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.

Sexual segregation in fallow deer: are mixed-sex groups especially unstable because of asynchrony between the sexes?

In gregarious ruminants, females and males tend to live in separate groups outside the rutting season. According to the 'activity budget' hypothesis, this is due to an activity asynchrony between the two sexes reducing the lifetime of mixed-sex groups. We tested this hypothesis in a fallow deer population. Activity asynchrony was more frequent in mixed-sex than in single-sex groups. In addition, mixed-sex groups had a higher probability of splitting-up than all-female groups, and they mainly split up into single-sex groups. However, activity asynchrony did not appear as a major cause of splitting-up.

Can dental microwear textures record inter-individual dietary variations?

BACKGROUND: Dental microwear analyses are commonly used to deduce the diet of extinct mammals. Conventional methods rely on the user identifying features within a 2D image. However, recent interdisciplinary research has lead to the development of an advanced methodology that is free of observer error, based on the automated quantification of 3D surfaces by combining confocal microscopy with scale-sensitive fractal analysis. This method has already proved to be very efficient in detecting dietary differences between species. Focusing on a finer, intra-specific scale of analysis, the aim of this study is to test this method's ability to track such differences between individuals from a single population. METHODOLOGY/PRINCIPAL FINDINGS: For the purposes of this study, the 3D molar microwear of 78 individuals from a well-known population of extant roe deer (Capreolus caprelous) is quantified. Multivariate statistical analyses indicate significant seasonal and sexual differences in individual dental microwear design. These are probably the consequence of seasonal variations in fruit, seed and leaf availability, as well as differences in feeding preference between males and females due to distinct energy requirements during periods of rutting, gestation or giving birth. Nevertheless, further investigations using two-block Partial Least-Squares analysis show no strong relationship between individual stomach contents and microwear texture. This is an expected result, assuming that stomach contents are composed of food items ingested during the last few hours whereas dental microwear texture records the physical properties of items eaten over periods of days or weeks. CONCLUSIONS/SIGNIFICANCE: Microwear 3D scale-sensitive fractal analysis does detect differences in diet ranging from the inter-feeding styles scale to the intra-population between-season and between-sex scales. It is therefore a possible tool, to be used with caution, in the further exploration of the feeding biology and ecology of extinct mammals.

Density dependence of developmental instability in a dimorphic ungulate.

The use of fluctuating asymmetry (FA) for biomonitoring environmental stress is limited by the lack of work on how FA in particular traits responds to specific stresses. Here, by manipulating the number of individuals in an enclosed fallow deer (Dama dama) population, we describe, for the first time, clear density dependence in the FA of juvenile jaw morphology. The impact of high population density on FA was strong for both sexes, supporting the use of FA for indexing environmental stress. In addition, there was some indication that the change in FA was greater in males (43.6%) than females (28.5%). Finally, the ability to buffer density-dependent stress was independent of body condition. We suggest that, under highly limiting conditions, whole cohorts may be unable to buffer against developmental error, irrespective of individual quality.

An experimental study of social attraction and spacing between the sexes in sheep.

Most ungulates are gregarious species and outside the mating season are typically observed in single-sex groups. However little is known about the mechanisms underlying social segregation between sexes. We investigated the effect of conspecific attraction on individual spacing between unrestrained merino sheep Ovis aries and confined conspecifics. We considered differences between males and females and whether attractiveness of the confined conspecifics depends on their sex. A series of binary choice experiments was conducted in a large outdoor arena, located in pastures. One or two stimulus animals were placed in small individual cages (1.5 m x 1 m) on opposite sides of the arena. Sheep were tested with one fixed peer of the same or opposite sex vs an empty cage, and with two fixed peers of either the same sex as themselves, or one male and one female. Sheep in a control condition were exposed to two empty cages. In all of the test conditions, confined sheep were highly attractive. Males were more attracted by single stimulus peers of the same than the opposite sex, whereas females did not display such a preference. Sheep confronted with two restrained conspecifics tended to remain between the stimuli. This also occurred when the stimuli were of opposite sex, although the males tended to be located nearer the same-sex peer. Our findings can explain the strong aggregative behaviour of merino sheep, but also the social segregation previously observed in a mixed-sex group through higher attraction for same-sex than opposite-sex peers in males.