Why Some Wild Animals Tolerate Humans More Than Others

First Posted: Nov 18, 2015 07:30 AM EST

Why do some wild animals tolerate humans while others don't? Scientists are taking a closer look at animal-human interactions to get to the bottom of human tolerance.

Over time, some species become more tolerant of humans' presence. However, the extent to which they do is largely driven by the type of environment in which the animals live, and by the animals body size.

In this latest effort, the researchers analyzed 75 studies conducted over the past half-century of 212 animal species-mostly birds, but also mammals and lizards. The scientists estimated species' tolerance to human disturbance by comparing how far away from humans an animal would have to be before it fled.

So what did they find? It turns out that birds in more heavily populated urban areas are much more tolerant of humans than birds in rural areas. In addition, larger birds are more tolerant of humans in general than smaller birds.

"This new finding flips previous recommendations about large-bodied species being more vulnerable to the presence of humans, and shows that large-bodied species are more tolerant," said Daniel Blumstein, one of the researchers, in a news release. "It is likely costly for animals to respond fearfully to people that are not harming them. The key question to ask now is which species can tolerate humans enough so as to habituate to them."

Other factors such as the birds' diet, the openness of their habitats, and the number of eggs they lay, had some impact on their tolerance of humans. However, it wasn't as much as urban-rural differences and body size differences.

The new findings could help shape wildlife conservation practices, including how best to protect small and large birds.

The findings are published in the journal Nature Communications.

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Tagsbird, Birds, Conservation, Biological Conservation, Human, Humans, Animal Behavior, Animals, Animal