Human Shields

There was a moose wandering around Sil-Terhar Motors in Broomfield earlier this month. Everybody wondered what the heck he was doing there. Maybe the moose knew best.Photo courtesy National Park Service
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Mammals like moose may use the presence of humans to protect them from natural predators, according to new research from the Wildlife Conservation Society. Looking at moose behavior in the Greater Yellowstone Ecosystem, WCS biologist Joel Berger found that moose may use human infrastructure as a shield. Their chief natural predators, grizzly bears and wolves, usually avoid human contact.

Berger studied pregnant moose in the Yellowstone area, finding that over a ten year period, the animals tended move closer to human infrastructure to give birth. The distance in particular between birth sites and roads — which bears tend ot avoid — decreased considerably over the ten years of the study. And as the bear density increased, the distance between moose birth sites and roads became even smaller.

In a paper published in the Royal Society’s Journal Biology Letters, Berger wrote:

“The strength of interaction that once involved only native prey and native predator is now modulated by a complex, three-way community- level interaction involving people, predators and prey.”

“The study’s results indicate that moose and other prey species find humans more benign and hence move to humans for safety whereas predators do not because we humans tend to be less kind to predators,” he said.

Berger’s work verifies a phenomenon that’s been observed anecdotally for a long time. In 1910, Sierra Club founder John Muir said:

“Most of the animals seen today were on the Athi Plains (Kenya) and have learned that the nearer the railroad the safer they are from the attack of either men or lions.”

Berger also cited several observations of species that appear to use human presence to keep their natural predators away — the vervet monkey, gelada baboon and elephants in Africa; and marmots and red deer in the Rockies.

This implication that humans are nicer to wild beasts than their predators has its limits, of course. Its better to be a moose than a mouse if you’re going hang around at the car dealer.

On the other hand, there are neither grizzly bears nor wolves in Colorado that a lonely moose needs protection from. And our Broomfield moose was a male, so it wasn’t pregnant. Perhaps he simply needed a new car. Or maybe he was just confused.