As they are our closest living relatives and so like us in so many ways, we would expect chimpanzees to experience the world in similar ways to us.
It is therefore not surprising that a new study has shown that keeping chimps captive in zoos causes abnormal behaviours indicative of mental health problems.
Researchers from the University of Kent’s School of Anthropology and Conservation observed 1200 hours of footage of 40 socially-housed zoo-living chimpanzees from six collections in the USA and UK. They measured the prevalence, diversity, frequency, and duration of abnormal behaviours such as self-mutilation, repetitive rocking, as well as the eating of faeces and drinking of urine.
They found that all of the chimps performed abnormal behaviour of some kind and for some individuals it may dominate much of their activity. They concluded that abnormal behaviour is endemic in these captive chimps.
Abnormal behaviours are thought to be caused by the restricted and unnatural zoo enclosures compared to the chimps’ natural habitat, and the fact that they have large parts of their lives managed by humans. For example, controlled diets and feeding regimes contrast radically with the ever-changing foraging and decision-making processes of daily life in the wild.
One of the researchers, Dr Newton-Fisher, a primate behavioral ecologist and expert in wild chimpanzee behavior, said: “The best zoo environments, which include all zoos in this study, try hard to enrich the lives of the chimpanzees in their care. Their efforts include providing unpredictable feeding schedules and extractive foraging opportunities, and opportunities for normal social interactions by housing chimpanzees in social groups. There are limits to what zoos can provide, however; the apes are still in captivity.
“What we found in this study is that some abnormal behaviors persist despite interventions to 'naturalize' the captive conditions. The pervasive nature of abnormal behavior, and its persistence in the face of environmental enrichment and social group housing, raises the concern that at least some examples of such behavior are indicative of possible mental health problems.
“We suggest that captivity itself may be fundamental as a causal factor in the presence of persistent, low-level, abnormal behavior - and potentially more extreme levels in some individuals. Therefore, it is critical for us to learn more about how the chimpanzee mind copes with captivity, an issue with both scientific and welfare implications that will impact potential discussions concerning whether chimpanzees and similar species should be kept in captivity at all.”
Parallels can be drawn between the imprisoning of humans behind bars and the keeping of animals captive in zoos. But these animals are innocent of any crime. It is surely not surprising that when deprived of the social and physical richness and diversity of life in the wild, intelligent and emotional animals such as chimpanzees suffer. Research such as this adds to the growing weight of evidence supporting increasing concerns about the continued keeping of animals in zoos – especially our closest living relatives.