The Influence of Age and Sex on Measures of Body Size in Captive Chimpanzees (Pan troglodytes) Cared for in African Wildlife Sanctuaries and Zoological Collections

Introduction

The typical growth pattern of chimpanzees (Pan troglodytes) has largely been  derived from captive  research populations, as methodological and ethical  challenges limit assessment of  their wild counterparts.  Despite a lack of empirical evidence, captive research chimpanzees have been suggested to display accelerated growth compared to wild animals. Wild-born sanctuary chimpanzees may provide a more ecologically valid population from which to infer species-typical growth. The aim of this study was to investigate the growth pattern of  male  and  female sanctuary chimpanzees and compare these data to animals in zoological and research facilities.

Methods

Body mass and crown-rump length were obtained from 150 male and 148 female (aged 1-38 years) African sanctuary chimpanzees. Sex-specific piecewise linear regressions were  performed to estimate growth rates and age at maturation. Body mass regressions were  compared to those of 454 male and 623 female chimpanzees (aged 1-40 years) acquired from a centralised zoological database. A literature search of peer-reviewed publications was conducted to identify body mass data of research facility populations, which were presented for comparison.

Results

Male sanctuary chimpanzees attain body mass maturation at an older age compared to females (13.8 vs 12.4 years), but sex differences were not observed in maturation age for crown-rump length or the growth rates for either measure. In comparison to zoological  animals, sanctuary chimpanzees had a slower estimated rate of body mass growth and attained maturation at an older age (males:13.8 vs. 12.2 years; females: 12.4 vs. 12.2 years). Sanctuary chimpanzees were also lighter than zoological (males: 53 vs. 61 kg; females: 44 vs. 52 kg) and research animals.

Conclusion

Together, these results suggest that growth patterns between African sanctuary, zoological and research facility populations of chimpanzees differ. These differences need to be considered when examining life history characteristics in this species.   Additionally, these sanctuary data contribute significantly to current understanding of chimpanzee growth.