Are Yellowstone’s bears running out of food sources?

Outside Magazine, June 2012

Are Hungry Bears in Yellowstone Attacking Humans for Food?

For 24 years, from 1986 until 2010, there were no mortal encounters with grizzlies in Yellowstone National Park. But four deadly incidents over the past two summers have hikers on edge, reigniting the fierce debate over bear management.

By: Jeff Hull

... WHY THE SUDDEN SPIKE in fatal bear encounters? Part of the problem, believes U.S. Fish and Wildlife Service grizzly bear recovery coordinator Chris Servheen, who has spearheaded the government’s efforts to bolster bear populations for over a quarter-century, is messaging. One of Servheen’s great vexations is an inability to make the millions of Yellowstone visitors pay attention to a few basic rules of travel in grizzly country: don’t hike alone, make lots of noise, carry bear spray, and, if a grizzly still keeps coming, drop into a prone position. Wallace, Evert, and the Matayoshis had all, on more than one occasion, seen grizzly literature or signage. Yet none carried bear spray, and Evert and Wallace were hiking alone—acts that ignore official warnings and recommendations.

... At the heart of that lawsuit was an issue that is also part of the mystery of why grizzly attacks on humans are increasing: Are Yellowstone’s bears running out of food sources?

At issue is the whitebark pine, a species that produces cones full of seeds. Red squirrels collect and hoard the seeds in caches, which grizzlies rob and gobble. In good seed-production years—sometimes as often as every other year—some of Yellowstone’s grizzlies might derive as much as 90 percent of their autumn protein intake from seed middens. But whitebark pine trees are dying en masse, victims of mountain pine beetle infestations and white pine blister rust exacerbated, many scientists believe, by global warming. Grizzly managers and conservation groups don’t agree about the implications of that decline, and the disagreement has become divisive.


http://www.outsideonline.com/outdoor-adventure/natural-intelligence/The-Grizzly-Truth.html?page=all