Department of Ecology and Evolutionary Biology, Princeton University, Guyot Hall, Princeton, NJ 08544-2016, USA.
Physiol Behav. 2010 Mar 30;99(4):544-8. doi: 10.1016/j.physbeh.2010.01.016. Epub 2010 Jan 25.
Island tameness is a widely documented phenomenon in which island species, particularly those that have evolved with no or few natural predators, show a greatly reduced behavioral response when faced with unfamiliar predators. This insufficient anti-predator response has led to widespread population declines among many island species exposed to novel predators, and has become a serious conservation problem. Despite its prevalence, the underlying physiology of island tameness is not known. Here we report that although Galápagos marine iguanas (Amblyrhynchus cristatus) initiated flight from an evolutionarily recent and unfamiliar potential predator (humans), they failed to show the cardiovascular stress response that facilitates successful escape, even after a prior capture experience. In contrast, when approached by a native predator (the Galápagos hawk; Buteo galapagoensis), marine iguanas show markedly increased heart rate independent of initiating escape movement. The secretion of catecholamines appears to be central to the initiation of escape behavior: naïve animals remotely injected with epinephrine immediately increased flight initiation distance, whereas those injected with corticosterone did not. Our results provide the first evidence that muted escape behavior in predator-naïve species is indicative of both a cognitive deficit in recognizing potential predators and a catecholamine deficit in response. Understanding how the response to predators differs in predator-naïve species could enable the design of maximally effective techniques for inducing an anti-predator response in these vulnerable species.
岛屿温顺性是一种广泛记录的现象，其中岛屿物种，特别是那些在没有或很少有自然捕食者的情况下进化而来的物种，在面对陌生的捕食者时表现出大大降低的行为反应。这种不足的抗捕食者反应导致许多暴露于新型捕食者的岛屿物种的种群数量广泛下降，并且已成为一个严重的保护问题。尽管如此，岛屿温顺性的潜在生理学尚不清楚。在这里，我们报告说，尽管加拉帕戈斯海鬣蜥（Amblyrhynchus cristatus）从最近进化而来的陌生潜在捕食者（人类）中启动了飞行，但它们未能表现出促进成功逃脱的心血管应激反应，即使在先前的捕获经验之后也是如此。相比之下，当加拉帕戈斯鹰（Buteo galapagoensis）等本地捕食者接近时，海鬣蜥的心率明显增加，而无需启动逃脱运动。儿茶酚胺的分泌似乎是启动逃避行为的核心：未经训练的动物通过远程注射肾上腺素立即增加了飞行起始距离，而注射皮质酮的动物则没有。我们的研究结果首次提供了证据，表明在对捕食者一无所知的物种中，逃避行为的减弱既表明了对潜在捕食者的认知缺陷，也表明了对儿茶酚胺的反应缺陷。了解在对捕食者一无所知的物种中，对捕食者的反应如何不同，可能会为设计最大程度地有效诱导这些脆弱物种产生抗捕食者反应的技术提供依据。
