When wolves were reintroduced to Yellowstone National Park in 1995, the effects were dramatic. Among other things, the number of moose fell much more than expected.
It turns out that just being afraid of wolves had a big impact. In places where moose thought wolves might be present, they spent much more time searching for them and less time for feeding. In a article published in 2001biologist John Laundré, who died in 2021used the term “fearland” to describe this effect.
The idea was not entirely new. Previous laboratory experiments have shown that fear of predators alone can affect prey. Yet at the time, the prevailing view was that predators only affect wild prey populations through direct predation. The observations of Laundré and others suggested that this was wrong, but did not prove causality.
That’s what Liana Zanette at Western University in Ontario, Canada, has conducted a series of experiments over the past two decades. In British Columbia, Zanette and her colleagues played recordings of predators near wild song sparrows. Fewer eggs were laid, fewer hatched and fewer hatchlings survived. Overall, less than half as experienced compared to those who played non-predator sounds. THEn in other words, fear can have an even greater impact than direct predation.
It’s all about the food, says Zanette. In addition to spending more time on the lookout for predators, prey simply avoids certain areas altogether, he says, “even though it might be the best food in town.”
This concept of a landscape of fear is extremely important because of the ripple effects on ecosystems. In many places on the west coast of Canada, for example, people have been killed by bears, cougars and wolves that feed on raccoons. These raccoons now spend a lot of time on the shore looking for food such as crabs.
When Zanetta’s team visited and played the dog barking recordings, the raccoons mostly avoided visiting the seashore, and when they did, they spent much more time looking for predators. This led to a dramatic reflection in the abundance of coastal animals raccoons feed. In contrast, where the team played recordings of seals barking, these effects were not seen.
The landscape of fear is the key to fully understanding the impact of humans on wildlife. In one study, Zanette and her team used camera traps film how wildlife responded to sounds in the Kruger National Park in South Africa. “The fear of lions should be at a maximum there,” he says, “but we found that humans were twice as scary.”
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