Mothers of disabled infants had higher cortisol levels in a free‐ranging group of Japanese macaques (Macaca fuscata)

• Published in: American journal of primatology 2023-07, Vol.85 (7), p.e23500-n/a
• Main Authors: Turner, Sarah E., Fedigan, Linda M., Joyce, Megan M., Matthews, H. Damon, Moriarity, Robert J., Nobuhara, Hisami, Nobuhara, Toshikazu, Stewart, Brogan M., Shimizu, Keiko
• Format: Article
• Language: English
• Subjects: Adults; Animals; Availability; Behavioral plasticity; Biological markers; Biomarkers; Birth season; Congenital defects; congenital limb malformation; Cortisol; disability; Dominance; dominance rank; Enzyme immunoassay; Feces; Female; Females; Glucocorticoids; Homeostasis; Hormones; Humans; Hydrocortisone; Immunoassay; Impairment; Infancy; Infants; Japanese monkey; Limb malformations; Limbs; Macaca fuscata; maternal care; Mothers; People with disabilities; Physical disabilities; physical impairment; Physiology; Plasticity; Predators; Rainfall; Reproduction; Reproductive status; Social factors; Social interactions; Social support; stress; Values; Well being; Wild fruit
• ISSN: 0275-2565; 1098-2345
• DOI: 10.1002/ajp.23500

Glucocorticoids (GCs) are hormones released in response to stressors and can provide insight into an organism's physiological well‐being. Experiencing chronic challenges to homeostasis is associated with significant deviations from baseline fecal GCs (fGCs) in many species, providing a noninvasive biomarker for assessing stress. In the group of free‐ranging Japanese macaques (Macaca fuscata) at the Awajishima Monkey Center in Japan, ~17% have congenital limb malformations. We collected 646 fecal samples from 27 females over three consecutive birth seasons (May–August) and analyzed them using enzyme immunoassay to extract fGCs. We explored the relationship between fGC levels and individual (physical impairment and reproductive status), social (dominance rank and availability of kin for social support), and ecological variables (exposure to potential predators, rainfall, and wild fruit availability). A disabled infant was associated significantly with higher fGC in the mother; however, physical impairment in adult females was not significantly related to fGC levels. Females with higher dominance rank had significantly lower fGC levels than lower ranking females. Other factors did not relate significantly to fGC. These results suggest that providing care that meets the support needs of disabled infants poses a physiological challenge for mothers and suggests that physically impaired adults are able to effectively compensate for their disabilities with behavioral plasticity. Once an individual with congenital limb malformations survives infancy through their mother's care, physical impairment does not appear to influence fGC values, while social variables like dominance rank significantly influenced cortisol values in free‐ranging female Japanese macaques. Mothers of disabled infants and lower ranking females, but not disabled adult females, had higher fecal cortisol values among free‐ranging female Japanese monkeys. We considered physical impairment, maternity and individual, and social and ecological factors that may impact stress among adult females in a free‐ranging group of Japanese macaques (as depicted in the pictogram illustration of our main statistical model). Photos show (from left to right) a nondisabled macaque mother grooming her disabled juvenile daughter; a close‐up image of a nursing infant with extensive physical impairments (congenital absence of hands); a group of Japanese macaque females sitting in contact, including individuals with and w