The arrival of novel predators can trigger trophic cascades driven by shifts in prey numbers. Predators also elicit behavioral change in prey populations, via phenotypic plasticity and/or rapid evolution, and such changes may also contribute to trophic cascades. Here, we document rapid demographic and behavioral changes in populations of a prey species (grassland melomys Melomys burtoni, a granivorous rodent) following the introduction of a novel marsupial predator (northern quoll Dasyurus hallucatus). Within months of quolls appearing, populations of melomys exhibited reduced survival and population declines relative to control populations. Quoll-invaded populations were also significantly shyer than nearby, quoll-free populations of conspecifics. This rapid but generalized response to a novel threat was replaced over the following 2 yr with more threat-specific antipredator behaviors (i.e., predator-scent aversion). Predator-exposed populations, however, remained more neophobic than predator-free populations throughout the study. These behavioral responses manifested rapidly in changed rates of seed predation by melomys across treatments. Quoll-invaded melomys populations exhibited lower per-capita seed take rates, and rapidly developed an avoidance of seeds associated with quoll scent, with discrimination playing out over a spatial scale of tens of meters. Presumably the significant and novel predation pressure induced by quolls drove melomys populations to fine-tune behavioral responses to be more predator specific through time. These behavioral shifts could reflect individual plasticity (phenotypic flexibility) in behavior or may be adaptive shifts from natural selection imposed by quoll predation. Our study provides a rare insight into the rapid ecological and behavioral shifts enacted by prey to mitigate the impacts of a novel predator and shows that trophic cascades can be strongly influenced by behavioral as well as numerical responses.

中文翻译：

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当幼稚的猎物迅速适应新的捕食者时，由行为微调驱动的营养级联

新捕食者的到来可以触发由猎物数量变化驱动的营养级联反应。捕食者还通过表型可塑性和/或快速进化引起猎物种群的行为变化，这种变化也可能导致营养级联反应。在这里，我们记录了在引入一种新型有袋动物捕食者（北袋鼬Dasyurus hallucatus）后，一种猎物（草地 melomys Melomys burtoni，一种食谷啮齿动物）种群的快速人口统计学和行为变化。）。在袋鼬出现的几个月内，与对照种群相比，melomys 种群表现出存活率降低和种群下降。与附近无袋鼬鼠的同种种群相比，被袋鼬入侵的种群也明显更害羞。在接下来的 2 年里，这种对新威胁的快速但普遍的反应被更多特定于威胁的反捕食者行为（即捕食者气味厌恶）所取代。然而，在整个研究过程中，暴露于捕食者的种群仍然比没有捕食者的种群更怕新。这些行为反应迅速表现在处理过程中 melomys 对种子捕食率的变化。Quoll-ingressed melomys 种群表现出较低的人均种子摄取率，并迅速发展出避免与 Quoll 气味相关的种子，在几十米的空间尺度上进行区分。据推测，袋鼬引起的重大而新颖的捕食压力驱使 melomys 种群对行为反应进行微调，使其随着时间的推移变得更具捕食性。这些行为变化可能反映了个体行为的可塑性（表型灵活性），或者可能是袋鼬捕食强加的自然选择的适应性变化。我们的研究为猎物为减轻新型捕食者的影响而制定的快速生态和行为转变提供了罕见的见解，并表明营养级联会受到行为和数值反应的强烈影响。据推测，袋鼬引起的重大而新颖的捕食压力驱使 melomys 种群对行为反应进行微调，使其随着时间的推移变得更具捕食性。这些行为变化可能反映了个体行为的可塑性（表型灵活性），或者可能是袋鼬捕食强加的自然选择的适应性变化。我们的研究提供了对猎物为减轻新型捕食者的影响而制定的快速生态和行为变化的罕见见解，并表明营养级联可以受到行为和数值反应的强烈影响。据推测，袋鼬引起的重大而新颖的捕食压力驱使 melomys 种群对行为反应进行微调，使其随着时间的推移变得更具捕食性。这些行为变化可能反映了个体行为的可塑性（表型灵活性），或者可能是袋鼬捕食强加的自然选择的适应性变化。我们的研究为猎物为减轻新型捕食者的影响而制定的快速生态和行为转变提供了罕见的见解，并表明营养级联会受到行为和数值反应的强烈影响。