Bruno Cargnelutti

Landscape connectivity influences gene flow in a roe deer population inhabiting a fragmented landscape: an individual-based approach

Changes in agricultural practices and forest fragmentation can have a dramatic effect on landscape connectivity and the dispersal of animals, potentially reducing gene flow within populations. In this study, we assessed the influence of woodland connectivity on gene flow in a traditionally forest‐dwelling species — the European roe deer — in a fragmented landscape. From a sample of 648 roe deer spatially referenced within a study area of 55 × 40 km, interindividual genetic distances were calculated from genotypes at 12 polymorphic microsatellite loci. We calculated two geographical distances between each pair of individuals: the Euclidean distance (straight line) and the ‘least cost distance’ (the trajectory that maximizes the use of wooded corridors). We tested the correlation between genetic pairwise distances and the two types of geographical pairwise distance using Mantel tests. The correlation was better using the least cost distance, which takes into account the distribution of wooded patches, especially for females (the correlation was stronger but not significant for males). These results suggest that in a fragmented woodland area roe deer dispersal is strongly linked to wooded structures and hence that gene flow within the roe deer population is influenced by the connectivity of the landscape.

Genetic structure is influenced by landscape features: empirical evidence from a roe deer population

The delimitation of population units is of primary importance in population management and conservation biology. Moreover, when coupled with landscape data, the description of population genetic structure can provide valuable knowledge about the permeability of landscape features, which is often difficult to assess by direct methods (e.g. telemetry). In this study, we investigated the genetic structuring of a roe deer population which recently recolonized a fragmented landscape. We sampled 1148 individuals from a 40 × 55‐km area containing several putative barriers to deer movements, and hence to gene flow, namely a highway, rivers and several canals. In order to assess the effect of these landscape features on genetic structure, we implemented a spatial statistical model known as geneland which analyses genetic structure, explicitly taking into account the spatial nature of the problem. Two genetic units were inferred, exhibiting a very low level of differentiation (FST = 0.008). The location of their boundaries suggested that there are no absolute barriers in this study area, but that the combination of several landscape features with low permeability can lead to population differentiation. Our analysis hence suggests that the landscape has a significant influence on the structuring of the population under study. It also illustrates the use of geneland as a powerful method to infer population structure, even in situations of young populations exhibiting low genetic differentiation.

Red deer stags use formants as assessment cues during intrasexual agonistic interactions

While vocal tract resonances or formants are key acoustic parameters that define differences between phonemes in human speech, little is known about their function in animal communication. Here, we used playback experiments to present red deer stags with re-synthesized vocalizations in which formant frequencies were systematically altered to simulate callers of different body sizes. In response to stimuli where lower formants indicated callers with longer vocal tracts, stags were more attentive, replied with more roars and extended their vocal tracts further in these replies. Our results indicate that mammals other than humans use formants in vital vocal exchanges and can adjust their own formant frequencies in relation to those that they hear.

Contexts and possible functions of barking in roe deer

We studied the barking behaviour of free-ranging roe deer, Capreolus capreolus, in response to disturbance provoked by a human observer and in response to the playback of recorded barks. Three alternative functions of this behaviour were hypothesized: barking is an alarm call, a pursuit-deterrent call or a territorial call. Our observational data showed that, in the presence of a source of disturbance, solitary individuals barked more frequently than deer in groups, suggesting that barking does not serve to warn conspecifics of potential danger, but rather to inform any potential predator that it has been identified. The frequencies of both barking and counterbarking (barking of a second deer in response to the barks of an initiator) were inversely correlated with ambient luminosity, probably because the assessment of danger is more difficult when visibility is low. Males barked more frequently than females when disturbed. Moreover, when we played back a series of barks from within a bucks territory, this provoked counterbarking or aggressive behaviours rather than flight. Older bucks responded more frequently to playbacks than younger bucks. We suggest that while barking may initially have evolved as a signal to deter predator pursuit, it could play an important, secondary role in the territorial system of this species. Copyright 1999 The Association for the Study of Animal Behaviour.

Landscape composition influences roe deer habitat selection at both home range and landscape scales

Understanding how patterns of habitat selection vary in relation to landscape structure is essential to predict ecological responses of species to global change and inform management. We investigated behavioural plasticity in habitat selection of roe deer (Capreolus capreolus) in relation to variable habitat availability across a heterogeneous agricultural landscape at the home range and landscape scales. As expected, woodland was heavily selected, but we found no functional response for this habitat, i.e. no shift in habitat selection with changing habitat availability, possibly due to the presence of hedgerows which were increasingly selected as woodlands were less abundant. Hedgerows may thus function as a substitutable habitat for woodlands by providing roe deer with similar resources. We observed a functional response in the use of hedgerows, implying some degree of landscape complementation between hedgerows and open habitats, which may in part compensate for lower woodland availability. We also expected selection for woodland to be highest at the wider spatial scale, especially when this habitat was limiting. However, our results did not support this hypothesis, but rather indicated a marked influence of habitat composition, as both the availability and distribution of resources conditioned habitat selection. There was no marked between-sex difference in the pattern of habitat selection at either scale or between seasons at the landscape scale, however, within the home range, selection did differ between seasons. We conclude that landscape structure has a marked impact on roe deer habitat selection in agricultural landscapes through processes such as landscape complementation and supplementation.

Testing Global Positioning System Performance for Wildlife Monitoring Using Mobile Collars and Known Reference Points

Abstract To determine the spatial resolution of Global Positioning System (GPS) receiver data, rigorous testing is essential. We tested performance of the Lotek 3300 GPS collar for medium-sized mammals (Lotek Engineering, Inc., Newmarket, ON, Canada). To mimic real wildlife monitoring situations, we performed both static (stationary receiver) and mobile tests, placing the receiver collar on a dog. We compared fix locations of the mobile receiver with the actual trajectory described by a portable Trimble high-precision GPS. We determined performance in relation to habitat type and leaf cover. Location error was habitat-dependent, with the best results in open habitat and much poorer ones in forest, particularly coniferous-dominated forest. For both static and mobile tests, location accuracy was higher when the number of satellites contacted was high and when the residual positional dilution of precision (PDOP) value was low. However, location error was highly variable, even for a given PDOP value and a given number of satellites contacted. Finally, mobile collars performed less well than their static counterparts, presumably because of frequent changes of GPS position and orientation.

Habitat use under predation risk: hunting, roads and human dwellings influence the spatial behaviour of roe deer

Wildlife populations are subjected to increasing pressure linked to human activities, which introduce multiple stressors. Recently, in addition to direct effects, it has been shown that indirect (non-lethal) effects of predation risk are predominant in many populations. Predation risk is often structured in space and time, generating a heterogeneous “landscape of fear” within which animals can minimize risks by modifying their habitat use. Furthermore, for ungulates, resource quality seems to be positively correlated with human-related sources of risk. We studied the trade-off between access to resources of high-quality and risk-taking by contrasting habitat use of roe deer during daytime with that during nighttime for 94 roe deer in a hunted population. Our first hypothesis was that roe deer should avoid human disturbance by modifying their habitat use during daytime compared to nighttime. Our results supported this, as roe deer mainly used open fields during nighttime, but used more forested habitats during daytime, when human disturbance is higher. Moreover, we found that diel patterns in habitat use were influenced by hunting disturbance. Indeed, the roe deer decreased their use of high-crops during daytime, an important source of cover and food, during the hunting season. The proximity of roads and dwellings also affected habitat use, since roe deer used open fields during daytime to a greater extent when the distance to these sources of disturbance was higher. Hence, our results suggest that roe deer resolve the trade-off between the acquisition of high-quality resources and risk avoidance by modifying their habitat use between day and night.

The Effect of Capture on Ranging Behaviour and Activity of the European Roe Deer Capreolus capreolus

Locating and monitoring animals using tracking devices is a method commonly used for many taxa to study characteristics such as home-range size, habitat selection, movement patterns and other aspects of ranging behaviour. Fitting such devices requires the capture and handling of the study organism and researchers must then assume that a monitored animal behaves in a ‘normal’ way. We investigated whether the capture and handling of roe deer Capreolus capreolus induced behavioural alterations. In particular, we expected that the roe deer would exhibit a ‘seeking a refuge and waiting before returning’ strategy immediately after release, taking shelter far from the capture scene, in closed habitat, and exhibiting a reduced activity level. We evaluated the effect of capture and handling on 112 roe deer equipped with GPS collars, during a period of 50 days after release. We compared the first 10 days after release with the subsequent days for the following behavioural parameters: distance to the barycentre of their GPS fixes, presence in forest habitat, distance to the nearest forest patch, distance to a source of human disturbance, and activity level. We found pronounced differences in terms of spatial behaviour, habitat use and overall activity level between the two periods in GPS monitored roe deer. We also found differences in terms of spatial displacement between the sexes, with females responding less than males, and among age classes, with yearlings responding most and fawns least, to the capture and handling event. Finally, spatial displacement of roe deer increased with openness of the habitat due, in part, to the scarcity of available shelter in open areas. We conclude that the roe deer exhibited a strategy consisting of seeking a refuge and waiting before returning after capture, handling and fitting of a collar, with displacement towards a refuge habitat, in or near woodland, avoidance of sources of human disturbance and reduced activity levels. From a practical point of view, we recommend removing data during the first days of monitoring as behavioural alterations due to capture and handling may be pronounced.

Landscape fragmentation generates spatial variation of diet composition and quality in a generalist herbivore

Forest fragmentation may benefit generalist herbivores by increasing access to various substitutable food resources, with potential consequences for their population dynamics. We studied a European roe deer (Capreolus capreolus) population living in an agricultural mosaic of forest, woodlots, meadows and cultivated crops. We tested whether diet composition and quality varied spatially across the landscape using botanical analyses of rumen contents and chemical analyses of the plants consumed in relation to landscape metrics. In summer and non-mast winters, roe deer ate more cultivated seeds and less native forest browse with increasing availability of crops in the local landscape. This spatial variation resulted in contrasting diet quality, with more cell content and lower lignin and hemicellulose content (high quality) for individuals living in more open habitats. The pattern was less marked in the other seasons when diet composition, but not diet quality, was only weakly related to landscape structure. In mast autumns and winters, the consumption of acorns across the entire landscape resulted in a low level of differentiation in diet composition and quality. Our results reflect the ability of generalist species, such as roe deer, to adapt to the fragmentation of their forest habitat by exhibiting a plastic feeding behavior, enabling them to use supplementary resources available in the agricultural matrix. This flexibility confers nutritional advantages to individuals with access to cultivated fields when their native food resources are depleted or decline in quality (e.g. during non-mast years) and may explain local heterogeneities in individual phenotypic quality.

VOCAL BEHAVIOUR IN THE ENDANGERED CORSICAN DEER: DESCRIPTION AND PHYLOGENETIC IMPLICATIONS

ABSTRACT Here we present the first description of the vocal behaviour of the Tyrrhenian subspecies of Red Deer, the Corsican Deer. Vocalisations from calves, hinds and stags were recorded. Their acoustic characteristics were analysed in order to contrast these with published data characterising central European Red Deer hind and calve contact calls and Scottish Red Deer stag mating calls. We found that the vocal repertoire of Corsican Deer was very comparable with that of central European and Scottish Red Deer, with the exception of one call type, the harsh roar, absent in the Corsican Deer repertoire. Because Corsican Deer are the smallest subspecies of Red Deer, we expected calls to be characterised by higher spectral components. However, while male roars did have higher vocal tract resonances, consistent with a shorter vocal tract, we found that the fundamental frequency (FO) was much lower than predicted, in fact the lowest recorded in any studied Red Deer subspecies. We also found a strong sexual dimorphism in FO, with male calls approximately twice as low as female calls, suggesting that the low FO observed in Corsican male roars is a result of sexual selection for lower-pitched males. The results of this study emphasise the phenotypic originality of Corsican Deer, and strengthen the case for its conservation. We also argue that future studies should compare the vocal behaviour of Corsican Deer with that of other circum-Mediterranean populations.