Assessing Allostatic Load in Ring-Tailed Lemurs (Lemur catta)

SIMPLE SUMMARY: Our ability to measure and understand chronic stress in animals is limited by animals’ inability to communicate to us their perception of stressors. Researchers have developed tools to measure stress in animals, but these tools have many limitations. A novel measurement of chronic stress using several biomarkers has been studied in humans and great apes, but no research has assessed this tool in other primates, including lemurs. Our aim was to determine the relationship between allostatic load index (ALI), a measurement of chronic stress, and individual, social, medical and husbandry factors that may impact stress in lemurs housed under human care. Smaller group sizes, a higher percentage of time spent indoors, and more frequent group changes were associated with a higher ALI, indicating that these factors may be associated with chronic stress and potential deleterious health effects. This research presents support for ALI as a tool to help us better understand and mitigate stress in animals under our care. ABSTRACT: Responses to stress are unavoidable, adaptive mechanisms in humans and non-human animals. However, in humans, chronic stress has been linked to poor health outcomes and early mortality. Allostatic load, the physiologic dysregulation that occurs when an organism is exposed to chronic stressors, has been used to assess stress in humans; less work has been done using non-human primates. Our aim was to determine the relationship between allostatic load in ring-tailed lemurs (Lemur catta) under human care and potentially stressful individual, social, medical and husbandry factors, as well a sex and age. An allostatic load index (ALI) was calculated for 38 lemurs using six biomarkers measured in serum (albumin, cortisol, dehydroepiandrosterone-sulfate, DNA damage, glucose and prostaglandin E2). Potentially stressful factors were recorded over the lifetime of each lemur using medical and husbandry records. Animals with a higher percentage of time spent indoors, those kept in smaller average group sizes, and those with fewer minor group composition changes had, or tended to have, higher ALI. There was no relationship between ALI and sex or age. Some social and husbandry factors were associated with allostatic load in lemurs, indicating that this index may be a useful tool in assessing and determining factors contributing to stress of lemurs and other animals under human care.