Behavioral interactions and glucocorticoid production of Somali wild ass (Equus africanus somaliensis) mothers and foals

Publication Type:
Journal Article
Year of Publication:
Corinne P Kozlowski, Eli Baskir, Helen L Clawitter, Ashley D Franklin, Tim Thier, Martha Fischer, David M Powell, Cheryl S Asa
Applied Animal Behaviour Science
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Somali wild ass (Equus africanus somaliensis) are the most endangered species of wild equid, and little is known about their reproductive biology. Here, we describe social interactions and glucocorticoid production of five pairs of Somali wild ass females and their foals, which were born within a two-month period at the Saint Louis Zoo. Behavioral data were recorded from 0–3 months (Infant), and again from 6–12 months of age (Older Foal). Fecal samples were collected three times a week for 12 months, starting when foals were born, and analyzed for glucocorticoids using a validated assay. Generalized linear mixed models assessed differences in behavior and glucocorticoid concentrations between foals and mothers, in regard to foal sex, foal age, and season. Nursing bout frequency and total nursing duration, but not bout duration, decreased with age. Low nursing rates were still observed in 11 to 12-month-old foals, suggesting that weaning occurs after one year. Rates of social behaviors were similar between mothers and their foals, and rates of agonistic behavior were similar to rates of affiliative behavior. Male foals initiated and received agonistic behaviors more than female foals. Patterns of interactions varied with foal age. Infants interacted primarily with their mothers, whereas interactions among foals were common during the Older Foal period. Glucocorticoid concentrations of foals and mothers varied in relation to foal age; concentrations for both were highest in the first months of life. Seasonal differences in glucocorticoid concentrations were also observed, but no evidence of elevated glucocorticoid production was found except around the time of parturition. This suggests that neither mothers nor foals experienced chronic stress. Our study presents new information on the biology of Somali wild ass and is one of the few to document behavior and physiology in a non-domestic equid. This information may contribute to improved management of ex situ populations by enhancing individual welfare and increasing reproductive success.


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