Wyse J Max, Hardy Ian C W, Yon Lisa, Mesterton-Gibbons Mike
Department of Mathematics, Florida State University, 1017 Academic Way, Tallahassee, FL 32306-4510, USA.
School of Biosciences, Sutton Bonington Campus, University of Nottingham, Loughborough LE12 5RD, UK.
J Theor Biol. 2017 Mar 21;417:109-130. doi: 10.1016/j.jtbi.2017.01.025. Epub 2017 Jan 20.
Mature male African Savannah elephants are known to periodically enter a temporary state of heightened aggression called "musth", often linked with increased androgens, particularly testosterone. Sexually mature males are capable of entering musth at any time of year, and will often travel long distances to find estrous females. When two musth bulls or two non-musth bulls encounter one another, the agonistic interaction is usually won by the larger male. However, when a smaller musth bull encounters a larger non-musth bull, the smaller musth male can win. The relative mating success of musth males is due partly to this fighting advantage, and partly to estrous females' general preference for musth males. Though musth behavior has long been observed and documented, the evolutionary advantages of musth remain poorly understood. Here we develop a game-theoretic model of male musth behavior which assumes musth duration as a parameter, and distributions of small, medium and large musth males are predicted in both time and space. The predicted results are similar to the musth timing behavior observed in the Amboseli National Park elephant population, and further results are generated with relevance to Samburu National Park. We discuss small male musth behavior, the effects of estrous female spatial heterogeneity on musth timing, conservation applications, and the assumptions underpinning the model.
已知成年雄性非洲草原象会周期性地进入一种称为“狂暴期”的暂时攻击性增强状态，这通常与雄激素增加有关，尤其是睾酮。性成熟的雄性在一年中的任何时候都可能进入狂暴期，并且常常会长途跋涉去寻找处于发情期的雌性。当两头处于狂暴期的公牛或两头非狂暴期的公牛相遇时，争斗互动通常由体型较大的雄性获胜。然而，当一头体型较小的处于狂暴期的公牛遇到一头体型较大的非狂暴期公牛时，体型较小的处于狂暴期的雄性可能会获胜。处于狂暴期的雄性相对较高的交配成功率部分归因于这种战斗优势，部分归因于处于发情期的雌性普遍偏爱处于狂暴期的雄性。尽管长期以来人们一直在观察和记录狂暴期行为，但对其进化优势仍知之甚少。在此，我们建立了一个关于雄性狂暴期行为的博弈论模型，该模型将狂暴期持续时间作为一个参数，并预测了不同体型的处于狂暴期的雄性在时间和空间上的分布情况。预测结果与在安博塞利国家公园大象种群中观察到的狂暴期时间行为相似，并针对桑布鲁国家公园得出了进一步的结果。我们讨论了体型较小的雄性的狂暴期行为、处于发情期的雌性空间异质性对狂暴期时间的影响、保护应用以及该模型的假设。
