Msindai, Nadejda Josephine; (2018) Chimpanzees of Rubondo Island: ecology and sociality of a reintroduced population. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Chimpanzees (Pan troglodytes) display considerable intraspecific variation in behaviour, although the extent of this remarkable adaptability to different ecological conditions is not fully understood. The current investigation, based on extended "natural history" fieldwork, focusses on a community originating from 17 ex-captive apes released into the wild half a century ago (1966-1969), who then went on to live independently without further human intervention: the chimpanzees of Rubondo Island in Lake Victoria, Tanzania. Such research can inform about the adaptive scope of chimpanzees in particular, and the merits and shortcomings of reintroductions of captive apes in general. The behavioural differences between wild and released Rubondo chimpanzees were quantified (nesting, party size, and homerange use). Several hypotheses have been proposed to explain the function of great ape nests: thermoregulation, predation and pathogen avoidance. Preliminary evidence indicates that Rubondo’s chimpanzees are selecting warmer nesting sites, during periods of colder wet weather. Plant material contains volatile compounds which can have biocidal effects on parasites. The chimpanzees nested most often in Synsepalum brevipes trees which are used by local people as an antimalarial treatment, potentially indicating a strategy by the chimpanzees to deter biting insects from the nest. Rubondo chimpanzees, like their native counterparts, form fluid patterns of association and maintain a home-range of roughly 95-115 km2 , much larger than what has been reported for other released chimpanzees. A first investigation into their genetic diversity revealed that the Rubondo chimpanzees represent a mixture of the subspecies P. t verus and P. t. troglodytes making this population unique because apes of West- and Central African origin survive in East Africa. Current IUCN guidelines stipulate that subspecies should not be mixed, partly due to concerns about preserving genetic diversity. While there is likely subspecies inter-mixing on Rubondo there is no evidence of outbreeding depression, as the population has increased in number since release to 28-78 individuals. The implications of these findings are discussed within the broader context of current recommendations to manage chimpanzees at the level of the subspecies. The datadriven sections then inform a discussion of current discourses regarding great ape releases for purpose of conservation and animal welfare.

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