The Effects of Poaching on African Elephants
Background
The poaching related decline of African elephants from 1.3 million to 500,000 individuals (between 1979-1987) was unusually concentrated on adults.

Many family groups lost their matriarchs (adult females that control group structure), compromising their social, competitive and physiological functioning. The youngest offspring often perished with their mothers, causing a disrupted age structure. Many older offspring were orphaned, and are currently ranging solitarily or in atypical groups of unrelated females. Documenting the long term consequences of social disruption caused by poaching on the African elephant is crucial to the conservation and management of this species.
Figure 1. Comparison of poached and unpoached populations.
Objectives
We are examining long-term impacts of poaching in Tarangire National Park and the Mikumi-Selous Ecosystem, Tanzania. The latter area contains one of the largest and most heavily poached elephant populations on the continent.
Methods

We are comparing group structure, social cohesiveness and physiological health of poached versus unpoached elephant groups.

DNA extracted from feces is being used to determine the degree of relatedness among group members.

Hormones extracted from feces are used to quantify physiological stress and reproductive function in these groups.

Rates of aggression, affiliative behavior and competitive exclusion from resources are also being compared across groups.
Results

We have discovered that the following demographic signature of poaching exists: There is a high percentage of single adult female families, the average family size is atypically small at only 2 adult females, and there is a high variance in adult relatedness, with some families consisting entirely of non-kin.  This is unusual for a species characterized as forming close family units of several related adult females, and quite consistent with our predictions for a heavily poached elephant population.  We also found that relatedness correlates with strength of social association for adult female elephants in Mikumi.  Small families tend to be less closely related and exhibit very fluid, uncohesive social behavior, whereas the larger families, which are more consistently closely related, tend to form stronger bonds and tighter social units.

Deviations in the structure and relatedness of poached versus nonpoached groups are also being examined by comparing genetic relatedness among adults in the poached families we have sampled to those expected based on simulation data for an unpoached family structure.
Validation Results
We have demonstrated that stress and reproductive hormones accurately reflect physiological stress and reproductive function in captive and wild African elephants.
Figure 2. Stress levels (line graph) in wild elephants are highest in the dry season following a wet season of low rain (bars). (From Foley, C.A.H., S. Papageorge, S.K. Wasser. 2001.  Conservation Biology 15:1134-1142).
Implications

There is considerable controversy surrounding the management and trade policies for African elephants. Results of this study will help determine whether African elephants have had insufficient time to recover from the 60% poaching-related decline of the 1980's, as well as assess the impacts of renewed illegal trade in elephant ivory. Such information is vital to management and international trade decisions impacting this highly intelligent, majestic species.
Collaborators

Sokoine University of Agriculture , Tanzania and Tarangire Elephant Project
For Further Information
Wildlife Conservation Society, Tarangire Elephant Project
Kathleen Gobush, Ph.D. Candidate