Chimpanzees stayed in ‘invisible cage’ after zoo upgrade

Two chimps sitting atop a framework, looking at the camera, with greenery in the background.
A new study shows that chimpanzees remained in their previous spaces in tight groups even after the zoo enlarged their enclosure. Image via Satya Deep/ Unsplash.

By Luke Mangaliso Duncan, University of Warwick

Captive chimpanzees are one of the most popular species kept in zoos because of their charismatic appeal and similarity to humans. They are the closest living relatives of humans because of the shared genes and behavioral and psychological similarities.

Zoos are ethically bound to care for the animals they house. Many provide environments that care for animals’ welfare needs. However, the impact of zoo environment on the behavior, psychology and welfare of animals is sometimes overlooked or poorly understood.

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Historically, some people have criticized zoos and labeled them as “animal prisons”. But based on my experience and research, it’s clear that modern zoos play an important multifaceted role as centers of education, recreation, conservation and research.

Focusing on chimpanzees

Chimpanzees have been the focus of much zoo-based research, including research on their welfare. Most people – researchers, zoo workers and the public alike – assume that providing animals with larger, more “naturalistic” spaces improves their welfare. And, indeed, existing evidence suggests this is usually the case.

Few studies have focused on the long-term effects of these enclosures, however.

A recent paper I co-authored with colleagues fills this gap. We observed a stable group of eight chimpanzees at Johannesburg Zoo in South Africa. Our observations came five years after the zoo revamped their outdoor housing for a more naturalistic design. The chimpanzees benefited from the new enclosure. But they appeared to use the space in an unusual way.

We found that the chimpanzees preferred to spend time in the space that was their original enclosure. Also, they formed remarkably tight-spaced groups.

We suggest the experience of the previous, smaller, barren housing altered the chimpanzees’ perception of space. We also find this limited their space use in the naturalistic enclosure through what appears to be a self-imposed “invisible cage”.

The role that the “invisible cage” might play in other settings is unclear. However, we believe our findings have implications for animal welfare, husbandry and broader conservation of endangered species.

Our paper shows that zoo-based research can teach us about the needs of animals in our care, and how their environment and experiences shape their biology and behavior. It can even give us a glimpse into their minds and perceptions.

Enclosures for the chimpanzees

The Johannesburg Zoo turns 120 years old in 2024. Located in Saxonwold in Johannesburg, the zoo covers an area of 55 hectares (136 acres) and is the second-largest zoo in South Africa. It hosts 320 species of animals and is a member of the World Association of Zoos and Aquariums.

In 2004, the chimpanzee outdoor enclosure at the Johannesburg Zoo – originally from the 1970s – got an extensive upgrade. The chimpanzee space was increased from a pair of concrete and wood enclosures, each measuring 10 meters by 10 meters (11 by 11 yards), to a large, naturalistic enclosure encompassing about 2,500 square meters (27,000 sq ft) of grass, shrubs, trees, rocks and streams. It occupied the same site as the previous housing. Most of the chimpanzees had lived their entire lives in the old enclosures, while two had only lived there for a few years.

Upgrades to naturalistic designs have become the standard for zoos. They are often followed by evaluations to determine how the new space affects the welfare of the animals. Such evaluations typically find that welfare is improved with naturalistic enclosures. This was true at the Johannesburg Zoo too. Chimpanzees exhibited persistent beneficial changes in behavior, such as decreased abnormal or repetitive behavior, suggesting improved welfare in their naturalistic enclosure.

Analysis after the change

Our study started in 2009, five years after the overhaul of the enclosure. In this study, the chimpanzees appeared to use all the enclosure to some degree but showed a preference for the area where the previous enclosure had been.

Curiously, the chimpanzees also appeared to exhibit a strong tendency to form tightly spaced groups. These groups matched the exact dimensions of the previous housing. And these groups formed regardless of when or where in the enclosure the chimpanzees were, the environmental conditions at the time or which individual chimpanzees were involved.

This unusual pattern had not previously been reported and appeared contrary to what might be expected for a group of animals that had lived in such a large space for five years. This space-use behavior appeared to reflect a perceived, self-imposed, intangible barrier to the spacing of the chimpanzees. It was as if an invisible cage surrounded the groups.

Animal welfare and the use of space

Space use is difficult to interpret in terms of animal welfare. That’s because it’s often context-dependent and so is usually ignored when doing evaluations after an enclosure overhaul. When an animal chooses to use a small amount of space, it may be because the space is attractive and meets their welfare needs. However, an animal may choose to remain in a small area because they perceive larger space as unpleasant or even dangerous.

For the chimpanzees, nothing suggested the spacing pattern indicated distress or compromised welfare. Other aspects of the chimpanzees’ behavior suggested improved welfare in the naturalistic enclosure. Instead, it appeared the invisible cage reflected a persistent psychological barrier, learned in the previous housing and then imposed in the naturalistic enclosure years later.

These findings mirror a psychological effect of learned helplessness. It appears in many species, including humans. In situations where individuals are helpless or lack control, they learn their actions cannot affect the outcome. Then, they carry this perception into later situations where they can affect the outcome, acting as though still helpless.

We need further research to understand the welfare implications and broader application of these findings. However, they highlight some important issues around the role of zoos and how zoos affect species conservation.

The importance of zoos

Zoos help raise awareness around conservation issues. They also provide a haven for species under threat. Many facilities breed and reintroduce these species into nature. The Johannesburg Zoo in particular has several conservation programs, including a breeding program for the endangered Pickersgill’s reed frog.

As sanctuaries sustaining threatened populations, zoos actively conserve biodiversity on many ways (creating gene banks, breeding animals and conserving biological and behavioral diversity) while providing critical access to rare species for observation and research.The Conversation

Luke Mangaliso Duncan, Postdoctoral Fellow, University of Warwick

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: A new study found that chimpanzees in a zoo in South Africa stayed in tight groups in their previous territory even after the zoo enlarged and upgraded their enclosure.

Read more: Origins of teamwork found in chimpanzees

Read more: See a zoo of animals in the Rosette Nebula

March 26, 2024

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