Patterns of association between mothers and offspring and their outcomes in a polygynous ungulate

Abstract

Prolonged association between mothers and their offspring is common in ungulates, with the level of maternal investment likely to play a central role in shaping this trait. Here we examined patterns of association between mothers and offspring over time, the apparent benefits of association to offspring, and costs to mothers. We analyzed 40 years worth of census data from an individually-monitored, food-limited population of red deer (Cervus elaphus) on the Isle of Rum, Scotland. Starting from birth, female calves associated more frequently with their mothers than male calves in their first year. Calves also associated less with their mothers if the mother did not conceive a new calf. Association frequency decreased with mothers age and population density, and survival over the first year was not related to mother-calf association. Yearlings, now in their second year, were more often associated with their mothers if they were female, if there was no subsequent calf (or the subsequent calf died as a neonate), and if they were still being suckled. Increased association between mothers and yearlings was associated with increased survival to adulthood at 28 months, but suckling a yearling did not improve its probability of survival. For individuals that reached maturity, increased association in the yearling year was associated with slightly shorter adult life spans. The level of association between a calf and mother was not associated with the mothers immediate survival or fecundity. Our findings suggest that juveniles born to poor-condition mothers benefit from prolonged association through improved yearling survival.