WASHINGTON: The grizzly bears of the American west have a fearsome reputation, but as a population boom forces them from their deep wilderness habitat of the Rocky Mountains, their increasingly close encounters with humans are altering their lifestyles, making them lazy and fat, conservation experts say.

''We've got bears spending the whole summer eating oats in the field, out there with the elk and the deer, and getting fatter and fatter,'' said Jamie Jonkel, a grizzly manager and wildlife conflict specialist with Montana Fish, Wildlife and Parks, the state government's conservation agency.

''They've started really loving the good life, much like the average American.''

''Some of them still move into the high country in the summer, but some of them just set up shop and don't move. You can see grizzlies out there in the fields all day lazing about grazing on alfalfa while a kid is kicking a soccer ball around,'' he said.

A recent census by scientific agencies put the grizzly population in Yellowstone National Park and surrounding areas of Wyoming, Montana and Idaho at 603.