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Babweteera F.,Budongo Conservation Field Station | Brown N.,University of Oxford
Journal of Tropical Ecology | Year: 2010

The direct removal of adult trees by logging affects tree recruitment in tropical rain forests. However, secondary effects of logging, such as loss of vertebrate seed dispersers may also affect tree recruitment. We studied the recruitment and spatial distribution of five tree species namely Balanites wilsoniana, Celtis zenkeri, Chrysophyllum albidum, Cordia millenii and Ricinodendron heudelotii in Kibale, Budongo and Mabira Forests in Uganda. These forests have been subjected to varying degrees of disturbance leading to changes in their vertebrate seed dispersers. Vertebrate frugivores of the five tree species were identified. Three 1-ha plots were established around adult trees of the same five species in each forest and the distance from the juveniles to the nearest adult conspecific was measured to generate a recruitment curve. Frugivore visitation rates were high in the less disturbed Budongo and Kibale (2.2 and 1.6 individuals h-1 respectively) compared with the highly disturbed Mabira (0.9 individuals h-1). In the frugivore-impoverished forest, 70-90% of juveniles established beneath adult conspecifics, whereas in the less-disturbed forests juveniles were established up to 80 m from adult conspecifics. Shade-tolerant species capable of recruiting beneath adult conspecifics appeared to maintain their populations without dispersal. Consequently, disturbances leading to significant loss of vertebrates may alter tree recruitment and spatial distribution with consequences for long-term population viability of shade-intolerant tropical trees. Copyright © 2010 Cambridge University Press. Source

Hobaiter C.,University of St. Andrews | Poisot T.,University of Quebec at Rimouski | Poisot T.,Quebec Center for Biodiversity science | Zuberbuhler K.,University of St. Andrews | And 4 more authors.
PLoS Biology | Year: 2014

Social network analysis methods have made it possible to test whether novel behaviors in animals spread through individual or social learning. To date, however, social network analysis of wild populations has been limited to static models that cannot precisely reflect the dynamics of learning, for instance, the impact of multiple observations across time. Here, we present a novel dynamic version of network analysis that is capable of capturing temporal aspects of acquisition—that is, how successive observations by an individual influence its acquisition of the novel behavior. We apply this model to studying the spread of two novel tool-use variants, “moss-sponging” and “leaf-sponge re-use,” in the Sonso chimpanzee community of Budongo Forest, Uganda. Chimpanzees are widely considered the most “cultural” of all animal species, with 39 behaviors suspected as socially acquired, most of them in the domain of tool-use. The cultural hypothesis is supported by experimental data from captive chimpanzees and a range of observational data. However, for wild groups, there is still no direct experimental evidence for social learning, nor has there been any direct observation of social diffusion of behavioral innovations. Here, we tested both a static and a dynamic network model and found strong evidence that diffusion patterns of moss-sponging, but not leaf-sponge re-use, were significantly better explained by social than individual learning. The most conservative estimate of social transmission accounted for 85% of observed events, with an estimated 15-fold increase in learning rate for each time a novice observed an informed individual moss-sponging. We conclude that group-specific behavioral variants in wild chimpanzees can be socially learned, adding to the evidence that this prerequisite for culture originated in a common ancestor of great apes and humans, long before the advent of modern humans. © 2014 Hobaiter et al. Source

Gruber T.,University of St. Andrews | Potts K.B.,Augsburg College | Krupenye C.,Connecticut College | Krupenye C.,Duke University | And 6 more authors.
Journal of Comparative Psychology | Year: 2012

The influence of ecology on the development of behavioral traditions in animals is controversial, particularly for chimpanzees (Pan troglodytes), for which it is difficult to rule out environmental influences as a cause of widely observed community-specific behavioral differences. Here, we investigated 3 potential scenarios that could explain the natural variation in a key extractive tool behavior, "fluid-dip," among several communities of chimpanzees of the Pan troglodytes schweinfurthii subspecies in Uganda. We compared data from previous behavioral ecological studies, field experiments, and long-term records of chimpanzee tool-using behavior. We focused on the quality of the available food, dietary preferences, and tool sets of 5 different communities, and carried out a standardized field experiment to test systematically for the presence of fluid-dip in 4 of these communities. Our results revealed major differences in habitat, available diet, and tool use behavior between geographically close communities. However, these differences in ecology and feeding behavior failed to explain the differences in tool use across communities. We conclude that ecological variables may lead both to innovation and loss of behavioral traditions, while contributing little to their transmission within the community. Instead, as soon as a behavioral tradition is established, sociocognitive factors likely play a key maintenance role as long as the ecological conditions do not change sufficiently for the tradition to be abandoned. © 2012 American Psychological Association. Source

Schel A.M.,University of York | Townsend S.W.,University of Zurich | Machanda Z.,Harvard University | Zuberbuhler K.,Budongo Conservation Field Station | And 3 more authors.
PLoS ONE | Year: 2013

Determining the intentionality of primate communication is critical to understanding the evolution of human language. Although intentional signalling has been claimed for some great ape gestural signals, comparable evidence is currently lacking for their vocal signals. We presented wild chimpanzees with a python model and found that two of three alarm call types exhibited characteristics previously used to argue for intentionality in gestural communication. These alarm calls were: (i) socially directed and given to the arrival of friends, (ii) associated with visual monitoring of the audience and gaze alternations, and (iii) goal directed, as calling only stopped when recipients were safe from the predator. Our results demonstrate that certain vocalisations of our closest living relatives qualify as intentional signals, in a directly comparable way to many great ape gestures. We conclude that our results undermine a central argument of gestural theories of language evolution and instead support a multimodal origin of human language. © 2013 Schel et al. Source

Murphy D.,University of Exeter | Murphy D.,University of Aberdeen | Lea S.E.G.,University of Exeter | Zuberbuhler K.,Budongo Conservation Field Station | And 2 more authors.
Animal Behaviour | Year: 2013

There is considerable controversy about what is encoded when primates produce alarm calls to an external event. Results are often compatible with multiple explanations, such as differences in a caller's perceived level of threat, direction of attack or category of predator. Using acoustic predator models, we investigated how male blue monkeys', Cercopithecus mitis stuhlmani, alarm calls were affected by predator type, distance, and elevation. We found that individuals produced two types of acoustically distinct alarm calls, 'pyows' and 'hacks'. Males produced these calls in predator-specific ways, but call rates were also affected by the distance and location of the predator. We discuss these findings in relation to the different predator hunting techniques and two common antipredator strategies pursued by monkeys, predator deterrence and conspecific warning. © 2012 The Association for the Study of Animal Behaviour. Source

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