Techniques Used by Bearded Capuchin Monkeys (Sapajus libidinosus) to Access Water in a Semi-Arid Environment of North-Eastern Brazil.

The exploratory behaviour and the ability of capuchin monkeys to use tools allows them to thrive at times and places of limited food and water abundance, such as in semi-arid environments. Here, we report the behaviours employed by individuals belonging to a wild group of bearded capuchin monkeys (Sapajus libidinosus) to access natural water sources in a dry forest of north-eastern Brazil. An adult female employed a twig as a tool and her tail to gain access to accumulated rainwater in a tree hole, and other individuals used their hands and mouth to manipulate orchids' pseudobulbs and the liquid endosperm of palm nuts. The behaviour of wild Sapajus to access water from non-food sources may enable them to circumvent the risk of dehydration in environments with reduced availability of fleshy fruits and with ephemeral and rare water sources. Our findings contribute to the still scarce but accumulating reports on primate drinking behaviour and to the knowledge of tool use in wild populations of capuchin monkeys, enriching our understanding of primate strategies to gain access to a vital resource under challenging conditions.

Vocalisations of wild common marmosets are influenced by diurnal and ontogenetic factors.

The vocalisations of wild common marmosets, Callithrix jacchus, were recorded to investigate whether call rate by individuals is affected by time of day, age, sex or dominance rank within a group. We also investigated how vocalisation pitch was affected by age, focussing on a single common call, the trill call. Adults vocalised more than juveniles or infants during the majority of daylight hours. Only the call rate of juveniles varied significantly over the day. No differences were found between either sex or dominance rank with respect to rate of vocalisations. The trill calls emitted by young wild common marmosets were of a higher pitch than those emitted by adults. We conclude that the auditory communication of wild common marmosets is related to the age of the animals, both in terms of call rate and the physical characteristics of their vocalisations.