Yellowstone's buffalo will continue to roam outside the park, but a resident biologist says policy should be aimed at keeping the animals inside the park boundaries.

"Don't allow them to think they can colonize," said Mary Meagher, who has conducted years of research on Yellowstone's herd. The bison are "not just filling up (he park) and spilling over. They are all on the move and trying to recolonize the Yellowstone Valley," she said.Meagher spoke Saturday at the Greater Yellowstone Coalition meeting in Lake Lodge.

Montana established a hunting season in 1985 to kill bison that wandered out of the park's northern range. Montana stockmen fear the bison will transmit brucellosis, a disease that causes miscarriages in their cattle.

Left alone, the bison would not only recolonize the Yellowstone Valley but beyond, Meagher said.

"If we allow them to recolonize, I have no doubt they would recolonize the Great Plains," she said.

But a return to the great herds of the 1800s is not feasible because of the threat of brucellosis, ungulate fever, and the bison's lack of respect for fences, she said.

Officials in the park and Montana should re-examine the current policy of trying to keep the bison in the park and killing them when they leave, and substitute a policy similar to elk management, she said.

Elk leave Yellowstone's northern range for winter habitat in Montana, where hunters are allowed to kill a portion of the herd. Meagher suggested a similar hunt in which bison are allowed to leave the park.

She also recommended a program of harassment of the herd in Montana to persuade the bison to return to the park in the spring.

A federal judge recently ruled that Yellowstone did not have to keep the bison in the park as the Fund For Animals, an animal rights group, had demanded.

The group's leader, Cleveland Amory, and some Montana officials also have suggested the Park Service vaccinate the bison to rid them of brucellosis. But Meagher said it would be impractical and possibly harmful biologically.

Philosophically, the disease is believed to have been carried in bison since they arrived on the continent, she said.

"Are we not obligated to protect the brucella microbe as a native species?" Meagher said.