Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-response task. Our results confirm previous findings that longer delays decrease memory performance across species and taxa. Our analyses demonstrate a considerable contribution of phylogeny over ecological and social factors on the distribution of short-term memory performance in primates; closely related species had more similar short-term memory abilities. Overall, individuals in the branch of Hominoidea performed better compared to Cercopithecoidea, who in turn performed above Platyrrhini and Strepsirrhini. Interdependencies between phylogeny and socioecology of a given species presented an obstacle to disentangling the effects of each of these factors on the evolution of short-term memory capacity. However, this study offers an important step forward in understanding the interspecies and individual variation in short-term memory ability by providing the first phylogenetic reconstruction of this trait’s evolutionary history. The dataset constitutes a unique resource for studying the evolution of primate cognition and the role of short-term memory in other cognitive abilities.

Sexual dimorphism is thought to be the result of sexual selection, food competition and/or niche differentiation, or simply the result of differential growth between the sexes. Despite the fact that sexual dimorphism is common among primates, lemurs are thought to be largely monomorphic. Yet, females of the species Microcebus are known to be larger than males. Here, we investigate if dimorphism in head dimensions is present in a colony of captive grey mouse lemurs Microcebus murinus. Moreover, we test whether any observed shape dimorphism is associated with differences in bite force between the sexes. Our results show that male and female grey mouse lemurs are indeed sexually dimorphic in head dimensions, with females having taller and wider heads than males. Moreover, we confirm previous observations that females are heavier than males. Bite force was principally determined by head dimensions and age in our dataset, and differed between sexes, with females biting harder than males. These data suggest a potential role for niche dimorphism in driving the observed shape and performance dimorphism as female reproductive output may depend upon the ability of animals to obtain resources that are difficult to ingest

Grasping is important for arboreal species as it allows them to hold on to branches. Although grasping has been studied previously in the context of primate origins and as an indicator of age-induced loss in overall performance, little is known about the proximate determinants of variation in strength. We measured hand pull strength in 62 adult captive individuals of grey mouse lemurs Microcebus murinus of known age. In addition, we measured the body mass and the length of the forearm in each individual. Our results showed that animals with a longer ulna, and animals that weighed more, and had a greater relative body mass had higher pull strength. However, despite the fact that females are bigger than males, differences in pull strength were not significantly different between the two sexes. Although comparative data for other species of vertebrates are scarce, our data suggest that mouse lemurs have relatively high pull strength for their size that may be interpreted as an adaptation to arboreal locomotion