Data from: Female-biased dispersal in a bat with a female-defence mating strategy

The ultimate causes for predominant male-biased dispersal (MBD) in mammals and female-biased dispersal (FBD) in birds are still subject to much debate. Studying exceptions to general patterns of dispersal, for example, FBD in mammals, provides a valuable opportunity to test the validity of proposed evolutionary pressures. We used long-term behavioural and genetic data on individually banded Proboscis bats (Rhynchonycteris naso) to show that this species is one of the rare mammalian exceptions with FBD. Our results suggest that all females disperse from their natal colonies prior to first reproduction and that a substantial proportion of males are philopatric and reproduce in their natal colonies, although male immigration has also been detected. The age of females at first conception falls below the tenure of males, suggesting that females disperse to avoid father–daughter inbreeding. Male philopatry in this species is intriguing because Proboscis bats do not share the usual mammalian correlates (i.e. resource-defence polygyny and/or kin cooperation) of male philopatry. They have a mating strategy based on female defence, where local mate competition between male kin is supposedly severe and should prevent the evolution of male philopatry. However, in contrast to immigrant males, philopatric males may profit from acquaintance with the natal foraging grounds and may be able to attain dominance easier and/or earlier in life. Our results on Proboscis bats lent additional support to the importance of inbreeding avoidance in shaping sex-biased dispersal patterns and suggest that resource defence by males or kin cooperation cannot fully explain the evolution of male philopatry in mammals.哺乳动物中普遍存在的雄性偏向扩散（male-biased dispersal, MBD）与鸟类中雌性偏向扩散（female-biased dispersal, FBD）的终极成因，至今仍存在广泛争议。对扩散通用模式的例外情况开展研究（例如哺乳动物中的雌性偏向扩散），可为检验已提出的进化压力假说的合理性提供宝贵契机。我们通过对经个体环志标记的长鼻蝠（Rhynchonycteris naso）开展长期行为学与遗传学研究，证实该物种是少数存在雌性偏向扩散的哺乳动物例外类群之一。研究结果显示，所有雌性个体均会在首次繁殖前离开出生群；尽管研究中也检测到雄性迁入现象，但绝大多数雄性具有留居习性（philopatric）并在此完成繁殖。雌性个体首次受孕时的年龄低于雄性的驻留时长，这表明雌性扩散的目的是避免父女近交。该物种的雄性留居习性（philopatry）十分有趣，因为长鼻蝠并不具备雄性留居所常见的哺乳动物相关特征——即资源防御型多配偶制与/或亲属合作。它们的交配策略基于雌性防御，据推测雄性亲属间的局部配偶竞争会十分激烈，这本应阻碍雄性留居习性的演化。然而，与迁入雄性相比，留居雄性可凭借对出生地觅食地的熟悉度获益，且可能更轻松、更早地在种群中获得优势地位。我们针对长鼻蝠的研究结果，进一步支持了避免近交在塑造性别偏向扩散模式中的重要性，同时表明雄性资源防御或亲属合作无法完全解释哺乳动物雄性留居习性的演化。