In response to this isolation, many species lose the ability to respond appropriately to their predators. However, some species, despite many years of isolation, retain anti-predator behavior.

UCLA professor, Dan Blumstein, reviewed the literature and suggests that the key factor responsible for persistence, despite the loss of some predators, is that anti-predator behavior does not evolve independently. Most species have more than a single predator and we should expect co-adapted suites of anti-predator behavior. Thus, the loss of a single predator should have a limited effect on overall anti-predator abilities as long as other predators remain.

Evidence in support of this 'multi-predator hypothesis' comes from studies of wallabies, which retained anti-predator behavior for thousands of years following isolation from some predators, but rapidly lost anti-predator behavior when isolated from all predators.

The multi-predator hypothesis has important implications for conservation biology: taking animals from a predator-free location and putting them back into a predator rich area is more likely to fail than taking animals from an area with a sub-set of historically-important predators.

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