Who can blame them? Humans kill animals at rates up to 14 times higher than other predators.
Humans have become the dominant predator in many ecosystems, killing adult prey at rates up to 14 times higher than other predators. This disproportionate killing of animals by people has led scientists to dub humans “super predators,” predators so deadly that their practices may very well be unsustainable. The term originated from a 2015 report that described the impact humans have on ecosystems.
Humans have diverged from other predators in behavior and influence. Geographic expansion, exploitation of naïve prey, killing technology, symbioses with dogs, and rapid population growth, among other factors, have long imposed profound impacts—including widespread extinction and restructuring of food webs and ecosystems—in terrestrial and marine systems.
Now, a new study from Western University in Ontario, Canada suggests that animals may be aware of the impact that humans have on their environments, as they are more afraid of humans than of any other predators. The study focused on mesocarnivores, carnivores whose diets consist of 50-70% meat, and tested the fearfulness demonstrated by European badgers (Meles meles) in reaction to humans as compared to other predators. For mesocarnivores such as badgers, humans are certainly “super predators," killing 4.3 times as many mesocarnivores as nonhuman predators do every year.
The study was conducted in Wytham Woods, a forest in Oxfordshire, UK that is home to many badgers that live in communal burrows known as setts. While it is illegal for people to hunt badgers in the United Kingdom, over 10% of farmers surveyed in 2013 admitted to killing badgers in the previous year, and an estimated 10,000 badgers are killed for sport every year in the UK. Apart from humans, dogs (Canis lupus familiaris) are the major predator of British badgers, and most farmers that live near the woods keep dogs as pets. Large carnivores like wolves (Canis lupus) and brown bears (Ursus arctos) are known to hunt and kill badgers in other parts of the world but have been extinct in Britain for hundreds of years.
To learn how the badgers would react to different predators, including humans, the researchers set up motion-activated video cameras around several setts. At the beginning of the night, the scientists played sound bites of bears, wolves, dogs, sheep, and finally humans, capturing the badgers’ reactions on the cameras when they finally ventured out to look for food.
The researchers found that bear and dog sounds delayed foraging but that badgers would eventually emerge from their homes to feed while the animal sounds were still playing. Sounds of humans, however, discouraged some badgers from leaving their burrows altogether. Those that did eventually leave in search for food waited 189%-228% longer than badgers exposed to bear or dogs sounds, with more than half of the badgers waiting until the human sounds stopped playing completely before leaving their homes. Hearing human voices also reduced the time that badgers spent foraging and led to increased vigilance. All of these results point to an unprecedented level of fear in badgers when they are exposed to human noises.
Our previous research has shown that the fear large carnivores inspire can itself shape ecosystems. These new results indicate that the fear of humans, being greater, likely has even greater impacts on the environment, meaning humans may be distorting ecosystem processes even more than previously imagined. These results have important implications for conservation, wildlife management and public policy.
The fear of being killed by a predator makes prey more cautious, preventing them from eating everything in sight. With the extinction of many large carnivores, however, this “landscape of fear” becomes lost, which could lead to a decline in many plant or insect populations. Some wonder if a fear of humans could replace the fear of large carnivores, but Zanette’s study shows that the fear of humans affects animal behavior in a much different way than the fear of other predators does. While it is not completely understood how these differences will shape ecosystems, it is unlikely that human "super predators" will make a sustainable substitute for large carnivores.