Effects of cortisol administration on cooperative behavior in meerkat helpers

Although the ultimate causes for variation in contributions to helping in cooperative breeders are increasingly well understood, the underlying physiological mechanisms remain largely unknown. Recent work has suggested that glucocorticoids may play an important role in the expression of cooperative behavior. Here, we present the first experimental test of the effects of glucocorticoids on helper behavior in a cooperative breeder. Glucocorticoid levels of adult female and male meerkat, Suricata suricatta, helpers were elevated with an intramuscular injection of cortisol (hydrocortisone 21-hemisuccinate sodium salt) dissolved in saline, whereas matched controls simultaneously received an injection of physiological saline. The treatment successfully elevated circulating glucocorticoid levels but did not result in significant changes in pup feeding or sentinel behavior. Females, however, spent less time foraging when glucocorticoid levels were elevated and appeared to spend more time in close proximity to pups. These results provide no evidence that glucocorticoids affect cooperative behaviors but suggest that there may be an effect on foraging effort and affiliation with pups.