Variation in early life testosterone in a wild population of red deer

1. Individual differences in circulating hormone concentrations can affect life history traits throughout an animal’s life. Despite this, relatively little is known about the potential drivers or consequences of individual variation in hormone levels, particularly in early life. In animals showing maternal care, early development is often dependent on maternal characteristics and condition. It is therefore possible that individual hormone profiles early in life are dependent on condition-linked characteristics of the mother. 2. Using data from a long-term study of a wild red deer (Cervus elaphus) population, we investigated the potential role of maternal effects on offspring early life testosterone concentrations and the relationship between these testosterone levels and juvenile survival. 3. Most of the variation among neonatal calves was accounted for by their age and sex. Both sexes showed a steep decline in testosterone levels within 24 hours of birth, although concentrations were c...