Compromised survivorship in zoo elephants.

We analyzed data from over 4500 elephants to show that animals in European zoos have about half the median life span of conspecifics in protected populations in range countries. This discrepancy is clearest in Asian elephants; unlike African elephants in zoos, this species' infant mortality is very high (for example, twice that seen in Burmese timber camps), and its adult survivorship in zoos has not improved significantly in recent years. One risk factor for Asian zoo elephants is being moved between institutions, with early removal from the mother tending to have additional adverse effects. Another risk factor is being born into a zoo rather than being imported from the wild, with poor adult survivorship in zoo-born Asians apparently being conferred prenatally or in early infancy. We suggest stress and/or obesity as likely causes of zoo elephants' compromised survivorship.