An example of segregation between age and sex classes only weakly related to habitat use in mouflon sheep (<i>Ovis gmelini</i>)

Cransac, Nathalie; Gérard, Jean‐François; Maublanc, Marie‐Line; Pépin, Dominique

doi:10.1111/j.1469-7998.1998.tb00042.x

Cited by 69 publications

(39 citation statements)

References 34 publications

(48 reference statements)

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“…Therefore the sexual-segregation peak we observed in spring in both populations (figure 2) cannot be accounted for by sexual differences in forage selection or activity budget caused by lactation alone, and is likely to be related to the antipredator behaviour. (c) Social segregation Sexual segregation was long thought to be a by-product of different habitat selection by females and males (Clutton-Brock et al 1987), even though some studies reported segregation despite small differences in habitat use between the sexes (Cransac et al 1998;Ruckstuhl 1998). Sexual segregation regardless of habitat (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Several studies dealing with sexual segregation have considered data from all seasons (e.g. Miquelle et al 1992;Villaret et al 1997;Cransac et al 1998;Bon et al 2001), but all except Cransac et al (1998), who presented monthly estimates for mouflon sheep (Ovis gmelini ), provided the segregation estimates on a coarse time-scale. High-resolution temporal patterns of sexual segregation covering the full year have therefore rarely been presented for ungulates, and previous studies have never taken advantage of methodological improvements that allow separation of the social and habitat components of segregation (Conradt 1998b).…”

Section: Introductionmentioning

confidence: 99%

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Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude

Bonenfant

Loe

Mysterud

et al. 2004

Proc. R. Soc. Lond. B

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Sexual segregation outside the mating season occurs in most species of sexually dimorphic ungulates and has been extensively described in the literature, but the mechanisms causing segregation are still debated. The detailed pattern of sexual segregation throughout the year has rarely been presented for mammals, and no study, to our knowledge, has used latitudinal-related variation in breeding phenology to shed light on the underlying mechanisms. Recent methodological developments have made it possible to quantify separate components of segregation (social, habitat) and activity synchrony in animal groups, but these major improvements have so far been little used. We observed European red deer year round at two widely different latitudes (France and Norway) and tested three different mechanistic hypotheses of segregation related to: (i) predation risk; (ii) body-size-related forage selection; and (iii) activity budget. Habitat segregation peaked during calving in both populations and dropped rapidly after calving. Females with calves were more segregated from males than were females without calves, pointing to a key role of antipredator behaviour even though large predators are absent in France and extremely rare in Norway. However, at both sites individuals also grouped with their own sex within habitat types (i.e. social segregation), and individuals in mixed-sex groups were less synchronized in activity type than individuals in either unisex male or unisex female groups, suggesting that differences in activity budgets are involved. Social segregation peaked during calving and was lowest during the rut (indicating aggregation) in both populations; these activities occurred one month later in the Northern populations, corresponding well with known differences in breeding phenology. We conclude that latitude-dependent breeding phenology shapes the seasonal pattern of sexual segregation and that sexual segregation in ungulates has multiple causes.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude

Bonenfant

Loe

Mysterud

et al. 2004

Proc. R. Soc. Lond. B

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“…Temperature (daily mean) and the date of surveys ranged from 6.3°C to 20.3°C and from 13 May to 14 June, respectively, for the pedestrian surveys, and from 11.0°C to 23.0°C and from 5 June to 12 July, respectively, for the helicopter surveys. The date of survey and the temperature are expected to influence counts because these variables influence the use of open areas by mouflons and the intensity of spatial and sexual segregation (Bon et al 1990;Santosa et al 1990;Cransac et al 1998). We also accounted for differences in PAI and in temperature according to transects due to differences in space use of mouflons and physical characteristics of the sample areas (e.g.…”

Section: Model Adjustmentmentioning

confidence: 99%

Monitoring the abundance of mouflon in South France

et al. 2005

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Monitoring change in the population size of mouflon (Ovis gmelini musimon · Ovis sp.) in rugged areas is an important yet difficult task for wildlife ecologists. To assess population change of mouflon inhabiting the Caroux-Espinouse massif, France, we compared a pedestrian and helicopter survey, using counts of animals as indices of abundance. Environmental factors such as date of survey and temperature affected the detection of mouflons from the ground and the air. Both indices were sensitive to observed changes in population size. A decrease in the pedestrian index was recorded in 1994, the year following an epizootic of keratoconjunctivitis, which markedly reduced the survival rate of mouflon. Variations in pedestrian index accounted for variations in harvests when excluding epizootic events. Both surveys detected a decrease in population size, which accounted for the recent increase of harvest. Helicopter and pedestrian surveys are reliable tools to monitor annually mouflons in mountainous areas. Simulations indicated that helicopter surveys should be preferred by managers because they provide the best trade-off between cost and precision.

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“…Studies of several ungulate species (Cransac et al 1998;Conradt 1999;Bon et al 2001;Bonenfant et al 2004) have consistently reported higher degrees of social than habitat segregation, suggesting that if environmental factors are involved, they are insufficient to explain the low occurrence of mixed-sex groups in wild populations. This has led to other hypotheses based on non-ecological mechanisms being proposed -in particular, the social affinity and activity budget hypotheses, both of which focus more specifically on the mechanisms involved in group formation and cohesion.…”

Section: Introductionmentioning

confidence: 96%

Sexual dimorphism, activity budget and synchrony in groups of sheep

et al. 2006

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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, activity synchrony would be reduced. Increased costs of maintaining synchrony despite differences in activity budget would facilitate group fragmentation and instability of mixed-sex groups. In this paper two prerequisites of the activity budget hypothesis were tested: (1) that males should spend less time feeding and more time resting than females in single-sex groups and (2) that lower activity synchrony should be observed in mixed-sex compared to single-sex groups. The activity budget and synchrony in mixed and single-sex groups of merino sheep (Ovis aries) of different sizes (2, 4, 6, 8 individuals) were measured in three contiguous 491-m2 arenas located in a natural pasture. Three same-size groups, one of each category, were observed simultaneously. We found no sexual differences in the time spent inactive and active (i.e. grazing, standing, moving, interacting). Males spent significantly more time grazing and less time standing than females. These differences disappeared when yearling males were omitted from the group. Males and females had similar bite and step rates. Sheep of both sexes spent less time resting and more time grazing and moving and had lower bite rates when in mixed-sex groups than when in single-sex groups. The synchrony among visually isolated groups was near zero, indicating that they changed activities independently. On the contrary, within-group synchrony was high; however it was higher in single-sex groups, in particular for males, than in mixed-sex groups. Our results suggest that differences in activity budget and synchrony alone are insufficient to explain social segregation.

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An example of segregation between age and sex classes only weakly related to habitat use in mouflon sheep (Ovis gmelini)

Cited by 69 publications

References 34 publications

Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude

Multiple causes of sexual segregation in European red deer: enlightenments from varying breeding phenology at high and low latitude

Monitoring the abundance of mouflon in South France

Sexual dimorphism, activity budget and synchrony in groups of sheep

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