responses contribute to loss of nutrients (synthesized by gut microbes) in the feces, and thus contribute to coprophagy in this group. Ruminants must rely almost entirely on the production of microbial volatile fatty acids for energy and postruminal digestion of microbes for other nutrients. With decreasing body size, the increasing rate at which energy must be produced per unit volume of the rumen cannot be matched by a concomitant increase in the fermentation rate of forages. Nonruminants are favored by the more efficient energy transfer of enzymatic digestion in the foregut of the low-fiber foods often required by small animals.-from Authors
In ungulates it is argued that specialization in the consumption of a particular type of food (feeding style) is reflected in morphological adaptations of the organs involved in the selection, processing and digestion of food. We analysed the differences in size and morphology of some oral traits that have been functionally related to food-selection ability (muzzle width, incisor-arcade shape, incisor shape), prehension of food (incisor protrusion), food comminution (molar occlusal surface area, hypsodonty (high-crowned molars)) and intake rate (incisor breadth) between ungulate species with different feeding styles (browser, mixed feeder, grazer). Grazers were characterized by large-body-size species. After controlling only for body mass, we found that grazers had wider muzzles and incisors, more-protruding incisors and more-bulky and higher-crowned molars than did mixed feeders and browsers. When the analyses took into account both body mass and phylogeny, only body mass and two out of the three hypsodonty indexes used remained significantly different between feeding styles. Browsers were smaller, on average, than mixed feeders and grazers, whilst grazers and mixed feeders did not differ in size. Also, browsers had shorter and less-bulky molars than did mixed feeders and grazers; the latter two feeding styles did not differ from each other in any of the hypsodonty indexes. We conclude that the adaptation to different dietary types in most of the oral traits studied is subsumed by the effects of body mass and the sharing of common ancestors. We hypothesize that differences in the ability to exploit different food resources primarily result from differences in body mass between species, and also discuss why hypsodonty characterizes feeding styles.