Primates have relatively larger brains than other mammals even though brain tissue is energetically costly. Comparative studies of variation in cognitive skills allow testing of evolutionary hypotheses addressing socioecological factors driving the evolution of primate brain size. However, data on cognitive abilities for meaningful interspecific comparisons are only available for haplorhine primates (great apes, Old- and New World monkeys) although strepsirrhine primates (lemurs and lorises) serve as the best living models of ancestral primate cognitive skills, linking primates to other mammals. To begin filling this gap, we tested members of three lemur species (Microcebus murinus, Varecia variegata, Lemur catta) with the Primate Cognition Test Battery, a comprehensive set of experiments addressing physical and social cognitive skills that has previously been used in studies of haplorhines. We found no significant differences in cognitive performance among lemur species and, surprisingly, their average performance was not different from that of haplorhines in many aspects. Specifically, lemurs’ overall performance was inferior in the physical domain but matched that of haplorhines in the social domain. These results question a clear-cut link between brain size and cognitive skills, suggesting a more domain-specific distribution of cognitive abilities in primates, and indicate more continuity in cognitive abilities across primate lineages than previously thought.

28Primates have relatively larger brains than other mammals even though brain tissue is 29 energetically costly. Comparative studies of variation in cognitive skills allow testing of 30 evolutionary hypotheses addressing socioecological factors driving the evolution of primate 31 brain size. However, data on cognitive abilities for meaningful interspecific comparisons are 32 only available for haplorhine primates (great apes, Old-and New World monkeys) although 33 strepsirrhine primates (lemurs and lorises) serve as the best living models of ancestral primate 34 cognitive skills, linking primates to other mammals. To begin filling this gap, we tested 35 members of three lemur species (Microcebus murinus, Varecia variegata, Lemur catta) with 36 the Primate Cognition Test Battery, a comprehensive set of experiments addressing physical 37 and social cognitive skills that has previously been used in studies of haplorhines. We found no 38 significant differences in cognitive performance among lemur species and, surprisingly, their 39 average performance was not different from that of haplorhines in many aspects. Specifically, 40 lemurs' overall performance was inferior in the physical domain but matched that of 41 haplorhines in the social domain. These results question a clear-cut link between brain size and 42 cognitive skills, suggesting a more domain-specific distribution of cognitive abilities in 43 primates, and indicate more continuity in cognitive abilities across primate lineages than 44 previously thought. 45 46

Abstract. Forest edges change micro-environmental conditions, thereby affecting the ecology of many forest-dwelling species. Understanding such edge effects is particularly important for Malagasy primates because many of them live in highly fragmented forests today. The aim of our study was to assess the influence of forest edge effects on activity budgets, feeding ecology, and stress hormone output (measured as faecal glucocorticoid metabolite – fGCM – levels) in wild Verreaux's sifakas (Propithecus verreauxi), a group living, arboreal lemur. We observed five habituated groups: three living in the forest interior and two at an established forest edge. There was no difference in average daily temperatures between edge and interior habitats; however, within the edge site, the average daily temperature incrementally increased over 450 m from the forest edge towards the interior forest of the edge habitat, and the population density was lower at the edge site. Activity budgets differed between groups living in the two microhabitats, with individuals living near the edge spending more time travelling and less time feeding. Groups living near the edge also tended to have smaller home ranges and core areas than groups in the forest interior. In addition, edge groups had elevated average fGCM concentrations, and birth rates were lower for females living in the edge habitat. Combined with lower levels of fruit consumption at the edge, these results suggest that nutritional stress might be a limiting factor for Verreaux's sifakas when living near a forest edge. Hence, Verreaux's sifakas appear to be sensitive to microhabitat characteristics linked to forest edges; a result with implications for the conservation of this critically endangered lemurid species.