Centre for Research in Animal Behaviour, University of Exeter, Exeter EX4 4QG, UK
Department of Biology, University of York, York YO10 5GE, UK.
Proc Biol Sci. 2017 Oct 25;284(1865). doi: 10.1098/rspb.2017.1313.
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 () 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 better access to social information and food-sharing opportunities which may enhance their survival in years of low salmon abundance. Our results show that observable variation in the social environment is linked to variation in mortality risk, and highlight how sex differences in social effects on survival may be linked to sex differences in life-history evolution.
个体的生态环境会影响其死亡率风险，而死亡率风险反过来又对生活史进化有根本影响。在许多物种中，社会关系很可能是个体环境的一个重要组成部分，因此也是其死亡率风险的一个重要组成部分。在这里，我们利用三十多年的社会和人口数据，研究了居留型虎鲸（）的社会地位与死亡率风险之间的关系。我们发现，雄性而非雌性虎鲸在其社会群体中的社会地位可以预测其死亡率风险。与社会边缘雄性相比，社会关系更融洽的雄性的死亡率风险显著更低，特别是在猎物数量较少的年份，这表明社会地位可以调节资源的获取。雄性虎鲸比雌性虎鲸体型更大，需要更多的资源，因此在鲑鱼数量较少的年份更容易挨饿。更融洽的雄性更有可能更好地获取社会信息和食物共享机会，这可能会提高它们在鲑鱼数量较少的年份的生存能力。我们的研究结果表明，可观察到的社会环境变化与死亡率风险的变化有关，并强调了社会对生存的影响在性别上的差异如何与生活史进化的性别差异有关。
