A one night stand? Reproductive excursions of female roe deer as a breeding dispersal tactic

Breeding dispersal, defined as the net movement between successive breeding sites, remains a poorly understood and seldom reported phenomenon in mammals, despite its importance for population dynamics and genetics. In large herbivores, females may be more mobile during the breeding season, undertaking short-term trips (excursions) outside their normal home range. If fertilisation occurs, leading to gene flow of the male genome, this behaviour could be considered a form of breeding dispersal from a genetic point of view. Here, we investigated ranging behaviour of 235 adult roe deer using intensive GPS monitoring in six populations across Europe within the EURODEER initiative. We show that excursions are common from June to August among females, with 41.8 % (vs. 18.1 % of males) making at least one excursion. Most individuals performed only one excursion per season and departure dates for females were concentrated in time, centred on the rutting period, suggesting a link with reproduction. The distance females travelled during excursions was significantly greater than the site-specific average diameter of a male home range, while travel speed decreased once they progressed beyond this diameter, indicating search behaviour or interaction with other male(s) outside the resident male’s territory. Because adults are normally highly sedentary, the potential for mating with relatives is substantial; hence, we conclude that rut excursions could be an alternative tactic enabling females to avoid mating with a closely related male. To understand better the ultimate drivers at play, it will be crucial to explore the genetic causes and consequences of this behaviour.     

Going Out to Mate: Excursion Behaviour of Female Roe Deer

Among mammals, female searching behaviour for a mate has been poorly investigated in behavioural studies on sexual selection. The social organization of roe deer and its physiological constraints suggest the existence of searching strategies by females. Using radiotracking and direct observation we studied the spatial behaviour and intersexual interactions of 32 roe does during the rut in two areas of Tuscany, central Italy. Respectively, 55% and 33% of females performed excursions outside their usual home ranges during the peak of the rut (15 Jul.–15 Aug.). Excursions ranged from 0.6 to 3.0 km, if measured in a straight line, and lasted 30–52 h. During excursions, females (1) moved quickly in one direction; (2) met and were courted by a male; (3) copulated with a male and (4) returned to their home ranges after mating. Before starting an excursion, roaming females were observed to approach unsuccessfully males already courting other females. Most likely excursions represent a condition dependent mating tactic adopted by a variable proportion of females and involving active searching behaviour.     

Home range dynamics of male roe deerCapreolus capreolus in a mountainous habitat

Male spacing behaviour of roe deer Capreolus capreolus (Linnaeus, 1758) was studied in a wooded mountainous habitat in the Casentinesi Forest National Park, Italy. Data were collected using radio-tracking techniques from March 1997 to February 1998. Annual, seasonal, and bimonthly home ranges were analysed. Different factors may influence male spacing behaviour throughout the year. Winter home range sizes may be dependent on environmental conditions, while social factors could determine a high level of individual variability during the territorial and reproductive period. Prime age males showed great spatial stability, in contrast to the ranging movements of yearlings.     

Breeding behavior of female white‐tailed deer relative to conception: Evidence for female mate choice

Female white‐tailed deer (Odocoileus virginianus) are thought to choose between two behavioral strategies to maximize the quality of potential mates: sit and wait, characterized by concentrating activity within a restricted area, and excursive behavior, characterized by increased activity and excursions outside the home range. As movement patterns may influence conception, our goal was to examine the patterns of female white‐tailed deer movements to evaluate which breeding strategy was employed. We equipped 36 female white‐tailed deer with GPS collars from August 2013 to December 2015. We found that movement rate and probability of activity were greatest near the peak of the breeding season, and we observed increases in both metrics during the 40 days prior to estimated conception. Peak size of home range and core area occurred in the days surrounding conception. We found that 11 deer performed an excursion, ranging from 43 days before until 36 days after conception, with the peak probability of being outside of an individual home range occurring 1 day prior to conception. Our results suggest that female white‐tailed deer may attempt to maximize the quality of their mates by advertising availability for breeding through excursive behaviors just prior to entering estrus.     

Experimental evidence for density-dependence of home-range size in roe deer (<Emphasis Type="Italic">Capreolus capreolus</Emphasis> L.): a comparison of two long-term studies

The effect of experimental manipulation of population density on home-range size was investigated in two free-ranging roe deer (Capreolus capreolus) populations under contrasting environmental conditions. In these two long-term monitoring studies, one in Bogesund, Sweden (12 years) and one in Dourdan, France (10 years), deer density varied fourfold through varying culling pressure. Home-range data were collected by radio-tracking across the periods of contrasting density of the studies. We predicted that home-range size for females should vary in relation to the level of feeding competition, while for males, competition for mating opportunities should also influence range size, at least in summer when roe bucks are territorial. We found a highly consistent pattern over the two populations, with strong effects of deer density on home-range size, as well as significant differences between winter and summer ranges and between the sexes. Home ranges were consistently smaller at high density compared to low density. Males had larger ranges than females and this was particularly so during summer. Lastly, winter ranges were generally larger than summer ranges, particularly among females, although males at Dourdan had larger summer ranges compared to winter ranges. We suggest that the reduction of range size at high deer density during winter, as well as summer, is linked to the solitary behaviour and territorial social system of roe deer, with possible effects of dominance rank, even outside the mating season.     

Do male roe deer clump together during the rut?

Movement s an d habitat use of 7 male and 7 female roe deerCapreolus capreolus (Linnaeus, 1758) were studied by radioteleme try from March 1999 to February 2001. Annual and bimonthly home ranges of males were small (ca 10 ha, 95% kernel), with large overlap among individuals throughout the year. Exclusive core areas (ca 0.4 ha, 25% kernel) were concentrated in the forest, a limited and sought-after resource in the study area. The difference in overlap between male exclusive core areas and female home ranges in the pre-rut and rut periods suggested that females made excursions to search for territorial males during the rut Our results support the mating strategy hypothesis of territorial behaviour Different space use patterns occurred between the sexes, with females apparently playing an active role in mate choice by visiting males at clumps of core areas in the forest.     

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.     

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.     

Life cycle period and activity of prey influence their susceptibility to predators

In a multi‐prey system, predators kill different kinds of prey according to their availability, where “availability” is a function of prey abundance and vulnerability (e.g. anti‐predator behavior). We hypothesized that prey availability changes seasonally, for instance because reproduction leads to a higher abundance of young in spring and summer or because changes in behavior such as during the mating season makes the prey periodically more vulnerable. We tested this hypothesis in a simple predator‐prey system in the Jura Mountains of Switzerland and France, where a single large mammalian predator, the Eurasian lynx, preys upon two ungulate species, the roe deer and the chamois. In 1996 and 1997 we were able to assign a total of 190 roe deer and 54 chamois killed by lynx to a specific age and sex class (males, females or juveniles). As expected, the proportion of juveniles killed varied considerably among periods, being at the highest from 1st of June to 15th of August. No significant seasonal differences were detected regarding the frequency of predation on males versus females. In particular, the interaction between species and period, expected because of different timing of the rutting period between roe deer and chamois, was not significant. Females were killed only slightly more often during gestation. The relationship between prey abundance and vulnerability is highly complex, as the lynx’ prey selection needs to be analyzed not only horizontally (changes of a specific prey category with season) but also vertically (an increase in the vulnerability of one category releases predation pressure on others). Second, we predicted that certain activities, such as feeding, expose prey to predation more than others. We found more chamois predated when feeding, whereas roe deer were predated mainly when ruminating. This interspecific discrepancy reflects differences either in the anti‐predator behavior of roe deer and chamois or in the relative time allocation to feeding and ruminating between the two species.     

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.     

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.     

Inter-specific competition from fallow deer Dama dama reduces habitat quality for the Italian roe deer Capreolus capreolus italicus

The roe deer of Mediterranean habitats in the central and southern parts of Italy has recently been recognised as a distinct subspecies, Capreolus capreolus italicus . A population of this endangered subspecies has been monitored in the Preserve of Castelporziano, near Rome, since 1988. We observed an abrupt population decline in 2000, which may severely threaten the sustainability of this population. We evaluated the hypothesis that competition by fallow deer may be a principal cause of this decline. By a new and innovative methodology, we modelled the spatial distribution of fallow deer density (FDD) in the study area to show that 1) habitat quality for roe deer was an inverse function of FDD, 2) habitat apportionment between fallow and roe deer increased as a function of FDD and – by applying structural equation modelling – 3) FDD was superior to habitat composition in explaining observed variations in home range size and probably in habitat quality for roe deer. This analysis is the first to document that inter-specific competition may influence the spatial behaviour of a deer species leading to poor phenotypic performance in the inferior competitor. We conclude that the conservation of this relict population would benefit by reducing fallow deer numbers at Castelporziano and from other measures aimed to decrease the level of inter-specific competition.     

Toward an identification of resources influencing habitat use in a multi-specific context

Interactions between animal behaviour and the environment are both shaping observed habitat use. Despite the importance of inter-specific interactions on the habitat use performed by individuals, most previous analyses have focused on case studies of single species. By focusing on two sympatric populations of large herbivores with contrasting body size, we went one step beyond by studying variation in home range size and identifying the factors involved in such variation, to define how habitat features such as resource heterogeneity, resource quality, and openness created by hurricane or forest managers, and constraints may influence habitat use at the individual level. We found a large variability among individual's home range size in both species, particularly in summer. Season appeared as the most important factor accounting for observed variation in home range size. Regarding habitat features, we found that (i) the proportion of area damaged by the hurricane was the only habitat component that inversely influenced roe deer home range size, (ii) this habitat type also influenced both diurnal and nocturnal red deer home range sizes, (iii) home range size of red deer during the day was inversely influenced by the biomass of their preferred plants, as were both diurnal and nocturnal core areas of the red deer home range, and (iv) we do not find any effect of resource heterogeneity on home range size in any case. Our results suggest that a particular habitat type (i.e. areas damaged by hurricane) can be used by individuals of sympatric species because it brings both protected and dietary resources. Thus, it is necessary to maintain the openness of these areas and to keep animal density quite low as observed in these hunted populations to limit competition between these sympatric populations of herbivores.     

Vulnerability of Domestic Sheep to Lynx Depredation in Relation to Roe Deer Density

Abstract The Eurasian lynx (Lynx lynx) causes large loss of free-ranging domestic sheep in Norway. We tested whether the observed higher kill rates by male lynx than female lynx were related to an association between the availability of the main natural prey, as measured by roe deer (Capreolus capreolus) habitat suitability, presence of sheep, and habitat selection of male and female lynx. We found that lynx selected areas with high roe deer suitability during summer and winter. Moreover, during summer, compared to male lynx, females had greater selection for roe deer areas and a stronger avoidance for sheep grazing areas, which suggests that previously observed differences in kill rates between male and female lynx can be attributed to sex-specific habitat use during summer. The connection between lynx habitat use and roe deer also was reflected in a positive relationship between the roe deer suitability of a sheep grazing area and the total loss of lambs, which suggests that livestock, rather than being actively selected, are mainly killed by lynx incidentally when encountered during other lynx activities (e.g., searching for natural prey species). Therefore, any management practice that separates lynx and sheep, such as concentrating livestock into small patches or less preferred habitats, may reduce depredation.     

Population responses of roe deer to the recolonization of the French Vercors by wolves

In a context of changing carnivore populations worldwide, it is crucial to understand the consequences of these changes for prey populations. The recolonization by wolves of the French Vercors mountain range and the long-term monitoring (2001–2017) of roe deer in this area provided a unique opportunity to assess the effects of wolves on this prey. Roe deer was the main prey of wolves in the west Vercors mountain range during this recolonization. We compared roe deer abundance and fawn body mass in two contrasted areas of a wolf pack territory: a central area (core of the territory characterized by an intense use by wolves) and a peripheral area (used more occasionally). Roe deer population growth rates were lower in the central area between 2001 and 2006, resulting in a decline in roe deer abundance. Roe deer abundance substantially dropped in the two study areas after an extremely severe winter but the abundance of roe deer in the central area facing with wolves was slower to recover and remained at lower abundance levels for 6 years. Fawn body mass was consistently lower in the central area, varied similarly as roe deer abundance, and was not influenced by weather conditions or red deer population abundance. Altogether, the effects of wolves on roe deer in the central area occurred during a 10-year period following the establishment of wolves, through the interplay between wolf predation (before wolves started preying on red deer), harsh winter conditions and possibly naivety of prey to this recolonizing predator.     

Behavioural and spatial adaptation of the Eurasian lynx to a decline in prey availability

The distribution and abundance of food resources is a major factor influencing animal populations. I studied the effect of a roe and red deer population decline on diet composition, home range size and foraging pattern in the Eurasian lynxLynx lynx (Linnaeus, 1758) in the Bia?owie?a Primeval Forest (BPF), eastern Poland. The population of cervids in BPF experienced a nearly two-fold reduction in size from 1991 through 2006 due to severe hunting pressure between 1991 and 1996. Comparison of published data on lynx diet during the high abundance of ungulates with new data obtained for the low abundance period showed that despite a significant decline in their availability, cervids (roe and red deer) continued to form the majority of the diet of lynx, with roe deer being most preferred in both periods. Home range sizes of lynx showed a tendency to increase with declining prey densities, as indicated by relative percentage increases in average yearly home range sizes amongst different sex/age groups. In response to lower availability of their main prey, lynx increased their daily straight-line movement distances by 44% and doubled the ranges covered in 5-day periods. This illustrated that, with declining prey abundance, the lynx increased their hunting efforts by either spending more time actively searching for prey or continuing foraging even after a successful hunt. Spatial analysis of the distribution of ungulates and lynx indicated that deer were evenly distributed throughout lynx ranges in BPF and spatial proximity of the predator to prey sites did not play an important role in the efficiency of hunting. Lynx may adapt to changing prey availability by increasing search effort, but this was not sufficient to prevent the negative influences of the prey decline on the lynx population. Prey depletion has an immediate effect on lynx spatial organization and, in consequence, on their density. This information has to be considered in prioritizing lynx conservation measures and management of ungulates.     

Seasonal home range shift of red deer in a forest-agriculture area in southern Hungary

A long-term radiotelemetry study on red deerCervus elaphus Linnaeus, 1758 was carried out in a lowland forest-agriculture area in Hungary between 1993–2000. Previous observations suggested seasonal changes in population distribution between forested and agricultural habitat. Red deer concentrated in the forest during winter, but they appeared in the agricultural field during the vegetational period. We investigated the ranging behaviour, testing two alternative hypotheses: home range expansion and home range shift. Weekly radiotelemetry localisations revealed that 9 of 28 hinds showed a clear home range shift from the forest to the agricultural area for a prolonged time during the vegetational period. The remaining portion of the animals used a home range within the forest throughout the entire year. Diet composition analysis using indicator plant species showed that neither daily passages between habitats, nor home range expansion exists. These ranging behaviours were stable hence, if an animal shifted one year it shifted again in consecutive years andvice versa. Our results could be useful for the successful management of red deer populations in such complex habitats and to decrease agricultural damage.     

Evaluating Indirect Effects of Hunting on Mule Deer Spatial Behavior

Mule deer (Odocoileus hemionus) are widely hunted throughout western North America and are experiencing population declines across much of their range. Consequently, understanding the direct and indirect effects of hunting is important for management of mule deer populations. Managers can influence deer mortality rates through changes in hunting season length or authorized tag numbers. Little is known, however, about how hunting can affect site fidelity patterns and subsequent habitat use and movement patterns of mule deer. Understanding these patterns is especially important for adult females because changes in behavior may influence their ability to acquire resources and ultimately affect their productivity. Between 2008 and 2013, we obtained global positioning system locations for 42 adult female deer at the Starkey Experimental Forest and Range in northeast Oregon, USA, during 5-day control and treatment periods in which hunters were absent (pre-hunt), present but not actively hunting (scout and post-hunt), and actively hunting male mule deer (hunt) on the landscape. We estimated summer home ranges and 5-day use areas during pre-hunt and hunt periods and calculated overlap metrics across home ranges and use areas to assess site fidelity within and across years. We used step selection functions to evaluate whether female mule deer responded to human hunters by adjusting fine-scale habitat selection and movement patterns during the hunting season compared to the pre-hunt period. Mule deer maintained site fidelity despite disturbance by hunters with 72 ± 4% (SE) within-year overlap between summer home ranges and hunt use areas and 54 ± 7% inter-annual overlap among pre-hunt use areas and 56 ± 7% among hunt use areas. Mule deer diurnal movement rates, when hunters are active on the landscape, were higher during the hunting period versus pre-hunt or scout periods. In contrast, nocturnal movement rates, when hunters are inactive on the landscape, were similar between hunting and non-hunting periods. Additionally, during the hunt, female mule deer hourly movements increased in areas with high greenness values, indicating that mule deer spent less time in areas with more vegetative productivity. Female mule deer maintained consistent habitat selection patterns before and during hunts, selecting areas that offered more forest canopy cover and high levels of vegetative productivity. Our results indicate that deer at Starkey are adopting behavioral strategies in response to hunters by increasing their movement rates and selecting habitat in well-established ranges. Therefore, considering site fidelity behavior in management planning could provide important information about the spatial behavior of animals and potential energetic costs incurred, especially by non-target animals during hunting season. © 2020 The Wildlife Society.     

Deer mouse movements in peridomestic and sylvan settings in relation to Sin Nombre virus antibody prevalence

Prevalence of antibody to Sin Nombre virus (SNV) has been found to be nearly twice as high in deer mice (Peromyscus maniculatus) in peridomestic settings as in sylvan settings in two studies in Montana and one in New Mexico. We investigated whether this difference may be related to a difference in deer mouse movements in the two settings. We used radiotelemetry to determine home range size and length of movement for 22 sylvan (1991-1992) and 40 peridomestic deer mice (1995-1999). We also determined the percentage of locations inside versus outside of buildings for peridomestic mice. Though variable, average home range size for female deer mice was significantly smaller for peridomestic deer mice than for sylvan deer mice. The smaller home range in peridomestic settings may concentrate shed SNV, and protection from solar ultraviolet radiation inside buildings may increase environmental persistence of SNV. Both these factors could lead to increased SNV exposure of deer mice within peridomestic populations and result in higher antibody prevalence. Peridomestic deer mice moved between buildings and outside areas, which is evidence that SNV can be transmitted between peridomestic and sylvan populations.