Age at weaning in Steller sea lions

The duration of offspring care is critical to female fitness and population resilience by allowing flexibility in life history strategies in a variable environment.  Yet, for many mammals capable of extended periods of maternal care, estimates of the duration of offspring dependency are not available and the relative importance of flexibility of this trait on fitness and population viability has rarely been examined.  We used data from 4,447 Steller sea lions Eumetopias jubatus from the Gulf of Alaska and multistate hidden Markov mark-recapture models to estimate age-specific weaning probabilities. Maternal care beyond age 1 was common: weaning was later for animals from Southeast Alaska (SEAK) and Prince William Sound (PWS, weaning probabilities: 0.538–0.648 / 0.784–0.873 by age 1 / 2) compared to animals born to the west (0.714–0.855 / 0.798–0.938).  SEAK/PWS animals were also smaller than those born farther west, suggesting a possible link.  Females weaned slightly earlier (+0.080 at...