Antler size provides an honest signal of male phenotypic quality in roe deer

Identifying factors shaping secondary sexual traits is essential in understanding how their variation may influence male fitness. Little information is available on the allocation of resources to antler growth in territorial ungulates with low sexual size dimorphism. We investigated phenotypic and environmental factors affecting both absolute and relative antler size of male roe deer in three contrasting populations in France and Sweden. In the three populations, we found marked age-specific variation in antler size, with an increase in both absolute and relative antler size between yearling and prime-age stages, followed by a decrease (senescence) for males older than 7 years. Antler size increased allometrically with body mass. This increase was particularly strong for senescent males, suggesting the evolution of two reproductive tactics: heavy old males invested particularly heavily in antler growth (potentially remaining competitive for territories), whereas light old males grew small antlers (potentially abandoning territory defense). Finally, environmental conditions had little effect on antler size: only population density negatively affected absolute antler size in one of the three populations. Antler size may therefore provide an honest signal of male phenotypic quality in roe deer. We discuss the implications of these results in terms of territory tenure and mating competition.     

Density-dependent responses of fawn cohort body mass in two contrasting roe deer populations

We investigated the influence of population density on juvenile body mass in two contrasting roe deer populations, in Sweden (Bogesund) and France (Chizé), in which density was monitored for ≥15 years. We investigated the effect of population density and climatic conditions on cohort performance. We predicted that: (1) body mass of growing fawns should be sensitive to environmental changes, showing marked between-year variation (i.e., cohort effects), (2) fawns in the less productive (weakly seasonal, weakly predictable summer weather) habitat of Chizé should show stronger density-dependent responses due to more severe food competition during summer than fawns in the more productive (markedly seasonal, moderately predictable summer weather) habitat of Bogesund, and (3) fawns at Bogesund should be heavier both in absolute terms and relative to their size than their conspecifics in Chizé due to a higher degree of fat accumulation in northern environments. In both study sites we found marked cohort variation and clear effects of density, with body mass varying by as much as 29% over years. While neither summer nor winter climate influenced fawn body mass at Bogesund, fawns tended to be lighter after summers with high temperatures at Chizé. In addition, fawns were heavier after acorn mast years experienced in utero at Bogesund. As expected, the strength of the density-dependent response of fawn body mass was greater at Chizé than at Bogesund. For a given density, male fawns were consistently heavier than females in both sites. Lastly, both sexes at Bogesund had higher absolute body mass and were larger for a given body size than in Chizé. Our results clearly demonstrate that absolute density is a poor predictor of roe deer performance and supports the view that habitat quality has an overwhelming importance for determining fawn body mass in roe deer populations.     

Large herbivore migration plasticity along environmental gradients in Europe: life‐history traits modulate forage effects

The most common framework under which ungulate migration is studied predicts that it is driven by spatio–temporal variation in plant phenology, yet other hypotheses may explain differences within and between species. To disentangle more complex patterns than those based on single species/ single populations, we quantified migration variability using two sympatric ungulate species differing in their foraging strategy, mating system and physiological constraints due to body size. We related observed variation to a set of hypotheses. We used GPS‐collar data from 537 individuals in 10 roe Capreolus capreolus and 12 red deer Cervus elaphus populations spanning environmental gradients across Europe to assess variation in migration propensity, distance and timing. Using time‐to‐event models, we explored how the probability of migration varied in relation to sex, landscape (e.g. topography, forest cover) and temporally‐varying environmental factors (e.g. plant green‐up, snow cover). Migration propensity varied across study areas. Red deer were, on average, three times more migratory than roe deer (56% versus 18%). This relationship was mainly driven by red deer males which were twice as migratory as females (82% versus 38%). The probability of roe deer migration was similar between sexes. Roe deer (both sexes) migrated earliest in spring. While territorial male roe deer migrated last in autumn, male and female red deer migrated around the same time in autumn, likely due to their polygynous mating system. Plant productivity determined the onset of spring migration in both species, but if plant productivity on winter ranges was sufficiently high, roe deer were less likely to leave. In autumn, migration coincided with reduced plant productivity for both species. This relationship was stronger for red deer. Our results confirm that ungulate migration is influenced by plant phenology, but in a novel way, that these effects appear to be modulated by species‐specific traits, especially mating strategies.     

Dynamics in space use of American mink (Neovison vison) in a fishpond area in Northern Germany

Telemetry of American mink Neovison vison revealed seasonal and sexual variations in home-range size, intersexual- and partially intrasexual range overlaps and spatial dynamic of territorial system. From 2003 to 2006, 14 mink (nine males and five females) were radio-tracked in a fishpond area in northern Germany. We observed comparatively large home ranges. Both sexes reduced their large summer home ranges to smaller ones in the winter period. In both seasons, male mink used significantly larger areas than female mink. During the mating season, males considerably enlarged their home ranges and roamed nearly through the entire study area. These variations and diversity of range size were discussed in connection with thermoregulatory behaviour, prey availability and distribution, population density and stability of the social system. Analysing intraspecific static interactions, we observed high intersexual overlapping rates in both the summer and winter periods. But there were no or rather very low levels of intrasexual overlapping. However, in the summer period, large home ranges of neighbouring males also overlapped to some extent, but temporal avoidance of adjacent territory holders was observed. Consequently, our results reveal intrasexual territoriality, with males having larger territories, overlapping those of females. The shifting of stable temporary home ranges observed within one season or between the same seasons of consecutive years demonstrates the highly dynamic nature of spatial behaviour among American mink. All these recorded characteristic features of spatial behaviour should be considered when planning mink control projects and measures for the management of this invasive carnivore.     

How does environmental variation influence body mass,body size,and body condition? Roe deer as a case study

We tested the influence of population density and of drought intensity (measured as the Gaussen Index in spring and summer of the year of birth) on winter body mass, hind foot length, and body condition of roe deer fawns. Body mass decreased with increasing density and increased with increasing Gaussen Index in summer, in a similar way for both males and females. Hind foot length of males showed the same response. On the other hand, hind foot length of females decreased with increasing density only after dry summers, hence when environmental conditions were very harsh. Body condition was affected neither by density nor by drought intensity. Our results indicate that body mass and size are much better indicators of phenotypic quality than body condition in roe deer. The sex-specific responses of body size to environmental conditions could correspond to a differential allocation in favour of daughters by heavier than average roe deer mothers.     

What shapes intra‐specific variation in home range size? A case study of female roe deer

Spatial distribution in mammals, and thereby home range size, is influenced by many different factors including body size, sex, age, reproductive status, season, availability of forage, availability of water, fragmentation of landscape, trophic level and intra- and inter-specific competition. Using linear mixed models, we looked for factors shaping the variation in size of spring-summer and winter home ranges for 51 radio-collared adult female roe deer at Trois Fontaines forest, Champagne–Ardenne, France (1996–2005). Home range size of females was larger in winter than in spring–summer, decreased with age, and decreased with increasing quality. Females in low quality areas adjusted the size of their home range to include more patches of habitat so that all female deer obtained similar amounts of food resources (total biomass of 6.73±2.34 tons (mean±SE) for each home range). Such adjustments of home range size in response to patchiness of resources led to marked between-female variation in home range size. Our results demonstrate that roe deer females have different tactics of habitat use according to spatial variations in habitat quality so that females get similar food resources in highly productive environments such as the Trois Fontaines forest.     

Partial migration in roe deer: migratory and resident tactics are end points of a behavioural gradient determined by ecological factors

Ungulate populations exhibiting partial migration present a unique opportunity to explore the causes of the general phenomenon of migration. The European roe deer Capreolus capreolus is particularly suited for such studies due to a wide distribution range and a high level of ecological plasticity. In this study we undertook a comparative analysis of roe deer GPS location data from a representative set of European ecosystems available within the EURODEER collaborative project. We aimed at evaluating the ecological factors affecting migration tactic (i.e. occurrence) and pattern (i.e. timing, residence time, number of migratory trips). Migration occurrence varied between and within populations and depended on winter severity and topographic variability. Spring migrations were highly synchronous, while the timing of autumn migrations varied widely between regions, individuals and sexes. Overall, roe deer were faithful to their summer ranges, especially males. In the absence of extreme and predictable winter conditions, roe deer seemed to migrate opportunistically, in response to a tradeoff between the costs of residence in spatially separated ranges and the costs of migratory movements. Animals performed numerous trips between winter and summer ranges which depended on factors influencing the costs of movement such as between‐range distance, slope and habitat openness. Our results support the idea that migration encompasses a behavioural continuum, with one‐trip migration and residence as its end points, while commuting and multi‐trip migration with short residence times in seasonal ranges are intermediate tactics. We believe that a full understanding of the variation in tactics of temporal separation in habitat use will provide important insights on migration and the factors that influence its prevalence.     

Population density and sex do not influence fine-scale natal dispersal in roe deer

It is commonly assumed that the propensity to disperse and the dispersal distance of mammals should increase with increasing density and be greater among males than among females. However, most empirical evidence, especially on large mammals, has focused on highly polygynous and dimorphic species displaying female-defence mating tactics. We tested these predictions on roe deer, a weakly polygynous species of large herbivore exhibiting a resource-defence mating tactic at a fine spatial scale. Using three long-term studies of populations that were subject to the experimental manipulation of size, we did not find any support for either prediction, whether in terms of dispersal probability or dispersal distance. Our findings of similar dispersal patterns in both sexes of roe deer suggest that the underlying cause of natal dispersal is not related to inbreeding avoidance in this species. The absence of positive density dependence in fine-scale dispersal behaviour suggests that roe deer natal dispersal is a pre-saturation process that is shaped by heterogeneities in habitat quality rather than by density per se.     

Dispersal is not female biased in a resource-defence mating ungulate, the European roe deer

Dispersal is frequently more prevalent in one sex compared to the other. Greenwood proposed that patterns of sex-biased dispersal among birds and mammals are linked to their mating strategies. For species where males defend resources rather than females, he predicted female-biased dispersal, because males should remain at their birth site where they are familiar with the distribution of the resources that they must defend. Greenwood's hypothesis has been extensively supported among birds, where most species exhibit a resource-defence mating strategy. However, almost no equivalent information is available for mammals as males generally defend mates in this group. An exception is the European roe deer, a resource-defence mating ungulate. We thus tested Greenwood's hypothesis on this atypical mammalian model, looking for female-biased dispersal using sex-specific inter-individual genetic distances. We conclusively show that gene flow is not higher among females compared to males in the studied roe deer population, and hence that dispersal is not female-biased, suggesting that male mating strategy is not the primary selective force driving the evolution of dispersal in roe deer. We discuss the role of female mate choice and intra-sexual competition as possible alternative selective pressures involved.     

Seasonal variation of activity patterns in roe deer in a temperate forested area

We investigated the activity patterns of a European roe deer (Capreolus capreolus) population living in a forested Apennine area in central Italy, in order to shed light on the environmental and biological factors that were expected to account for the observed activity patterns on daily and yearly bases. Daily and seasonal activity patterns of 31 radio-collared roe deer were assessed through sessions of radio tracking for a total period of 18 consecutive months. Roe deer showed bimodal activity patterns throughout the year, with the two highest peaks of activity recorded at dawn and dusk. Activity patterns of males and females differed during the territorial period (from early spring to late summer), whereas they did not during the nonterritorial period. Most likely, behavioral thermoregulation can be held responsible for variation of daily activity patterns in different seasons. In winter, for instance, activity during the dawn period was significantly higher than in other seasons and daylight activity was significantly higher than at night. Nocturnal activity was highest in summer and lowest in winter. During the hunting season, moreover, roe deer showed lower activity levels than during the rest of the year. The prediction that roe deer would show lower activity levels during full moon nights, when the predation risk was assumed to be higher, was not confirmed by our data. Activity rhythms in roe deer were thus subjected to both endogenous and environmental factors, the latter working as exogenous synchronization cues. Accordingly, in changing environmental and ecological conditions, a circadian cycle of activity could be seen as the result of complex interactions among daily behavioral rhythm, digestive physiology, and external modifying factors.     

High red deer density depresses body mass of roe deer fawns

Many previous studies have pointed out that, when resources are limited, the potential for competition should be high among sympatric species that display overlaps in habitat and nutritional niches. However, reliable evidence of competition between red deer (Cervus elaphus) and roe deer (Capreolus capreolus) has not been yet reported for life history traits directly measuring performance such as body mass, reproduction, or survival. From long-term monitoring of deer populations in the reserve of La Petite Pierre (France), we measured the sex-specific responses of roe deer fawn body mass to changes in red deer density after accounting for possible confounding effects of date of shooting, climatic conditions, and roe deer density. As expected under the hypothesis of competition, red deer density in a given year had a marked negative influence on body mass of roe deer fawns born the same year and the following year. Fawn mass of roe deer males and females responded in similar ways to changes in red deer density. Our study provides the first evidence of a negative response of roe deer performance to high red deer density.     

Use of space and habitat selection by roe deer Capreolus capreolus in a Mediterranean coastal area: how does woods landscape affect home range?

The home-range dynamics and habitat selection of nine roe deer were studied from March 1994 to August 1994 in the Maremma Natural Park along the Tyrrhenian coast of Italy. The habitat was highly fragmented, with open agricultural fields prevailing in the study area (57%); the climate was Mediterranean. Data on spatial behaviour were collected by radio-tracking techniques. Habitat selection and structure were investigated by compositional and landscape analysis, both within the study area and within the home ranges. Animals of our sample showed spatial-use patterns varying from stationary to roaming. Stationary individuals used small home ranges while roaming ones moved, especially during the reproductive period in July and August. The percentage and structure of woodlands influenced the size of home ranges and the behaviour of males: stationary males used large amounts of woodlands within their home ranges and showed a territorial behaviour whereas males that used a high percentage of fields showed wider home ranges even during the territorial period. Females seemed to be less influenced by the presence and patch-structure of woodland within their home range. Landscape structure and habitat composition seemed to be important factors influencing the spatial behaviour of this roe deer population.     

Evidence for a trade-off between growth and body reserves in northern white-tailed deer

We contrasted patterns of growth and accumulation of body reserves in autumn between two high-density (HD) white-tailed deer populations facing winters of different severity and length. Both populations occurred in the absence of effective predators and suffered from some forage competition based on reduced body masses. A third population living at low density (LD) and confronting long and severe winters (SW) served to distinguish the influence of food competition and winter severity on growth and body reserves. We estimated body components (water, protein, fat and ash) of deer during the first half of November and compared growth patterns between sexes and regions. HD-SW males continuted growth to an older age than HD males facing short and mild winters (MW) but females of both regions reached adult body mass at the same age. LD-SW deer exhibited a growth pattern similar to that of HD-SW animals but were the heaviest and the largest, suggesting that growth patterns are related to winter harshness (or length of the growing season) and that final body size is related to forage competition in summer. Sexual dimorphism became evident at an older age in the HD-SW population than in the HD-MW population, demonstrating that winter harshness does not affect immature males and females in the same manner. Fawns from the HD-SW population had proportionally longer legs and a higher percentage of body fat. Adaptations of immature deer to long and severe winters suggest that survival during the first winter represents the most critical step in the life span of northern white-tailed deer.     

Factors influencing home range and activity of wild boar (Sus scrofa) in a Mediterranean coastal area

This paper analyses the temporal variation in the size of home range and activity of adult wild boar ( Sus scrofa L.). Eighteen boar were radiotracked between 1991 and 1993 in the Maremma Natural Park (Central Italy). Variations of home-range size and activity were related to sex, winter food availability and population density. The hypotheses that home-range size was inversely related to food availability and population density, and that the amount of activity was directly related to population density and inversely related to food abundance, were tested. The size of the acorn crop was used as a measure of winter resource level. No differences were found in the size of ranges, core area, and activity between males and females. In 1991–92 home-range size was larger than in 1992–93; conversely, activity increased from 1991–92 to 1992–93. Winter food availability was high in 1991–92 and low in the following year. Population density increased greatly in spring 1992 but crashed in spring and summer 1993, when a high mortality of wild boar occurred due to starvation.
The decrease in home-range size during the food shortage was explained as a possible strategy adopted by wild boar to cope with starvation. The difference in home-range size and amount of activity found between the first and the second year of study were probably influenced by differences in population density, although the individual effects of food availability and population density were not clearly separable.     

Roe and fallow deer: are they compatible neighbours?

The analysis of the relationships between population density and habitat features is important to evaluate the ecological needs of a species, its potential impact on ecosystems and its interspecific interactions. We analysed the spatial variation of roe deer Capreolus capreolus and fallow deer Dama dama densities in a Mediterranean area in summer 2007 and winter 2007/2008. Previous research has shown that fallow deer can actively displace and exclude roe deer from natural feeding sites. Here we show that both species have the greatest densities in ecotone habitats between wood and open fields (abandoned olive groves and pastures), but with contrasting geographic patterns. The fallow deer showed the greatest densities in the central northern part of the study area near to local historical release sites. The densities of roe deer were great where fallow deer were rare and low where fallow deer were abundant. Spatial overlap was great at the habitat scale, indicating a high potential for competition, but was low at the plot scale, suggesting that partitioning of space occurred at a fine scale. Supporting great numbers of deer, the ecotone areas are crucial for the management of ecosystems. We suggest that roe deer avoid areas with great densities of fallow deer and that interspecific interference from the latter affects the density and distribution of the former both at a fine and at a large scale.     

Early survival in roe deer: causes and consequences of cohort variation in two contrasted populations

Time- and sex-specific summer survival of roe deer fawns was estimated using capture-mark-recapture methods in two enclosed populations living in contrasting conditions. The population of Trois Fontaines (eastern France) was roughly constant in size throughout the study period, while in Chizé (western France), the population experienced frequent summer droughts and numbers decreased continuously during the study. Early survival of fawns was low and highly variable over the years at both Chizé and Trois Fontaines, and demonstrated marked variations between cohorts that need to be taken into account when modelling roe deer population dynamics. In Trois Fontaines, fawn survival was positively correlated with early body growth and total rainfall in May and June. In Chizé, fawn survival decreased with increasing density and tended to increase with increasing rainfall in May and June and adult female body mass. These factors explained more than 75% of the variability in early survival observed in both populations. Variation between cohorts had different consequences for the two populations. At Trois Fontaines, cohort variation was limited to a numerical effect on early survival. However at Chizé, cohort variation was long-lasting and affected the phenotypic quality of survivors at later ages, and thereby future survival and breeding abilities (both numerical and quality effects). Male and female fawns had similar survival over their first summer in both populations. This result contrasts with the lower survival of young males often observed in ungulates. Two ultimate causes can be proposed to account for the low and variable survival of roe deer fawns over the first summer: the high energy expenditures incurred by does during each breeding attempt and/or the low absolute body size of newborn roe deer fawns. Received: 28 April 1997 / Accepted: 14 July 1997     

Variations in adult body mass in roe deer: the effects of population density at birth and of habitat quality

Body mass is a key determinant of fitness components in many organisms, and adult mass varies considerably among individuals within populations. These variations have several causes, involve temporal and spatial factors, and are not yet well understood. We use long-term data from 20 roe deer cohorts (1977-96) in a 2600 ha study area (Chizé, western France) with two habitats contrasting in quality (rich oak forest in the North versus poor beech forest in the South) to analyse the effects of both cohort and habitat quality on adult mass (i.e. median body mass between 4 and 10 years of age) of roe deer (Capreolus capreolus). Cohort strongly influenced the adult body mass of roe deer in both sexes: males born in 1994 were 5.2 kg heavier when aged between 4 and 10 years old than males born in 1986, while females born in 1995 were 4.7 kg heavier between 4 and 10 years old than females born in 1982. For a given cohort, adult males were, on average, 0.9 kg heavier in the rich oak forest than in the poor beech forest. A similar trend occurred for adult females (0.5 kg heavier in the oak forest). The effects of cohort and habitat were additive and accounted for ca. 40% of the variation observed in the adult mass of roe deer at Chizé (males: 41.2%; females: 40.2%). Population density during the spring of the birth accounted for about 35% of cohort variation, whereas rainfall in May-June had no effect. Such delayed effects of density at birth on adult body mass probably affect population dynamics, and might constitute a mechanism by which delayed density-dependence occurs in ungulate populations.     

Effects of population density and female body mass on litter size in European roe deer at a continental scale

Roe deer (Capreolus capreolus) has a wide distributional range in Europe and inhabits a broad range of habitats and environmental conditions. Thus, populations of roe deer show substantial variation in demographic parameters. We aimed to determine whether body mass and population density—which influence the reproductive potential of roe deer at a local scale—affect their reproductive potential at a biogeographical scale as well. We reviewed the literature (covering years 1948–2015) on in utero litter size in roe deer from 59 locations in 14 countries in Europe. Across study sites, mean litter size varied from 1.0 to 2.4 embryo or corpora lutea per female, and population density ranged from 4.5 to 73.5 individuals/km². Mean body mass varied from 11.2 to 20.8 kg in subadult females and from 12.1 to 22.4 kg in adult females. Between 46° and 56° N, body mass of females did not show a significant trend of increase, whereas between 56° and 63° N, it increased with latitude (Bergmann’s rule). We used linear mixed-effects models (LMMs) to analyse the influence of body mass and population density (analysed separately) on litter size. Females with larger body mass produced larger litters, and this pattern was pronounced at both higher and lower latitudes. Higher population densities negatively affected litter size in a sample of all females. This macroecological analysis showed that factors influencing the reproductive potential of roe deer females at local scales produce similar effects at the biogeographical scale.     

Ranging behaviour of roe deer in an experimental high-density population: Are females territorial?

We studied the ranging behaviour and spatial relationships between seven roe deer during more than 4 years in a partly wooded 14.2-ha enclosure. The animals (three young males, four adult females) were monitored with GPS telemetry collars. As expected, the surface area and overlap of the males’ bimonthly ranges decreased, and the distance between their arithmetic centres increased, as they became adult and, for two of them, territorial. Unexpectedly, females also tended to space out, the surface area and overlap of their bimonthly ranges being minimal in May to June, i.e. during the birth period. The distance between their arithmetic centres reached its maximum at the same time. Overlap between females’ ranges was consistently lower than those between males and females’ ranges, or between 1-year old males’ ranges. Our results raise the questions of female seasonal territoriality and of independence of the spacing systems of the two sexes in roe deer.     

Fighting behaviour in territorial male roe deer <Emphasis Type="Italic">Capreolus capreolus</Emphasis>: the effects of antler size and residence

In all areas where they have been studied, male roe deer are believed to have a territorial mating system, although few quantitative studies have been conducted and there remains considerable debate about the function of male roe deer territories. We observed 139 aggressive interactions between male roe deer in Storfosna Island (Norway) during one territorial season (March–August). We recognised seven rank levels of escalation according to the potential danger of the behaviour. On the basis of the number of escalation levels included in the interactions, the complexity of the fights was also scored. We recorded the presence of other individuals during the interaction, the age, the antler size, the territorial status and the residency status of the two contestants and tested how these variables affected escalation, complexity and outcome of the fights. Most of the interactions ended with low levels of escalation, and physical contact occurred only in fights between two territorial bucks. The escalation was also affected by the difference in antler size index (the bucks escalated more when the difference in antler size was smaller) and increased with an increasing number of female deer present during the interaction. The resident buck won in 81% of the fights. When it drew or lost, it was generally both inferior in age and antler size, and the duration and escalation of the interactions were higher. However, even when a fight was lost, no territory loss occurred. These results are consistent with the evolutionary game theory and the proposed low risk–low gain strategy of roe deer bucks.