Abstract # 2655 Event # 96:

Scheduled for Sunday, September 20, 2009 11:00 AM-11:10 AM: Session 8 (Shell Room) Oral Presentation


GELADA FEEDING ECOLOGY IN A TALL GRASS ECOSYSTEM: INFLUENCE OF BODY SIZE ON DIET

P. J. Fashing1 and N. Nguyen1,2
1Department of Anthropology, California State University Fullerton, Fullerton, CA 92834, USA, 2Wildlife Endocrinology Lab, Cleveland Metroparks Zoo, Cleveland, OH, 44109, USA
line
     

Variation in body size is an important predictor of dietary differences across primate species. Although they consume less food overall, smaller-bodied primates have higher basal metabolic rates and must maintain higher-quality diets than larger-bodied primates. Surprisingly, the influence of body size on diet within primate species has rarely been explored. We evaluated the relationship between body size and diet among geladas (Theropithecus gelada) at Guassa, Ethiopia. During 194 all-day follows of our ~220-member study band from February 2007-April 2008, we conducted scan samples every 30-minutes on the activity and diet of 5 nearby geladas. Annual diet consisted of tall grass blades [42%], herb leaves [29%], short grass blades [9%], herb roots [8%], invertebrates [3%], and other [9%; N=9,994 feeding records]. When individuals were divided into 5 categories of descending body size (adult males/females, large/medium/small juveniles), body size exerted a large influence on diet. Larger-bodied geladas devoted a significantly greater proportion of their diet to tall grass blades [ANOVA: F(4,70)=12.7,p<0.001] and a significantly smaller proportion of their diet to herb leaves [ANOVA: F(4,70)=4.2,p=0.004] than smaller-bodied geladas. These dietary differences may reflect differences in energetic needs. While much scarcer, herbs are higher in nutritional content and more digestible than grasses. Our results are consistent with patterns documented across species of different sizes; larger geladas ate more lower-quality but abundant grasses while smaller geladas ate more higher-quality but scarcer herbs.