1Department of Cell Biology and Anatomy, University of North Texas Health Science Center, 2Department of Anthropology, University of Minnesota, 3Department of Ecology, Evolution, and Behavior, University of Minnesota, 4Gombe Stream Research Center, Jane Goodall Institute
Friday All day, Clinch Concourse
Previous research indicates that adult chimpanzees accumulate injuries as they age, so that older chimpanzees have more skeletal traumata compared to younger conspecifics. We tested whether this same trend is apparent in sub-adults versus adults in an expanded skeletal sample of wild chimpanzees from Gombe National Park, Tanzania. We examined 30 chimpanzee skeletons (16 female, 14 male) for skeletal trauma, all with known sex and age (or a reliable age estimate), and represented by complete or near complete skeletons. Trauma incidence is the percent of observable bones affected by trauma, allowing for some broad comparisons between skeletons with differing numbers of bones (e.g. adults versus sub-adults, or in cases of a few missing hand or foot bones). We analyzed the relationship between trauma incidence and age using the statistical software Arc. This study confirms that number of traumata increases with age in adult chimpanzees. In the sample that includes chimpanzees of all ages, we did not find a linear relationship between age and trauma incidence (R2 = -0.065, p = 0.17). This is due to 4 influential cases whose trauma incidences are an order of magnitude larger than the other chimpanzees in the sample. We argue that the influential cases should not be considered outliers because cause of death is conspecific aggression, one of the leading causes of death for chimpanzees at Gombe, and because in a sub-sample including only adult chimpanzees, cause of death did not affect trauma incidence (chi-square = 0.868, df = 1, p > 0.1).
University of Minnesota Thesis Research Grant, University of Minnesota Graduate Research Partnership Program