Abstract # 152:

Scheduled for Friday, August 18, 2006 04:45 PM-05:05 PM: Session 15 (Regency East #3) Oral Presentation

Menopause and perimenopause in geriatric western lowland gorillas (Gorilla gorilla gorilla)

S. Margulis1,2 and S. Atsalis3
1Lincoln Park Zoo, 2001 N. Clark Street, Chicago, IL 60614, USA, 2University of Chicago, Committee on Evolutionary Biology, 3Chicago Zoological Society
     In a nationwide zoo-based study on behavioral and hormonal changes in female gorillas, we evaluated progestogen concentrations in 30 subjects, 22 of whom were geriatric (>30). Concurrent behavioral data were collected several times weekly on 16 of these females. While control females cycled regularly, approximately 23% of geriatric females are acyclic (menopausal), and another 32% showed irregular cycling patterns, suggestive of perimenopause, including extreme variability of cycle length, progesterone peaks that do not reach threshold values, and great inter-peak variability in maximal peak height. Acyclic females had significantly lower overall progestogen concentrations than did cycling control or geriatric females (F2,26=3.58, p<0.05), although differences were not significant when cycle phase was incorporated. Peak progestogen levels were significantly lower for noncycling than for cycling females (F2,26=5.76, p<0.05). Variability in estrous cycle lengths between control and geriatric cycling females was significantly different (F33,16=2.2, p<0.05). Nearly all cycling females exhibited estrus behavior. Proceptive behavior preceded ovulation on average by 6.6 days for geriatric females, and 4.3 days for control females. During estrus females spent more time in proximity to the silverback. Affiliative behavior between silverback and estrus females was observed in the control females, but not the geriatric females. As nutrition and health enhancements lead to increased longevity in our zoo populations of apes, our focus must shift to the physiological and behavioral changes in this demographic group.