Factors influencing hair loss among female captive rhesus macaques ( Macaca mulatta)

Abstract

Although rare among wild animals, hair loss is common among captive animals, which suggests that some aspect of the captive environment contributes to abnormal hair loss. Female rhesus macaques ( Macaca mulatta) at the California National Primate Research Center (CNPRC) housed in outdoor enclosures exhibited hair loss that varied significantly by pregnancy, season, ground substrate, rank, and age as well as by several pair-wise interactions. Pregnant females were 2.4 times more likely to have worse coat condition than non-pregnant females ( P < 0.001). Among pregnant females, pronounced hair loss was apparent 1–2 months into gestation, as well as during the month following parturition. Females in general exhibited the lowest degree of hair loss in Fall (Fall vs. Winter: P < 0.001; Fall vs. Spring: P < 0.001; Fall vs. Summer: P < 0.001). Independent of reproductive condition and seasonality, macaques housed in enclosures with gravel substrate were 3.7 times more likely to have greater hair loss than those in enclosures with grass substrate ( P < 0.001), and low-ranking females exhibited significantly greater hair loss than high-ranking females ( P < 0.001). Older females had significantly greater hair loss than younger females ( P < 0.001). Finally, females in larger groups tended to have greater hair loss than those in smaller groups. These results indicate that multiple factors influence the degree of hair loss among female captive rhesus macaques, some of which include housing conditions that can be modified to improve coat condition, such as planting grass in outdoor enclosures and adopting management procedures that reduce levels of social stress experienced by lower-ranking animals and animals living at higher densities.