ABSTRACT: Sexual segregation is common among marine mammals, leading to intraspecific differences in diet, diving behaviour, home range size and even latitudinal distribution and migratory patterns. Sperm whales Physeter macrocephalus present one of the most extreme examples of sexual dimorphism both in size and social structure, with males and females segregating at different latitudes across most of their range, but the underlying ecological drivers remain unclear. Studying fine-scale dietary and habitat differences where the sexes occur in sympatry could therefore provide insights into the mechanisms underpinning their large-scale segregation. In this study, we analysed the carbon and nitrogen stable isotope values in the skin of males and females from an isolated, endangered population inhabiting the Mediterranean Sea, sampled in a region where the sexes occur and feed regularly in the summer months but show subtle differences in habitat preference. We found marked differences in both carbon and nitrogen isotopic values between the sexes, indicating that they could be targeting prey items in different trophic levels and habitats. Combined with the evidence from habitat modelling studies, our results suggest that female and male sperm whales segregate even in the latitudinally restricted Mediterranean population, at a much smaller scale. This sympatric, fine-scale sexual segregation suggests that reduction of competition may have been a key factor in the evolution of the social structure and large-scale latitudinal segregation of this species.

中文翻译：

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稳定的同位素表明，一个孤立的，濒临灭绝的抹香鲸种群中存在着大规模的性别隔离

摘要：海洋哺乳动物普遍存在性别隔离，导致饮食，跳水行为，家庭范围大小乃至纬度分布和迁徙方式的种内差异。抹香鲸Physeter macrocephalus目前在规模和社会结构上都是最极端的性二态性例子之一，在其大部分范围内，男性和女性在不同的纬度上隔离，但是其潜在的生态驱动因素仍然不清楚。因此，研究在交配处发生性别的细微饮食和生境差异，可能有助于深入了解其大规模隔离的机制。在这项研究中，我们分析了居住在地中海的一个孤立，濒临灭绝的种群中雄性和雌性皮肤中碳和氮的稳定同位素值，该区域取样于性别在夏季发生并定期进食但存在细微差异的区域在栖息地方面 我们发现两性之间的碳和氮同位素值存在明显差异，表明他们可能针对营养级别和栖息地不同的猎物。结合栖息地建模研究的证据，我们的结果表明，即使在受纬度限制的地中海种群中，雌性和雄性抹香鲸的隔离规模也要小得多。这种同伴性，细微的性别隔离表明，竞争的减少可能一直是该物种社会结构演变和大规模纬度隔离的关键因素。