Hip joint mobility in free-ranging rhesus macaques

Objectives: We aimed to test for differences in hip joint range of motion (ROM) between captive and free-ranging rhesus macaques (Macaca mulatta), particularly for hip joint abduction, which previous studies of captive macaques have found to be lower than predicted. Materials and methods: Hip ROM was assessed following standard joint measurement methodology in anesthetized adult free-ranging rhesus macaques (n = 39) from Cayo Santiago, and compared with published ROM data from captive rhesus macaques (n = 16) (Hammond, American Journal of Physical Anthropology). Significant differences between populations were detected using one-way analysis of variance (p <.05). Results: In a sample of pooled sexes and ages, free-ranging macaques are capable of increased hip abduction, flexion, and internal rotation compared with captive individuals. These differences in joint excursion resulted in free-ranging individuals having significantly increased ROM for hip adduction–abduction, rotation, flexion–extension, and the distance spanned by the knee during hip abduction. When looking at data for a smaller sample of age-matched males, fewer ROM differences are significant, but free-ranging males have significantly increased hip abduction, internal rotation, range of flexion–extension, and distance spanned by the knee during hip abduction compared with captive males of similar age. Discussion: Our results suggest that a spatially restrictive environment results in decreased hip mobility in cage-confined animals and ultimately limits the potential limb postures in captive macaques. These results have implications for selection of animal samples in model validation studies, as well as laboratory animal husbandry practices. KEYWORDS caging, Cayo Santiago, hip abduction, Macaca mulatta, nonhuman primate captive care.