Abstract # 120:

Scheduled for Friday, June 22, 2007 02:45 PM-03:00 PM: Session 13 (North Main Hall F/G) Oral Presentation

Urinary Cortisol Variation in Captive Lowland Gorillas (Gorilla gorilla) Related to Visitors and Keepers

B. White1, D. M. Smith1, R. Elsner2 and V. Cool-Hines2
1Centre College, Psychobiology Program, 600 W. Walnut St., Danville, Kentucky 40422, USA, 2Louisville Zoo
     A recent behavioral study reported that visitors may be stressing captive gorillas. The popularity of gorillas among zoo patrons assures substantial exposure to visitors, and interaction with humans is a consequence of successful husbandry. The present study addressed this concern about human/gorilla interaction, using the pattern of cortisol excretion during the calendar year as an assessment of the human impact on the gorillas at the Louisville Zoo. Radioimmunoassay was used to determine urinary cortisol in 521 samples collected opportunistically from 17 gorillas over a 3-year span (mean of 12 animals per year). Urinary cortisol concentration was corrected for variation in hydration using specific gravity. Neither mean corrected cortisol nor the number of individual peak concentrations (1.5 s.d. above individual mean) was related to the daily [r(133)=0.02, p>0.05] and monthly [r(10)=0.36,p>0.05] patterns of visitors. Significantly more peak levels of cortisol [F(3,45)=3.07, p<0.05] were found in the final quarter of the calendar year than in the first quarter. During this latter period, cortisol excretion was negatively correlated [r(27)=-0.37, p=0.05] with gorilla-keeper interaction. The results do not support the notion that visitors stress the gorillas in this exhibit. Applying human norms, none of these animals appear to be stressed as measured by cortisol excretion. Interaction with keepers during training and movement of animals was associated with lower cortisol excretion.