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Irruptive Potential in Roe Deer: Density-Dependent Effects on Body Mass and Fertility
Abstract
We examined the irruptive potential of a roe deer (Capreolus capreolus) population on a 10-km(2) island 2 km off the coast of central Norway (63 degrees 40' N). As roe deer density increased from 10 to 34.5 animals/km(2) from spring 1991 to spring 1994, reproductive status was determined in 33 2-year old and 66 adult, radiocollared does. Body mass was known for 19 adults and 12 2-year old females. The studied population had a high overall rate of increase, r = 0.409, although this decreased with increasing population density. Density only explained 2.8% and 6.7% of the variation in maternal body mass of 2-year olds and adults, respectively, and an examination of individual trajectories showed that density did not affect litter size either. Body mass did not affect reproductive status in the 2 age groups; however, body mass affected the number of fawns produced. Females with above average body mass had 40% higher productivity than females with below average body mass. The ability of female roe deer to maintain high body condition and high reproductive rates at high density means that monitoring of vital rates alone will not allow managers to detect these potential rapid increases in density until they have irrupted. Therefore, direct monitoring of population size or an index of population abundance is needed to allow rapid changes in harvest level that can prevent irruptions.
... Population density and fecundity are inversely correlated in a multitude of populations (Clarke 1955;Christian 1961;French et al. 1965;Tanner 1966;Dahlgren 1979;Clark & Feldman 1981;Reznick & Endler 1982;Albon et al. 1983;Andersen & Linnell 2000;Bonenfant et al. 2009). Variation in reproductive output may be influenced by the densitydependent feedback of population sizes on food available for reproduction (Ashmole 1962;Ricklefs 1983). ...
... In the Czech Republic, roe deer population densities are commonly estimated to be much lower than, for example, in the study by Prokešová et al. 2006 7.0 ind.*km -2 . In other European countries, much lower values were also found, for example in France 19.9-23.5 ind.*km -2 (Reby et al., 1998), in Norway 10.1-34.5 ind.*km -2 (Andersen and Linnell, 2000) or in Sweden 10-23 ind.*km -2 (Jarnemo and Liberg, 2005). ...
We investigated selected study areas regarding natural and cultural development and changes in the last circa 200 years with the goal to reveal their heritage and values from point of view of many geographical disciplines. Using various types of data and methods of physical, social geography and geoinformatics we have analysed thirty study areas so far, especially landscapes, which went through massive changes such as vanishing of inhabitants and settlements and extensification or afforestation, urbanization and construction new water bodies. Here, we expertly chose areas with recreational use
and investigated their land cover changes between the 19th century and nowadays to find out whether and how land cover and recreation use are related. In addition, we would like to present wide range of outputs of our project and connections between heritage and its representation of the landscape, land cover change and recreation in the study areas. We concluded that landscape changes are hand in hand with current recreational use. There is a shift from productive to non-productive functions, however ways differed significantly, e.g. using old structures for new activities, activities based on new or transformed structures and landscape or even covering old structures by recreation.
... In the Czech Republic, roe deer population densities are commonly estimated to be much lower than, for example, in the study by Prokešová et al. 2006 7.0 ind.*km -2 . In other European countries, much lower values were also found, for example in France 19.9-23.5 ind.*km -2 (Reby et al., 1998), in Norway 10.1-34.5 ind.*km -2 (Andersen and Linnell, 2000) or in Sweden 10-23 ind.*km -2 (Jarnemo and Liberg, 2005). ...
Abstract
Within the project on monitoring of landscape changes in large-scale protected areas in Czechia we also monitor anthropogenic structures – roads, built-up and recreational areas. In this article we focused on anthropogenic structures in the five protected areas, which are protected and also highly visited by tourists especially for rock formations, particularly sandstone. Based on this similarity we would like to evaluate and compare the anthropogenic pressure in these areas. We used 500x500 m grid to visualize and analyse all the results, which contain relative distribution of anthropogenic structures and their standardization resulting in indices refer to anthropogenic pressure. In addition, 1)
we performed cluster analysis to find out different types of anthropogenic influence present within the study areas and 2) indices of anthropogenic pressure were analysed with habitat suitability for key species of the protected areas, 3) finally, we compared selected protected landscape area according to results and indices within the areas.
České Švýcarsko as National Park (NP) is at the lowest level of anthropogenic influence by permanent structures, however Broumovsko, Český ráj and Labské pískovce are facing significantly higher anthropogenic pressure influencing suitable habitats as well.
... Rates of implantation failure vary across Britain, in relation to climatic severity, whilst within populations there is no consistent effect of weather on female fecundity [14]. Similarly, fertility (the percentage of pregnant 2-year-old females) was lower in a Norwegian than in a French roe population of similar density, despite greater body mass [15]. In Britain, although fertility was positively related to body mass overall, the asymptote at which fertility became maximal differed among 15 populations [16]. ...
Effective landscape-scale management of source-sink deer populations will be strengthened by understanding whether local variation in habitat quality drives heterogeneity in productivity. We related female roe deer Capreolus capreolus fecundity and body mass to habitat composition and landscape context, separately for adults and yearlings, using multi-model inference (MMI) applied to a large sample of individuals (yearlings: fecundity = 202, body mass = 395; adults: fecundity = 908, body mass = 1669) culled during 2002–2015 from an extensive (195 km²) heterogeneous forest landscape. Adults were heavier (inter-quartile, IQ, effect size = +0.5kg) when culled in buffers comprising more arable lands while contrary to our prediction no effects on body mass of grassland, young forest or access to vegetation on calcareous soil were found. Heavier adults were more fertile (IQ effect size, +12% probability of having two embryos instead of one or zero). Counter-intuitively, adults with greater access to arable lands were less fecund (IQ effect of arable: -7% probability of having two embryos, instead of one or zero), and even accounting for greater body mass of adults with access to arable, their modelled fecundity was similar to or lower than that of adults in the forest interior. In contrast, effects of grassland, young forest and calcareous soil did not receive support. Yearling body mass had an effect on fecundity twice that found in adults (+23% probability of having one additional embryo), but yearling body mass and fecundity were not affected by any candidate habitat or landscape variables. Effect of arable lands on body mass and fecundity were small, with little variance explained (Coefficient of Variation of predicted fecundity across forest sub-regions = 0.03 for adults). More variance in fecundity was attributed to other differences between forest management sub-regions (modelled as random effects), suggesting other factors might be important. When analysing source-sink population dynamics to support management, an average value of fecundity can be appropriate across a heterogeneous forest landscape.
... In most ungulate species, as population density increases, females favour their body maintenance and survival by reducing reproductive effort (Bonenfant et al. 2009). This reduction may be achieved, for example, by reducing litter size (e.g., roe deer; Capreolus capreolus, Andersen and Linnell 2000;Flajšman et al. 2018, moose; Alces alces, Gingras et al. 2014) or delaying age at primiparity (e.g., roe deer; Gaillard et al. 1992, red deer; Cervus elaphus, Bonenfant et al. 2002, elk;Cervus canadensis, Stewart et al. 2005). Because females should take longer to regain body condition following reproduction at high density (Clutton-Brock and Coulson 2002), the energy allocated to current reproductive effort may reduce the probability of subsequent reproduction (Hamel et al. 2011). ...
Life-history strategies of female ungulates usually depend on density-dependent and independent processes affecting body condition. Using a long-term data set on life-history traits of female white-tailed deer (2002–2014), we investigated the influence of population density and environmental factors on the reproductive effort of females. We also evaluated post-reproductive consequences on body condition using body mass, body fat, and body protein contents in the autumn following conception. We found that under high densities, females had a lower reproductive rate, which corresponds to a conservative reproduction strategy. However, females born at high density were more likely to reproduce and conceive larger litter size than females born at low density, a possible consequence of strong selective pressure in early life. Body condition was affected by reproduction; lactation had a large negative impact on body mass and body reserves, and conception, irrespectively of litter size, had a negative impact on body fat. Our long-term study demonstrates that plasticity in life-history strategies is a major determinant of reproductive potential for females living at high density and under harsh climates.
... Studies have also shown that ungulates living in seasonal locations reflect seasonality in their feeding habits (Hofmann, 1989;Sherlock & Fairley, 1993;Zweifel-Schielly, Leuenberger, Kreuzer, & Suter, 2012). Plant quality and quantity influence growth, fecundity, and survival of individuals (Andersen & Linnell, 2000;Armstrong, Davidson, Perrott, Roygard, & Buchanan, 2005;Loison & Langvatn, 1998). Plant quality can be described in terms of protein, minerals, and fiber content among others (Robbins, 1983;Verheyden et al., 2011). ...
... The body of roe deer has been studied in light of relationships between body size/mass and life history traits [25,26], environmental variation [27,28], habitat characteristics [27], and population parameters [29][30][31]. Similar to most vertebrates, populations of a roe deer are strongly age structured [32] and therefore natural selection optimizes the most efficient combination of body traits allowed by developmental constraints and environmental filters acting at each ontogenetic stage. ...
Background
As a small artiodactyl, the roe deer (Capreolus capreolus L.) is characterized by biological plasticity and great adaptability demonstrated by their survival under a wide variety of environmental conditions. In order to depict patterns of phenotypic variation of roe deer body this study aims to quantify variation during ontogenetic development and determine how sex-specific reproductive investment and non-uniform habitat differences relate to phenotypic variation and do these differential investments mold the patterns of phenotypic variation through modular organisation.
Results
Patterns of phenotypic correlation among body traits change during the ontogeny of roe deer, with differential influence of sex and habitat type. Modularity was found to be a feature of closed habitats with trunk+forelimbs+hindlimbs as the best supported integration/modularity hypothesis for both sexes. The indices of integration and evolvability vary with habitat type, age and sex where increased integration is followed by decreased evolvability.
Conclusion
This is the first study that quantifies patterns of correlation in the roe deer body and finds pronounced changes in correlation structure during ontogeny affected by sex and habitat type. The correlation structure of the roe deer body is developmentally written over the course of ontogeny but we do not exclude the influence of function on ontogenetic changes. Modularity arises with the onset of reproduction (subadults not being modular) and is differentially expressed in males and females from different habitats. Both adult males and females show modularity in primordial, closed habitats. Overall, all these findings are important as they provide support to the idea that modularity can evolve at the population level and change fast within a species.
ABSTRAKT Analizowano różnice w strukturze wiekowej, masie ciała oraz masie i formie poroża samców saren pozyska-nych w drugiej dekadzie XXI wieku na dwóch terenach o różnej lesistości. Rogacze pozyskano zgodnie z za-sadami selektywnego odstrzału, które obowiązywały w Polsce w latach 2009-2017. W łowiskach leśnych intensywność odstrzału młodych i średniowiekowych samców była taka sama (41%), natomiast w łowiskach polnych najintensywniej strzelano osobniki średniowiekowe (48%). Na terenie leśnym pozyskiwano najczę-ściej widłaki (41%) i rogacze o nierozwidlonym porożu (34%), a na terenie polnym głównie szóstaki (49%) i widłaki (37%). W rejonie leśnym masa ciała wzrastała między osobnikami młodymi a średniowiekowymi, natomiast w łowiskach polnych także między średniowiekowymi i starszymi. Prawdopodobnie wynikało to z lepszych warunków żerowych na terenach polnych. Masa poroża w obu terenach wzrastała tylko między rogaczami młodymi i średniowiekowymi, a tymczasem kulminacja rozwoju parostków następuje w Polsce u osobników starszych. Selektywny odstrzał samców na badanych terenach można więc uznać za wadliwy. Wprowadzając zmiany, warto wykorzystać wyniki z tej pracy, wskazujące na średnią masę tuszy większą u osobników z bardziej rozbudowanym porożem. Ochronę najmocniejszych samców młodych i średniowie-kowych można więc osiągnąć przez ograniczenie odstrzału szóstaków. Takie zmiany są pożądane ze względu na przeciwny kierunek nowelizacji zasad odstrzału selektywnego wprowadzonej w Polsce w roku 2018, co ułatwia odstrzał rogaczy z parostkami szóstaka w wieku od 2. do 5. roku życia. Słowa kluczowe: sarna europejska, masa ciała, masa i forma poroża, odstrzał selektywny, środowisko
The information on absolute and/or relative abundance of wild ungulates is one of the key parameters for sustainable and efficient management. Wild ungulates are the most important and abundant group of game species in Slovenia; however, there are currently no standard census methods, which would be performed on the annual basis. There are various methods for estimating wild ungulate abundance and several criteria have to be met, when selecting the most suitable one. The most important criteria that have to be taken into account are studied species, habitat characteristics, size of the studied area, population density and cost efficiency. Besides the faecal pellet group method, which has already been used in Slovenia to estimate the abundance of roe deer and red deer, a suitable method is also the kilometre index. The reliable methods for wild boar are camera traps, drive counts and distance sampling with thermovision and, for chamois, ground counts and aerial counts.
Reproductive performance is one of the most important life-history traits that should be routinely studied and considered in adaptive wildlife management. In the case of roe deer (Capreolus capreolus), a species with delayed implantation, which complicates studies on fetuses, corpora lutea (CL) counting is the only alternative for routine monitoring. However, because of a possible implantation failure, the reliability of this method is questionable, and factors influencing implantation success have been poorly understood so far. We analyzed 2,594 intact uteri of roe deer hunted from 2006–2015 in an Apennine population, central Italy, during winter (mid-Jan to mid-Mar). By comparing the number of CL and fetuses in the same individuals (i.e., success in blastocyst implantation), we revealed a mean implantation failure of 8.6% in a pooled sample set (regardless of the age and origin of animals), with a high inter-annual variability (range = 3.6–19.8%). Contrary to adults ((Formula presented.) ± SE = 11.1 ± 1.9%), the implantation failure in yearlings was low (4.4 ± 1.9%). Implantation success was affected by individual maternal characteristics (positive effect of body mass and negative effect of age), climatic condition in summer (positive effect of July temperature up to 23.4°C, and negative effect above this threshold), winter harshness (negative effect of snow cover duration), and altitude (negative relation with the elevation). Reproductive performance of adult female roe deer cannot be adequately measured by CL counts because of high inter-annual variability in implantation failure and important effects of female attributes and environmental factors. However, for yearlings, which also express the highest variability in the ovulation rates, CL counts provide important information on their reproductive outcome because they have low implantation failure.
1. Summer home range size variation and habitat selection of 35 radio-collared adult female roe deer was studied, using kernel home range estimation and compositional analysis of habitat use. 2. Female roe deer adjust the size of their home range in response to decreasing food supply, and the hypothesis that female roe deer utilize the minimum area that sustain their energy requirement cannot be rejected. 3. Home range size increased with the visibility in the home range (the average distance at which sight is blocked by intervening vegetation). This supports the hypothesis that cover is important in reducing the risk of predation and thereby increasing adult survival. 4. Female roe deer spend more time near habitat edges, supporting the hypothesis that different habitat types contain complementary resources, e.g. food and cover or different nutrients. Simultaneous access to several habitat types did not have any effect on home range size, possibly because variation in heterogeneity between different home ranges was too low. 5. Females without fawns had smaller home ranges, possibly because they only need to sustain their own energetic requirements. 6. The analyses of habitat selection inside each home range showed that the forest types, characterized by high densities of food and low visibility, were preferred, suggesting that habitat use is allocated in proportion to either food or cover or both.
We present data on fidelity to territory, and length of tenure (multi-year) for bucks of European roe deer Capreolus capreolus (Linnaeus, 1758) based on 26 radio-collared individuals that were followed for up to 5 years. Individual bucks showed a high degree of fidelity to summer territory, with consecutive year's activity centres being less than 200 m apart on average. An average 70% of one year's territory was within the borders of the previous year's territory. No buck occupied a territory which did not overlap with the previous year's territory. Activity centres of consecutive winter home ranges were on average 502 m apart, although this difference was not significant. Several cases of switching between non-overlapping winter ranges between years were observed. Annual survival was high (97%) and we observed only a single case of an old buck losing dominance on his former territory after a very hard winter. All other surviving bucks regained their dominance on their territories. It is suggested that the roe deer bucks were demonstrating an 'always stay' strategy in order to gain the benefits of site familiarity. This is in keeping with the concept of roe deer territoriality being a relatively 'low-risk low-gain' strategy where emphasis is placed on survival and multi-year tenure of a territory.
The mortality of roe deer (Capreolus capreolus) fawns in summer was studied on Storfosna Island (10 km(2)), a predator-free island 2 km off the west-central coast of Norway, during a period of rapid population increase. Between 1991 and 1994 the population density increased from about 10 to 40 roe deer/km(2). During this period 285 live and 36 stillborn fawns were found and the live fawns were all subsequently radio-collared. All observed mortality occurred within the first 35 days of life. The main causes of death were stillbirth, starvation/hypothermia, drowning, car accidents, and falls. The average annual total mortality for all 4 years was 18%. Although there was a large increase in mortality between 1991 and 1992 (from 10 to 18%), there was little subsequent increase in the last 3 years, resulting in an overall weak density dependence in total mortality. However, the proportion of stillbirths (5% in 1991 to 15% in 1994) showed a clear and significant trend toward an increase with increasing density. Low temperatures in April, which strongly affect the timing of the spring flush of high-quality forage during late gestation, also tended to contribute to higher mortality. Fawns that died were found to have reduced individual growth rates prior to death compared with fawns that survived. Fawns born to relatively light mothers or in triplet litters had higher mortality rates than those born to heavy mothers or in smaller litters. Maternal age and date of birth or sex of fawn had no effect on mortality.
Both theory and empirical information support the conclusion that most density-dependent change occurs at high population levels (close to the carrying capacity) for species with life history strategies typical of large mammals. The reverse is true for species with life history strategies typical of insects and some fishes. Theoretical considerations that give rise to these conclusions involve natural selection and trophic dynamics. There is a large body of literature that contains descriptions of density dependence as based on empirical observations. These data, and the models used to represent them, indicate that species with high reproductive rates, short life-spans and populations held below the limits of environmental resources exhibit most density-dependent change at low population levels. Similar data for species with low reproductive rates, long life-spans and populations that are more limited by resources (large mammals in particular) indicate that most density-dependent changes in vital rates occur at levels of the population quite close to the carrying capacity.
The food limitation hypothesis of population regulation states that a stable equilibrium will exist between a population and its food resources due to a density-dependent decrease in fecundity and/or increase in mortality. This hypothesis was tested for the moose (Alces alces) by comparing regional variation in life history characteristics in four Norwegian study areas, chosen to represent a gradient both in summer and winter range conditions. The rate of body growth was most rapid in the northern study area with the best summer ranges. Lowest body growth occurred in the population living under the poorest winter conditions. After snow-free winters the rate of body growth increased substantially, leading to large annual variations in selective regimes. The peak timing of ovulation of old females in the autumn showed a latitudinal delay. Females in the alpine population, with the poorest winter conditions, had significantly later mean calving dates and produced fewest calves per year. Gestation length appears to be dependent on nutritional condition of females during pregnancy. Mortality was highest in the northern study are where most of the deaths occurred during the summer. Very few calves died during the winter. These results suggest that a stable high-density equilibrium between moose and their food resources as expected from the food limitation hypothesis is unlikely. The decrease in fecundity and the increase in mortality under poor nutritional conditions during the winter has only a small effect on the population growth rate and is therefore unlikely to have a strong regulatory effect. In the absence of large predators, this will lead to large fluctuations in population size that will overshoot the carrying capacity.
We present a model in continuous time that allows us to analyse how an individual should allocate resources to growth and reproduction in order to maximize its lifetime contribution to future generations. Assuming that the death rate only depends on age, the allocation of energy is the solution of an optimization problem defined by a life history model. Making particular assumptions for the individual’s potential for growth and reproduction covering many situations of biological interest, the precise solution can be written up explicitly. Hence the effect of the various parameters may be analysed in detail. In general, the individual should first use all its energy to growth, then at a certain age invest a proportion of energy into reproduction. This fraction increases as the individual grows older. In some situations growth finally stops, while for other parameter values the individual continues to grow until it dies. This model was used to examine, for the von Bertanlanffy’s growth curve, the effects on age and size at maturity of changing the age-specific mortality rates. In general, the growth changes from a determinate growth to an indeterminate growth pattern when the mortality rate increases. In particular, a strong effect was found when the juvenile mortality increased. Rapid growth was also found to favour early maturation.
Used life-history theory to predict reaction norms for age and size at maturation, assuming that fecundity increases with size and that juvenile mortality rates of offspring decrease as ages-at-maturity of parents increase, then calculated the reaction norm by varying growth rate and calculating an optimal age at maturity for each growth rate. The reaction norm for maturation should take 1 of at least 4 shapes that depend on specific relations between changes in growth rates and changes in adult mortality rates, juvenile mortality rates, or both. Most organisms should mature neither at a fixed size nor at a fixed age, but along an age-size trajectory. The model makes possible a clear distinction between the genetic and phenotypic components of variation. The evolved response to selection is reflected in the shape and position of the reaction norm. The phenotypic response of a single organism to rapid or slow growth is defined by the location of its maturation event as a point on the reaction norm. -from Authors
THE sizes of unexploited populations of roe deer (Capreolus capreolus) are regulated by spring migration. Individuals which have been able to establish a territory (bucks) or home range (does) force all other animals to move out of the habitat. This phenomenon is specific to age class, and if there is no mortality amongst adult animals, most yearlings emigrate to find new forest area13. Thus, in order to develop an intensive harvest policy for roe deer population, knowledge of the number of animals which can be supported by the habitat (that is, social carrying capacity) is essential to avoid undesirable population losses through emigration. During 1970–75, an intensive team research study was carried out in various regions throughout Poland6. Deer food resources were estimated by the harvest plot method3, and winter population densities were precisely determined by drive census techniques11. Based on these data, several study areas were selected in which hunting and natural mortality were very low, and where it was known that most juvenile animals emigrated each spring. We show here that summer food is a major factor limiting roe deer population size.
Odocoileus virginianus declined from a 60% pregnancy rate to <47% between 1952 and 1982. This change was inversely correlated (P = 0.010) with annual deer kill, which increased more than 18-fold over that period owing to herd eruption. Sustained high fecundity among doe fawns that bred suggests that nutritional resources on this prime agricultural land had not diminished during the interim. I hypothesize that the declining pregnancy rates were related to biosocial factors, namely the effect of orphaning in accelerating doe fawn sexual maturity (due to lack of maternal domination), associated with a reduction in the proportion of antlerless deer harvested as the population continued to rise over the three decades studied.
La frequence de la gemellite est un des indices de natalite utilises lors de la protection de la vie sauvage pour connaitre la bonne condition des populations. On compare ici cette frequence dans un habitat pauvre et dans un habitat favorable (Kenai Peninsula, Alaska, 1977-83)