The XX Factor

Replacing Pesticides with Fear

It’s tough to be a fuzzy little mammal. Death can come from the sky or beneath the earth or behind the next tree, so their lives are governed by constant, quivering fear. Prey species live in a dangerous neighborhood, and they must always be alert to their surroundings. That’s why a Middle Eastern plan to control pest populations with predatory birds is brilliant. Instead of pouring toxins on their crops to kill rodents, they are installing nest boxes for day-hunting kestrels and night-hunting barn owls to provide around-the-clock mouse munching.

While the kestrels and owls certainly do kill rodents directly, their very presence means that pest populations are reduced before they even lift a claw. Without predators around, the mice and insects stuff themselves all day long without fear. But once the prey know that they could get chomped at any moment, fear changes their behavior completely. They hide more, eat less, and have fewer babies. Even if they can get enough food, the incredible stress of being ready to flee at any moment reduces their lifespan. Past studies have shown that grasshoppers are so afraid of wolf spiders that they will starve to death in hiding rather than seeking food near the spider. And rabbit babies born to parents who are afraid of lynxes are less healthy than rabbit babies born to parents in lynx-free environments.

Fear can also change entire ecosystems. When wolves were reintroduced to Yellowstone , the fat, lazy elk were forced to run away instead of spending their days lounging by the river. Once the elk stopped overgrazing, willow trees were able to regrow near the water, creating bird habitat. Now that the willows have regrown, beavers might come back and dam up parts of the river, making homes for fish and wading birds. The wolves are killing relatively few elk, but the behavior of the entire population has changed.

I hope more farmers put out owl and raptor nest boxes-I’d much rather have my veggies taste of fear than of pesticides. And while bringing top predators like wolves and mountain lions back into densely populated areas is probably impractical, I think the fear that would induce might have other benefits. Can’t you envision the popularity of the “How To Lose Ten Pounds By Hiding From Ravenous Beasts” diet?

Photograph of mouse by John Foxx/Getty Images.