A new approach to estimate fecundity rate from inter-birth intervals

Funded by Department of Energy and Climate Change (UK), BES, ASAB, Greenpeace, Environmental Trust, Scottish Natural Heritage, Scottish Government, Whale and Dolphin Conservation, Talisman Energy (UK) Ltd., DECC, Chevron, Natural Environment Research Council Acknowledgments Funding for this work was provided by the Department of Energy and Climate Change (UK). Photo-identification data were collected during a series of grants and contracts from the BES, ASAB, Greenpeace Environmental Trust, Scottish Natural Heritage, Scottish Government, Whale and Dolphin Conservation, Talisman Energy (UK) Ltd., DECC, Chevron, and the Natural Environment Research Council. All survey work was carried out under Scottish Natural Heritage Animal Scientific Licences. The authors have no conflict of interest to declare. We thank Mark Bravington for his helpful advice at the early stages of this work and two anonymous reviewers for their useful comments on the manuscript.Peer reviewedPublisher PD

First observation of Dorylus ant feeding in Budongo chimpanzees supports absence of stick-tool culture

The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement no 283871.The use of stick- or probe-tools is a chimpanzee universal, recorded in all long-term study populations across Africa, except one: Budongo, Uganda. Here, after 25-years of observation, stick-tool use remains absent under both natural circumstances and strong experimental scaffolding. Instead, the chimpanzees employ a rich repertoire of leaf-tools for a variety of dietary and hygiene tasks. One use of stick-tools in other communities is in feeding on the aggressive Dorylus ‘army-ant’ species, consumed by chimpanzees at all long-term study sites outside of mid-Western Uganda. Here we report the first observation of army-ant feeding in Budongo, in which individuals from the Waibira chimpanzee community employed detached leaves to feed on a ground swarm. We describe the behaviour and discuss whether or not it can be considered tool-use, together with its implication for the absence of stick-tool ‘culture’ in Budongo chimpanzees.Publisher PDFPeer reviewe

Chimpanzees Share Forbidden Fruit

The sharing of wild plant foods is infrequent in chimpanzees, but in chimpanzee communities that engage in hunting, meat is frequently used as a ‘social tool’ for nurturing alliances and social bonds. Here we report the only recorded example of regular sharing of plant foods by unrelated, non-provisioned wild chimpanzees, and the contexts in which these sharing behaviours occur. From direct observations, adult chimpanzees at Bossou (Republic of Guinea, West Africa) very rarely transferred wild plant foods. In contrast, they shared cultivated plant foods much more frequently (58 out of 59 food sharing events). Sharing primarily consists of adult males allowing reproductively cycling females to take food that they possess. We propose that hypotheses focussing on ‘food-for-sex and -grooming’ and ‘showing-off’ strategies plausibly account for observed sharing behaviours. A changing human-dominated landscape presents chimpanzees with fresh challenges, and our observations suggest that crop-raiding provides adult male chimpanzees at Bossou with highly desirable food commodities that may be traded for other currencies

Reciprocal face-to-face communication between rhesus macaque mothers and their newborn infants

Human mothers interact emotionally with their newborns through exaggerated facial expressions, speech, mutual gaze, and body contact, a capacity that has long been considered uniquely human (1–4). Current developmental psychological theories propose that this pattern of mother-infant exchange promotes the regulation of infant emotions (4–6) and serves as a precursor of more complex forms of social exchange including perspective-taking and empathy. Here we report that in rhesus macaques, mother-infant pairs also communicate intersubjectively using complex forms of emotional exchanges including exaggerated lipsmacking, sustained mutual gaze, mouth-mouth contacts, and neonatal imitation. Infant macaques solicit their mother’s affiliative responses and actively communicate to her. However, this form of communication disappears within the infant’s first month of life. Our data challenge the view that the mother-infant communicative system functions in order to sustain proximity and that infants are simply passive recipients in such interaction. Thus, emotional communication between mother and infant is not uniquely human. Instead, we can trace back to macaques the evolutionary foundation of those behaviors that are crucial for the establishment of a functional capacity to socially exchange with others

Food sharing among captive gibbons ( Hylobates lar )

A captive family group of gibbons engages in food sharing during consistently patterned sequences of behaviors in which begging gestures are employed. The predominant occurrence of the behavior involves the juvenile female begging from her older, adult sister who acted as her “surrogate mother”. An examination of the variables potentially affecting the behavior, such as hunger, the availability and accessibility of preferred foods, the inability to forage individually, and the social relationships between members of the family, indicates that food sharing may assist the young in acquiring appropriate food habits, supplement their foraging capabilities, and may serve to reinforce the social bonds between adult and immature members of the family group.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41598/1/10329_2006_Article_BF02383142.pd

Mechanical analysis of infant carrying in hominoids

In all higher nonhuman primates, species survival depends upon safe carrying of infants clinging to body hair of adults. In this work, measurements of mechanical properties of ape hair (gibbon, orangutan, and gorilla) are presented, focusing on constraints for safe infant carrying. Results of hair tensile properties are shown to be species-dependent. Analysis of the mechanics of the mounting position, typical of heavier infant carrying among African apes, shows that both clinging and friction are necessary to carry heavy infants. As a consequence, a required relationship between infant weight, hair–hair friction coefficient, and body angle exists. The hair–hair friction coefficient is measured using natural ape skin samples, and dependence on load and humidity is analyzed. Numerical evaluation of the equilibrium constraint is in agreement with the knuckle-walking quadruped position of African apes. Bipedality is clearly incompatible with the usual clinging and mounting pattern of infant carrying, requiring a revision of models of hominization in relation to the divergence between apes and hominins. These results suggest that safe carrying of heavy infants justify the emergence of biped form of locomotion. Ways to test this possibility are foreseen here