Human shields

You've heard me say it here before. When the puma's image appears in my local camera traps the local black-tailed deer seem to spend more time lingering in the neighborhood gardens and driveways. The observations could be a coincidence, but maybe something else is going on. The puma, for example, could be following the deer, or the deer could be using the proximity of people and large dogs as a "human shield", a place where human disturbance is more likely to discourage most predators.

Well, Joel Berger of the Wildlife Conservation Society recently published a interesting example of how human activity affects wildlife ecology in wilderness areas. During the ten-year study, Joel showed that the moose in Yellowstone and the Grand Tetons adjust their use of space in relation to human infrastructure and activity.

Specifically, he found that over the years radiotracked moose have moved closer to roads at calving time. During the birth season, deer in general become secretive and restrict their movement to a very small portion of their home range. Since grizzlies feed on moose calves, but avoid roads in places like Yellowstone and the Grand Tetons, they are less likely to encounter this brief but nourishing windfall. The evidence suggests that moose and other prey species find humans more benign and at certain times gravitate to human-modified lanscapes for safety. People just don't tolerate predators as well as they do prey, and thus they create safe havens in the vicinity of buildings, roads, and campgrounds.

Good work, Joel (and send me a reprint, please!)