Yosemite National Park is home to only one rattlesnake–the Northern Pacific rattlesnake (Crotalus oreganus oreganus). Rattlesnakes, an important component of the park’s ecosystem, help control rodent populations. Predators, whether bobcats or coyotes or snakes, control prey that can grow out of balance otherwise. Beware of reaching in rock crevices or under rocks where rattlesnakes reside. Gary M. Stolz/U.S. Fish and Wildlife.