Data from: Lion (Panthera Leo) population sustainability: do nomadic males matter?

Key population processes are sometimes driven by male dynamics, but these drivers are often overlooked because of the scale over which they operate. Lions (Panthera leo) provide an ideal case study for investigating factors governing male dynamics and their influence on population sustainability. Lions display sexually selected infanticide, and resident males must defend their offspring from nomads that may have dispersed over long distances; factors affecting male-male competition over large spatial scales can have population wide consequences. We report here on the first systematic analysis of long-term individual-based data of male lions in the Serengeti National Park, Tanzania. From 1974-2012, we observed 471 coalitions (796 males) in our study area. We investigate factors affecting male immigration and the impacts on the resident population. The yearly number of nomadic males entering the study population affected cub survival and mating access. Success rates of nomadic males gaining tenure with a pride increased with age and coalition size. We observed a significant decline in male immigration, which resulted in lowered levels of male replacement in the study population, reduced infanticide, and greater cub survival. The decline in incoming males likely resulted from increased anthropogenic pressures in surrounding areas. Conversely, the core study population was largely buffered from anthropogenic threats and likely served as a source to neighboring sinks. Reduced infanticide in the core population might have compensated for rising lion mortalities in surrounding areas, but as human-wildlife conflicts intensify with the rapidly growing human population, compensatory mechanisms may become overwhelmed.种群关键过程有时由雄性群体动态驱动，但这类驱动因子常因作用尺度过大而被忽视。狮子（Panthera leo）是探究调控雄性群体动态及其对种群可持续性影响因素的理想研究案例。狮子存在性选择驱动的杀婴行为，定居雄性需抵御可能长距离扩散而来的流浪雄狮，以保护自身后代；在大空间尺度上影响雄性间竞争的因子，会对整个种群产生连锁效应。本研究首次对坦桑尼亚塞伦盖蒂国家公园内雄性狮子的长期个体追踪数据开展系统性分析。1974年至2012年间，我们在研究区域内共记录到471个雄狮联盟（总计796头雄狮）。本研究探究了影响雄性迁入的相关因子及其对定居种群的影响。进入研究种群的流浪雄狮年数量，会对幼崽存活率及交配机会产生影响。流浪雄狮获得狮群统治权的成功率，随年龄与联盟规模的增长而提升。我们观测到雄性迁入率显著下降，这导致研究种群内雄性更替水平降低、杀婴行为减少，同时幼崽存活率提升。迁入雄狮数量的下降大概率源于周边区域人类活动压力的加剧。与之相反，核心研究种群基本未受人类活动威胁，或可作为周边汇种群（sink population）的源种群。核心种群内杀婴行为的减少，或可弥补周边区域狮群死亡率的上升，但随着人口快速增长导致人兽冲突加剧，这种补偿机制可能会逐渐失效。