Implications of the forage maturation hypothesis for activity of partially migratory male and female deer

Partial migration is common in a large variety of taxa in seasonally variable environments. Understanding the mechanisms underlying migration is important, as migration affects individual fi tness. Migratory herbivores bene fi t from delayed forage maturation and hence higher food quality during migra- tion and at their summer range, termed the forage maturation hypothesis (FMH). The link between diet quality and rumination time allows migrants eating a higher quality diet to spend less time on rumination, and they can thus allocate more time to additional feeding. However, such an argument implicitly assumes that deer are energy maximizers, while studies have reported also time minimization strategies under risk of predation. Male and female distributions are limited by different factors linked to both body size differ- ences and reproductive strategies, but there is no study investigating differences in activity pattern accord- ing to the individual migratory patterns for male and female deer. We here unify the FMH with the hypotheses predicting sex-speci fi c time allocation strategies. To test predictions of sex-speci fi c activity of resident and migratory red deer ( Cervus elaphus ), we analyzed activity data of 286 individuals that were fi tted with GPS collars from a population in western Norway. While migrants were more active during the migration itself, we found no differences in activity pattern between migrant and resident deer during the main growth season, neither in terms of proportion of daily time active nor in terms of daily mean movement speed, thus rejecting that deer were energy maximizers. Overall, we found that females were more active during the main growth season even after controlling for body size differences. These patterns are consistent with patterns predicted from sexual segregation theory linked to the reproductive strategy hypothesis. Our study highlights how the understanding of migration can be advanced by considering it in the context of different reproductive strategies of males and females.publishedVersio

Island tameness and the repeatability of flight initiation distance in a large herbivore

This is the author accepted manuscript. The final version is available from NRC Research Press via the DOI in this record.Antipredator behaviours can be lost relatively quickly in populations that are relieved of predation, as is known for several species inhabiting islands. Flight initiation distance (FID) is often studied in the context of island tameness; however, little is known about the factors that influence and maintain FID variation in predation-free populations. Here, we studied FID in foals of an isolated predator-free population of feral horses (Equus caballus L., 1758) on Sable Island, Canada, to determine if FID could be used for research on consistent individual differences in risk aversion and island tameness. In addition to testing for temporal, spatial, and sex effects on FID, we compared repeatability estimates at two temporal scales (within and among days). Similar FID for measurements obtained on the same day and for males and females indicated an absence of short-term desensitization and sex effects. In contrast, FID decreased for measurements made on subsequent days and from east to west, which could reflect habituation to human presence and (or) other temporal and spatial processes. Repeatability was high (0.42 ± 0.06), but tended to decrease with increasing time intervals. This study highlights the potential of FID for individual-based research on the ecology and evolutionary dynamics of risk aversion in predation-free populations.Funding was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC Discovery Grant No. 371535-2009 to P.D.M.), the Canada Foundation for Innovation (Leaders Opportunity Grant No. 25046 to P.D.M.), and a Royal Society International Exchange grant (J.P. and P.D.M.). D.A. was supported by an NSERC Ph.D. scholarship. D.C. received support from the University of Exeter M.Sc. program in Evolutionary and Behavioural Ecology. J.P. was supported by a Leverhulme Trust Early Career Research Fellowship

Sex differences in condition dependence of natal dispersal in a large herbivore: dispersal propensity and distance are decoupled

International audienceEvolution should favour plasticity in dispersal decisions in response to spatial heterogeneity in social and environmental contexts. Sex differences in individual optimization of dispersal decisions are poorly documented in mammals, because species where both sexes commonly disperse are rare. To elucidate the sex-specific drivers governing dispersal, we investigated sex differences in condition dependence in the propensity and distance of natal dispersal in one such species, the roe deer, using fine-scale monitoring of 146 GPS-collared juveniles in an intensively monitored population in southwest France. Dispersal propensity increased with body mass in males such that 36% of light individuals dispersed, whereas 62% of heavy individuals did so, but there was no evidence for condition dependence in dispersal propensity among females. By contrast, dispersal distance increased with body mass at a similar rate in both sexes such that heavy dispersers travelled around twice as far as light dispersers. Sex differences in the strength of condition-dependent dispersal may result from different selection pressures acting on the behaviour of males and females. We suggest that females disperse prior to habitat saturation being reached, likely in relation to the risk of inbreeding. By contrast, natal dispersal in males is likely governed by competitive exclusion through male–male competition for breeding opportunities in this strongly territorial mammal. Our study is, to our knowledge, a first demonstration that condition dependence in dispersal propensity and dispersal distance may be decoupled, indicating contrasting selection pressures drive the behavioural decisions of whether or not to leave the natal range, and where to settle

Flexibility but no coordination of visits in provisioning riflemen

Parental care strategies occupy a continuum from fixed investments that are consistent across contexts to flexible behaviour that largely depends on external social and environmental cues. Determining the flexibility of care behaviour is important, as it influences the outcome of investment games between multiple individuals caring for the same brood. We investigated the repeatability of provisioning behaviour and the potential for turn taking among breeders and helpers in a cooperatively breeding bird, the rifleman, Acanthisitta chloris. First, we examined whether nest visit rate is an accurate measure of investment by assessing whether carers consistently bring the same size of food, and whether food size is related to nest visit rate. Our results support the use of visit rate as a valid indicator of parental investment. Next, we calculated the repeatability of visit rate and food size to determine whether these behaviours are fixed individual traits or flexible responses to particular contexts. We found that riflemen were flexible in visit rate, supporting responsive models of care over ‘sealed bids’. Finally, we used runs tests to assess whether individual riflemen alternated visits with other carers, indicative of turn taking. We found little evidence of any such coordination of parental provisioning. We conclude that individual flexibility in parental care appears to arise through factors such as breeding status and brood demand, rather than as a real-time response to social partners

Habitat quality, configuration and context effects on roe deer fecundity across a forested landscape mosaic

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

From the animal house to the field : are there consistent individual differences in immunological profile in wild populations of field voles (Microtus agrestis)?

Inbred mouse strains, living in simple laboratory environments far removed from nature, have been shown to vary consistently in their immune response. However, wildlife populations are typically outbreeding and face a multiplicity of challenges, parasitological and otherwise. In this study we seek evidence of consistent difference in immunological profile amongst individuals in the wild. We apply a novel method in this context, using longitudinal (repeated capture) data from natural populations of field voles, Microtus agrestis, on a range of life history and infection metrics, and on gene expression levels. We focus on three immune genes, IFN-γ, Gata3, and IL-10, representing respectively the Th1, Th2 and regulatory elements of the immune response. Our results show that there was clear evidence of consistent differences between individuals in their typical level of expression of at least one immune gene, and at most all three immune genes, after other measured sources of variation had been taken into account. Furthermore, individuals that responded to changing circumstances by increasing expression levels of Gata3 had a correlated increase in expression levels of IFN-γ. Our work stresses the importance of acknowledging immunological variation amongst individuals in studies of parasitological and infectious disease risk in wildlife populations

Sex-specific differences in spring and autumn migration in a northern large herbivore

Ongoing global warming is now affecting migratory cycles in a large variety of taxa in seasonally variable environments. Disruption of migratory systems can cause population decline and affect ecosystem function across the globe. It is therefore urgent to understand the drivers of migration and how the different fitness limitations of the sexes affect migration, but studies seldom considered the full annual cycle. We analysed the annual migration cycle of 237 red deer (Cervus elaphus) in Norway and investigate how different seasonal limitations affected the variation in a suite of migration characteristics. We found fundamental differences in migration phenology between seasons, and migratory traits were much more variable in males. Spring migratory movements were characterized by longer distance roamed, lower speed, lasted longer, more frequent use of stopovers, timing was more synchronized and coincided with onset of plant growth, and with higher daily activity levels. Timing of autumn migration was more variable and not closely related to cease of plant growth. Our study emphasizes the benefits of studying the full annual cycle to gain further insight into the migration process, and how understanding the limitations of the full annual migration process of both sexes is critical for conservation purposes

Evidence for a breeding dispersal tactic in a large herbivore

From an evolutionary stand point, breeding dispersal, the net movement between successive breeding sites, remains a poorly understood and seldom reported phenomenon, despite its potential importance for population dynamics. This is particularly so for mammals, however, recent descriptive data from several species of large herbivore indicate that females may be unusually mobile during the breeding season, undertaking short trips outside their normal home range. We suggest that if fertilisation occurs during these exceptional forays, then this behaviour could be considered as a form of breeding dispersal, at least from a genetic point of view. This behaviour could be motivated by inbreeding avoidance, the search for good genes and/or multiple paternity. We illustrate this by investigating the ranging behaviour of GPS-monitored adult roe deer from six intensively studied populations across Europe. We show that excursions are common from June to August, with almost half of females making at least one excursion. Excursions are concentrated in time and centred on the rutting period, indicating a link with reproduction. The distance females travel during excursions was significantly greater than the diameter of an average male home range, while travel speed decreased as the female progressed beyond this diameter, indicating searching behaviour or interaction with other male(s) outside the resident male’s territory. Because adults of both sexes are normally highly sedentary, the potential for mating with relatives is substantial; hence, we conclude that rut excursions could be an alternative tactic enabling roe deer females to avoid mating with a closely related male

Interindividual variability in habitat use: evidence for a risk management syndrome in roe deer?

International audienc

Negative covariance between parasite load and body condition in a population of feral horses

International audienceIn wild and domestic animals, gastrointestinal parasites can have significant impacts on host development, condition, health, reproduction and longevity. Improving our understanding of the causes and consequences of individual-level variation in parasite load is therefore of prime interest. Here we investigated the relationship between strongyle fecal egg count (FEC) and body condition in a unique, naturalized population of horses that has never been exposed to anthelmintic drugs (Sable Island, Nova Scotia, Canada). We first quantified variation in FEC and condition for 447 individuals according to intrinsic (sex, age, reproductive status, social status) and extrinsic (group size, location, local density) variables. We then quantified the repeatability of measurements obtained over a field season and tested for covariance between FEC and condition. FECs were high relative to other horse populations (mean eggs per gram ± SD = 1543·28 ± 209·94). FECs generally decreased with age, were higher in lactating vs non-lactating females, and unexpectedly lower in males in some part of the island. FECs and condition were both spatially structured, with patterns depending on age, sex and reproductive status. FECs and condition were both repeatable. Most notably, FECs and condition were negatively correlated, especially in adult females