The bighorn sheep (Ovis canadensis) is named for its large curved horns – a pair might weigh up to 14 kg (30 lb). Female sheep have shorter, less curved horns. Native to North America, the desert bighorn sheep subspecies are indigenous to the hot desert ecosystems of the Southwestern United States and Mexico. The Rocky Mountain and Sierra Nevada bighorn sheep occupy the cooler mountainous regions of Canada and the United States. They are typically not aggressive animals, but can get defensive - especially during rutting season.