1Karisoke Research Center, Dian Fossey Gorilla Fund International, 2Anthropology & Center for the Advanced Study of Hominid Paleobiology, The George Washington University, 3Mbeli Bai Study, Nouabalé-Ndoki National Park, Wildlife Conservation Society, 4Director of Primate Research, Zoo Atlanta, 5Division of Mammals, National Museum of Natural History, Smithsonian Institution
March 26, 2015 , Archview Ballroom
Physical ontogeny is critical to understanding life history evolution. Great apes, including gorillas, have shown diverse life history strategies attributed to differences in their dietary ecology and social behavior. Virunga mountain gorillas are characterized by earlier ages at weaning, female first birth, and higher fertility compared to more frugivorous western gorillas. However, variation in postnatal growth among wild gorillas is poorly understood. We used non-invasive parallel-laser photogrammetry to characterize linear growth of six body measurements collected from wild Virunga mountain gorillas monitored by the Karisoke Research Center, Rwanda. In a pilot study of Zoo Atlanta gorillas (N=4), mean body measurements obtained using this method differed by 2.7-5.2% from corresponding measurements obtained manually. Head measurements, arm length, shoulder width and body length were collected from eight Karisoke social groups (N=63M, 52F; 0-35y) over four months, and growth curves generated for each sex using regression analysis; all data were treated cross-sectionally. For all measures, males and females showed similar growth rates from 0-8 years of age, after which time female growth slowed; adult female body length was reached by approximately 11 years. However, an interesting contrast emerged between wild mountain and western gorillas: male mountain gorillas reached adult body length by 14 years of age, which is 3.5 years earlier than reported for male western lowland gorillas at Mbeli Bai, Congo. These results support the prediction that mountain gorillas, characterized by reduced feeding competition associated with more folivorous diets, reach adult body size at earlier ages compared to western gorillas.
Funding support was provided by The Leakey Foundation, The Wenner Gren Foundation, and The George Washington University CIFF and Selective Excellence funding to CASHP.