Abstract # 2853 Poster # 54:

Scheduled for Thursday, June 17, 2010 07:00 PM-09:00 PM: Session 11 (Medallion Ballroom C/D/E/F) Poster Presentation


SOCIAL ADJUSTMENTS AND CORTISOL EXCRETION IN A BACHELOR GROUP OF LOWLAND GORILLAS

K. Burke, S. Royalty, K. Jamison, M. Wade and B. White
Centre College, Psychobiology Program, 600 W. Walnut Street, Danville, KY 40422, USA
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Western lowland gorillas (Gorilla gorilla gorilla) are characterized by a harem mating system with fewer adult males than adult females. This leaves some males without mating opportunities, at least temporarily. As a result these males may form bachelor groups. In captive settings, a harem is likely to have only one adult male. In this context the surplus males are also managed through the formation of bachelor groups. For five years, we have studied the social adjustments and the urinary cortisol in a group of five males at the Louisville Zoo. For 3.5 years an old silverback was housed with four juveniles. Focal scans during this time show social distances that were similar to those when three of the animals were in a mixed group. By one year after the death of the silverback, the two older males were increasing their social distance [X2(2)=17.17, 6.01; α=0.05]. Mean individual cortisol levels and number of peak cortisol samples declined dramatically when the bachelor group was formed in comparison with the previous mixed group condition [Kruskal-Wallace AOV Pairwise Comparisons: α=0.05]. Over these five years we find no evidence that the bachelor group housing elevates cortisol. In fact, removal from females appears to moderate cortisol excretion.