School of Life and Environmental Sciences, Centre for Integrative Ecology, Deakin University, Waurn Ponds, Victoria, 3220, Australia.
Komodo Survival Program, Denpasar, Bali, 80223, Indonesia.
Ecology. 2020 Apr;101(4):e02970. doi: 10.1002/ecy.2970. Epub 2020 Feb 3.
Apex predators can have substantial and complex ecological roles in ecosystems. However, differences in species-specific traits, population densities, and interspecific interactions are likely to determine the strength of apex predators' roles. Here we report complementary studies examining how interactions between predator per capita metabolic rate and population density influenced the biomass, population energy use, and ecological effects of apex predators on their large mammalian prey. We first investigated how large mammal prey resources and field metabolic rates of terrestrial apex predators, comprising large mammals and the Komodo dragon (Varanus komodoensis), influenced their biomass densities and population energy use requirements. We next evaluated whether Komodo dragons, like apex mammalian predators, exerted top-down regulation of their large mammal prey. Comparison of results from field studies demonstrates that Komodo dragons attain mean population biomass densities that are 5.75-231.82 times higher than that of apex mammalian predator species and their guilds in Africa, Asia, and North America. The high biomass of Komodo dragons resulted in 1.96-108.12 times greater population energy use than that of apex mammalian predators. Nevertheless, substantial temporal and spatial variation in Komodo dragon population energy use did not regulate the population growth rates of either of two large mammal prey species, rusa deer (Rusa timorensis) and wild pig (Sus scrofa). We suggest that multiple processes weaken the capacity of Komodo dragons to regulate large mammal prey populations. For example, a low per capita metabolic rate requiring an infrequent and inactive hunting strategy (including scavenging), would minimize lethal and nonlethal impacts on prey populations. We conclude that Komodo dragons differ in their predatory role from, including not being the ecological analogs of, apex mammalian predators.
顶级掠食者在生态系统中可能具有重要而复杂的生态作用。然而，物种特异性特征、种群密度和种间相互作用的差异可能决定顶级掠食者作用的强度。在这里，我们报告了互补的研究，这些研究考察了捕食者个体代谢率与种群密度之间的相互作用如何影响顶级掠食者对其大型哺乳动物猎物的生物量、种群能量利用和生态影响。我们首先研究了大型哺乳动物猎物资源和包括大型哺乳动物和科莫多巨蜥（Varanus komodoensis）在内的陆地顶级掠食者的野外代谢率如何影响它们的生物量密度和种群能量利用需求。我们接下来评估了科莫多巨蜥是否像顶级哺乳动物捕食者一样对其大型哺乳动物猎物施加了自上而下的调节。来自实地研究的结果比较表明，科莫多巨蜥的平均种群生物量密度是非洲、亚洲和北美的顶级哺乳动物捕食者物种及其群体的 5.75-231.82 倍。科莫多巨蜥的高生物量导致其种群能量利用比顶级哺乳动物捕食者高 1.96-108.12 倍。尽管如此，科莫多巨蜥种群能量利用的大量时间和空间变化并没有调节两种大型哺乳动物猎物物种——梅花鹿（Rusa timorensis）和野猪（Sus scrofa）的种群增长率。我们认为，多个过程削弱了科莫多巨蜥调节大型哺乳动物猎物种群的能力。例如，低个体代谢率需要一种不频繁和不活跃的狩猎策略（包括食腐），这将最大限度地减少对猎物种群的致死和非致死影响。我们得出的结论是，科莫多巨蜥在其捕食作用上与顶级哺乳动物捕食者不同，包括不是它们的生态类似物。
