Jean-François Gérard

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In large mammalian herbivores, the increase of group size with habitat openness was first assumed to be an adaptive response, encoded in the individual. However, it could, alternatively, be an emergent property: if groups were nonpermanent units, often fusing and splitting up, then any increase of the distance at which animals perceive one another could(More)
It is generally assumed that an individual of a prey species can benefit from an increase in the number of its group's members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan(More)
The activity budget hypothesis has been proposed to explain the social segregation commonly observed in ungulate populations. This hypothesis suggests that differences in body size – i.e. between dimorphic males and females – may account for differences in activity budget. In particular, if females spend more time grazing and less time resting than males,(More)
We investigated the effects of activity, group size and sex composition on the cohesion of merino sheep (Ovis aries) groups. Mixed-sex (50% of each sex) and single-sex groups of 2, 4, 6 and 8 sheep were placed within 491-m arenas located in natural pastures and were video recorded during 6 daily hours. The behaviour, orientation and location of each sheep(More)
Observations on the behaviour and ecology of the beira (Dorcatragus megalotis) were made during spring 2004 in a wild population discovered in 1993 in a low mountain range in the South of the Republic of Djibouti. Spring was found to be both a birthing and a mating season. Beiras fed in the first and last daylight hours, mainly on dicotyledons and in(More)
In March 2002, ten roe deer (Capreolus capreolus) were released in a partly wooded 14.2-ha enclosure to investigate the effect of high population density on vegetation cover and demographic parameters. However, in mid 2003, five animals died after rapid emaciation. Two other deer were killed to carry out further post-mortem examination. In addition to a(More)
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(More)
The way in which animals move and use the landscape is influenced by the spatial distribution of resources, and is of importance when considering species conservation. We aimed at exploring how landscape-related factors affect a large herbivore's space-use patterns by using a combined approach, integrating movement (displacement and recursions) and habitat(More)
Activities ordinarily performed by an animal in a given place may influence the way it behaves towards an object newly found there. We examined the use of probing tools in a group of 4 wedge-capped capuchins (Cebus olivaceus), in the home cage into which we simultaneously introduced two identical apparatuses, one at a site ordinarily used to manipulate(More)
We studied the social and spatial organisation of the beira (Dorcatragus megalotis) in arid low mountains in the South of the Republic of Djibouti. Beira was found to live in socio-spatial units whose ranges were almost non-overlapping, with a surface area of about 0.7 km2. Each unit included a single adult male, and from one to three adult females. On(More)