Article

Digestive strategies in two sympatrically occurring lagomorphs

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Abstract

Separation of low digestible fibres and fermentation of the digestible part of the food in the caecum is an adaptation of some small herbivores to cope with low-quality forage. The caecum content is later re-ingested as soft faeces so that the herbivore can benefit from this protein-rich material. This is known as caecotrophy and is a common phenomenon in species of leporids, although differences exist between hares and rabbits. Hares have amorphous soft faeces and the amount of soft faeces produced is smaller compared to that of rabbits. Both factors suggest that hares have smaller benefits from re-ingestion of the caecal contents compared with rabbits and, as a consequence, have a less efficient digestion (mainly of nitrogen) compared to rabbits. The assertion was tested whether digestive efficiency is different between the two herbivores and how this affects the choice of food plants in a natural situation. A feeding trial was conducted using hares and rabbits fed with diets with a range of fibre contents. Dry matter digestibility was not different, but nitrogen digestibility was lower in hares than in rabbits, indicating a less efficient digestion of protein. Both taxa showed a different response to increased fibre content in the diet. Rabbits maximized digestibility by increasing retention time of the food, hares maximized digestion rate by increasing the passage rate of the food through the digestive tract. The daily digestible nitrogen intake was higher in hares Lepus europaeus than that in rabbits Oryctolagus cuniculus, indicating that hares compensated for their lower nitrogen digestibility. Hares were predicted to select for higher quality plant species in a natural situation, but they had, on average, a lower nitrogen and higher total fibre content in their diet compared to sympatrically occurring rabbits. This indicated that hares did not compensate for their lower digestive efficiency by selecting higher quality food plants. The present experiment shows that hares and rabbits have different digestive strategies to cope with low quality forage. Rabbits had a higher N-digestibility by increasing the retention time, whereas hares appeared to compensate for their lower N-digestibility by increasing the processing rate, when food quality deteriorated.

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... Niche overlap between two prey species can drive competition. Although hares and rabbit have a considerable overlap in their diet (Kuijper et al., 2004), it is still unclear what mechanism maintains allopatry or drives competition between the two species (Flux, 2008). The competitive advantage of a species depends on its capacity to reduce the availability of resources for the competitor, but also on its capacity to withstand a reduction in the availability of resources by its competitor (Persson, 1985). ...
... Hares and rabbits have a considerable dietary overlap (Kuijper et al., 2004), and Homolka (1987) classified them as trophic competitors when sympatric (but see Katona et al., 2004). Although we found no indication of interference competition, avoidance between hares and rabbits in open vegetation structures, as in our data, could be the result of exploitative competition. ...
... Non-centralplace foragers like hares, however, are more capable of shifting their use of space, as they have larger home ranges, have access to a wider range of food resources (Stott, 2007), and possess multiple escape modes (Wirsing et al., 2010). Moreover, hares have a relatively small digestive system, which acts as a weight-minimizing adaptation to enhance flight (Stott, 2007) and maximizes the passage rate to cope with low-quality forage (Kuijper et al., 2004). Therefore, hares can compensate for a poorer diet that comes at the cost of a shift in space . ...
... Leporids are small mammalian herbivores that select food to obtain the necessary amount of nutrients and energy for their bodies, and despite similarities in size and appearance, hares (Lepus spp.) and rabbits (Oryctolagus spp.) differ in their feeding strategy and digestive physiology. The ability to digest nitrogenous compounds is greater in rabbits than in hares (Kuijper et al. 2004), and similarly, the digestibility of hemicelluloses is higher in rabbits than in hares, although both species are poor digesters of fibre (Stott 2008). In cases where only low-quality forage is available, hares maximise food processing by increasing their intake rate and decreasing the digesta retention time, while rabbits maximise digestion by increasing the mean digesta retention time (Kuijper et al. 2004). ...
... The ability to digest nitrogenous compounds is greater in rabbits than in hares (Kuijper et al. 2004), and similarly, the digestibility of hemicelluloses is higher in rabbits than in hares, although both species are poor digesters of fibre (Stott 2008). In cases where only low-quality forage is available, hares maximise food processing by increasing their intake rate and decreasing the digesta retention time, while rabbits maximise digestion by increasing the mean digesta retention time (Kuijper et al. 2004). The gut passage rate has been found to be significantly faster in hares than in rabbits (Stott 2008). ...
... The reingestion of soft faeces provides additional protein, minerals and vitamins to the animal (Hirakawa 2001), but this mechanism is not identical in both rabbits and hares. Rabbits are better able to separate the fibrous fraction and to produce larger amounts of soft faeces as a cluster surrounded by a mucilaginous membrane than hares, which produce an amorphous type of soft faeces that lacks a membrane (Hirakawa and Okada 1995;Hirakawa 2001;Kuijper et al. 2004). ...
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The products of the microbial activity in the large intestine are an important source of energy for herbivores. A previous study showed differences in caecal methanogenesis and short-chain fatty acid (SCFA) profiles between brown hares and domestic rabbits. The present study was performed on animals which were offered the same diet to eliminate the impact of diet on the comparative analyses of microbial metabolites. Caecal samples of hares and rabbits were incubated in triplicate, i.e. without any supplementary substrate (control) or with the addition of wheat bran or oat bran. Calculated as percentage of body weight, the stomachs of the rabbits were heavier than those of the hares, but caeca of the hares weighed more than those of the rabbits. The total SCFA concentration in caecal samples was higher in rabbits than in hares, and it increased in both species when the supplementary fermentation substrates were added. In hares, the molar proportion of propionate was higher and that of butyrate was lower compared to rabbits. The addition of substrate decreased acetate and propionate but increased the molar proportion of butyrate. Microbial fermentation resulted in greater gas release in rabbit caecal samples compared to those of hares. Methanogenesis tended to be lower in hares than in rabbits, but high individual variability was observed, especially in hares. Our study stated lower microbial activity in the caeca of brown hares compared to domestic rabbits. The presented results might lead to assumption that differences between fermentation patterns were not caused by diet but resulted from the peculiarities of both species.
... In another natural experiment, in a juniper scrubland habitat in Hungary, where the same epidemic occurred and wiped out most of the rabbit population, there was no increase in hare abundance and the moderate dietary overlap seemed to indicate no significant competition for food between the two species (Katona et al. 2004). However, other studies show evidence of significant dietary overlap and competition between the two species (Chapuis, 1990;Kuijper et al. 2004) and hares were very efficient in outcompeting rabbits from small islands; equally, in most situations they are able to occupy most of the habitat of the other species in its absence . Rabbits, in particular bucks, are known to be more aggressive towards other species such as hares and it was hypothesised that this behaviour would force hares out of the area shared by the two species but more recent direct observations of the two species feeding together dismissed this idea as antagonism is very rare . ...
... In common with most successful colonisers, rabbits display an extreme environmental plasticity which allows them to adapt to new areas and conditions by including new plant species in their diets (Lees & Bell, 2008) or quick transitions between preferred and unpreferred food resources (Ferreira & Alves, 2009). Equally, rabbits are capable of highly efficient food conversion through re-ingestion of soft faeces (Kuijper et al. 2004) making them adaptable and resistant to adverse conditions (Stott, 2008). However, rabbits are typically selective grazers feeding on a variety of gramineous species (Williams et al. 1974) including cereal crops. ...
... On the other hand, rabbits have also been shown to be facilitated by both cattle (Bakker et al. 2009) and sheep (Petrovan et al. 2011) probably as a result of the rabbit preference for shorter swards during foraging, irrespective of biomass intake (Iason et al. 2002). Competition between hares and rabbits has been investigated in the past but results remain unclear with confirmation of extensive overlap in the diet of the two species in some studies (Kuijper et al. 2004) but not in others (Katona et al. 2004). ...
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The declines of the brown hare (Lepus europaeus), a priority species for conservation in the UK, may have been caused by changes in agricultural management. This study aims to identify hare distribution, density, habitat selection and demography in grasslands in order to benefit their future conservation. In addition, this study aims to investigate the impact of current agricultural management on the populations of the European wild rabbit (Oryctolagus cuniculus), a major agricultural pest and potential competitor for hares. Hare and rabbit populations were surveyed in several large, pasture-dominated, sites in north –east England between 2007 and 2009. Estimated density of brown hares in the studied region was far higher than the published national average density for this species in pastures but with very large variation between superficially similar sites. We explored a new method to survey hares using night-time line transect distance sampling and compared this method with day time surveys. Night-time distance sampling produced improved precision estimates of hares with considerably less survey effort by maximising detectability during surveys. Hares and rabbits had different habitat requirements in grassland areas and areas dominated by intensive sheep grazing produced the lowest hare densities and in most cases were associated with high rabbit densities. Field size was an important determinant of the distribution of both hares and rabbits but with contrasting effects for the two species. Predator control appeared more important in increasing rabbit numbers than hares in the studied region. Our results indicate that recent changes in pasture management in the UK might favour high rabbit densities with potentially significant economic impacts for the agricultural sector. Hare productivity was high but female fertility and survival, in particular juvenile survival, were relatively low. Hares in the studied region were generally in good condition and reached sizes comparable with hares from arable areas. Population modelling suggested the hare population in the area was slowly increasing but was susceptible to decline even at relatively moderate levels of hunting. Radio-tracking indicated that habitat heterogeneity was important for hares at both between and within field levels. Hares preferentially used field margins during both active and inactive periods and selected woodland edges and unimproved grassland during diurnal periods, suggesting that they might benefit from measures designed to increase heterogeneity and re-establishment of non-farmed habitat features, particularly field margins. Equally, hares avoided sheep grazed fields with short swards for both foraging and resting indicating that reducing grazing intensity in pastural areas would also be beneficial for hare conservation. We suggest that grassland management could be adapted in order to minimize damage by high numbers of rabbits and increase the presence and abundance of the brown hare, a species of conservation concern in Europe and the UK.
... Rabbits form soft faeces as a cluster surrounded by a mucilaginous membrane, which are consumed and then continue to ferment in the stomach for several hours. In contrast, hares produce amorphous soft faeces that lack a membrane and become barely distinguishable from other materials in the stomach once ingested [4,5,6,7]. ...
... Hares maximize the processing of the food by increasing intake rate and decreasing digesta retention time. Rabbits maximize digestion of the food by increasing the mean digesta retention time [7]. Moreover, Stott [8] found that the caecum of the brown hare, like its other digestive organs, had a relatively smaller size compared with that of the rabbit and that the gut passage rate was significantly faster in hares than in rabbits. ...
... The diet of wild rabbits is considered to be more abundant in protein than that of hares because wild rabbits primarily choose plants that grow close to their burrows and because this intense grazing in the same area results in the consumption of young, protein-rich plants. In contrast, hares feed over a far larger area and their diet is more diverse [50] but contains less protein and more fibre overall [7]. The higher caecal concentration of iso-acids and the tendency toward higher ammonia level suggest a higher proteolytic and deamination activity in hare caecum compared with that of the rabbit, but this needs to be confirmed by additional research. ...
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The brown hare and the domestic rabbit are mid-sized herbivorous mammals and hindgut fermenters, though their digestive physiologies differ in some traits. The objective of this study was to estimate and compare the caecal microbial activity in hares and rabbits via an analysis of the following end-products of in vitro caecal fermentation: methane, total gas production, short chain fatty acids and ammonia concentration. Hare caecal methanogenesis occurred at a much lower level (0.25 mmol/kg for samples incubated without substrate and 0.22 mmol/kg for samples incubated with substrate) than that of the rabbit (15.49 and 11.73 mmol/kg, respectively) ( P <0.001). The impact of the substrate’s presence on caecal methanogenesis was not significant, though its presence increased the total gas production during fermentation ( P <0.001). Hare caecal microflora produced a lower short chain fatty acids concentration than did rabbit microorganisms (
... Daily intake and digestive efficiency do not only depend on the body mass of the forager, but also on the food resource, and either intake or digestion or both decrease with decreasing forage quality, caused by increased fibre contents (Demment & Van Soest, 1985, Duncan et al., 1990. In ruminants increased dietary fibre concentrations have been found to increase retention times and therefore lower daily intake (Poppi et al., 1980), and the same has been found for rabbits (Kuijper et al., 2004). Equids on the other hand have been reported to increase their dry matter intake when forage quality decreases (Crawley, 1983, Laut et al., 1985, Demment & Greenwood, 1988). ...
... This is in agreement with Gidenne et al. (2000), who showed for hybrids of New Zealand and Californian rabbits (with an adult body mass of 3 kg) that reducing the dietary fibre content for growing rabbits below 20% led to reductions in both food intake and growth rate. On the other hand, a reduction in food intake and an increase in retention time, leading to a decrease in digestible nitrogen intake as consequence of increased dietary fibre was observed by Kuijper et al. (2004) for Dutch belted rabbits. ...
... The Polish and harlequin rabbits which had lower fibre digestion and high intakes, performed well on our swards of relatively intermediate fibre content, while the breeds with higher fibre digestibility were only able to maintain body mass (Dutch belted) or lost body mass. The study of Kuijper et al. (2004) furthermore indicates that also for diets with higher fibre contents a high-intake-fast throughput strategy is more successful than a more intensive fibre fermentation at least for the smaller breeds. ...
... Thus, a decrease of crude protein content in herbaceous plants, as well as a decrease in water and biomass and an increase in fiber content is observed (Alves and Rocha 2003). On the other hand, dicotyledonous plants generally have higher protein content and lower fiber content (Kuijper et al. 2004). Therefore, it seems that the higher consumption of herbs and shrubs, as well as of reproductive plant parts by Iberian hares observed in summer can be associated with a compensation strategy for the lower quality of the vegetative part of grasses in this season. ...
... On the other hand, comparative studies of the digestive strategies of Brown hare and domestic rabbits (O. cuniculus ) report that there are differences in nitrogen digestion efficiency between these species (Kuijper et al. 2004). However, hares are reported to compensate their lower digestive efficiency by increasing the intake and the passage rate of the food through the digestive tract (Kuijper et al. 2004). ...
... cuniculus ) report that there are differences in nitrogen digestion efficiency between these species (Kuijper et al. 2004). However, hares are reported to compensate their lower digestive efficiency by increasing the intake and the passage rate of the food through the digestive tract (Kuijper et al. 2004). A previous study by Kronfeld and Shkolnik (1996) compared digestibility and food intake by brown hares from southern France and by Cape hares (L. ...
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The diet of the Iberian hare (Lepus granatensis) was studied through microhistological pellet analysis in two areas from a mountain ecosystem in Central Portugal. Fecal pellets were collected monthly in 24 plots spatially distributed throughout the two study areas. For each period, a sample of 15 to 20 pellets was milled and 400 epidermal fragments were identified, by comparison with a reference collection. A wide range of plant species was observed in hare’s diet. Grasses represent the basis of the Iberian hare diet, with frequencies always higher than 50% in both study areas (annual average = 69.98%). Most of the 35 species of grasses assembled for the reference collection (91.43%) were identified in the pellets. Nevertheless, only six of these were consumed in proportions greater than 5%, being Anthoxanthum odoratum, Secale cereale and Agrostis spp. the species ingested in higher frequencies. The rate of grasses consumption reached 80.69% in winter but decreased in summer to around 55%. In this season, a concurrent rise in the ingestion of other plant groups, like herbs and shrubs, and of plant inflorescences was observed. This work provides the first results on the Iberian hare’s diet on mountain ecosystems, and suggests that the Iberian hare diet in a mountain ecosystem is similar to the observed in L. europaeus and L. timidus.
... Daily intake and digestive efficiency do not only depend on the body mass of the forager, but also on the food resource, and either intake or digestion or both decrease with decreasing forage quality, caused by increased fibre contents (Demment & Van Soest, 1985, Duncan et al., 1990. In ruminants increased dietary fibre concentrations have been found to increase retention times and therefore lower daily intake (Poppi et al., 1980), and the same has been found for rabbits (Kuijper et al., 2004). Equids on the other hand have been reported to increase their dry matter intake when forage quality decreases (Crawley, 1983, Laut et al., 1985, Demment & Greenwood, 1988). ...
... This is in agreement with Gidenne et al. (2000), who showed for hybrids of New Zealand and Californian rabbits (with an adult body mass of 3 kg) that reducing the dietary fibre content for growing rabbits below 20% led to reductions in both food intake and growth rate. On the other hand, a reduction in food intake and an increase in retention time, leading to a decrease in digestible nitrogen intake as consequence of increased dietary fibre was observed by Kuijper et al. (2004) for Dutch belted rabbits. ...
... The Polish and harlequin rabbits which had lower fibre digestion and high intakes, performed well on our swards of relatively intermediate fibre content, while the breeds with higher fibre digestibility were only able to maintain body mass (Dutch belted) or lost body mass. The study of Kuijper et al. (2004) furthermore indicates that also for diets with higher fibre contents a high-intake-fast throughput strategy is more successful than a more intensive fibre fermentation at least for the smaller breeds. ...
Article
Differences in body mass are assumed to be a major factor leading to resource partitioning and the reduction of competition between species within a guild. To study the effects of body mass on foraging behaviour of grazers independently of morphological adaptations we used intra-specific size differences between subspecies of the Canada goose Branta canadensis and between breeds of domestic rabbits Oryctolagus cuniculus . First we measured instantaneous intake rate and daily intake on small, monospecific Lolium perenne plots. The different goose sizes showed very similar dome-shaped functional responses, with an optimum at low grass biomass. On a daily time scale food intake in rabbits was little affected by sward characteristics and scaled with body mass to the power of 0.75, just as metabolic requirements. We did not find differences in food digestibility between breeds. When comparing food selection on the plant/leaf level, there were no differences in the choice of leaves between goose size classes; however, the large geese removed a larger fraction of each individual leaf. Consequently, patch use in an allopatric situation did not reveal large differences between the size classes; all geese preferred short swards. The largest geese used taller swards more than the two smaller subspecies. When all three size classes were grazing in the same enclosure patch use did not differ from the allopatric situation: the small and intermediate-sized geese were very similar and the largest size class again used taller patches more than the other two, but all showed a preference for the shortest patches. Patch depletion negatively affected foraging efficiency in the short term as daily foraging time increased with increasing depletion and the geese showed a preference for ungrazed patches. Furthermore our results indicate that patch depletion affected the larger geese more than the smaller ones. Therefore competitive exclusion of the larger geese by the smaller geese will occur on very short swards.
... A higher abundance of Bacteroidetes (genus Bacteroides) has been linked to consumption of diets rich in protein and fat in humans (Wu et al., 2011), and indeed, hares are known to prefer diets rich in crude fat and protein (Schai-Braun et al., 2015). Despite having a higher daily digestible nitrogen intake, hares tend to have less efficient protein digestion compared to rabbits, potentially due to the absence of key microbes in their gastrointestinal tract (Kuijper, Van Wieren & Bakker, 2004). Another apparent difference in the faecal microbiomes of these species was the presence of phylum Verrumicrobia in rabbits. ...
... The observed differences in faecal microbiota could also be related to other known differences in digestive physiology between rabbits and hares. For example, hares have a higher gastrointestinal passage rate compared to rabbits, while rabbits retain digesta longer in order to maximise the efficiency of nutrient extraction (Kuijper, Van Wieren & Bakker, 2004). Rabbits also have a greater ability to digest hemicelluloses and have a higher rate of methanogenesis compared to hares (Miśta et al., 2015;Marounek, Brezina & Baran, 2000;Miśta et al., 2018;Stott, 2008). ...
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Background European brown hares ( Lepus europaeus ) and European rabbits ( Oryctolagus cuniculus ) are invasive pest species in Australia, with rabbits having a substantially larger environmental impact than hares. As their spatial distribution in Australia partially overlaps, we conducted a comparative microbiome study to determine how the composition of gastrointestinal microbiota varies between these species, since this may indicate species differences in diet, physiology, and other internal and external factors. Methods We analysed the faecal microbiome of nine wild hares and twelve wild rabbits from a sympatric periurban reserve in Canberra, Australia, using a 16S rRNA amplicon-based sequencing approach. Additionally, we compared the concordance between results from Illumina and Nanopore sequencing platforms. Results We identified significantly more variation in faecal microbiome composition between individual rabbits compared to hares, despite both species occupying a similar habitat. The faecal microbiome in both species was dominated by the phyla Firmicutes and Bacteroidetes , typical of many vertebrates. Many phyla, including Actinobacteria , Proteobacteria and Patescibacteria , were shared between rabbits and hares. In contrast, bacteria from phylum Verrucomicrobia were present only in rabbits, while phyla Lentisphaerae and Synergistetes were represented only in hares. We did not identify phylum Spirochaetes in Australian hares; this phylum was previously shown to be present at high relative abundance in European hare faecal samples. These differences in the composition of faecal microbiota may be indicative of less discriminate foraging behaviour in rabbits, which in turn may enable them to adapt quicker to new environments, and may reflect the severe environmental impacts that this species has in Australia.
... The high-risk open vegetation structures provide quality foraging ground for hares and rabbits (Kuijper & Bakker, 2008). Hares and rabbits have a considerable resource overlap (Kuijper, Wieren, & Bakker, 2004), and Homolka (1987) considered them as competitors when sympatric. Rabbits maintain high-quality patches with short vegetation (Bakker et al., 2005). ...
... Moreover, hares have a relatively small digestive system, which acts as a weight-minimizing adaptation to enhance flight and maximizes the passage rate to cope with low-quality forage (Kuijper et al., 2004;Stott, 2007). Therefore, hares can compensate for a poorer diet that comes at the cost of a shift in space (Laundré, Hernández, & Ripple, 2010). ...
Article
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Spatial variation in habitat riskiness has a major influence on the predator–prey space race. However, the outcome of this race can be modulated if prey shares enemies with fellow prey (i.e., another prey species). Sharing of natural enemies may result in apparent competition, and its implications for prey space use remain poorly studied. Our objective was to test how prey species spend time among habitats that differ in riskiness, and how shared predation modulates the space use by prey species. We studied a one‐predator, two‐prey system in a coastal dune landscape in the Netherlands with the European hare (Lepus europaeus) and European rabbit (Oryctolagus cuniculus) as sympatric prey species and red fox (Vulpes vulpes) as their main predator. The fine‐scale space use by each species was quantified using camera traps. We quantified residence time as an index of space use. Hares and rabbits spent time differently among habitats that differ in riskiness. Space use by predators and habitat riskiness affected space use by hares more strongly than space use by rabbits. Residence time of hare was shorter in habitats in which the predator was efficient in searching or capturing prey species. However, hares spent more time in edge habitat when foxes were present, even though foxes are considered ambush predators. Shared predation affected the predator–prey space race for hares positively, and more strongly than the predator–prey space race for rabbits, which were not affected. Shared predation reversed the predator–prey space race between foxes and hares, whereas shared predation possibly also released a negative association and promoted a positive association between our two sympatric prey species. Habitat riskiness, species presence, and prey species’ escape mode and foraging mode (i.e., central‐place vs. noncentral‐place forager) affected the prey space race under shared predation.
... This supports to some extent the Bell-Jarman principle. However, lagomorphs, as with larger herbivores, are hind gut fermenters and are able to digest higher quantities of lower quality food, enabling them to adapt their diets to the availability of forage rather than select solely for more highly nutritious forage (Sakaguchi, 2003;Kuijper, van Wieren & Bakker, 2004b). This similarity in diet Significantly different between hare and rabbit diet (MANOVA, df = 1, P = < 0.05). ...
... There was no evidence of competitive exclusion between rabbits and hares on the basis of diet but the effects of livestock and pasture management on diet may influence indirect competition in favour of rabbits over hares. It is perhaps the differences in the ability of hares to consume swards with higher biomass on poorer quality patches when resource competition occurs (Kuijper et al., 2004b) that has enabled the coexistence of two herbivore species by providing an adequate nutritional niche (van Langevelde et al., 2008). ...
Article
Coexistence of ecologically similar species is sustained by niche partitioning, a fundamental element of which is diet. Overlapping of resource requirements between sympatric species can create interspecific competitive or facilitative effects on the foraging behaviour of herbivores. Brown hares (Lepus europaeus) and European rabbits (Oryctolagus cuniculus) are similar in size, morphology, feeding type and occupy the same habitats, but direct evidence of competition for resources between them is lacking. Both species are widespread and simultaneously pests and species of conservation concern in different parts of their range. We investigated dietary overlap of brown hares and European rabbits in pastures in relation to pasture management and hare and rabbit abundance. Grasses were the predominant component in both hare and rabbit diets with high overlap of plant species. Both rabbits and hares showed some selectivity for particular plants with evidence of consistent selection for Phleum spp. and relative avoidance of Poa spp. However, differences in the smaller components of hare and rabbit diet resulted in significant differences in diet overall. There was no evidence that higher relative density of one species led to dietary shifts but pasture management affected the diet of both species. Nutritional composition of diets of both species also differed between cattle and sheep pastures with higher fibre, ash and fat in the former. Our data provide no evidence of competitive exclusion between rabbits and hares on the basis of diet, but suggest that the effects of livestock on their respective diets may influence indirect competition in favour of rabbits over hares.
... Caecal concentration of total volatile fatty acids were higher and ammonia concentrations was lower in rabbits than in hares (98. 9 In the natural environment the hare's diet is similar to the rabbit's diet. In both species the caecum is the primary site of digesta retention and microbial fermentation. ...
... Comparative nutritional trials with rabbits and hares are scarce. Kuijper et al. [9] carried out a feeding trial using rabbits and hares fed diets with a range of fibre contents. Dry matter digestibility was not different, but nitrogen digestibility was lower in hares than in rabbits, possibly because hares produced smaller amount of soft faeces. ...
... But there is a tradeoff: retaining food for longer presumably maximises the extraction of nutrients from each meal, but reduces the amount of food the animal can process per unit time. Some mammals respond to high fibre diets by either increasing the MRT of the food to increase digestibility in rabbits (Kuijper et al. 2004) and colobus monkeys (Edwards and Ullrey 1999) or by increasing the passage rate of the food through the digestive tract to allow a high intake of food, while sacrificing some digestibility as occurs in Japanese macaques (Sawada et al. 2011), cavies (Sassi et al. 2010), gerbils (Quan-Sheng and De-Hua 2007) and hares (Kuijper et al. 2004). Our results suggest that howler monkeys adopt neither approach. ...
... But there is a tradeoff: retaining food for longer presumably maximises the extraction of nutrients from each meal, but reduces the amount of food the animal can process per unit time. Some mammals respond to high fibre diets by either increasing the MRT of the food to increase digestibility in rabbits (Kuijper et al. 2004) and colobus monkeys (Edwards and Ullrey 1999) or by increasing the passage rate of the food through the digestive tract to allow a high intake of food, while sacrificing some digestibility as occurs in Japanese macaques (Sawada et al. 2011), cavies (Sassi et al. 2010), gerbils (Quan-Sheng and De-Hua 2007) and hares (Kuijper et al. 2004). Our results suggest that howler monkeys adopt neither approach. ...
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Mantled howler monkeys (Alouatta palliata) occupy a wide variety of tropical habitats and are the most folivorous of New World primates. However, their diet may include fruits, buds, petioles, and flowers, as well as leaves, suggesting they must cope with variations in the nutrient composition of their food. We studied the physiological basis of the dietary flexibility of these monkeys by comparing food choice, digestive performance and patterns of digesta flow in six adults, fed diets of either leaves or a mixture of fruit and leaves. Although monkeys ate similar amounts of the two diets, they ingested more digestible protein when offered the leaf diet, on which they lost body mass, but they ingested much more soluble sugars when offered fruit and leaves on which they gained mass. Digestibilities of dry matter, fat, energy and fibre did not differ between diets, but those of crude protein, soluble sugars and minerals were higher on the fruit-leaf diet. Mean retention times in the gut of solute (Co-EDTA) and particulate markers (Cr-mordanted cell walls) did not differ between diets, but on both diets the monkeys retained the particulate marker (mean retention time ca 55 h) for longer than they did the solute marker (MRT ca 50 h). A lack of selective retention of solutes and small particles in the gastro-intestinal tract of howler monkeys probably restricts them to mixed diets but their digestive strategy is sufficiently flexible to allow them to feed on a diet of leaves when fruit is unavailable.
... It was suggested above that the high prevalence of C 4 grasses in parts of Argentina might impede its invasion by rabbits. Hares might be better adapted than rabbits to exploit C 4 grasses because, of the two species, they possess the digestive system better able to cope with low-quality vegetation (Kuijper et al. 2004). The evolutionary origin of this difference in digestive strategy is unclear because the grasses are predominantly C 3 in the natural ranges of both the hare and the rabbit in Europe and Asia (see distribution maps in Flux and Angermann 1990;Gibb 1990;Sage et al. 1999). ...
... The evolutionary origin of this difference in digestive strategy is unclear because the grasses are predominantly C 3 in the natural ranges of both the hare and the rabbit in Europe and Asia (see distribution maps in Flux and Angermann 1990;Gibb 1990;Sage et al. 1999). Kuijper et al. (2004) also showed that wild rabbits selected a diet higher in nitrogen and lower in fibre than hares in the same area. These differences in feeding and digestive strategy between rabbits and hares would be expected to give hares a greater capacity than rabbits to utilise C 4 forage, and possibly provide hares with a greater capacity to invade C 4 grasslands. ...
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European rabbits are exotic pests in Australia, New Zealand, parts of South America and Europe, and on many islands. Their abundance, and the damage they cause, might be reduced by the release of naturally occurring or genetically modified organisms (GMOs) that act as biological control agents (BCAs). Some promising pathogens and parasites of European rabbits and other lagomorphs are discussed, with special reference to those absent from Australia as an example of the range of necessary considerations in any given case. The possibility of introducing these already-known BCAs into areas where rabbits are pests warrants further investigation. The most cost-effective method forfinding potentially useful but as-yet undiscovered BCAswould be to maintain a global watch on newdiseases and pathologies in domestic rabbits. The absence of wild European rabbits from climatically suitable parts of North and South America and southern Africa may indicate the presence there of useful BCAs, although other explanations for their absence are possible. Until the non-target risks of deploying disseminating GMOs to control rabbits have been satisfactorily minimised, efforts to introduce BCAs into exotic rabbit populations should focus on naturally occurring organisms. The development of safe disseminatingGMOsremains an important long-term goal, with the possible use of homing endonuclease genes warranting further investigation.
... Based on their dependence on high-quality forage (Prop & Vulink 1992), we expect that geese prefer plots with increased quality. Hares can cope with less nutritious food (Kuijper, Van Wieren & Bakker 2004). For hares, we therefore hypothesize that they select plots with high biomass even with a lower nutritional value. ...
... This decrease in the functional response is usually explained as a response to the handling problems of long leaves which decreases intake rate (Van der Wal et al. 1998b;Hassall, Riddington & Helden 2001;Durant et al. 2003;Bos et al. 2004), increased costs of locomotion and increased vigilance due to changes in the perception of predation risks (Van de Koppel et al. 1996). Because of their high receptiveness for short grass swards of high nutritional value (this study; Durant et al. 2003) we expect geese to show an optimal grazing response at low biomass levels while hares are able to cope with swards of higher biomass (Kuijper et al. 2004). Our experimental data demonstrate that foraging choices of sympatrically occurring small herbivores on coastal salt marshes are influenced by a complex interplay of facilitative and competitive processes. ...
Article
1. Overlap in habitat use between herbivores can result in facilitative interactions, through enhancement of forage quality, as well as competitive interactions. The latter result from either interference or indirectly from resource depletion. 2. We investigated competitive and facilitative interactions between wild Barnacle and Brent Geese and European Brown Hares on a salt marsh in the Dutch Wadden Sea. In a multifactorial experimental design, we manipulated biomass and quality of grass swards and determined foraging preferences of the wild herbivores. 3. We found that both Barnacle and Brent Geese select plots with plants that have a higher nitrogen content. Barnacle Geese avoid plots with high plant biomass. 4. Hares prefer the combination of high biomass with high plant quality, when geese are absent. However, in the natural situation with geese present, hares select high biomass swards. 5. Grazing increases the quality of the vegetation within one season. Geese mainly select plots that have been previously grazed by either geese or hares within the same season. 6. We conclude that indirect competition through forage depletion by large numbers of geese in spring plays a significant role determining the foraging choices of hares, while Barnacle Geese profit from grazing facilitation by other small herbivores which prevents the maturation of forage tissues.
... Sinclair et al. (1988b) have shown that the resin of the shrub birch B. glandulosa, which also contains PA (Williams et al., 1992), reduces the apparent digestibility of protein by half. However, both theoretical analysis (Moran and Hamilton, 1980) and experimental studies (Kuijper et al., 2004) have concluded that reduced protein digestibility is likely to cause compensatory feeding in small mammals (Meyer et al., 2010), and therefore, an increase in daily intake by herbivores. Compensatory feeding is likely in the case of ceacalids, such as the snowshoe hare, that rapidly pass plant biomass through the gut (Kuijper et al., 2004;Stott, 2008). ...
... However, both theoretical analysis (Moran and Hamilton, 1980) and experimental studies (Kuijper et al., 2004) have concluded that reduced protein digestibility is likely to cause compensatory feeding in small mammals (Meyer et al., 2010), and therefore, an increase in daily intake by herbivores. Compensatory feeding is likely in the case of ceacalids, such as the snowshoe hare, that rapidly pass plant biomass through the gut (Kuijper et al., 2004;Stott, 2008). Therefore, an alternative mechanism is needed to explain the negative effects of birch resin on intake by hares. ...
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The plant secondary metabolite papyriferic acid (PA) deters browsing by snowshoe hares (Lepus americanus) on the juvenile developmental stage of the Alaska paper birch (Betula neoalaskana). However, the physiological mechanism that reduces browsing remains unknown. We used pharmacological assays and molecular modeling to test the hypothesis that inhibition of succinate dehydrogenase (SDH) is a mode of action (MOA) of toxicity of PA in snowshoe hares. We tested this hypothesis by measuring the effect of PA on the activity of SDH in liver mitochondria isolated from wild hares. In addition, we used molecular modeling to determine the specific binding site of PA on SDH. We found that PA inhibits SDH from hares by an uncompetitive mechanism in a dose-dependent manner. Molecular modeling suggests that inhibition of SDH is a result of binding of PA at the ubiquinone binding sites in complex II. Our results provide a MOA for toxicity that may be responsible for the concentration-dependent anti-feedant effects of PA. We propose that snowshoe hares reduce the dose-dependent toxic consequences of PA by relying on efflux transporters and metabolizing enzymes that lower systemic exposure to dietary PA.
... Some herbivores respond to high fibre diets by increasing the MRTs of the diet to increase digestibility (Kuijper et al., 2004). ...
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We evaluated food intake, digestibility, digesta retention and digestible energy (DE) intake in four three‐toed sloths (Bradypus variegatus, body mass 2.86 ± 0.10 kg) fed two leaf‐based diets containing different neutral detergent fibre (NDF) and lignin contents. Total dry matter intake (DMI), and intake in relation to body mass and metabolic body weight were higher for the mixed diet with lower NDF content based on Pterondon sp. + Inga sp. (47 g day−1, 16 g kg−1 day−1 and 21 g kg−0.75 day−1) compared to the treatment with higher content of NDF from only Cecropia pachystachya leaves (37 g day−1, 14 g kg−1 day−1 and 18 g kg−0.75 day−1). The digest�ibility of dry matter (dDM) and neutral detergent fibre (dNDF) were higher in the mixed diet (60% and 61% respectively). There was a higher supply of DE and metabolisable energy (ME) on the mixed diet, at 221 and 199 kJ kg−0.75 day−1, meeting the average energy requirement of 185 kJ ME kg−0.75 day−1 ME estimated for sloths in this study. In contrast, the diet with C. pachystachya generated a deficit of 31 kJ ME kg−0.75 day−1. There was a correlation between DMI and dNDF (r2 = 0.89), and between dNDF and dDM (r2 = 0.98) across treatments. The mean retention times for a liquid and a particle marker were lower on the mixed diet with the higher intake at 133 h (passage rate = 0.75% h−1) and 181 h (0.55% h−1), and longer on the single‐species diet with lower intake at 204 h (0.49% h−1) and 261 h (0.38% h−1). The results suggest that it may be beneficial for sloths to be offered a variety of browse from which they can choose low‐NDF components. Further, we suggest that these sloths perform ‘digesta washing’ to increase the microbial yield in the stomach to maximise the digestion of NDF and dry matter.
... Castellaro et al. [36] underline the great importance of this group of plant species in the nutrition of herbivores with cecal fermentation, given the characteristics of their digestive system and the way in which nutrients are used. The increased palatability of forbs in the dry period could be attributed to their higher water and lower fibre contents in tissues in comparison with grasses [37,38]. Palatability was defined by Greenhalg and Reid [39] as the dietary characteristics that stimulate a selective response by the animal. ...
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This study was focused on the diet and feeding behaviour of Lepus corsicanus in two protected coastal areas of Latium, Castelporziano Presidential Estate (CPE) and Circeo National Park (CNP). Plant frequency was assessed by the quadrat method, while diet composition was determined by microhistological analysis of faecal samples. Over the year, the Italian hare fed on 185 of the 229 plant species identified in vegetation, with most of them ingested in low percentages (≤1%). During the dry season (DS), in both areas, Brachypodium sylvaticum, Cynodon dactylon, and Avena fatua were among the most consumed species. In the wet season (WS) the most common plant species in diet were B. sylvaticum, Poa trivialis, and Carex distachya in CPE and Dactylis glomerata, Cynosurus echinatus, and Spartium junceum in CNP. In both sites, considering the annual selection of life forms, grasses and leguminous forbs were preferred, while non-leguminous forbs and shrubs were used less than expected according to their availability. ANOSIM analysis showed significant differences between sites in DS and WS diets. Our study evidenced that the Italian hare behaved as generalist, revealing its capability for exploiting several plant species and to adapt its diet preferences to space-time variation of food availability.
... In the long-term process of natural selection and evolution, rabbits have developed and maintained the behavior and habit of eating soft feces to adapt to the adverse environmental conditions and their characteristics of digestive tract Hui He and Zhichao Li have contributed equally to this paper. [1]. Studies showed that the fecal-eating behavior plays an important role in maintaining microbial homeostasis and health in rabbits. ...
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Background The selection and validation of stably expressed reference genes is key for accurately quantifying the mRNA abundance of genes under different treatments. In the rabbit model of fasting caecotrophy, reports about the selection of stable reference genes are not available.Methods and resultsThis study aims to screen suitable reference genes in different tissues (including uterus, cecum, and liver) of rabbits between control and fasting caecotrophy groups. RT-qPCR was used to analyze the expression levels of eight commonly used reference genes (including GAPDH, 18S rRNA, B2M, CYP, HPRT1, β-actin, H2afz, Ywhaz), and RefFinder (including geNorm, NormFinder, and BestKeeper) was used to analyze the expression stability of these reference genes. Our results showed that the most stable reference genes were different in different tissues and treatments. In the control and fasting caecotrophy groups, CYP, GAPDH and HPRT1 were proven to be the top stable reference genes in the uterus, cecum, and liver tissues, respectively. GAPDH and Ywhaz were proven to be the top two stable reference genes among uterus, cecum, and liver in both control and fasting caecotrophy groups.Conclusions Our results indicated that the combined analysis of three or more reference genes (GAPDH, HPRT1, and Ywhaz) are recommended to be used for RT-qPCR normalization in the rabbit model of fasting caecotrophy, and that GAPDH is a better choice than the other reference genes for normalizing the relative expression of target genes in different tissues of fasting caecotrophy rabbits.
... Un apport plus conséquent en fibres permet donc d'augmenter la vitesse de transit favorisant l'ingestion , jusqu'à une teneur en ADF de 25% dans l'aliment pour les lapins domestiques au-delà de laquelle l'ingestion serait limitée par la capacité d'ingestion (GIDENNE 2003). L'ingestion de fourrages à concentration élevée en ADF serait plus forte pour des lapins sauvages (KUIJPER et al. 2004). Deux digestions sont observées chez le lapin : une digestion endogène enzymatique dans l'estomac et l'intestin grêle, et une digestion bactérienne dans le caecum qui est particulièrement développé. ...
Thesis
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L’étude des interactions entre système fourrager, santé et croissance des lapins contribuera à proposer de nouvelles pratiques pour des systèmes d’élevage cunicole alternatifs, tels que ceux en agriculture biologique (AB) incluant une gestion intégrée de la santé. Mais cette stratégie est limitée par le manque de références sur la cuniculture AB, i) sur l'alimentation au pâturage (ingestion de fourrages verts, qualités nutritionnelles pour les lapins, etc) ; et ii) sur les risques sanitaires notamment le parasitisme, identifié comme un frein important au développement de la cuniculture AB. L’emploi de plantes riches en tannins condensés (TCs) comme le sainfoin, permettrait de diminuer l’utilisation d’antiparasitaires comme cela a été montré chez les petits ruminants, tant pour la gestion des nématodes que celle des coccidies. Mais le potentiel d’activité des TCs chez le lapin, tout comme le niveau d’ingestion et les performances de croissance, restent à explorer, et pourra servir la cuniculture AB et conventionnelle. Ce travail de thèse a pour objectif i) d’étudier l’intérêt du sainfoin comme ressource pour l’alimentation du lapin, et pour ses propriétés antiparasitaires, ii) définir le niveau d’ingestion au pâturage des lapins et les conséquences sur la production et iii) d’évaluer, le risque parasitaire au pâturage pour des lapins en production. Nous avons montré qu’un aliment enrichi en sainfoin distribué à partir du sevrage, avec une teneur en tannins de 1,8% d’équivalent d’acide tannique, n’a pas réduit l’installation de L3s de Trichostrongylus colubriformis, ni la fertilité des vers adultes, mais a réduit le potentiel d’éclosion des œufs (-27 points), contribuant à réduire l’infestation de l’environnement. Un aliment enrichi en sainfoin contenant 1,2% d’équivalent d’acide tannique, distribué aux mères et aux lapins en croissance a eu un effet coccidiostatique : l’excrétion oocystale fécale de lapins nourris avec un aliment enrichi en sainfoin a été réduite de 60% par rapport à ceux ayant reçus l’aliment témoin. Si la réduction de l’excrétion oocystale de l’espèce Eimeria magna n’a pas pu être démontrée, en revanche, la réduction d’oocystes toutes espèces confondues dans l’environnement pourrait contribuer à diminuer le risque de coccidiose en élevage. Comparé à la luzerne, le sainfoin, plus riche en lignines, a une forte concentration en énergie (11,2 MJ/kg) et en protéines digestibles (110 g/kg). Au pâturage, lorsque la quantité d’herbe offerte dépasse 85 g MS/kg0,75, il semble que l’ingestion d’herbe soit régulée d’une part lorsque la teneur en énergie digestible de l’herbe dépasse 9 MJ/kg (régulation chémostatique), ou d’autre part si la teneur en lignocellulose (ADF) dépasse 350 g d’ADF/kg (régulation physique : encombrement digestif). Mais la quantité d'herbe disponible dépasse rarement 85 g MS/kg0,75. C’est-à-dire que dans la majorité des cas, une surface pâturable de 0,4 m² (minimum réglementaire) n’a pas permis de combler la capacité d’ingestion et les besoins énergétiques de lapin en croissance. De plus, si l’offre d’herbe est limitante, le lapin ne peut pas exprimer une préférence alimentaire vers des plantes plus jeunes et riches en protéines. La limitation de l’ingestion de protéines a aussi pour conséquence de réduire les potentialités de croissance des lapins et d’allonger la période d’engraissement. Au cours de trois saisons successives de pâturage (université de Perpignan), la pression parasitaire (nématodes et coccidies) a augmenté, avec des infestations par Trichostrongylus sp. et de Graphidium strigosum. Si le délai d'attente entre deux pâturages n’a pas eu d’effet visible sur l’infestation par des nématodes, cela influerait le niveau d’infection par les coccidies. Nos travaux établissent l’intérêt de l’incorporation du sainfoin dans l’alimentation du lapin et ouvrent des perspectives pour établir des pratiques innovantes et bénéfiques à la production cunicole biologique et conventionnelle
... produce faeces that are very loose, in which the vegetation included in their diet can be easily recognized (Domínguez, 2018). On the contrary, lagomorphs produce two types of faeces: one soft, which is excreted first and still retains nutrients and minerals, and a second that is hard, composed mainly of fibre (Kuijper et al., 2004). Soft faeces are ingested again after egestion (caecotrophy) and undergo a bacterial fermentation process that enables optimal nutrient consumption. ...
Article
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Dissolved organic matter (DOM) input is a key factor for freshwater ecology, since it regulates many aspects of aquatic ecosystem metabolism. Aquatic and terrestrial animals that inhabit or frequent aquatic environments also influence the DOM inputs via their faeces, supplying nutrients such as carbon (C), nitrogen (N), and phosphorus (P). Here, we analyse the response of a bacterial community in the newly formed proglacial Lake Ventisquero Negro (Mount Tronador) to the addition of dissolved nutrients from faeces leachate of the native goose (Chloephaga poliocephala Sclater, 1857; locally called “cauquén”) and the European hare (Lepus europaeus Pallas, 1778). A laboratory incubation experiment was carried out with unenriched lake water and lake water enriched with leachate from hare or goose faeces. The results showed that faeces and leachates of geese were richer in nutrients than those of hares. Spectrofluorometric analysis of the DOM also showed differences between the two sources. Nutrient enrichment positively affected bacterial respiration and short-term carbon consumption. Thus, the faeces of these two animals may play an important ecological role by supplying allochthonous DOM and nutrients to this new ecosystem.
... The colonic separation mechanism involves wriggling the chyme in the caecum to the proximal colon, and small particles of digestive material are returned to the caecum to form soft faeces, while large particles accumulate in the fusus coli to form hard faeces (Schulze, 2015). Cecotrophy refers to the behaviour of animals eating caecal faeces, and the rabbit is one of the most typical small-and medium-sized herbivores that practices cecotrophy (Kuijper, Wieren, & Bakker, 2010). ...
Article
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Cecotrophy is a special behaviour of rabbits. Eating soft faeces can improve feed efficiency and maintain gut flora in rabbits. In our previous study, we found that fasting from soft faeces significantly reduced growth rate and total cholesterol (TC) in New Zealand white rabbits (NZW rabbits), thereby resulting in lower values for body weight and fat deposition in the soft faeces fasting group than in the control group. However, it has not been demonstrated whether cecotrophy by NZW rabbits can regulate lipid metabolism by changing the diversity of caecal microorganisms. In this study, thirty‐six 28‐day‐old weaned NZW female rabbits were randomly divided into two groups (the soft faeces fasting group and the control group) and fed to 90 days. Rabbits in the experimental group were treated with an Elizabeth circle to prevent them from eating their soft faeces. Then, the caecal contents of three rabbits from the soft faeces fasting group and three rabbits from the control group were collected for metagenomic sequencing. We found that the abundance of Bacteroides increased, while Ruminococcus decreased, compared with the control group after fasting from soft faeces. Relative abundance was depressed for genes related to metabolic pathways such as ascorbate and aldarate metabolism, riboflavin metabolism and bile secretion. Moreover, there was a general correlation between variation in microbial diversity and fat deposition. Bacteroides affects body weight and TC by participating in the riboflavin metabolism pathway. By investigating the effect of cecotrophy on caecal microorganisms of rabbits, we identified the key microorganisms that regulate the rapid growth performance of NZW rabbits, which may provide useful reference for the future research and development of microecological preparations for NZW rabbits.
... Lagomorphs are hind gut fermenters and, unusually, they perform coprophagy (re-ingesting the soft faeces initially produced after a feeding bout) that enables them to more effectively digest lower quality forage (in comparison to other mammalian herbivore species their size) ( Kuijper et al. 2004). This allows their diet to be incredibly varied and provides the flexibility to adapt to changes in plant availability, management of agricultural land or competition from other herbivores. ...
Chapter
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Since the publication of the “The Ecology of Browsing and Grazing” (Gordon and Prins, The ecology of browsing and grazing. Springer, 2008), a number of researchers have taken the approach outlined in the book to assess the impacts of differences in food and nutrient supply on the ecology of other vertebrate taxa. In line with the slightly altered emphasis of the current book (The Ecology of Browsing and Grazing II), we also asked the authors of the Sections in this Chapter to provide insights into the impacts that these different vertebrate taxa have on the ecosystems in which they exist. As you will see, the depth of research on the ecology and impacts of the different herbivorous vertebrate taxa varies considerably and demonstrates the importance of further research endeavours, on herbivore/plant interactions, across the board.
... Additional activity increases the energy expenditure of cottontails by 30-60% (Rose, 1973). In addition to the bodies native rabbits are smaller and their fermentation capacity (i.e., size of ceca) is low that due to they have a faster throughput of ingesta and less efficient digestion of plant fiber (Kuijper et al., 2004). We could recommend with the diet containing 2500 Kcal/kg diet digestible energy and 14.5 % CP for Native Middle-Egypt rabbits (NMER) during the growing period; from 5 to 16 weeks of age. ...
... We found positive selection for Fabaceae and Rubiaceae families in the Aleria site. According to Paupério and Alves (2008) and Kuijper et al. (2004), many species of Fabaceae family are important as food sources for different herbivores, because of their higher protein content and for their lower fibre content in comparison with grasses in which fibre incidence increases more during dry season compared with herbs and shrubs. ...
Article
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In this research, the diet composition and feeding selection of the Italian hare were evaluated and compared in two sites of Haute-Corse region localised in the territories of Tallone and Aleria. The present study is the first considering feeding selection of Lepus corsicanus. The considered period ranged from June to October. Quadrat method was used to assess plant frequency, while diet composition was determined by microhistological analysis of faecal pellets collected monthly. Grasses represented the basis of the diet, with frequencies around 50% in both study areas, followed by non-leguminous forbs with an incidence of 29% in Aleria and over 31% in Tallone. Leguminous forbs and shrubs complemented its diet. Poaceae resulted to be the most preferred and selected family in the diet in both sites. In the diet, we observed 79 species, but only a few of them were in percentages greater than 5%. The most utilised species in the diet were Brachypodium sylvaticum, Briza maxima, and Trifolium angustifolium in Aleria and Digitaria sanguinalis, Briza maxima, and Daucus carota in Tallone. Our study evidenced that in the considered areas, characterised also in the dry period by wide plant diversity, the Italian hare behaved as generalist. Significant differences in the diet composition and in the diversity index between the two sites showed the adaptability of the Italian hare to different habitats and the influence of the vegetation on feeding habits of the species.
... Red fox can substantially impact hare populations as a predator (Knauer, Küchenhoff, & Pilz, 2010;Schmidt, Asferg, & Forchhammer, 2004). European hares and rabbits have a substantial overlap in resources (Kuijper, van Wieren, & Bakker, 2004) and are classified as trophic competitors when sympatric (Homolka, 1987). Rabbits are central-place foragers that are smaller than hares and more ecologically specialized, and thus, we expect rabbits to outcompete hares (Shipley, 2007). ...
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During times of high activity by predators and competitors, herbivores may be forced to forage in patches of low‐quality food. However, the relative importance in determining where and what herbivores forage still remains unclear, especially for small‐ and intermediate‐sized herbivores. Our objective was to test the relative importance of predator and competitor activity, and forage quality and quantity on the proportion of time spent in a vegetation type and the proportion of time spent foraging by the intermediate‐sized herbivore European hare (Lepus europaeus). We studied red fox (Vulpes vulpes) as a predator species and European rabbit (Oryctolagus cuniculus) as a competitor. We investigated the time spent at a location and foraging time of hare using GPS with accelerometers. Forage quality and quantity were analyzed based on hand‐plucked samples of a selection of the locally most important plant species in the diet of hare. Predator activity and competitor activity were investigated using a network of camera traps. Hares spent a higher proportion of time in vegetation types that contained a higher percentage of fibers (i.e., NDF). Besides, hares spent a higher proportion of time in vegetation types that contained relatively low food quantity and quality of forage (i.e., high percentage of fibers) during days that foxes (Vulpes vulpes) were more active. Also during days that rabbits (Oryctolagus cuniculus) were more active, hares spent a higher proportion of time foraging in vegetation types that contained a relatively low quality of forage. Although predation risk affected space use and foraging behavior, and competition affected foraging behavior, our study shows that food quality and quantity more strongly affected space use and foraging behavior than predation risk or competition. It seems that we need to reconsider the relative importance of the landscape of food in a world of fear and competition.
... Цинк бере участь у нейрогуморальних і клітинно- молекулярних механізмах розвитку загального адаптаційного синдрому за дії екстремальних факторів [5]. Його застосування дозволяє знизити вміст гідропероксидів ліпідів в організмі сільськогосподарських тварин і суттєво підвищити супероксиддисмутазну та глутатіонпероксидазну активність [9,11]. L-аргінін є джерелом утворення оксиду азоту (NO), який обмежує деструктивний вплив стресу, шляхом зменшення активації вільнорадикального окиснення, за рахунок підвищення активності антиоксидантних ферментів [14]. ...
... The length of time food remains inside the gastrointestinal tract of an animal can influence many interrelated biological functions, such as the concentration and composition of intestinal microflora (Bailey and Coe 2002;Fogel 2015), extent of nutrient breakdown and absorption (Flores Miyamoto et al. 2005), energetic yield (Blaine and Lambert 2012), metabolic rate (Müller et al. 2013), and detoxification of secondary plant metabolites (Cork and Foley 1991). Depending on the food ingested, some mammal species modulate this rate of passage (Edwards and Ullrey 1999a;Kuijper et al. 2004) to enhance the digestibility of poor-quality food, speed up the intake of food items high in easily digestible nutrients (Caton et al. 1996;Sawada et al. 2011), or eliminate nondigestible food items (Dierenfeld et al. 1982;Power 2010). Measurements used to estimate the food passage rate include transit time (TT) and mean retention time (MRT) (Warner 1981). ...
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The characteristics of food ingested by a primate affect its assimilation of energy by modulating food passage rate. In general, digestive time increases in folivorous primates and decreases in frugivorous primates when they are fed higher fiber diets but this relationship is understudied in exudativorous primates. We compared the food passage rate of five slow loris species. We studied 34 wild-caught slow lorises (15 Nycticebus coucang, 15 N. javanicus, and 4 N. menegensis) in an Indonesian rescue center and four captive-born slow lorises (2 N. bengalensis and 2 N. pygmaeus) in a UK institution. We fed the Indonesian subjects two different diets: a captive-type diet comprising fruits, vegetables, and insects and a wild-type diet formulated to be similar in nutrients to that consumed by slow lorises in the wild, consisting of gum, insects, vegetables, and nectar. We fed the UK subjects a diet of gum, vegetables, insects, and hard-boiled eggs. We formulated this diet to mimic the wild diet, with notably higher fiber fractions and lower soluble sugars than the previous diet. We measured two variables: the transit time (TT) and the mean retention time (MRT). We mixed 1 tsp. of glitter in bananas or gum as our markers and fed them to the slow lorises immediately before their main diet. We noted the date and time of feeding and of appearances of the marker in feces. We weighed food given and left over for each individual to calculate ingested foods and nutrients. We found that TTs were not affected by diet treatment but MRTs were significantly longer for all species fed the wild-type diet. Our results show that Nycticebus spp. have long MRTs for their body weight, and N. pygmdaeus may have the slowest MRT of all primates in relation to body mass. The digestive flexibility of exudativorous primates should allow them to maximize fermentation opportunities when they ingest more (appropriate) fiber by increasing the amount of time the fiber substrate stays in the large intestine. Exudativorous primates appear to have plastic digestive strategies that may be an adaptation to cope with relatively nutrient-poor staple food sources such as gum. The provision of gum in a captive setting may therefore provide benefits for gut health in slow lorises.
... Most shrubs of lower altitudes, being perennial and evergreen, still constitute available food during winter. Caecotrophy al- lows the hares to increase their efficiency to digest low-quality food items such as leaves and twigs of woody plants ( Hirakawa 2001;Kuijper et al. 2004). Despite the prevalence of shrubs in the vegetation of lower altitudes, the high resin content explains the use with avoidance of L. divaricata, the dominant shrub of Monte that was included in the diet only during the winter food decline. ...
Article
Predictions derived from the optimal foraging theory are interesting to test on wild herbivores living in mountain environments, considering the expected vegetation changes across altitudinal gradients. A lower food richness and a more generalist diet are expected as altitude increases, with higher diet diversity and a shift to browsing as food availability decreases seasonally. With broad diets and ecological adaptability, Lepus europaeus is a non-native herbivore inhabiting Andean altitudinal gradients. Diet and vegetation were analyzed using microhistological analysis and point-quadrat transects at six sampling sites, representative of altitudinal phytogeographic belts. The diet included 67 of the 109 species present in the vegetation. Lepus europaeus proved to be an intermediate feeder with a generalist and selective diet. Following the prediction for altitudinal gradients, dietary generalism increased as plant cover and diversity decreased with altitude. Differences in plant phenology and toxins justified changes in food preferences, from shrubs at the summit to grasses at lower altitudes. Seasonal changes in diet diversity were consistent with different hypotheses depending on altitude. The tundra climate at the summit determined a strong phenological decline and food scarcity during winter, when the less diverse diet was more focused on a preferred shrub, following the selective quality hypothesis. With a milder climate at lower altitudes, the winter increase in diet diversity, with inclusion of avoided shrubs, agrees with the food abundance hypothesis. Climate severity, food shortage, plant phenology, and secondary compounds are relevant for explaining the feeding strategy of European hares in these mountain environments.
... The thick solid line represents the standard curve from Van Soest (1965) for sheep. (Monk 1989, Wenger 1997, García et al. 2000, Sponheimer et al. 2002, Kuijper et al. 2004, Thines et al. 2007), (b) rodents (Campbell & MacArthur 1994, Meyer et al. 1996, Wenger 1997, Kenagy et al. 1999, Felicetti et al. 2000, (c) voles and gophers (Loeb et al. 1991, Young Owl & Batzli 1998. The thick solid line represents the standard curve from Van Soest (1965) for sheep. ...
Article
1. It is generally assumed that animals compensate for a declining diet quality with increasing food intake. Differences in the response to decreasing forage quality in herbivores have been postulated particularly between cattle (ruminants) and horses (hindgut fermenters). However, empirical tests for both assumptions in herbivorous mammals are rare. 2. We collected data on voluntary food intake in mammals on forage-only diets and related this to dietary neutral detergent fibre (NDF) content, assuming a nonlinear correlation between these measurements. Generally, the paucity of corresponding data is striking. 3. Elephants and pandas showed very high food intakes that appeared unrelated to dietary fibre content. Only in small rodents, and possibly in rabbits, was an increase in food intake on forages of higher NDF content evident. In particular, other large herbivores, including horses, followed patterns of decreasing intake with increasing forage NDF, also observed in domestic cattle or sheep. 4. For large herbivores, empirical data therefore do not – so far – support the notion that intake is increased in response to declining diet quality. However, data are in accord with the assumption that most large herbivores have an anticipatory strategy of acquiring body reserves when high-quality forage is available, and reducing food intake (and potentially metabolic losses) when only low-quality forage is available. 5. Intake studies in which the influence of digestive strategy on food intake capacity is tested should be designed as long-term studies that outlast an anticipatory strategy and force animals to ingest as much as possible. 6. We suggest that a colonic separation mechanism coupled with coprophagy, in order to minimize metabolic faecal losses, is necessary below a body size threshold where an anticipatory strategy (living off body reserves, migration) is not feasible. Future studies aimed at investigating fine-scale differences, for example between equids and bovids, should focus on non-domesticated species.
... Ambas especies tienen dietas diversas y comparten el consumo de los ítemes herbáceos de mayor cobertura vegetal. Se ha descrito que las liebres responden a una dieta de baja calidad nutricional y alto contenido de fibras, incrementando la ingesta y disminuyendo el tiempo medio de retención del alimento (Kuijper et al. 2004), lo que puede afectar negativamente a otras especies de herbívoros. En este sentido, se ha descrito competencia nutricional intensa de L. europaeus sobre roedores y conejos nativos en Bolivia, Argentina, Brasil y Perú (i.e., Dolichotis spp., Sylvilagus brasiliensis) (Amori & Gippoliti 2003). ...
... Ambas especies tienen dietas diversas y comparten el consumo de los ítemes herbáceos de mayor cobertura vegetal. Se ha descrito que las liebres responden a una dieta de baja calidad nutricional y alto contenido de fibras, incrementando la ingesta y disminuyendo el tiempo medio de retención del alimento (Kuijper et al. 2004), lo que puede afectar negativamente a otras especies de herbívoros. En este sentido, se ha descrito competencia nutricional intensa de L. europaeus sobre roedores y conejos nativos en Bolivia, Argentina, Brasil y Perú (i.e., Dolichotis spp., Sylvilagus brasiliensis) (Amori & Gippoliti 2003). ...
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The native rodents Abrothrix andinus, Phyllotis xanthopygus and the introduced lagomorph Lepus europaeus coexist in the highlands of north-central Chile, where food availability is scarce. We hypothesized that in these environments, the studied species would behave as generalist herbivores and where the diet of native rodents would overlap that of hares greatly. The aim of this study was to quantify feeding habits, amplitude, diet preferences and overlap of these three species through microhistological analysis of fresh faeces. While all three species behaved as herbivore-folivores, L. europaeus showed the largest niche breath. Abrothrix andinus selected all consumed items, while P. xanthopygus and L. europaeus exhibited a more opportunistic consumption food items. The highest diet overlap was observed between native rodents.
... Furthermore, a rapidly growing population of red foxes (Vulpes vulpes L.), that is the result of the success of the aerial rabies vaccinations and less interest in hunting, is also a critical factor influenced on decreasing the brown hare population [3]. The occurrence of brown hares is closely linked with an agricultural landscape, as they are significantly less common in forested areas [4,5]. In addition to human and predators pressure, brown hares as wildlife animals are also subjected to nutritional stress associated with seasonal changes that affect the availability and quality of food, which is reflected in the rate and type of metabolism in the body of the animal [6,7]. ...
Article
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The aim of the study was to evaluate the effect of low concentrations of selenium in the environment on the activity of selected antioxidant enzymes: Se-GSHPx, total GSHPx, SOD, CAT, and GST as well as fatty acid profile in the livers of brown hares during winter and spring. Liver tissues obtained from 20 brown hares collected in the north-eastern Poland in the winter and spring season were analyzed. In the tissue analyzed, a significantly lower level of selenium was noticeable in the spring compared to winter; however, values measured in both seasons indicated a deficiency of this element in the analyzed population of brown hares. There were no differences found that could indicate the influence of Se deficiency on the activity of antioxidant enzymes. The determined activity of antioxidant enzymes and fatty acid composition suggest a negligible impact of the low concentration of Se on the analyzed biochemical parameters of brown hare livers.
... Pellet Kuijper et al. 2004). Using these figures and the rates of pellet recruitment observed in this study, we estimate that vegetation consumption by hares ranges from just 1.4 kg ha -1 year -1 at Turoa to about 188 kg ha -1 year -1 at the Tukino site (Table 3). ...
Article
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Faecal pellet counts are commonly used as indices of lagomorph abundance but uncertainty over variation in decay rates among sites has led to most researchers recommending the use of pellet accumulation rates in previously cleared plots rather than the simpler and quicker method of counting uncleared plots. We use data from cleared and uncleared 0.1-m(2) brown hare pellet plots at six sites in the central North Island of New Zealand to test the reliability of the two methods. The sites varied considerably in hare pellet density and also varied in altitude and rainfall, but the initial cleared count was extremely tightly correlated with the subsequent pellet accumulation rate (r = 0.987) suggesting there is minimal bias from differential decay rates in uncleared plot counts. Our results show that the simpler and less time-consuming uncleared-plot method is an adequate index of hare density across a range of hare densities and climates and is not unduly biased by differential decay rates. This should simplify the work of land managers interested in assessing relative abundance. At one site (the area round Manson Hut on the Kaweka Range) where the plots were followed for a year in a variety of habitat types, there were strong seasonal changes in hare abundance (peaking in summer and declining through winter), and strong habitat preferences for exotic grasslands and grassland-herbfield mixes, while pure herbfield, and particularly rocky scree and southern beech forest were not favoured. We estimated that based on published defecation rates of hares, population densities at our six sites varied from 0.03 to 3.93 hares per hectare and that they consumed between 1.4 and 188 kg ha(-1) of biomass annually.
... Condensed tannins can reduce the digestibility of protein by mammalian herbivores (Robbins 2001). However, a reduction in dietary digestible protein can cause compensatory feeding that increases the per capita daily intake of plant biomass by mammalian herbivores, especially ceacalids that rapidly pass plant biomass through the gut (Pehrson and Lindlöf 1984, Cheeke 1987, Kuijper et al. 2004). If the condensed tannins of non-resin birches (Julkunen-Tiitto et al. 1996) were to cause compensatory feeding, this would increase the rate of browsing damage to non-resin birches. ...
Article
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Global climate warming is projected to promote the increase of woody plants, especially shrubs, in arctic tundra. Many factors may affect the extent of this increase, including browsing by mammals. We hypothesize that across the Arctic the effect of browsing will vary because of regional variation in antibrowsing chemical defense. Using birch (Betula) as a case study, we propose that browsing is unlikely to retard birch expansion in the region extending eastward from the Lena River in central Siberia across Beringia and the continental tundra of central and eastern Canada where the more effectively defended resin birches predominate. Browsing is more likely to retard birch expansion in tundra west of the Lena to Fennoscandia, Iceland, Greenland and South Baffin Island where the less effectively defended non-resin birches predominate. Evidence from the literature supports this hypothesis. We further suggest that the effect of warming on the supply of plant-available nitrogen will not significantly change either this pan-Arctic pattern of variation in antibrowsing defense or the resultant effect that browsing has on birch expansion in tundra. However, within central and east Beringia warming-caused increases in plant-available nitrogen combined with wildfire could initiate amplifying feedback loops that could accelerate shrubification of tundra by the more effectively defended resin birches. This accelerated shrubification of tundra by resin birch, if extensive, could reduce the food supply of caribou causing population declines. We conclude with a brief discussion of modeling methods that show promise in projecting invasion of tundra by woody plants.
... We can hence conclude that the rabbits selected the forage with the highest nutritional quality. This preference for high quality forage has been suggested for rabbits (KUIJPER et al., 2004; RÖDEL, 2005) and also for other relatively small mammal herbivores, e.g. small ruminants (WILMSHURST et al., 2000) and mountain hares (Lepus timidus (Linnaeus, 1758)) (LINDLÖF et al., 1974). ...
Article
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When foraging, small mammalian herbivores do not show a preference for the forage with the highest biomass, which can be explained by several hypotheses (e.g. antipredator considerations, more difficult handling of tall swards and/or the higher nutritional quality of shorter grasses). We tested the ability of rabbits to discriminate between plants of different nutritional value and whether they prefer the most nutritious. A feeding trial in which rabbits (Oryctolagus cuniculus (Linnaeus, 1758)) were offered two different types of grasses (fertilised and unfertilised) was executed under experimental conditions. The rabbits pre- ferred the grasses with the highest protein percentage, when conditions were controlled for sward height/plant biomass. This obser- vation is equivalent to results obtained in geese and provides experimental evidence about the capability of rabbits to select for plants with the highest nutritional quality.
... Ambas especies tienen dietas diversas y comparten el consumo de los ítemes herbáceos de mayor cobertura vegetal. Se ha descrito que las liebres responden a una dieta de baja calidad nutricional y alto contenido de fibras, incrementando la ingesta y disminuyendo el tiempo medio de retención del alimento (Kuijper et al. 2004), lo que puede afectar negativamente a otras especies de herbívoros. En este sentido, se ha descrito competencia nutricional intensa de L. europaeus sobre roedores y conejos nativos en Bolivia, Argentina, Brasil y Perú (i.e., Dolichotis spp., Sylvilagus brasiliensis) (Amori & Gippoliti 2003). ...
Article
Full-text available
The native rodents Abrothrix andinus, Phyllotis xanthopygus and the introduced lagomorph Lepus europaeus coexist in the highlands of north-central Chile, where food availability is scarce. We hypothesized that in these environments, the studied species would behave as generalist herbivores and where the diet of native rodents would overlap that of hares greatly. The aim of this study was to quantify feeding habits, amplitude, diet preferences and overlap of these three species through microhistological analysis of fresh faeces. While all three species behaved as herbivore-folivores, L. europaeus showed the largest niche breath. Abrothrix andinus selected all consumed items, while P. xanthopygus and L. europaeus exhibited a more opportunistic consumption food items. The highest diet overlap was observed between native rodents.
... It is a habitat generalist species, highly mobile, adaptable, and it has colonized and invaded different habitats, ranging from meadows to scrubland, steppe, forest clearings, high mountains, and farms (Bonino 1995; Vázquez 2002). This species is able to use low-quality food resources, with high fiber content, because it increases ingestion and decreases retention time (Kuijper et al. 2004). In northern Patagonia, the European hare is considered a competitor of domestic herbivores such as sheep and goats (Bonino et al. 1986; Bonino 1999 ). ...
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As medium-sized herbivores, the exotic Lepus europaeus (European hare) and the native Dolichotis pata- gonum (mara) have been considered ecological equivalents. These species coexist in Ischigualasto Provincial Park, a hyper-arid ecosystem with scarce food resources. Our ob- jective was to evaluate diet composition, relationship be- tween diets and food availability, and trophic relationships between both herbivores. Collection of feces and vegetation sampling were made in the Mesquite woodland community. Diet composition was analyzed by microhistological analy- sis of feces. In both seasons, shrub species represented the most abundant cover type in the area, and annual forbs and grasses appeared in the wet season. Herbivores showed similar dietary ecology: shrubs were the main food items along the year, showing a higher plasticity compared to their diets in other ecosystems, where they selected mostly grasses. The mara selected shrubs such as Atriplex sp. and Prosopis torquata, whereas the European hare selected Cyclolepis genistoides, Atriplex sp., and Bulnesia retama. During the wet season, both herbivores supplemented their diets with grasses and annual forbs. In the dry season, there was increased consumption of cacti, such as Tephrocactus sp. The mara and the European hare are likely close ecological equivalents, in terms of dietary similarity, and they showed strong dietary overlap across the dry season (over 60 %). Thus, we can assume the existence of a potential trophic competition between mara and European hare, especially during the season when food resources are scarce. These results can be important for the management of drylands in South America, where populations of threatened herbivorous species, such as the mara, coexist with exotic animals, sharing spatial and trophic resources even in protected areas.
... The thick solid line represents the standard curve from Van Soest (1965) for sheep. (Monk 1989, Wenger 1997, García et al. 2000, Sponheimer et al. 2002, Kuijper et al. 2004, Thines et al. 2007), (b) rodents (Campbell & MacArthur 1994, Meyer et al. 1996, Wenger 1997, Kenagy et al. 1999, Felicetti et al. 2000, (c) voles and gophers (Loeb et al. 1991, Young Owl & Batzli 1998. The thick solid line represents the standard curve from Van Soest (1965) for sheep. ...
Article
1.It is generally assumed that animals compensate for a declining diet quality with increasing food intake. Differences in the response to decreasing forage quality in herbivores have been postulated particularly between cattle (ruminants) and horses (hindgut fermenters). However, empirical tests for both assumptions in herbivorous mammals are rare. 2.We collected data on voluntary food intake in mammals on forage-only diets and related this to dietary neutral detergent fibre (NDF) content, assuming a nonlinear correlation between these measurements. Generally, the paucity of corresponding data is striking. 3.Elephants and pandas showed very high food intakes that appeared unrelated to dietary fibre content. Only in small rodents, and possibly in rabbits, was an increase in food intake on forages of higher NDF content evident. In particular, other large herbivores, including horses, followed patterns of decreasing intake with increasing forage NDF, also observed in domestic cattle or sheep. 4.For large herbivores, empirical data therefore do not – so far – support the notion that intake is increased in response to declining diet quality. However, data are in accord with the assumption that most large herbivores have an anticipatory strategy of acquiring body reserves when high-quality forage is available, and reducing food intake (and potentially metabolic losses) when only low-quality forage is available. 5.Intake studies in which the influence of digestive strategy on food intake capacity is tested should be designed as long-term studies that outlast an anticipatory strategy and force animals to ingest as much as possible. 6.We suggest that a colonic separation mechanism coupled with coprophagy, in order to minimize metabolic faecal losses, is necessary below a body size threshold where an anticipatory strategy (living off body reserves, migration) is not feasible. Future studies aimed at investigating fine-scale differences, for example between equids and bovids, should focus on non-domesticated species.
... Hirakawa (2001) has recognised that leporids re-ingest both caecotrophs and daytime hard faeces, and so that portion of a marker excreted in the early daytime hard faeces could be delayed by a second passage. An interspecific difference in the degree of coprophagy would influence comparisons of rates of marker clearance, and the finding recorded by Kuijper et al. (2004) that far fewer caecotrophs were found in the stomachs of hares compared with rabbits, together with the inter-specific difference in the availability of hard faeces for daylight collection in my study, suggest less re-passaging of digesta by the hare. However, whether during one passage or two, the polypropylene markers gave an indication of the time during which the ingesta was exposed to the digestive processes. ...
Article
The European hare Lepus europaeus and the European rabbit Oryctolagus cuniculus are sympatric in many areas of the world. They are medium-sized herbage-feeding lagomorphs and trophic competitors. Both species feed on twigs under extreme and perhaps limiting conditions. To ascertain whether fine niche separation mechanisms occur, several comparative tests of digestive function were undertaken on samples of animals drawn from sympatric populations. The weights of the organs constituting the abdominal alimentary canal, the rates of passage and the extent of trituration of dietary markers intended to mimic twigs, and the digestibility of fibre, protein, and fat were compared. Both the stomach and the caecum of the hare were significantly smaller as a proportion of body weight, and this would result in a higher power-weight ratio. Both species rapidly passed the digestive marker, but passage was significantly faster in the hare. The rabbit chewed twig-like material with a scissor cutting and crushing action, whereas the action of the hare included a stripping action that would more efficiently access soluble carbohydrates stored in vascular rays. Both species were poor digesters of fibre, but digestibility of hemicelluloses was significantly greater in the rabbit. The faeces of both species of lagomorphs contain nutrients that can be attractive to more efficient fermenters of plant fibre, and consumption of those faeces may confound lagomorph population surveys that rely on dung counts. (c) 2007 Deutsche Gesellschaft fur Saugetierkunde. Published by Elsevier GrnbH. All rights reserved.
... Fiber digestibility of pygmy rabbits and cottontails in our study was generally consistent with that of European rabbits (O. cuniculus; Kuijper et al., 2004) and snowshoe hares (Holter et al., 1974). ...
Article
Sagebrush (Artemisia tridentata) comprises up to 99% of the winter and 50% of the summer diets of pygmy rabbits (Brachylagus idahoensis). Few animals specialize on such plants as sagebrush, which contain high levels of plant chemicals that can be toxic. We investigated the nutritional requirements of pygmy rabbits and their ability and propensity to consume sagebrush alone and as part of a mixed diet. We compared diet choices of pygmy rabbits with that of a generalist forager, the eastern cottontail (Sylvilagus floridanus). Pygmy rabbits had a moderately low nitrogen requirement (306.5 mg N/kg(0.75)/d), but a relatively high energy requirement, needing 750.8 kJ digestible energy/kg(0.75)/d to maintain their body mass while residing in small cages. They digested fiber in pelleted diets similarly to other small hindgut fermenters, but both cottontails and pygmy rabbits digested the fiber in sagebrush better than expected based on its indigestible acid detergent lignin content. Pygmy rabbits consumed more sagebrush than cottontails, regardless of the amount and nutritional quality of supplemental pellets provided. When consuming sagebrush alone, they ate barely enough to meet their energy requirements, whereas cottontails ate only enough sagebrush to meet 67% of theirs. Both rabbit species ate more sagebrush as the quality and quantity of supplemental pellets declined, and more greenhouse-grown sagebrush than sagebrush grown outside. Urine was more acidic when consuming sagebrush than when consuming pellets, indicating detoxification by the liver. Pygmy rabbits do not require sagebrush to survive, but seem to tolerate terpenes and other plant chemicals in sagebrush better than cottontails do.
... It is noteworthy that O. cuniculus on nearby heaths appear to select seeds of plants with unpalatable foliage (Pakeman et al. 1999). Lepus europaeus dispersed fewer seeds and species than O. cuniculus, most likely because O. cuniculus select higher quality forage, including flower and seed heads, while L. europaeus browses to a greater extent on shrub foliage (Kuijper et al. 2004). ...
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Endozochorous seed dispersal by herbivores can affect plant spatial dynamics and macroecological patterns. We have investigated the number and species composition of viable seeds deposited in faeces of a full guild of macroherbivores (four deer and two lagomorph species) in a forest in eastern Britain. One hundred and one plant species germinated from faecal pellet material, 85 of which were among the 247 vascular plant species recorded in the forest. However, three species - Chenopodium album, Urtica dioica and Agrostis stolonifera - comprised 56% of the seedlings recorded. Of the species recorded in faecal samples, 36% had no recognised dispersal mechanism, while very few (7%) were adapted to endozoochorous dispersal (fleshy fruit or nut). The number of species dispersed by the herbivores was ranked Cervus elaphus and Dama dama (96) > Capreolus capreolus (40) > Muntiacus reevesi (31) > Oryctolagus cuniculus (21) > Lepus europaeus (19), with the other taxa dispersing subsets of those dispersed by C. elpahus and D. dama. The invasive M. reevesi deposited the fewest seeds per gram of faecal pellet material (0.4 g(-1)) and hence fewer seeds per unit area than other deer species despite their numerical dominance, while C. elaphus/D. dama deposited the most (0.43 seeds m(-2) year(-1)). Due to differences in faecal seed density among habitats combined with the ranging behaviour of animals, more seeds were deposited in younger stands, enhancing the potential contribution of macroherbivores to population persistence by dispersal and colonisation in a successional mosaic.
Thesis
This thesis focuses on the positive interaction ‘feeding facilitation’ which is predicted to occur in assemblages of large and small(er) herbivore species. The main hypothesis of the research is that introduced large herbivores facilitate rabbits (medium-sized herbivores) by modification of the vegetation. This modification involves creating short swards, creating denser (more productive) swards, creating swards that have a high food quality for rabbits and influencing vegetation composition. By conducting field observation, semi-controlled field experiments up to entirely controlled feeding experiments, we tried to test several aspects of the main hypothesis. From our results, we conclude that the main hypothesis could not be affirmed, although some causal mechanisms of feeding facilitation have been affirmed. We suggest that feeding facilitation is not necessarily absent, but is hard to detect or is not present under particular conditions. Experimental research is needed for further unravelling causal mechanisms about feeding facilitation and alternative approaches, while field observations remain necessary to gain insight into other variables (e.g. habitat productivity, predators, food accessibility, seasonality) that may shift the balance between the occurrence and absence of feeding facilitation.
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Summary • Characteristics of internal seed dispersal (endozoochory) by European Brown Hares were compared with similar dispersal by Brent Geese. Hares deposited more seeds of mid-successional, perennial, high-marsh species than did geese, which deposited more seeds of early successional, annual, low-marsh species. • Seed survival and germination of salt-marsh species were higher after ingestion and passage through the digestive system of hares compared with geese. Both hares and geese had a negative effect on the percentage of seeds that germinated in comparison with uningested seeds. • Small herbivores (hares and geese) dispersed two orders of magnitude fewer seeds than those dispersed by tidal water. • Thus these herbivores are not likely to be important filters (constraints) in community assembly at this salt-marsh site on a coastal island in the Netherlands. Functional Ecology (2005) 19, 665 –673 doi: 10.1111/j.1365-2435.2005.01011.x
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In agrocenoses and forest borders, for the greater part of the year, the trophic niches of hare and rabbit overlapped. In both localities quantitative food composition was similar in 69% of cases; qualitative food composition was similar in 78% in the agrocenosis and in 49% in the highlands. -from Author
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To estimate the contribution of coprophagy to protein intake, we observed the behavior, particularly that associated with coprophagy, in adult and young captive nutrias (experiment 1), and analyzed chemical composition and amino acid composition, including di-aminopimeric acid (DAP), an indication of bacterial-deprived protein, of soft feces, entire hard feces, and the black part and green part of hard feces (experiment 2). Nutrias practiced coprophagy 48 times per 24 h in adults, and 28 times in young animals, which not only had a 24-h rhythm but also had 1-h or 2-h short-term rhythms. Nutrias ingested food and drank water vigorously after sunset, following which they practiced co-prophagy from midnight to morning, before lying down for much of the day. When coprophagy was prevented we sampled soft feces, produced from midnight to noon, which had high (P < 0.05) concentration of crude protein (CP), DAP on a dry matter (DM) basis and 13 amino acids on a 16 g N basis than hard feces, and had a low (P < 0.05) content of acid detergent ®ber (ADF). CP was greater in the black part than the green part of hard feces (P < 0.05) although ADF was less (P < 0.05). The chemical composition of the black part of hard feces was not signi®cantly di€erent from that of soft feces. The dry weight of soft feces excreted in experiment 1 was 34.5 g and 9.7 g DM per 24 h in adult and young animals, respectively. Using this value, the contribution of soft feces to CP intake in adult nutrias was estimated as 16%, superior to that obtained in rabbits for a diet with similar ADF concentration. To Met and Lys intake the contribution of soft feces was 26% and 19%, respectively in adult animals. These results suggest that coprophagy is quite an e€ective manner for nutrias to ingest extra protein.
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Allometric considerations have suggested that small herbivores are inefficient at or incapable of extracting energy from the microbial fermentation of structural carbohydrates. This notion is at odds with accumulating empirical evidence that demonstrates well-developed fiber digestion abilities for a number of small rodent genera. To examine the apparent inconsistency, we have constructed a model of plant fiber utilization tailored specifically for hindgut fermenters. Computer simulations provide estimates of fiber and overall dry-matter digestibilities as a function of body size, energy demand, and diet. Our calculations indicate that small mammals can obtain significant benefit from fiber fermentation, especially at moderate fiber levels. Comparisons with literature data are in general agreement, although fiber digestion abilities are still underestimated for the smallest animals. In an empirical test of the model, Neotoma obtained over 21% of their digestible energy solely from the microbial fermentation of plant fiber. We also observed an interesting pattern of allometric sorting predicted by the model. Smaller woodrats significantly reduced the fiber content of their diet, a behavior presumably reflecting energy limitations.
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The effect of fibre on rate of passage, control of gut flora, caecal fermentation, and performance of rabbits has been reviewed. Both physical and chemical characteristics of fibre affect these variables. An increase of the proportion of fine particles (< 0.315 mm) increases NDF digestibility, acidity and weight of caecal contents, fermentation time and microbial protein recycled through caecotrophy, but decreases rate of passage and intake. A minimal proportion of large particles (> 1.25 mm) is also required to allow an adequate turnover rate of caecal contents, and then to maximise microbial efficiency. The fraction of pectin components (arabinose, galactose and uronic acids) of cell walls accounts for most of the total fibre digestibility. An increase in the dietary concentration of these constituents leads to an increase of acidity of caecal contents and microbial protein recycled through caecotrophy. Dietary lignin content is negatively related to energy digestibility and also to the accumulation of digesta in the caecum. Both excessive and insufficient dietary fibre levels lead to an impairment of rabbit's performance. Practical recommendations on optimal fibre concentrations and minimal proportion of large particles are given for breeding does, fattening rabbits and mixed diets. (C)Elsevier/Inra.
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Barnacle geese (Branta leucopsis) wintering on the island of Schiermonnikoog in the Netherlands abruptly switch all their foraging activities from a dairy pasture (a polder) to an adjacent salt-marsh during the early spring. We present evidence to show that this shift is related to changes in the quality of the diet available in these different habitats. Barnacle geese shift from polder to salt-marsh at the precise time that these are equal in dietary protein availability, which occurs as the food plants on the salt-marsh undergo a sudden spring growth. The dairy pasture undergoes its own spring growth shortly afterwards, and more dietary protein is available there for the rest of the year. We suggest that the salt-marsh is a more preferred habitat, but that low dietary protein during the winter prevents its use by barnacle geese. We hypothesize that the salt-marsh may be more preferred due to a lower level of disturbance which permits geese to graze more slowly, improving the utilization of food plants.
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Field metabolic rates (FMR) measured using doubly labeled water, of 23 species of eutherian mammals, 13 species of marsupial mammals, and 25 species of birds were summarized and analyzed allometrically. FMR is strongly correlated with body mass in each of these groups. FMR scales differently than does basal or standard metabolic rate in eutherians (FMR slope=0.81) and marsupials (0.58), but not in birds (0.64 overall, but 0.75 in passerines and 0.75 in all other birds). Medium-sized (240-550 g) eutherians, marsupials, and birds have similar FMRs; these are approx 17 times as high as FMRs of like-sized ectothermic vertebrates such as iguanid lizards. For endothermic vertebrates, the energy cost of surviving in nature is enormous compared with that for ectotherms. Within eutherians, marsupials or birds, FMR scales differently for the following subgroups: rodents, passerine birds, herbivorous eutherians, herbivorous marsupials, desert eutherians, desert birds, and seabirds. Equations are given for use in predicting daily and annual FMR and food requirement of a species of terrestrial vertebrate, given its body mass.-from Author
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The influence of fiber source on fiber digestion and mean retention time was investigated. Six fibrous feedstuffs with wide differences in chemical composition and particle size were selected: paprika meal, olive leaves, alfalfa hay, soybean hulls, sodium hydroxide-treated barley straw, and sunflower hulls. Six diets were formulated to contain one of these ingredients as the sole source of fiber. To avoid nutrient imbalances, fiber sources were supplemented with different proportions of a concentrate free of fiber based on soy protein isolate, wheat flour, lard, and a vitamin and mineral mix to obtain diets containing at least 18.5% CP and 5% starch. Fecal apparent digestibility of nonstarch polysaccharides (NSPd) and its monomers, NDF, NDF-ADL, and ADF-ADL, were determined using four New Zealand White x California growing rabbits per diet. Total, ileorectal, and cecal mean retention times (tMRT, i-rMRT, and cMRT, respectively) were determined for diets based on paprika meal, olive leaves, soybean hulls, and sunflower hulls in 16 does (four per diet) fitted with T-cannulas at the terminal ileum. In both trials, DMI was negatively correlated with the proportion of fine particles (FP: < .315 mm) and positively correlated with the proportion of large particles (LP: > 1.25 mm) (P < .01). Stepwise regression analysis showed that FP was the dietary characteristic best related to digestibilities of NSP, uronic acids, glucose and NDF, tMRT, and cMRT (P < .001), showing a positive correlation with these variables. In all these cases, this procedure selected the proportion of large particles as a second variable in the model. Degree of lignification of NDF, considering lignin as the difference between ADL and acid detergent cutin, was only included as the third variable for the model of NDF digestibility. Digestibility of NSP was positively correlated with those of NDF, NDF-ADL, and ADF-ADL (r = .82, .87 and .85, respectively, P < .001); the latter was also highly correlated with the digestibility of the glucose included in the NSP fraction (r = .86; P < .001). Cecal mean retention time accounted for 63% of average tMRT, for most of the variability in tMRT (r = .99; P < .001), and was positively related to NSPd (r = .89; P < .001). From these results, we conclude that particle size is a major factor affecting fiber digestion efficiency, rate of passage, and feed intake in rabbits.
Chapter
However well the anatomy of the gastro-intestinal tracts of a wide range of mammals is described and quantified, there can be no real explanation of observed patterns without consideration of the mechanical and chemical properties of the food consumed, and of the digestive stages involved in its processing. This book aims to integrate findings from the many different types of investigations of mammalian digestive systems into a coherent whole. Using the themes of food, form and function, researchers discuss models of digestive processes, linking this with evolutionary aspects of food utilisation. Macroscopic and ultrastructural studies of the gastro-intestinal tract are also presented, as are physiological, ecological and biochemical aspects of the digestion of different food types. The book ends with an integrative chapter, bringing together the themes running through the earlier sections.
Article
Techniques for evaluating fecal analysis were investigated using examples from studies on European waterfowl. Visual classification of droppings in the field on the basis of color or the presence of macroscopically identifiable material gave a good indication of the use of particular foods. Quantitative microscopic analysis techniques were investigated in detail. Identification of epidermis in waterfowl fecal material posed no great problems with relatively small numbers of plant species. Point sampling gives an accurate area measurement, and corrections can be made for differential fragmentation of plants and for differences in weight/surface area ratio of food items. Much work is needed before diet analysis can be accurately related to the energy budget of wild birds.
Article
(1) The foraging activities of a large flock of barnacle geese (Branta leucopsis Bechstein) wintering on the West Frisian island of Schiermonnikoog were monitored during the spring of 1978. On fourteen sites distributed over the grazing area we measured grazing intensity, plant species presence and abundance, standing cropherbage accumulation, and crude protein content of Festuca rubra L., the primary food plant of barnacle geese. Two of the sites had nitrogen fertilizer applied to them. (2) Almost all the sites were grazed repeatedly, but barnacle geese utilized different areas with different mtensities. In spite of this, the standing crops did not differ between sites, and the standing crop on all the sites remained relatively constant throughout the spring, including the sites that received a nitrogen fertilizer. (3) Areas with the highest rates of herbage accumulation were grazed most intensely. Barnacle geese displayed no consistent preference for other site characteristics. (4) High levels of protein in Festuca rubra were a direct result of repeated grazing of sites by barnacle geese, and the consequent sustained regeneration of young, protein-rich plant tissues.
Article
1. The range size of adult female mountain hares (Lepus timidus L.) and European rabbits (Oryctolagus cuniculus L.), occupying a landscape composed of moorland, young forest and upland pasture, were studied by radio-telemetry. The factors that affect range size of the two species were identified and interpreted with regard to their respective feeding strategies; mountain hares are summer grazers that browse in winter whereas rabbits eat grasses throughout the year. 2. Individual mountain hares were classified as 'moorland', 'forest' or 'pasture' hares, and individual rabbits were classified as 'forest', 'pasture' or 'mixture' rabbits according to the frequency with which they used each habitat. Home-range size of both species was highly variable with a mean area (and standard deviation) of 22.2 ha (SD = 18.5) for hares and 6.3 ha (SD = 3.9) for rabbits. 3. Home-range size of mountain hares varied according to habitat and season. There was a negative correlation between home-range size and the available green biomass of grass. This suggests that the large home ranges of 'moorland' hares during the breeding and post-breeding seasons may have been a consequence of low food availability. 4. Home-range size of rabbits also varied according to habitat and season, but was not clearly associated with food availability, feeding strategy or social behaviour. 5. In the early years following planting, extensive afforestation of upland moorlands is unlikely to affect mountain hare and rabbit populations if an abundant ground flora is available. Individuals of both species may even remain entirely within the plantation using very small home-ranges. However, single age plantations would have to be restructured to increase the age diversity and hence the availability of suitable habitats for long-term maintenance of viable populations of mountain hares.
Article
Several methods are available for estimating the proportion, by area, of leaf cuticles of a given species in a rumen or fecal sample. They all involve choosing a line transect on a microscope slide and noting the cuticles that intercept the line. In this paper estimates based on lengths or squared lengths of intercept are compared. When there are several transects a jackknife method of combining the data is recommended. Simulation experiments indicate that this method provides satisfactory estimates, as far as bias and precision are concerned.
Article
1. Mountain hares (Lepus timidus L.) are summer grazers that switch to browse in winter, while rabbits (Oryctolagus cuniculus L.) eat mostly grasses throughout the year. These different feeding strategies may underlie seasonal patterns of habitat selection by the two species. 2. In this study the habitat utilization by adult female mountain hares and adult female rabbits was studied by radio-tracking in a habitat composed of open moorland, upland pasture and young forestry plantation with an abundant ground flora. The selection of feeding habitats by populations of both species was assessed by faecal counts within the same landscape. 3. Despite the common perception that mountain hares in Britain are associated with moorland, open moorland was avoided by the radio-tracked adult female mountain hares relative to its availability. Throughout the year, the radio-tracked hares preferred the forest and pasture habitats relative to availability. Only seven of the 20 hares radio-tracked were ever located on the moorland, which would suggest that the presence of moorland is not a prerequisite for the presence of mountain hares. 4. Radio-tracked adult female rabbits utilized the habitats in proportion to their availability. 5. Counts of faecal pellets indicated that utilization of forestry plantations by both species declined as a spruce forest matures although hare populations persist in mature pine plantations with an abundant ground flora. 6. Mountain hares appear to be more adaptable than rabbits in their use of the habitats in this study, a behavioural tactic underpinned by their flexible feeding strategy. Rabbit populations would persist in areas following afforestation, especially where upland pastures are in close proximity to woodland and mountain hares would be capable of exploiting many of the new habitats that are created, at least in the early years of forest development.
Article
Structural carbohydrates in plants are hard to digest by the animals that eat them, and they ham-per digestion of the content of the plant cells. The efficiency of digestion by herbivores is, there-fore, closely related to both the retention time of the food in the digestive tract and the propor-tion of cell walls in the food. This study examined food digestion by free-living barnacle geese Branta leucopsis in relation to food quality and retention time. At the range of short winter days (8 h light) to continuous light in the Arctic breeding area, the geese increased the food retention time 2-4-fold. Low throughput rates in summer resulted in enhanced digestion of the food. The organic matter digestibility of graminoids, corrected for dif-ferences in protein content, was 37% in winter, and 56% in summer. Enhanced digestion allowed the geese to extend their food spectrum by exploiting mosses (bryophytes), which are, at least temporarily, the only plants available in the summer range. The disadvantage of prolonged food retention time is the concurrent decrease of the amount of food that can be processed per time unit. The digestion pattern in the successive periods of the year can be regarded as an adaptation to differences in energy needs, and to differences in the selective force acting on the geese to mini-mize feeding time.
Article
The objective of this study was to determine the effect of low-quality diets and increased energy needs on nutritional aspects of the prairie vole (Microtus ochrogaster). In the laboratory, high-fiber diets were correlated with higher rates of food intake and larger hindguts, as well as a lower digestibility of dry matter, cell solubles, energy, and nitrogen, but higher fiber digestibilities than low-fiber diets. Acclimation to cold temperatures resulted in higher rates of food intake than acclimation to warm temperatures. In addition, the size of the small intestine and cecum increased in response to cold acclimation. Although increases in intake, resulting from acclimation to cold temperatures, did not result in changes in the digestibility of the diet or dietary components, they did result in decreases in the dietary turnover time. Thus, increases in transit rate through the gut do not necessarily result in declines in the amount of energy extracted per gram of food ingested. More energy per unit time, however, can be extracted from the diet, perhaps because of increases in the size of the gut allowing maintenance of digestibilities and energy need in the face of higher transit times.
Article
The food of the mountain hare Lepus timidus scoticus Hilzheimer was studied by means of stomach analysis, and the use of hare-proof enclosures on moorland; and grazing habits by regular visits to a study area in Banffshire. The main grazing period is at night, varying seasonally in relation to sunset and sunrise. During the day grazing may occur sporadically, or intensively if before rain or during heavy snow cover. Refection, that is the production of soft faeces which are swallowed directly from the anus, occurs during the period between the end of morning grazing and the start of the next evening's grazing. On ground covered with young ling Calluna vulgaris, mountain hares removed 27 per cent of the vegetation (dry weight) from the control plot, and on cotton grass Eriophorum spp. ground, 20 per cent and 24 per cent from control plots. In three of the eight enclosures used, on various herbage complexes, there was no appreciable difference from the control plots. Analysis of the dried stomach contents of forty-seven mountain hares, collected at monthly intervals over a period of a year, showed that ling formed 90 per cent of the winter and about half the summer diet. Cotton grass made up about a tenth of the winter and a fifth of the summer diet, while grass species, present as a trace in winter stomachs, increased to a quarter of the total food in summer. Food plants of particular importance during storms and complete snow cover may be missed by the method of sampling or the use of enclosures. The extent to which hares grazed these plants was verified by visits during snow. Gorse Ulex europaeus, juniper Juniperis communis and soft rush Juncus effusus, are among the chief food plants in storms and snow cover.
Article
The paper deals with caecotrophy in captive Mountain hares fed normal hare browse. The daily and seasonal patterns of hard and soft faeces excretion are described. Chemical analyses of the faeces have also been performed.
Article
Both domestic and wild-type European Rabbits Oryctolagus cuniculus (L.) have been liberated on islands all over the world for a variety of reasons: for sport, to farm for meat or fur, as food for other animals or bait for lobster pots, to control vegetation, amuse tourists, and even to conserve representative populations from myxomatosis. Results of these introductions have likewise varied, from complete failure to densities so high as to denude completely the island of vegetation and soil. Some interesting populations have survived remarkably adverse conditions for up to 100 years before becoming extinct. Others provide natural experiments on the effects of introduced predators, competitors, or diseases like myxomatosis. We list 800 islands or island groups on which Rabbits have been liberated, giving name, location, latitude and longitude, and area, followed by date of introduction, type of rabbit, population changes, present status, and effects of the Rabbits on their environment. For many islands information is still meagre or completely lacking; we hope that this provisional list will stimulate readers to send us additions and corrections, or to publish the data themselves.
Article
Leporids have long been known to reingest soft faeces. However, it was recently found that they regularly reingest hard faeces, too. During the daytime, both soft and hard faeces are defecated and all of the faeces are reingested. Excreted at night are the hard faeces, which are normally discarded but reingested in starvation. The separation mechanism in the proximal colon, which diverts fine particles into the caecum and thus only passes large food particles, produces hard faeces. When the mechanism ceases acting, fermented caecal materials are excreted as soft faeces. The reingestion of soft faeces, rich in vitamins and microbial proteins, is physiologically imperative. Hard faeces are basically a refuse, but their thorough mastication at reingestion reduces poorly digestible large particles to fine ones good for fermentation. The regular reingestion of daytime hard faeces thus promotes food digestibility. The temporary use of night-time hard faeces allows leporids to do without food for some time. It thus gives leporids behavioural flexibility and thereby an ecological advantage. Reingestion is also known in other small- to medium-sized herbivores, which are all caecal fermenters. Morphological differentiation between faeces is reported only in larger species, but all ingested faeces are found to be richer in nutrients than discarded ones. Thus a separation mechanism is probably present in all reingesting species. Reingestion activity is deeply related to other behavioural and physiological traits of small mammalian herbivores, hence its study is important to understanding of their ecology and biology. Leporids are the largest of the reingesting species except for the semi-aquatic Coypu, and reingestion by leporids is certainly the most sophisticated. This development of a reingestion-involved digestive system has probably brought them to their present niche, as terrestrial medium-sized generalist mammalian herbivores, and consequently made their characteristic hide-and-run lifeforms by exposing them to a strong predation pressure.
Article
I address the selection of plants with different characteristics by herbivores of different body sizes by incorporating allometric relationships for herbivore foraging into optimal foraging models developed for herbivores. Herbivores may use two criteria in maximizing their nutritional intake when confronted with a range of food resources: a minimum digestibility and a minimum cropping rate. Minimum digestibility should depend on plant chemical characteristics and minimum cropping rate should depend on the density of plant items and their size (mass). If herbivores do select for these plant characteristics, then herbivores of different body sizes should select different ranges of these characteristics due to allometric relationships in digestive physiology, cropping ability and nutritional demands. This selectivity follows a regular pattern such that a herbivore of each body size can exclusively utilize some plants, while it must share other plants with herbivores of other body sizes. I empirically test this hypothesis of herbivore diet selectivity and the pattern of resource use that it produces in the field and experimentally. The findings have important implications for competition among herbivores and their population and community ecology. Furthermore, the results may have general applicability to other types of foragers, with general implications for how biodiversity is influenced.
Article
We examined digestibility of dry matter, nutrients, and fiber, and food intake, metabolic fecal losses, weight change, and gut size of pocket gophers (Thomomys bottae) in relation to diet quality in the laboratory. Pocket gophers were maintained for 15–20 days on one of seven diets which contained from 18% to 56% neutral detergent fiber (NDF). NDF content of the diet was an excellent predictor of diet quality. Digestibility of dry matter, NDF, and nitrogen all decreased with increasing NDF content of the diet. In general, pocket gophers compensated for low diet quality by increasing dry matter intake, but those given high quality forage before the lowest quality diet reduced their intake. Thus, the response of pocket gophers to low quality diets may depend on their body condition. Because increased food intake resulted in increased total metabolic fecal losses and metabolic fecal nitrogen losses, decreasing food intake on low-quality diets may be advantageous. A further response of pocket gophers to decreased food quality was an increase in size of cecum and large intestine, suggesting that fermentation of cell walls became increasingly important as diet quality decreased.
Article
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
Article
Allometric considerations suggest that small mammals should be unable to eat highly fibrous diets. A combination of the selective and more rapid passage of fibrous material through the gut, together with changes in gut capacity when energy requirements increase, may allow small mammals to escape these allometric constraints. Recent evidence that birds can absorb essential amino acids from the caecum (which has hitherto been considered insignificant in mammals) suggests that birds and mammals have evolved very different ways to be a herbivore.
Article
Seventy-five New Zealand White x Californian rabbits were used to study the influence of the chemical composition of lucerne hay on caecal and caecotrophy characteristics. Five lucerne hays varying in chemical composition were ground and formed into pellets. These were the sole form of nutrition during the experiment. The type of lucerne hay did not affect caecal volatile fatty acid concentration, pattern of fermentation or pH. However, the caecal ammonia concentration decreased linearly (by 30% between extreme diets, P = 0.002) when dietary fibre proportion increased. The weight of caecum and caecal contents increased linearly (by 12%, P = 0.010, and 35%, P < 0.001, respectively, between extreme diets) with dietary fibre proportion. Soft faeces excretion and contribution of soft faeces to dry matter intake were not influenced by the type of lucerne hay. The proportion of caecal content that appeared daily as soft faeces and the total and microbial nitrogen concentrations in soft faeces were higher (42, 14 and 39%, respectively) for the lucerne hay with the lowest dietary fibre proportion than for the average of the other hays.
1. Digestibility of fibre was higher in guinea-pigs than in rabbits, however, the digestibility of hemicellulose fraction containing agar was similar in both animals. 2. The digestibility of fibre of a fine particle diet was higher than that of a large particle diet in the rabbit permitted coprophagy, whereas it was lower in the rabbit prevented from coprophagy. 3. The fine particle diet tended to cause shorter retention time of digesta in the rabbit prevented from coprophagy. 4. These suggest that the digestibility of fine components relates to their physical properties which affect the retention time of digesta in the rabbit.
Article
One hundred thirty New Zealand White x California rabbits were used to study the influence of the source of dietary fiber on several digestive criteria. Five diets were formulated to provide 10% crude fiber (CF) on a DM basis. Sixty percent of this dietary fiber was supplied by alfalfa hay, citrus pulp, beet pulp, grape marc, or rice hulls in the diets. Weights of cecal contents, cecal ammonia concentration, and molar proportion of acetic acid in diets including pulps were higher and cecal levels of DM, CP, and molar proportion of butyric acid were lower than those of the alfalfa diet. Cecal ammonia, VFA, and CF concentrations of the grape marc diet were the lowest of all the diets studied; cecal CF level and molar proportion of acetic acid were significantly higher and CP level and molar proportion of butyric acid were lower in rice hull than in alfalfa diets. Diet had no influence on daily soft feces excretion (10 g DM/d), but N contribution of soft feces to N intake was higher in the diet with citrus pulp (18.7%) than in the other diets (12%). Mean retention time (R) was measured using fuchsin-stained feed and was found to be higher (21.3 h) in the rice hull diet and lower (9.3 h) in the grape marc diet than in the other diets. When coprophagy was prevented, R decreased by 0 to 7 h. In conclusion, the use of byproducts to substitute for traditional sources of fiber in rabbit diets influenced the retention time of the digesta in some segments of the gut and thus altered several digestive criteria.(ABSTRACT TRUNCATED AT 250 WORDS)
Article
We examined the size of the "safety margin," if any, by which the small intestine's daily capacities to absorb nutrients exceed prevailing daily intakes of those nutrients. This safety margin, also known as reserve capacity, is widely assumed to be enormously large. As a test, we suddenly transferred mice from an ambient temperature of 22 to 6 degrees C and measured food intake, apparent digestive efficiency, intestinal morphometrics, and intestinal brush-border uptake capacities for D-glucose and L-proline over the next 28 days. Food intake jumped 68% within the first 12 h and rose in 2 days to a new plateau level 2.5 times the previous intake. Nevertheless, apparent digestive efficiency remained unchanged, even within the first 12 h, and intestinal transit times also remained unchanged, implying the existence of at least some safety margin. Masses of the small and large intestine, liver, kidneys, and spleen nevertheless increased within 4 days by 16-20%. Glucose and proline uptakes per milligram intestine increased by approximately 5%, so that the intestine's summed uptake capacities for these solutes increased by 24-26%. The animal's intestinal adaptation expressed in these increased uptake capacities implies that safety margins at the new plateau value of food intake would otherwise have been dangerously narrow. Comparison of calculated summed uptake capacities with measured dietary intakes suggests that safety margins are approximately 220-300% in mice at 22 degrees C, only 27-50% in mice at 6 degrees C before intestinal adaptation, but 60-88% in mice at 6 degrees C after intestinal adaptation.
Article
The role of vicinal sulfhydryls in the stimulation by insulin of system A amino acid uptake in mammalian skeletal muscle was investigated. Neutral amino acid uptake via system A carriers was assessed using the nonmetabolizable analogue alpha-(methylamino)isobutyric acid (MeAIB). Phenylarsine oxide (PAO), a trivalent arsenical that interacts with vicinal sulfhydryls, at 40 microM inhibited basal and insulin-stimulated (2 mU/ml) MeAIB uptake in rat epitrochlearis muscles by approximately 50% and approximately 80%, respectively. No significant changes in the ATP level or in the lactate-to-pyruvate ratio were observed. Both inhibitory effects were completely preventable by coincubation with dimercaptopropanol, a vicinal dithiol, indicating the effects were mediated specifically by interactions with vicinal sulfhydryls. Stimulation of MeAIB uptake by the insulin-mimicker vanadate (10 mM) or by insulin-like growth factor I (IGF-I, 20 nM) was also inhibited by 80-90% by PAO. Kinetic analysis showed that PAO decreased the apparent Vmax for basal and insulin-stimulated MeAIB uptake without altering the apparent Km. MeAIB uptake already maximally stimulated by insulin was rapidly (half-time = approximately 10 min) reversed by the addition of PAO so that the rate of MeAIB uptake was the same as in muscles incubated throughout with insulin and PAO. These results implicate a major role for vicinal sulfhydryls in the stimulation by insulin of amino acid uptake via system A carriers in skeletal muscle and suggest that the site of action of PAO on this system is distal to the insulin receptor, possibly at the carrier molecule itself.
Article
Adult male rabbits, wearing a plastic collar to prevent coprophagy, excreted soft faeces during the first half of the light phase, starting at about the time the light switched on at 0600. While soft faeces were being excreted, food intake was reduced considerably in collared as well as in non-collared animals. Rate of passage of gastrointestinal contents in the rabbit was extremely high. Chromic oxide appeared in the faeces 4-5 h after it had been ingested in pelleted food. Coprophagy had no effect upon the rate of passage of gastrointestinal contents, and chromic oxide passed through at the same rate, whether it was incorporated in soft faeces or in pelleted diet.
Article
Seventy-five New Zealand White x Californian rabbits were used to study the influence of the chemical composition of lucerne hay on caecal and caecotrophy characteristics. Five lucerne hays varying in chemical composition were ground and formed into pellets. These were the sole form of nutrition during the experiment. The type of lucerne hay did not affect caecal volatile fatty acid concentration, pattern of fermentation of pH. However, the caecal ammonia concentration decreased linearly (by 30% between extreme diets, P = 0.002) when dietary fibre proportion increased. The weight of caecum and caecal contents increased linearly (by 12%, P = 0.010, and 35%, P < 0.001, respectively, between extreme diets) with dietary fibre proportion. Soft faeces excretion and contribution of soft faeces to dry matter intake were not influenced by the type of lucerne hay. The proportion of caecal content that appeared daily as soft faeces and the total and microbial nitrogen concentrations in soft faeces were higher (42, 14 and 39%, respectively) for the lucerne hay with the lowest dietary fibre proportion than for the average of the other hays.
Article
To estimate the contribution of coprophagy to protein intake, we observed the behavior, particularly that associated with coprophagy, in adult and young captive nutrias (experiment 1), and analyzed chemical composition and amino acid composition, including diaminopimeric acid (DAP), an indication of bacterial-deprived protein, of soft feces, entire hard feces, and the black part and green part of hard feces (experiment 2). Nutrias practiced coprophagy 48 times per 24 h in adults, and 28 times in young animals, which not only had a 24-h rhythm but also had 1-h or 2-h short-term rhythms. Nutrias ingested food and drank water vigorously after sunset, following which they practiced coprophagy from midnight to morning, before lying down for much of the day. When coprophagy was prevented we sampled soft feces, produced from midnight to noon, which had high (P < 0.05) concentration of crude protein (CP), DAP on a dry matter (DM) basis and 13 amino acids on a 16 g N basis than hard feces, and had a low (P < 0.05) content of acid detergent fiber (ADF). CP was greater in the black part than the green part of hard feces (P < 0.05) although ADF was less (P < 0.05). The chemical composition of the black part of hard feces was not significantly different from that of soft feces. The dry weight of soft feces excreted in experiment 1 was 34.5 g and 9.7 g DM per 24 h in adult and young animals, respectively. Using this value, the contribution of soft feces to CP intake in adult nutrias was estimated as 16%, superior to that obtained in rabbits for a diet with similar ADF concentration. To Met and Lys intake the contribution of soft feces was 26% and 19%, respectively in adult animals. These results suggest that coprophagy is quite an effective manner for nutrias to ingest extra protein.
Article
It is known from the literature that lactic acid is produced in the rabbit stomach and that the accumulation of the acid is accompanied, paradoxically, by an increase in pH. The bacteria in soft pellets are likely candidates for the role of lactic acid production; with this in mind the distribution of soft pellets and of lactic acid in the stomach was studied. It was found that pellets taken from the rectum contain lactic acid and that the pellets after ingestion are lodged in the fundus of the stomach. Consistent with this is the fact that the absolute amount and the concentration of lactic acid are highest in the fundus. The soft pellets possess a tough membrane which remains morphologically intact for at least 6 hours after ingestion. The membrane encloses a collection of bacteria including lactobacilli, and homogenates of the pellets possess marked amylase activity and a high level of phosphate buffer which maintains the pH of the homogenate at about 6.0 to 6.5. Consistent with these facts, the homogenates can form lactic acid from starch and from glucose. The high pH maintained by the buffer permits fermentation of carbohydrate to take place in intact pellets, even when the external medium of the stomach is strongly acid. The buffering action of the pellets can explain the apparent contradiction of an increase in pH in the stomach associated with lactic acid accumulation. It is concluded that the fundus of the rabbit stomach, loaded with soft pellets, is analogous to the rumens of sheep and cattle.
Compound feed digestibility and nitrogen balance in rabbits dependent on crude fiber level