Armed with a speaker system and a bucket full of peanuts, wildlife ecologist Liana Zanette hiked into the Wytham Woods with just one mission: to terrorize some woodland creatures with recordings of the BBC.
For five nights, she broadcast snippets of BBC documentaries and news programs — as well as clips from the Canadian radio show "Quirks and Quarks" and the audiobook of "The Wind in the Willows" — to a forest full of unsuspecting English badgers. She and her colleagues then monitored the animals' response to the sounds in order to measure how much they feared humans.
"Oh, I don't want to be dissing public radio and television," Zanette hurriedly insisted when I asked whether she thought the BBC was frightening. She laughed, "I had all these clips on hand because it's what I love to listen to."
Zanette, a professor at Western University in Ontario, has spent much of her career studying "the landscape of fear," how animals' anxiety about getting eaten by predators shapes their behavior and in turn, shapes the ecosystem in which they live. She's used a similar methodology — playing predator sounds through a speaker system, then watching to see how animals respond — at least a dozen times before. Then, last year, she read a study in Science claiming that humans had become a "superpredator," killing mesocarnivores like badgers four times as much as non-human predators do.
"So badgers should be really afraid of us," Zanette said.
Based on the results of her experiment in the Wytham Woods, a forest near the University of Oxford in the United Kingdom, they certainly are. When confronted with two hours of BBC footage, the majority of badgers stayed hidden inside their burrows, waiting for the human sounds to vanish. Those that did venture out to a food patch (a bucket full of peanuts prepared by the scientists) were watchful and hesitant, spending as much time with their heads in the air listening for predators as they did looking down at their meal.
By comparison, the animals showed no response to audio of howling wolves, which once preyed on badgers but were driven to extinction in the U.K. about five centuries ago. They reacted slightly to the sounds of bears, which disappeared from England 1,000 years ago (Zanette couldn't explain why they responded to bears but not wolves, but suggested that perhaps bears were more deadly when they lived, so fear of them is more deeply ingrained), and to dogs, which still harass badgers in British forests. And when subjected to sounds of a control group, sheep, the badgers quite sensibly ignored the braying and chowed down.
"It's really quite extraordinary," Zanette said of the results, which were published in Behavioral Ecology this week. "We weren’t expecting this massive response."
Technically speaking, badgers should have nothing to fear from people. They are a protected species in Britain — a 1992 act made it illegal to willfully kill, injure, take or cruelly ill-treat one of the mustelids. But it's estimated that 10,000 British badgers are killed every year for "sports" like badger baiting and digging. And a 2013 survey found that one in eight British farmers kill badgers each year.
"These animals live amongst us for heaven's sakes," Zanette continued. "And to find they’re really terrified of us is really incredible."
Dan Blumstein, a professor of ecology and evolutionary biology at the University of California, Los Angeles, called the study "eye opening."
"They take the methodology that has been used to ask questions about how animals respond to predators, and then throw in people. The insight to me is that, of course, why not ask that question?" he said. "There's a whole literature of how people scare animals, so why not try to quantitatively evaluate people and the effect of people's sounds on prey behaviors?"
Blumstein, who wrote an entire book on animal fear and escaping from predators, noted that scientists have spent years studying how fear can impact ecosystems.
The most famous case study took place in Yellowstone, where wolves were reintroduced in the mid-1990s. Within a few years, the park's elk and bison had dramatically changed their behavior to account for the fearsome new predator. They spent more time watching and listening for wolves, rather than eating, and were less likely to forage in open areas where they were vulnerable to attack. That in turn led to the recovery of trees those herbivores once chowed down on, which allowed for the reemergence of beavers and songbirds.
"It's not just the killing of prey, which is important, but it's these fear effects contributing as well, so that the total effect on prey populations is way more than just the killing," Zanette said.
In this way, "restoring the fear of a top predator has all these cascading effects on other tiers in the food chain," she continued. "Restoring fear can actually restore the ecosystem."
If that's the case, then isn't it a good thing that creatures like badgers are petrified of us humans? Not quite, Zanette warned.
"It's not a one-to-one relationship," she said. We may be scaring badgers, but we're also killing their predators, providing them with new sources of food like crops and trash, and reshaping their habitats. Zanette said much more study is needed to understand the cascading effects of this new landscape of fear. And Blumstein added that he'd like to see Zanette and her colleagues study habituation — whether badgers, once they've been protected for a while, learn to stop fearing humans.
"Humans are distorting ecosystems in new ways that we haven’t really thought about before," Zanette said. It's not clear how things will shake out in the end.
But one thing is obvious, she said: "It's quite clear that having humans in the environment is not keeping ecosystems healthy." Perhaps that is truly the scariest thing about us.