Abstract

The physical environments of captive and wild animals frequently differ in substrate types and compliance. As a result, there is an assumption that differences in rearing environments between captive and wild individuals produce differences in skeletal morphology. Here, this hypothesis is tested using a sample of 42 captive and wild common chimpanzees (Pan troglodytes). Articular surface areas of the humerus, radius, ulna, femur, and tibia were calculated from linear breadth measurements, adjusted for size differences using Mosimann shape variables, and compared across sex and environmental groups using two-way ANOVA. Results indicate that the articular surfaces of the wrist and knee differ between captive and wild chimpanzees; captive individuals have significantly larger distal ulna and tibial plateau articular surfaces. In both captive and wild chimpanzees, males have significantly larger femoral condyles and distal radius surfaces than females. Finally, there is an interaction effect between sex and rearing in the articular surfaces of the femoral condyles and distal radius in which captive males have significantly larger surface areas than all other sex-rearing groups. These data suggest that long bone articular surfaces may be sensitive to differences experienced by captive and wild individuals, such as differences in diet, body mass, positional behaviors, and presumed loading environments. Importantly, these results only find differences due to rearing environment in some long bone articular surfaces. Thus, future work on skeletal morphology could cautiously incorporate data from captive individuals, but should first investigate potential intraspecific differences between captive and wild individuals.

Highlights

  • Morphological studies on primates tend to focus on osteological samples that derive from wild-caught individuals because of the assumption that the skeletons of individuals raised in captive environments differ from those living in wild or large range sanctuary environments (e.g., Albrecht, 1982)

  • The distal ulna is 7.1% larger in captive females and 8.6% larger in captive males compared to wild individuals (Table 3)

  • There was a significant sex*rearing interaction effect in the femoral condyles, humeral head, and distal radius (Tables 4 and 5). For each of these interaction effects, captive males were significantly different from other sex-rearing groups (Table 5)

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Summary

Introduction

Morphological studies on primates tend to focus on osteological samples that derive from wild-caught individuals because of the assumption that the skeletons of individuals raised in captive environments differ from those living in wild or large range sanctuary environments (e.g., Albrecht, 1982). This perception is especially true among studies of great apes given the potentially large differences in wild versus captive ape environments. Other issues related to potential differences in nutrition, growth, and physiology, skeletons of wild-caught individuals have been preferred for studies of morphological variation

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