JOIN USObserving wild animals in the zoos is a refreshing break for most of us. For the zoo animals, on the other hand, it’s a stressful life. Animals in zoos show certain specific behaviours not seen in their wild counterparts: elephants sway their heads from side to side, chimps rock back and forth, giraffes lick walls, and leopards pace in their cages, to mention a few. Known as ‘stereotypy’, these behaviours are coping responses commonly observed in captive wild animals.
Being held behind bars — literally or figuratively — can be depressing for anyone. Wild animals, as such, are not evolved to exist in the zoo environments, and they tend to face a number of challenges in captivity, for which they are not equipped. The climatic conditions, the food provided, and the size and nature of captive habitat are very different from what exists in the wild or natural habitat.
Stereotypic behaviour is a repetitive pattern of action displayed by such animals, which have no obvious purpose; it is a sort of restlessness. Although not directly linked, stereotypy has been associated with factors related to captivity such as enclosure or cage size, social atmosphere with conspecific (their own species), human intervention, etc. This, therefore, suggests that the animals perform such actions when they are stressed or have been habituated to it.
Assessing their stress levels
Professor Nagarajan Baskaran, and his team from AVC College in Tamil Nadu, studied stereotypic behaviour in tigers and leopards, to test whether stereotypy and stress were correlated. “The idea was that if an animal is showing stereotypic behaviour, then it is stressed and therefore the stress hormone levels in the animal should be accordingly high. As what we expected, our study proved that this is true,” says Janice Vaz, the lead author of the study. Studying stress in animals isn’t as easy as done with humans. Researchers, therefore, measure Faecal Corticosterone Metabolite (FCM) levels to analyse the amount of stress the animal is dealing with. The theory is simple — when animals are stressed, their bodies produce more stress hormones, and a large amount of this is excreted in their faeces. And, obviously, obtaining faeces to measure hormone levels is far less complicated than drawing blood samples each time.
The researchers studied animals from six zoos, located in Pune, Thiruvananthapuram, Thrissur, Chennai, and Delhi. They monitored 41 Royal Bengal tigers and 21 Indian leopards for over a period of seven months, for stereotypic behaviour and the presence of stress hormones in their faeces. They even assessed environmental parameters such as the size of captive space, its resemblance to the wild habitat, temperature, number of zoo visitors and the zookeepers’ attitude towards the animals. They then statistically analysed their observations, comparing stereotypic behaviour with hormone levels and habitation characteristics.
Various factors
Of the 19 environmental and biological factors assessed, differences in stereotypic behaviours were only observed in enclosure size and keeper attitude in case of tigers and tree density in case of leopards. Tigers in larger enclosures and with positive keeper attitude had significantly lower stereotypy than those maintained in smaller enclosures or with negative or neutral keepers, while the leopards managed in enclosures with higher tree density had significantly lower stereotype than those managed in enclosures with lower tree density.
Similarly, among 19 factors tested, differences in FCM levels were observed only with health matters in the case of tigers — tigers with severe health problems had significantly more FCM than those with minor or without health problems and in case of leopards, the ones that were cared for by active, interested zoo keepers had lower FCM levels than those supervised by keepers who didn’t care as much.
Other factors such as the percentage of grass and tree cover, presence of stones and ponds and ambient temperature did not influence FCM levels but did contribute significantly to stereotypy. Nagarajan who has been studying large mammals for over two decades, explains how stereotypy serves as a coping mechanism. “FCM levels are not always the best indicators of stress,” he says. “If an animal is continuously exposed to a certain form of stressful environment, which is beyond its ability to cope with, then the animal may begin to exhibit higher FCM levels. Thus, it is better to study the stereotypy as an indicator of stress because it reflects the animal’s first attempt to cope with the stress.”
Recalling an 11-month old leopard cub that she visited during the research, Janice observes, “It was born in the zoo to parents who were caught from the wild. It was expected that the cub would display wild behaviour. But at 11 months, the cub was already showing stereotypic behaviour although it did exhibit some wild behaviour as well. For instance, leopards in the wild and in zoo eat their prey off the ground. The cub would carry its food to the top of a tree, sit there on top and eat — this was her wild behaviour. It was a very playful creature, but it couldn’t play much because the enclosure was too small. So, she would sit in a place and move her neck in a particular angle continuously from one direction to other — this was her stereotypic behaviour.”
The professor and his team have communicated the results of the study along with their recommendations with the participating zoos that cooperated with them. “But we cannot expect immediately much from the zoo authorities,” explains Janice. “For most local zoos, changes such as increased enclosure size and habitat enrichment are difficult to implement because of constraints in space and funds.” Perhaps we can hope that in future, zoo designers and policy makers take measures to ensure that our wild animals get their due.
(The author is with Gubbi Labs, a Bengaluru-based research collective)