Chronic Stress in Elephants

Chronic stress can cause long-term escape behaviour in elephants, affecting their use of habitat.

Chronic stress can cause long-term escape behaviour in elephants, affecting their use of habitat. This according to a study on three African elephant (Loxodonta africana) populations in small fenced nature reserves in South Africa. The work is published, February 22 in the open access journal PLoS ONE.

The refuge behaviour of African elephants is relatively well documented through long-term behavioral studies. Such refuge behavior is likely to take two forms, where an individual or population restricts its space use patterns spatially (spatial refuge hypothesis), or alters its use of space temporally (temporal refuge hypothesis).

The researchers, led by David Jachowski of the University of Missouri, also measured levels of FGM (fecal glucocorticoid metabolite), a proxy of physiological stress, in the three populations.

"In South Africa, where elephants are being reintroduced to relatively small fenced reserves, there is a particular need to consider the potential for refuge behavior. Elephants have been translocated for reintroduction into over 58 reserves in South Africa. The process of translocation is well established and designed to be as unobtrusive to the animals as possible, but still results in an elevated physiological stress response for up to 30 days post-release. However, little is known about the potential for longer-term stress responses in elephants following translocation, despite the need to understand how they habituate to their new surroundings, and if they exhibit aberrant behavior that poses a risk to elephants, other animals and people."

For six years from 2000, the research team collected more than 700 elephant poop samples in the Phinda Private Game Reserve, iSimangaliso Wetland Park and the Pilanesberg National Park. FGM levels were significantly higher for the elephants in the iSimangaliso Wetland Park, and were also at a level indicative of a chronic stress response.

The researchers found that the elephant population in iSimangaliso Wetland Park used a smaller portion of this reserve throughout the year. "These results contrast with findings for other translocated populations with lower FGM concentrations, and other wild elephant populations.

Restricted space use patterns indicative of refuge behavior have been documented for a variety of species, but few previous studies have linked the internal physiological status and selection of refugia. Our results suggest that if stressors are persistent and result in a chronic physiological state, populations will restrict space use and occupy refugia for an extended period of time."

"Chronic stress and refuge behavior by elephants could be linked to multiple elephant management problems, ranging from habitat destruction to aggression towards and killing of humans", says Dr. Jachowski. Wildlife translocation or reintroduction projects should consider these effects in their planning, the authors write.

"Managers considering the translocation or reintroduction of wildlife should consider the possibility of chronic stress and potential consequences of refuge behavior. Chronic stress is common following wildlife translocation, and has been associated with reproductive failure, increased predation risk, disease risk, and movement away from the release site.

Our results suggest that chronic stress is associated with refuge behavior in translocated elephants, and we predict that it is likely to occur as a common facultative response in other species following translocation. Thus, future efforts to predict when, where, and to what extent wildlife populations will exhibit refuge behavior could likely be improved by an understanding of their physiological response."

[Jachowski DS, Slotow R, Millspaugh JJ]

Kruger National Park - South African Safari