Weight and age in wild olive baboons


  • S. C. Strum

    Corresponding author
    1. Department of Anthropology, University of California, San Diego
    2. Institute of Primate Research, Nairobi, Kenya
    • Uaso Ngiro Baboon Project, c/o Wildlife Conservation International, Box 62844, Nairobi, Kenya
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Data on weight, toothwear, cape length, testes size, canine size, and age from wild olive baboons are presented in order to consider the nature of the growth curve, the differences between males and females in a sexually dimorphic species, and the effect of nutrition on growth parameters. Longitudinal and cross-sectional data on weight and age in three troops that lived under a variety of ecological circumstances showed a good fit to the von Bertalanffy growth equation. Male and female baboons have different growth constants (K) and different asymptotic weights and ages resulting in the observed baboon sexual dimorphism. Within sexes, growth constants and asymptotic weights varied between troops in the same year and for the same troop in different years. Improvements in nutrition increased growth rate and final weight and decreased age at asymptote in both naturally foraging and in food-enhanced wild groups. Testes and cape length follow the same growth pattern and have the same asymptotic age as body mass among naturally foraging males. Canine growth is different with full size achieved nearly 2 years earlier. Toothwear is an accurate relative age indicator for immature and adult females and for immature males but not for adult males because of the role that large canines play in occlusion and wear. The data suggest that creating a dichotomy between captive and wild primates is overly simplistic since conditions for growth in the wild can overlap those of captivity, not just for food enhanced individuals but also among naturally foraging troops. The nutritional perspective on primate growth exposes inherent problems in our present system of primate age classification which have serious implications for the use of age classes in behavioral analyses.