Abstract
The impact of alien predators on native prey populations is often attributed to prey naiveté towards a novel threat. Yet evolutionary theory predicts that alien predators cannot remain eternally novel; prey species must either become extinct or learn and adapt to the new threat. As local enemies lose their naiveté and coexistence becomes possible, an introduced species must eventually become ‘native’. But when exactly does an alien become a native species? The dingo (Canis lupus dingo) was introduced to Australia about 4000 years ago, yet its native status remains disputed. To determine whether a vulnerable native mammal (Perameles nasuta) recognizes the close relative of the dingo, the domestic dog (Canis lupus familiaris), we surveyed local residents to determine levels of bandicoot visitation to yards with and without resident dogs. Bandicoots in this area regularly emerge from bushland to forage in residential yards at night, leaving behind tell-tale deep, conical diggings in lawns and garden beds. These diggings were less likely to appear at all, and appeared less frequently and in smaller quantities in yards with dogs than in yards with either resident cats (Felis catus) or no pets. Most dogs were kept indoors at night, meaning that bandicoots were not simply chased out of the yards or killed before they could leave diggings, but rather they recognized the threat posed by dogs and avoided those yards. Native Australian mammals have had thousands of years experience with wild dingoes, which are very closely related to domestic dogs. Our study suggests that these bandicoots may no longer be naïve towards dogs. We argue that the logical criterion for determining native status of a long-term alien species must be once its native enemies are no longer naïve.
Highlights
The devastating impact of alien predators on native wildlife within their new ranges [1], is often attributed to prey naivete, or a failure to recognize and respond appropriately to a novel predation threat due to lack of experience [2,3,4]
It follows logically that alien predators cannot remain eternally novel; evolutionary theory predicts that prey species that do not become extinct must learn and adapt to new threats [6,7], and there is recent evidence for this [e.g. 8]
One critical question remains unanswered: at what point after establishment and naturalization is an alien species sufficiently integrated into its new ecosystem to be considered native? We suggest that the logical, objective criterion that distinguishes this long-term change is the loss of ecological novelty, or in other words, the loss of naiveteof the alien species’ native enemies in its new range
Summary
The devastating impact of alien predators on native wildlife within their new ranges [1], is often attributed to prey naivete, or a failure to recognize and respond appropriately to a novel predation threat due to lack of experience [2,3,4]. Prey naivetehas been considered an all-or-nothing status, closely akin to island syndrome [2,3] It is inarguably a more complex phenomenon, involving multiple levels through which native prey might progress towards predator-wariness [5], with each level closely tied to degrees of experience with a novel predator. It follows logically that alien predators cannot remain eternally novel; evolutionary theory predicts that prey species that do not become extinct must learn and adapt to new threats [6,7], and there is recent evidence for this [e.g. 8]. One critical question remains unanswered: at what point after establishment and naturalization is an alien species sufficiently integrated into its new ecosystem to be considered native? One critical question remains unanswered: at what point after establishment and naturalization is an alien species sufficiently integrated into its new ecosystem to be considered native? We suggest that the logical, objective criterion that distinguishes this long-term change is the loss of ecological novelty, or in other words, the loss of naiveteof the alien species’ native enemies in its new range
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