Maternal stress and plural breeding with communal care affect development of the endocrine stress response in a wild rodent.

Maternal stress can significantly affect offspring fitness. In laboratory rodents, chronically stressed mothers provide poor maternal care, resulting in pups with hyperactive stress responses. These hyperactive stress responses are characterized by high glucocorticoid levels in response to stressors plus poor negative feedback, which can ultimately lead to decreased fitness. In degus (Octodon degus) and other plural breeding rodents that exhibit communal care, however, maternal care from multiple females may buffer the negative impact on pups born to less parental mothers. We used wild, free-living degus to test this hypothesis. After parturition, we manipulated maternal stress by implanting cortisol pellets in 0%, 50-75%, or 100% of adult females within each social group. We then sampled pups for baseline and stress-induced cortisol, negative feedback efficacy, and adrenal sensitivity. From groups where all mothers were implanted with cortisol, pups had lower baseline cortisol levels and male pups additionally had weaker negative feedback compared to 0% or 50-75% implanted groups. Contrary to expectations, stress-induced cortisol did not differ between treatment groups. These data suggest that maternal stress impacts some aspects of the pup stress response, potentially through decreased maternal care, but that presence of unstressed mothers may mitigate some of these effects. Therefore, one benefit of plural breeding with communal care may be to buffer post-natal stress.