"Encounters between bears and humans are likely to increase in Yellowstone National Park this fall as a scarce supply of nuts forces hungry grizzlies to seek food closer to the U.S. park's popular tourist areas, officials warned on Wednesday."

"Conservationists say that climate change has caused a decline in whitebark pines in recent years, which produce the nuts that are a food source for grizzlies and black bears. During this same time, several attacks on visitors have been recorded in the park straddling Wyoming, Montana and Idaho.

"We are expecting an increase in human-bear encounters and we are reinforcing safety messages," said park spokesman Al Nash.

Officials with the park and two national forests that border it said numerous recent sightings of bears seeking berries and other foods near roadways and popular trails prompted them to issue the advisory, which calls on outdoor enthusiasts to take precautions like carrying bear spray and hiking in groups."

Laura Zuckerman reports for Reuters September 13, 2013. [2]