Abstract

In traditional definitions of endurance rivalry, individuals compete to remain reproductively active longer than their rivals, but these time periods are typically brief, such as a single breeding season. Here, we explored endurance rivalry among adult males in a long-lived species that breeds year-round, the spotted hyena (Crocuta crocuta). We found that most dispersing males navigated the adaptive challenges of remaining in their new clans (“enduring”) for over 2 years before siring their first cub. Additionally, sires remained in their new clans at least 4 years, whereas males that never sired any cubs typically disappeared by their fourth year of tenure. This suggests that males might incorporate their initial reproductive success in the clan into their decisions regarding whether to “endure” by remaining in the current clan or to disperse again to another clan. Finally, we used Bayesian mixed modeling to explore variation in annual male reproductive success, which we found to have a positive linear relationship with tenure and a quadratic relationship with age. A male’s rate of social associations with adult females, but not aggressive interactions with those females, was predictive of his annual reproductive success. We also found substantial individual variation in annual reproductive success across males. Our results support the notion that male spotted hyenas compete via an extended endurance rivalry; tenure unequivocally improves male reproductive success, but advanced age does not, and questions remain regarding other traits that might be salient to the rivalry or to female mate choice in this species.

Significance statement

Some animals compete indirectly for mates by trying to outlast their competitors during a finite breeding season; individuals that can endure the longest in this “marathon” reap the reproductive rewards. Male spotted hyenas face a different challenge because females breed year-round, so the competition to remain viable as mates is seemingly endless. Here, we show that male spotted hyenas seem to make decisions about whether to stay in a clan based on their initial reproductive success in that clan. For males with early success, the longer they stay and the more time they spend with females, the more cubs they sire each year. Our findings suggest that male spotted hyenas compete for mating opportunities via an “ultramarathon” in which they must remain in a single social group at the bottom of the hierarchy for many years to demonstrate to females their ability to endure.

中文翻译：

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雄性斑鬣狗之间的耐力竞争：“忍受”是什么意思？

摘要

在耐力竞争的传统定义中，个体竞争以比他们的对手更长时间地保持生殖活跃，但这些时间段通常很短，例如单个繁殖季节。在这里，我们探讨了终年繁殖的长寿物种斑点鬣狗（Crocuta crocuta ）中成年雄性之间的耐力竞争。）。我们发现，大多数分散的雄性在生下第一只幼崽之前，已经克服了留在新氏族（“持久”）中超过 2 年的适应性挑战。此外，公牛在他们的新氏族中至少保留了 4 年，而从未生育过任何幼崽的公牛通常在其任期的第四年消失。这表明雄性可能会将他们在氏族中最初的繁殖成功纳入他们关于是否通过留在当前氏族中“忍受”或再次分散到另一个氏族的决定中。最后，我们使用贝叶斯混合模型来探索男性年度繁殖成功率的变化，我们发现这与任期呈正线性关系，与年龄呈二次关系。男性与成年女性的社会交往率，但不是与这些女性的积极互动，预示着他每年的繁殖成功。我们还发现男性的年度繁殖成功率存在很大的个体差异。我们的结果支持雄性斑鬣狗通过延长耐力竞争进行竞争的观点。任期明确地提高了雄性的繁殖成功率，但高龄并没有，而且对于可能对该物种的竞争或雌性配偶选择具有显着性的其他特征仍然存在疑问。

意义陈述

一些动物通过在有限的繁殖季节内试图超越竞争对手来间接竞争配偶；能够在这场“马拉松”中坚持最久的人将获得生殖奖励。雄性斑点鬣狗面临着不同的挑战，因为雌性全年都在繁殖，因此保持配偶生存能力的竞争似乎是无止境的。在这里，我们展示了雄性斑点鬣狗似乎会根据它们在该氏族中最初的繁殖成功率来决定是否留在一个氏族中。对于早期成功的雄性来说，它们停留的时间越长，与雌性相处的时间越多，它们每年生育的幼崽就越多。