Mortality risk and social network position in resident killer whales: sex differences and the importance of resource abundance

An individual’s ecological environment affects their mortality risk, which in turn has fundamental consequences for life history evolution. In many species social relationships are likely to be an important component of an individual’s environment, and therefore their mortality risk. Here we examine the relationship between social position and mortality risk in resident killer whales (Orcinus orca) using over three decades of social and demographic data. We find that the social position of male, but not female, killer whales in their social unit predicts their mortality risk. More socially integrated males have a significantly lower risk of mortality than socially peripheral males, particularly in years of low prey abundance, suggesting that social position mediates access to resources. Male killer whales are larger and require more resources than females, increasing their vulnerability to starvation in years of low salmon abundance. More socially integrated males are likely to have bet...