During the last Ice Age, large mammals such as mammoths, horses
, ground sloths
, short-faced bears
, and saber-toothed cats roamed North America and Idaho’s Snake River Plain. Today, twelve large mammals (weight over 100 pounds) exist in North America, but 11,000 years ago more than 30 large mammals roamed the continent.
Around 13,000 years ago, mammoths, mastodon, saber-toothed cats and other large mammals began to disappear. Two different theories explain the mass extinction of the Ice Age animals. The first theory claimed that humans had over-hunted the mammals into extinction. More recently, other scientists have argued that climate change caused the extinctions. They contend that the animals couldn’t survive the drastic changes in environment and plant life that occurred as the Ice Age ended.
By around 10,000 years ago, the glaciers had retreated from the continental United States and the majority of the large Ice Age mammals were extinct. The remaining animals that could adapt to the changes included bison, elk, bighorn sheep, pronghorn, and moose. The extinction of so many large mammals forced Native Americans to shift toward other hunting opportunities and food sources, including smaller mammals, fish, and possibly a greater reliance on plant foods.
Pronghorn antelope were one of many smaller
species of mammals that adapted to the drier
climate change after continental glaciation.