How abnormal is the behaviour of captive, zoo-living chimpanzees?

Publication Type:
 Journal Article
Year of Publication:
 2011
Authors:
 L.P. Birkett, N.E. Newton-Fisher
Publication/Journal:
 Plos One
Keywords:
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Abstract:

Background: Many captive chimpanzees (Pan troglodytes) show a variety of serious behavioural abnormalities, some of
which have been considered as possible signs of compromised mental health. The provision of environmental enrichments
aimed at reducing the performance of abnormal behaviours is increasing the norm, with the housing of individuals in (semi-
)natural social groups thought to be the most successful of these. Only a few quantitative studies of abnormal behaviour
have been conducted, however, particularly for the captive population held in zoological collections. Consequently, a clear
picture of the level of abnormal behaviour in zoo-living chimpanzees is lacking.
Methods: We present preliminary findings from a detailed observational study of the behaviour of 40 socially-housed zooliving
chimpanzees from six collections in the United States of America and the United Kingdom. We determined the
prevalence, diversity, frequency, and duration of abnormal behaviour from 1200 hours of continuous behavioural data
collected by focal animal sampling.
Results, Conclusion and Significance: Our overall finding was that abnormal behaviour was present in all sampled
individuals across six independent groups of zoo-living chimpanzees, despite the differences between these groups in size,
composition, housing, etc. We found substantial variation between individuals in the frequency and duration of abnormal
behaviour, but all individuals engaged in at least some abnormal behaviour and variation across individuals could not be
explained by sex, age, rearing history or background (defined as prior housing conditions). Our data support a conclusion
that, while most behaviour of zoo-living chimpanzees is ‘normal’ in that it is typical of their wild counterparts, abnormal
behaviour is endemic in this population despite enrichment efforts. We suggest there is an urgent need to understand how
the chimpanzee mind copes with captivity, an issue with both scientific and welfare implications.

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