Evaluation and Validation of Measures of Chronic Stress in Ring-tailed Lemurs (Lemur catta)
Year: 2017
Type: article
Abstract: Chronic stress can have detrimental long-term health effects but is challenging to measure.In humans, and recently gorillas (Gorilla gorilla), allostatic load index (ALI) has been utilized to measure the impact that exposure to chronic stressors has on somatic systems.The goal of this project was to validate ALI in ring-tailed lemurs (Lemur catta) as a potential means of evaluating health in captive and wild lemur populations.The specific objectives of the project were 1) validate the use of commercially available assays to measure six biochemical markers to calculate ALI in ring-tailed lemurs, and 2) determine the effects of age, sex, and stressors on ALI in ring-tailed lemurs.Commercial ELISA assays were utilized to measure and validate the following ALI biomarkers: cortisol, DHEA-S, DNA oxidative damage and PGE2.Serial dilutions of pooled serum were run and compared to the standard curve to ensure that the antigen of interest was accurately being measured.Albumin and glucose were obtained through standard chemistry analysis at a commercial laboratory.Allostatic loads indexes were calculated for each individual by dividing the raw values for each biomarker into quartiles.Among the biomarkers chosen, albumin and DHEA-S have a higher likelihood iii of causing impairment of the physiologic regulatory mechanisms when in the lowest quartile, while all other biomarkers show increased risk of physiologic dysregulation in the highest quartile.Since cortisol can be either elevated or depressed in association with chronic stress, a two-tailed cut-off was applied with the highest and lowest 12.5% of values being classified as high risk.Each biomarker within the high-risk quartile for an individual lemur was scored 1; biomarkers not within the high-risk quartile were scored zero.Scores were summed for each lemur as a composite allostatic load index creating an ALI from 0 to 6.The effects of sex and age were tested using two-sample t-test and linear regression, respectively.Associations between ALI and stressors (numbers of: anesthetic events, manual restraint, institutional transfers, enclosure changes, trauma, illnesses, pregnancy, group composition changes, % of time spent indoors/outdoors in semi-free ranging enclosures, participation in research trials (both frequency and time in minutes), and average group size) were tested using linear regression.When a significant association was found between ALI and a stressor males and females were evaluated separately to determine if there were differences by sex.ALI was associated with percent time spent indoors/outdoors in semi-free ranging enclosures.Lemurs that spent a larger percentage of their time outside in a semi-free ranging habitat had a lower ALI.Average group size had an effect also, with individuals maintained in smaller social groupings having higher ALI.Allostatic load index in females, but not males, was associated with group composition changes; animals with fewer group changes had higher ALI.Continuing to validate allostatic load as an indicator of chronic stress in nonhuman primates may not only improve their care in zoological collections, but also provide a means of evaluating the impact of human disturbances on wild populations, providing quantitative data to inform management decisions and improve species conservation.
Author: Kathryn E. Seeley
Institution: The Ohio State University
Language: English
Subfield: Small Animals
Field: Veterinary
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2786891935