In the December 12 issue of the journal Science Ros Clubb of the Royal Society for the Protection of Animals and colleagues, including well known elephant researcher Cynthia Moss, report that captive elephants do not live as long as their free-living counterparts, or even as long as working elephants in Burmese timber camps.
Collecting data from over 4,500 elephants from European Zoos, wild populations in Amboseli National Park in Kenya and working elephants in Burmese logging camps, the authors found a significant correlation between captivity and longevity. Females from a well studied population of African Savannah Elephants (Loxodonta africana) in Amboseli National Park in Kenya exhibited a median life span of 56.0 years (these data excluded mortality from humans). African Savannah Elephants in zoos have a median life span of only 16.9 years. As of 2005 when the study ended female African Savannah Elephants in captivity experienced a mortality risk 2.8 times higher than the natural mortality of wild female elephants in Amboseli. Captive-born female African Savannah Elephants die earlier in zoos than in the wild but infant and juvenile mortality was similar between wild and captive elephants.
For Asian Elephants (Elephas maximus) the effect of zoo captivity on mortality was also significant. Captive female Asian Elephants in the study exhibited a median life span of 18.9 years while working Asian Elephants in a Burmese timber operation had a median life span of 41.7 years. While mortality risk in African Savannah Elephants went down over time, suggesting improved captive management, there was no significant reduction in mortality for Asian Elephants. Also, being born in a zoo versus born in the wild had a significant effect on surviorship in Asian Elephants. Ironically, wild-caught Asian Elephants did better in captivity than their captive-born counterparts.
Elephants live in tightly knit social groups of females and juveniles with very long-term associations among individuals. Wild female elephants rarely move between groups, but, zoos regularly transfer individuals among institutions. Female Asian Elephants are moved around among European Zoos approximately once every 7-years. Transfers have an effect on the health of captive elephants. This study found that inter-zoo transfers significantly reduced survivorship in Asian Elephants.
Georgia Mason, a co-author on this study and zoologist at the University of Guelph in Ontario, Canada, discussed the results on the December 12 Science Magazine podcast. According to Mason the situation for American zoo elephants is no better than their European counterparts. 15% of zoo-born elephants in Europe die in their first year while in the USA 40% of zoo-born elephants die before the age of one.
Small group size, frequent inter-zoo transfers, and comparatively tiny enclosures for an animal that has orders magnitude greater home range area in the wild are all likely contributors to the problem of reduced survivorship in zoo elephants. However, solutions to this problem are not straightforward. Large sums of money have been spent in European and US zoos to build larger enclosures for captive elephants but the study by Clubb and colleagues found little evidence that such improvements have resulted in increased survivorship in captive elephants. Some increases in survivorship for African Savannah Elephants have occurred but not nearly enough to bring their surviorship on par with wild counterparts and the study found that despite increased spending and larger enclosures there was no increase in survivorship for Asian Elephants. Mason in the Science Podcast interview pointed out that recent expenditures of approximately 23 million US dollars spent on improving enclosures for the elephants at the Oklahoma City Zoo were greater than the entire annual budget for the Kenya Wildlife Service or the South African National Parks Authority. Perhaps the greatest concern is that captive elephant populations are not self sustaining and can not survive without introduction of individuals taken from the wild.
This study provides a compelling argument for an elevated discussion on not just captive elephants but the welfare of other large-ranging, social mammals as well. Hopefully this study will place a renewed emphasis on future research and novel approaches to captive husbandry of these magnificent mammals.
Clubb, R., Rowcliffe, M., Lee, P., Mar, K. U., Moss, C., Mason, G. J. (2008). Compromised Survivorship in Zoo Elephants Science, 322 (5908) DOI: 10.1126/science.1164298