The National Park Service plans to thin a herd of bison in the Grand Canyon through roundups and by seeking volunteers who are physically fit and proficient with a gun to kill the animals that increasingly are damaging park resources. Some bison would be shipped out of the area and others legally hunted on the adjacent forest. Within the Grand Canyon, shooters would be selected through a lottery to help bring the number of bison roaming the far northern reaches of the park to no more than 200 within three to five years. About 600 of the animals now live...