green foreground with smilodon cat, giant cave bear, camels in middle ground, and glacier-covered mountains in distance, with incredible teratorn flying overhead
Scene of Pleistocene landscape in the Great Basin. It was much wetter, with bristlecone pines extending on rocky outcroppings into the valleys. Predators like smilodon cats and giant cave bears sought out prey like camels, small horses, and pronghorn. Giant raptors, included the Incredible Teratorn.

NPS/Ray Vermiglio

What lived when there were glaciers near the highest peaks? Glaciers flowed in many mountain ranges in the Great Basin during the Pleistocene, about 10,000 to 1.2 million years ago. At the end of the Pleistocene, huge lakes filled the valley bottoms. Trees, such as bristlecone and limber pines, grew much lower on the mountains and on rocky outcroppings in the valleys.

Until about 10,000 years ago, many different animals lived on the landscape. Grazers included camels, various small horse species, large-headed llamas, and a variety of pronghorn species. Harrington’s mountain goats lived on rocky slopes. Predators like Smilodon cats, American cheetahs, jaguars, and giant bears prowled the area. The sky was filled with many raptor species, including the Incredible Teratorn, with a wingspan of 16 feet!

A warmer and drier climate caused the lakes and glaciers to shrink, the trees to move up the mountain slopes, and one of the biggest extinction events on earth. Today we look for signs of the past with old shorelines, U-shaped valleys, and bones of these past animals.

Last updated: April 14, 2021

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