Sexual dimorphism, activity budget and synchrony in groups of sheep

Michelena, Pablo; Noël, Sarah; Gautrais, Jacques; Gérard, Jean‐François; Deneubourg, Jean‐Louis; Bon, Richard

doi:10.1007/s00442-005-0347-2

Cited by 45 publications

(31 citation statements)

References 46 publications

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“…So, the males and females would separate to aggregate in same-sex groups, respectively, to keep behavioral synchrony (Ruckstuhl 1998(Ruckstuhl , 2006. Some studies support the activity budget hypothesis (Conradt 1998;Ruckstuhl and Kokko 2002) and some do not (Michelena et al 2006;Mooring et al 2003;Yearsley and Perez-Barberia 2005). For example, studies on red deer (Cervus elaphus) showed that mixed-sex groups were more likely to break up than single-sex groups because of sex differences in activity rhythm (Conradt 1998), and this result supports the activity budget hypothesis.…”

supporting

confidence: 59%

Test of the activity budget hypothesis on Asiatic ibex in Tian Shan Mountains of Xinjiang, China

Ming

Yang

et al. 2011

Eur J Wildl Res

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Asiatic ibex (Capra sibirica) is a threatened species in China and is distributed in the mountains of Central Asia. It is a sexually dimorphic ungulate. The males are much larger than females, and except for the breeding season, both sexes live in separate groups. Many hypotheses have been developed to explain the sexual segregation in sexually dimorphic ungulates. These hypotheses are not mutually exclusive, and in recent years, the activity budget hypothesis has received special attention. To test this hypothesis, we studied the activity budget of Asiatic ibex in the autumn of 2005. According to the activity budget hypothesis, females should spend more time feeding than the males, and the degree of activity synchronization should be higher in same-sex groups than in mixed-sex groups. Our results are consistent with the hypothesis. Both sexes of the Asiatic ibex spent most of the time feeding, and females spent a significantly longer time feeding than males, and males spent a significantly longer time standing. Activity synchronization indexes of both the female groups and males groups were significantly higher than mixed-sex groups. These results indicated that in Asiatic ibex, the activity budget hypothesis about sexual segregation is supported.

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supporting

confidence: 59%

Test of the activity budget hypothesis on Asiatic ibex in Tian Shan Mountains of Xinjiang, China

Ming

Yang

et al. 2011

Eur J Wildl Res

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“…Other authors have noted considerable differences in individual vigilance levels between females and males (Childress and Lung 2003;Michelena et al 2006;Monclus and Rodel 2008). Some have argued that females are often more vigilant than males because males are larger and stronger, and therefore can escape from predators more easily (Clutton-Brock et al 1982).…”

Section: Discussionmentioning

confidence: 97%

“…Studies on vigilance have shown sex to be an important factor influencing vigilant behavior (Hunter and Skinner 1998;Cameron and Du Toit 2005;Michelena et al 2006;Li and Jiang 2008). Although several studies have shown that the vigilance levels are usually different between females and males, reports have not suggested any consistent pattern regarding the more vigilant sex (Elgar 1989;Laundre et al 2001;Cameron and Du Toit 2005).…”

Section: Introductionmentioning

confidence: 94%

Seasonal and sexual variation in vigilance behavior of goitered gazelle (Gazella subgutturosa) in western China

Xia

Yang

et al. 2011

J Ethol

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Animals receive benefits from social behavior. As part of a group, individuals spend less time having to be vigilant. This phenomenon, called the ''group size effect,'' is considered the most dominant factor in an animal's demonstrated level of vigilance. However, in addition to group size, many other social and environmental factors also influence the degree of vigilance, including the season of the year and the sex of the individual. In our study, we examined the vigilant behavior of goitered gazelles in the Xinjiang Province in western China to test whether and how seasons, the yearly breeding cycle, and group size affect vigilance. According to our results, we found that seasonal factors were not a substantial influence on a gazelle's level of vigilance, while group size had a tangible effect. In comparison, the yearly breeding cycle (a natural phenomenon) was the most powerful factor: it significantly changed the degree of vigilance in females during birthing and males during rut. Anthropogenic factors (unnatural phenomena) were also potential causes of increased vigilance in both sexes during winter.

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“…In sexually dimorphic ungulates, it is predicted that the mass-speciWc energy requirements of sub-adult males are higher than those of fully grown adults, due to their smaller body sizes and the substantial energetic costs of growth (Ruckstuhl et al 2003). Ultimately, this could lead to segregation between age groups as well as sex (Ruckstuhl 1998;Bon et al 2001;Michelena et al 2006).…”

Section: Discussionmentioning

confidence: 97%

The role of foraging behaviour in the sexual segregation of the African elephant

Shannon¹,

Page²,

Duffy³

et al. 2006

Oecologia

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Elephants (Loxodonta africana) exhibit pronounced sexual dimorphism, and in this study we test the prediction that the differences in body size and sociality are significant enough to drive divergent foraging strategies and ultimately sexual segregation. Body size influences the foraging behaviour of herbivores through the differential scaling coefficients of metabolism and gut size, with larger bodied individuals being able to tolerate greater quantities of low-quality, fibrous vegetation, whilst having lower mass-specific energy requirements. We test two distinct theories: the scramble competition hypothesis (SCH) and the forage selection hypothesis (FSH). Comprehensive behavioural data were collected from the Pongola Game Reserve and the Phinda Private Game Reserve in South Africa over a 2.5-year period. The data were analysed using sex as the independent variable. Adult females targeted a wider range of species, adopted a more selective foraging approach and exhibited greater bite rates as predicted by the body size hypothesis and the increased demands of reproductive investment (lactation and pregnancy). Males had longer feeding bouts, displayed significantly more destructive behaviour (31% of observations, 11% for females) and ingested greater quantities of forage during each feeding bout. The independent ranging behaviour of adult males enables them to have longer foraging bouts as they experience fewer social constraints than females. The SCH was rejected as a cause of sexual segregation due to the relative abundance of low quality forage, and the fact that feeding heights were similar for both males and females. However, we conclude that the differences in the foraging strategies of the sexes are sufficient to cause spatial segregation as postulated by the FSH. Sexual dimorphism and the associated behavioural differences have important implications for the management and conservation of elephant and other dimorphic species, with the sexes effectively acting as distinct "ecological species".

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Sexual dimorphism, activity budget and synchrony in groups of sheep

Cited by 45 publications

References 46 publications

Test of the activity budget hypothesis on Asiatic ibex in Tian Shan Mountains of Xinjiang, China

Test of the activity budget hypothesis on Asiatic ibex in Tian Shan Mountains of Xinjiang, China

Seasonal and sexual variation in vigilance behavior of goitered gazelle (Gazella subgutturosa) in western China

The role of foraging behaviour in the sexual segregation of the African elephant

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