Stratégie alimentaire et dominance des femelles Propithèque de Verreaux (Propithecus v. verreauxi) dans la forêt à Didiereaceae du sud de Madagascarie

Résumé En

Feeding strategy and social dominance in female sifakas (Propithecus v. verreauxi) living in a Didiereaceae forest in southern Madagascar. We addressed the issue of female social dominance as an adaptive response to seasonal energy stress in white sifakas living in a fragment of Didiereaceae forest of southern Madagascar. We tested whether female and male sifakas would exhibit different activity budgets, food choices and energy input given harsh ecological constraints that prevail in such xerophytic ecosystems. Behavioural data were obtained on 2 groups (including 8 focal individuals) during a 2-month study in the late wet season. We analysed forest composition, based on a sample of more than 1000 trees, shrubs and lianas, and phenology through a regular survey of 479 tagged individuals. Males and females were mostly feeding on mature leaves of common plant species, to which they added a range of minor food items. The activity budgets (5-min scan interval) did not differ significantly between sexes. In contrast, marked differences of food intake (using a quantitative method) were observed : we evaluated that females consumed daily 30-40% more food than males while the ranking of preferred foods remained globally similar between sexes. Ad libitum records confi rmed female dominance over males in a feeding context, although few aggressive events were recorded. We conclude that (1) time sampling methods may not be appropriate to assess food intake because ingestion rates likely vary among individuals and (2) high food intake of adult females relative to males during the early gestation period is uncoupled with immediate physiological needs and may reflect a sex-specific fattening strategy allowing females to increase their reproductive success.