Berger J
Proc Biol Sci. 1999 Nov 22;266(1435):2261-7. doi: 10.1098/rspb.1999.0917.
The recent extinction of grizzly bears (Ursus arctos) and wolves (Canis lupus) by humans from 95-99% of the contiguous USA and Mexico in less than 100 years has resulted in dramatically altered and expanded prey communities. Such rampant ecological change and putative ecological instability has not occurred in North American northern boreal zones. This geographical variation in the loss of large carnivores as a consequence of anthropogenic disturbance offers opportunities for examining the potential consequences of extinction on subtle but important ecological patterns involving behaviour and interspecific ecological interactions. In Alaska, where scavengers and large carnivores are associated with carcasses, field experiments involving sound playback simulations have demonstrated that at least one prey species, moose (Alces alces), is sensitive to the vocalizations of ravens (Corvus corax) and may rely on their cues to avoid predation. However, a similar relationship is absent on a predator-free island in Alaska's Cook Inlet and at two sites in the Jackson Hole region of the Rocky Mountains (USA) where grizzly bears and wolves have been extinct for 50-70 years. While prior study of birds and mammals has demonstrated that prey may retain predator recognition capabilities for thousands of years even after predation as a selective force has been relaxed, the results presented here establish that a desensitization in interspecific responsiveness can also occur in less than ten generations. These results affirm (i) a rapid decoupling in behaviour involving prey and scavengers as a consequence of anthropogenic-caused predator-prey disequilibriums, and (ii) subtle, community-level modifications in terrestrial ecosystems where large carnivores no longer exist. If knowledge about ecological and behavioural processes in extant systems is to be enhanced, the potential effects of recently extinct carnivores must be incorporated into current programmes.
在不到100年的时间里，人类使美国本土与墨西哥接壤地区95% - 99%的灰熊（棕熊，学名：Ursus arctos）和狼（学名：Canis lupus）灭绝，这导致猎物群落发生了巨大变化且范围扩大。这种猖獗的生态变化以及假定的生态不稳定在北美北方寒带地区并未出现。由于人为干扰导致大型食肉动物消失的这种地理差异，为研究灭绝在涉及行为和种间生态相互作用的微妙但重要的生态模式上的潜在后果提供了机会。在阿拉斯加，食腐动物和大型食肉动物与尸体有关联，涉及声音回放模拟的野外实验表明，至少有一种猎物——驼鹿（学名：Alces alces），对渡鸦（学名：Corvus corax）的叫声敏感，可能依靠它们的线索来避免被捕食。然而，在阿拉斯加库克湾的一个无捕食者岛屿以及落基山脉（美国）杰克逊霍尔地区的两个地点，情况并非如此，在那里灰熊和狼已经灭绝了50 - 70年。虽然先前对鸟类和哺乳动物的研究表明，即使捕食作为一种选择压力已经减弱，猎物可能在数千年内仍保留对捕食者的识别能力，但这里呈现的结果表明，种间反应性的脱敏也可能在不到十代的时间内发生。这些结果证实了：(i) 由于人为导致的捕食者 - 猎物失衡，猎物和食腐动物在行为上迅速脱钩；(ii) 在大型食肉动物不复存在的陆地生态系统中，存在微妙的、群落层面的变化。如果要增进对现存系统中生态和行为过程的了解，就必须将最近灭绝的食肉动物的潜在影响纳入当前的研究项目中。
