Stress in the African elephant on Mabula game reserve, South Africa.

Abstract

The current study contributes to the science of biology in that it describes different methods of measuring stress in animals and distinguishes between different types of stress that animals are exposed to. The main aim of this type of research is to obtain as much information as possible on what more specifically elephants require from their environment in order to create a more suitable habitat under conditions that vary considerably from the environment in which the elephant evolved in. Two types of possible stress for elephants on small reserves were investigated: social stress and stress caused by direct human disturbances (for example tourists on game drive vehicles in fenced reserves without wilderness areas). The study group of elephants which were introduced to the study reserve ten years earlier as a group of unrelated juveniles from culling operations differed significantly according to social role play and behaviour from normal elephant societies as described by literature. None of the adult elephants from the study group initiated change of activity more than the other adult elephants on the reserve and although one of the female cows was dominant over all the other adult female cows she was dominated by the twenty-year-old bull on the reserve. The twenty-year-old bull was with the cowherd for most of the time and was aggressive towards other cowherd members when present. All the stress parameters used to monitor the influence of direct human disturbances also changed significantly in the presence and absence of game drive vehicles in the elephant's environment. The group of elephants moved more and clustered together more, individual elephants showed more behaviours associated with stress and vocalized more and adult female elephants secreted more from their temporal glands in the presence of game drive vehicles compared to periods when game drive vehicles were absent. Stress hormone metabolite levels in the dung of elephant differed significantly among individuals being highest for the twenty-year-old bull on the reserve. One section area on the reserve with the highest load of human activity also produced the highest levels of stress for elephants when group mobility, group spacing and faecal stress hormone metabolite levels were used as stress parameters. Social stress for the study group of elephants may have enhanced stress response of elephants towards direct human disturbances. Small fenced reserves hosting elephants should monit.or and control game drive vehicle activity around elephants and should consider expanding their property in order to first of all provide wilderness areas to where animals can escape to when stressed by direct human disturbances and secondly to be able to introduce older female and male elephants to control and lead young animals if not present. Implementation of stress monitoring programs as part of the elephant management plan of a reserve may reduce and possibly prevent any future incidences of aggression from elephants towards humans and other species.