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 non-lethal 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.

中文翻译：

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科莫多巨蜥不是顶级哺乳动物捕食者的生态类似物

顶级捕食者可以在生态系统中扮演重要而复杂的生态角色。然而，物种特定性状、种群密度和种间相互作用的差异可能决定了顶级捕食者角色的强度。在这里，我们报告了补充研究，研究捕食者人均代谢率和种群密度之间的相互作用如何影响顶级捕食者对其大型哺乳动物猎物的生物量、种群能量使用和生态影响。我们首先研究了大型哺乳动物的猎物资源和陆地顶级捕食者（包括大型哺乳动物和科莫多巨蜥）的野外代谢率如何影响它们的生物量密度和种群能量使用需求。我们接下来评估了科莫多巨蜥是否像顶级哺乳动物掠食者一样，对它们的大型哺乳动物猎物施加自上而下的调节。实地研究结果的比较表明，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公会的 5.75-231.82 倍。科莫多巨蜥的高生物量导致人口能源消耗是顶级哺乳动物捕食者的 1.96-108.12 倍。然而，科莫多巨蜥种群能量使用的显着时空变化并没有调节两种大型哺乳动物猎物物种的种群增长率，rusa deer (Rusa timorensis) 和野猪 (Sus scrofa)。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，低人均代谢率需要不频繁和不活跃的狩猎策略（包括清除），将最大限度地减少对猎物种群的致命和非致命影响。我们得出的结论是，科莫多巨蜥的捕食角色不同于顶级哺乳动物捕食者，包括不是生态类似物。