Panthera, New York, NY, USA.
Institute for Communities and Wildlife in Africa, University of Cape Town, Cape Town, South Africa.
J Anim Ecol. 2020 Feb;89(2):589-600. doi: 10.1111/1365-2656.13109. Epub 2019 Oct 29.
Individual specialization, when individuals exploit only a subset of resources utilized by the population, is a widespread phenomenon. It provides the basis for evolutionary diversification and can impact population and community dynamics. Both phenotypic traits and environmental conditions are predicted to influence individual specialization; however, its adaptive consequences are poorly understood, particularly among large mammalian carnivores that play an important role in shaping ecosystems. We used observations of 2,960 kills made by 49 leopards Panthera pardus in the Sabi Sand Game Reserve, South Africa, to quantify the magnitude of individual dietary specialization in a solitary large carnivore, and to examine the proximate and ultimate drivers of this behaviour. We found evidence of individual specialization in leopard diet, with respect to both the species and size of prey killed. Males tended to be more specialized than females, likely because they could access a wider range of prey due to larger body size. Similarly, individuals that encountered a greater diversity of prey tended to be more specialized. Our results confirmed that ecological opportunity was a key determinant of individual specialization; however, contrary to predictions, per capita resource availability (and by extension, intraspecific competition) did not affect the degree of specialization exhibited by individuals. Surprisingly, dietary specialization appeared to disadvantage male leopards. Specialist males overlapped with fewer resident females, had fewer cubs born on their home ranges and had fewer cubs survive to independence on their home ranges than generalist males. This may have resulted from the high degree of environmental stochasticity experienced during our study, as dietary specialization is expected to advantage individuals more during periods of resource predictability. In summary, we showed that a species usually considered to be a dietary generalist was in fact a heterogeneous collection of specialist and generalist individuals. Individual specialization is typically assumed to be maintained by disruptive and/or fluctuating selection; hence, the somewhat paradoxical coexistence of both in the same population might be explained by a dynamic evolutionary equilibrium that exists between specialists and generalists, in which each benefit under different conditions.
个体特化是指个体只利用种群中利用的资源子集，是一种广泛存在的现象。它为进化多样化提供了基础，并可能影响种群和群落动态。表型特征和环境条件都被预测会影响个体特化；然而，其适应后果还知之甚少，特别是在大型哺乳动物肉食动物中，它们在塑造生态系统方面起着重要作用。我们使用南非萨比沙禁猎区 49 只豹子 Panthera pardus 捕杀的 2960 次猎物观察数据，来量化独居大型肉食动物的个体饮食特化程度，并研究这种行为的近因和终极驱动因素。我们发现豹子的饮食存在个体特化的证据，无论是猎物的种类还是大小。雄性比雌性更特化，这可能是因为它们由于体型较大，能够获取更广泛的猎物种类。同样，遇到更多种类猎物的个体往往更加特化。我们的结果证实，生态机会是个体特化的关键决定因素；然而，与预测相反，人均资源可用性（以及由此延伸的种内竞争）并不影响个体表现出的特化程度。令人惊讶的是，饮食特化似乎对雄性豹子不利。特化的雄性豹子与更少的常驻雌性豹子重叠，在其领地内出生的幼崽更少，在其领地内独立存活的幼崽也更少，而一般的雄性豹子则更多。这可能是由于我们的研究期间经历了高度的环境随机性，因为在资源可预测性期间，饮食特化预计会使个体更具优势。总之，我们表明，一种通常被认为是杂食性的物种实际上是由特化和一般化的个体组成的异质集合。个体特化通常被认为是由破坏性和/或波动选择维持的；因此，在同一群体中同时存在特化和一般化的个体可能可以用专家和一般化个体之间存在的动态进化平衡来解释，在这种平衡中，每个个体在不同的条件下都受益。
