Data from: Social conflict and costs of cooperation in meerkats are reflected in measures of stress hormones

Measures of glucocorticoid stress hormones (e.g. cortisol) have often been
used to characterize conflict between subordinates and dominants. In
cooperative breeders where subordinates seldom breed in their natal group
and assist in offspring rearing, increases in subordinate glucocorticoid
levels may be caused by conflict among subordinates as well as by the
energetic costs of helping behavior and fluctuations in food availability
may exacerbate these effects. During a 6-year study of Kalahari meerkats
(Suricata suricatta), we investigated how social, environmental, and
individual characteristics influenced subordinate plasma cortisol levels.
Subordinate females, who are often the target of aggression from dominant
females, had higher cortisol levels when the dominant female in their
group was pregnant while the cortisol levels of subordinate males were
unaffected by the reproductive state of dominant females. Subordinates of
both sexes had higher cortisol levels if they belonged to groups 1) where
neither of the dominant breeders in the group were their parents, 2) that
contained a high proportion of subordinate females, or 3) that were either
very large or very small, especially when the weather was cold and dry.
Subordinates in groups containing young pups had higher cortisol levels.
Finally, cortisol levels were higher in subordinates of both sexes if they
were lighter for their age or had lost little body mass the night prior to
sampling. Our results show that both social conflict and cooperative
behavior can elevate glucocorticoid levels in subordinates and that both
effects can be modified by variation in weather and food availability.