There are many reasons why a species might go extinct, but it turns out that even just the fear of a predator may be sufficient to cause populations of prey to go extinct.
The research hinges on a curious observation within population biology. It is well understood that over-population of a species can inhibit the animals, as individuals compete for scarcer and scarcer resources (such as food or mates), which results in a drop to their reproductive success and survival. From this, you might therefore assume that in smaller populations, where there is an abundance of food and other resources, the opposite would hold true and that populations would quickly rebound from decline.
Strangely, this is frequently not the case – often to the dismay of conservationists working with rare and endangered animals. Known as the Allee effect, when populations are low, survival rates actually decrease. Various studies have attempted to explain this paradox, including highlighting reasons such as inbreeding, difficulty finding a mate, and social dysfunction.
When it comes to prey species, however, researchers may have overlooked the role that predators play. This latest research, published in the Proceedings of the Royal Society B, has shown that the even if a predator is not preying on a species, just the fear of it alone can be enough to slash their survival rates. “Fear tended to destabilize population dynamics and increase the risk of extinction up to sevenfold,” write the authors.
They found that within small populations of fruit flies, the scent of praying mantises would cause the flies to spend more time being vigilant, less time eating or having sex, and subsequently having less offspring. It seems that just the fear of a mantis may be enough to cause an animal with a small population size to go extinct.
While this impact had been shown for some cases of wild mammals living in social groups, this study suggests for the first time that the same effect also occurs in species that are not particularly social, and as such could have a much wider impact on plummeting populations.
Small populations are not a certain predictor of extinction, as many species have been shown to return. However, by knowing the impact that fear can have on a species, conservationists may be able to better ensure the survival of endangered animals.
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