Data from: Selfish partners: resource partitioning in male coalitions of Asiatic lions

Behavioral plasticity within species is adaptive which directs survival traits to take multiple pathways under varying conditions. Male-male cooperation is an evolutionary strategy often exhibiting an array of alternatives between and within species. African male lions coalesce to safeguard territories and mate-acquisition. Unique to these coalitions is lack of strict hierarchies between partners, who have similar resource-securities possibly because of many mating-opportunities within large female-groups. Skewed mating and feeding rights have only been documented in large coalitions where males were related. However, smaller modal prey coupled with less simultaneous mating-opportunities for male Asiatic lions in Gir forests, India would likely result in a different coalition-structure. Observations on mating-events (n=127) and feeding-incidents (n=44) were made on 11 male-coalitions and 9 female-prides in Gir, to assess resource distribution within- and among- different sized male-coalitions. Information from 39 males were used to estimate annual tenure-holding probabilities. Single-males had smaller tenures and appropriated fewer matings than coalition-males. Pronounced dominance-hierarchies were observed within coalitions, with one partner getting >70% of all matings and 47% more food. Competition between coalition-partners at kills increased with decline in prey-size, increase in coalition-size and the appetite-states of the males. However, immediate subordinates in coalitions had higher reproductive fitness than single-males. Declining benefits to partners with increasing coalition-size, with individuals below the immediate subordinates having fitness comparable to single-males, suggest to an optimal coalition-size of two lions. Lions under higher competitive selection in Gir show behavioral plasticity to form hierarchical-coalitions, wherein partners utilize resources asymmetrically, yet coalesce for personal gains.

物种内的行为可塑性（Behavioral plasticity）具有适应性，可引导生存性状在多变环境中呈现多条演化路径。雄性间合作是一类演化策略，往往在不同物种间以及同一物种内部展现出丰富的备选形式。非洲雄狮会结成联盟以保卫领地并获取交配机会。这类联盟的独特之处在于，联盟伙伴间不存在严格的等级体系，这可能是因为大型雌狮群内存在大量交配机会，使得它们的资源保障程度相近。仅在存在亲缘关系的大型雄狮联盟中，才有交配与取食权利不均等的相关记录。然而，印度吉尔森林的亚洲雄狮，其猎物体型普遍偏小，且雄性可获得的同步交配机会更少，这大概率会催生不同的联盟结构。研究人员针对吉尔森林中的11个雄性联盟与9个雌狮群开展了观察，累计记录交配事件127次（n=127）、取食行为44次（n=44），以此评估不同规模雄性联盟内部以及联盟间的资源分配情况。同时利用39头雄狮的相关数据，估算了其年度居留概率。单只雄狮的居留时长更短，获得的交配次数也少于联盟内的雄性个体。研究观察到联盟内部存在显著的优势等级体系，其中一头伙伴可获得超过70%的交配机会，取食份额也比其他个体高出47%。猎物体型越小、联盟规模越大、雄性食欲越旺盛，联盟伙伴在猎物进食时的竞争就越激烈。不过，联盟中的直接从属个体的繁殖适合度（reproductive fitness）仍高于单只雄狮。随着联盟规模扩大，伙伴间的收益逐渐降低，且地位低于直接从属个体的个体，其适合度与单只雄狮相当，这表明雄狮联盟的最优规模为2头。处于更高竞争选择压力下的吉尔森林狮群，展现出了形成等级化联盟的行为可塑性，此类联盟中伙伴间的资源利用并不均等，但仍会为了个体收益而结成联盟。