Abstract
Life history data from wild primate populations are necessary to explain variation in primate social systems and explain differences between primates and other mammals. Here we report life history data from a 12.5βyear study on wild Thomas langurs. Mean age at first reproduction was 5.4 years and the sex ratio at birth was even. The mean interbirth interval (IBI) after a surviving infant was 26.8βmo, after nonsurviving infants 17.7βmo, and combined 22.0βmo. Mean annual birth rate of adult females was 0.44, while reaching a peak at 6 years of age and showing no decrease with age. Mortality was highest during the first year of life (48.0% for males and 43.0% for females) and consistently higher for males than females. The oldest female observed during the study was estimated to be 20 years of age, whereas the oldest male disappeared at age 13 years, indicating that males die at a much earlier age than females. A Leslie matrix based on these estimates yielded a growth rate of 1.01, which is comparable to the nonsignificant increase in density indicated by our longβterm field data. A comparison with life history data for sympatric frugivorous primates suggests that folivory might be associated with faster life history. Am. J. Primatol. 69:641β651, 2007. Β© 2006 WileyβLiss, Inc.