Data from: Lion population dynamics: 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.

种群关键动态有时由雄性种群动态驱动，但这类驱动因子常因作用尺度较大而被忽视。狮子（Panthera leo）为探究调控雄性种群动态及其对种群可持续性影响的因子提供了理想的案例研究对象。狮子存在性选择引发的杀婴行为，定居雄性需抵御可能长距离扩散而来的流浪雄狮，以保护自己的后代；影响大空间尺度下雄性间竞争的因子，可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（Serengeti National Park）内雄性狮子的长期个体跟踪数据进行了系统性分析。1974年至2012年间，我们在研究区域内共记录到471个雄狮联盟（共计796只雄性狮子）。本研究探究了影响雄性雄狮迁入的因子，及其对定居种群的影响。每年迁入研究种群的流浪雄狮数量，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，会随年龄及联盟规模的增长而提升。我们观测到雄性迁入率出现显著下降，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，可能源于周边地区人类活动压力的加剧。与之相对，核心研究种群基本未受人类活动威胁，且可能作为种群源地，为周边的种群汇区提供个体补充。核心种群内杀婴行为的减少，或许能弥补周边地区狮子死亡率上升的缺口，但随着人口快速增长导致人狮冲突加剧，这种补偿机制终将难以为继。