Blumstein Daniel T, Daniel Janice C
Department of Ecology and Evolutionary Biology, University of California, 621 Young Drive South, Los Angeles, CA 90095-1606, USA.
Proc Biol Sci. 2005 Aug 22;272(1573):1663-8. doi: 10.1098/rspb.2005.3147.
When isolated from predators, costly and no longer functional anti-predator behaviour should be selected against. Predator naiveté is often pronounced on islands, where species are found with few or no predators. However, isolation on islands involves other processes, such as founder effects, that might be responsible for naiveté or reduced anti-predator behaviour. We report the first comparative evidence that, in macropodid marsupials, isolation on islands may lead to a systematic loss of 'group size effects'-a behaviour whereby individuals reduce anti-predator vigilance and allocate more time to foraging as group size increases. Moreover, insular animals forage more, and are less vigilant, than mainland ones. However, we found no evidence that animals on the mainland are 'flightier' than those on islands. Remarkably, we also found no evidence that isolation from all predators per se is responsible for these effects. Together, these results demonstrate that anti-predator behaviour may indeed be lost or modified when animals are isolated on islands, but it is premature to assume that all such behaviour is affected.
当与捕食者隔离时，代价高昂且不再起作用的反捕食行为应会被淘汰。在岛屿上，捕食者天真现象往往很明显，在这些地方发现的物种几乎没有或根本没有捕食者。然而，岛屿上的隔离涉及其他过程，例如奠基者效应，这可能是导致捕食者天真或反捕食行为减少的原因。我们报告了首个比较性证据，即在有袋类有袋动物中，岛屿隔离可能会导致“群体规模效应”系统性丧失——随着群体规模增加，个体降低反捕食警惕性并将更多时间用于觅食的一种行为。此外，岛屿动物比大陆动物觅食更多且警惕性更低。然而，我们没有发现证据表明大陆上的动物比岛屿上的动物“更易受惊”。值得注意的是，我们也没有发现证据表明与所有捕食者的隔离本身是造成这些影响的原因。总之，这些结果表明，当动物在岛屿上隔离时，反捕食行为确实可能丧失或改变，但假设所有此类行为都会受到影响还为时过早。
