While in spawning streams, Yellowstone cutthroat trout are preyed upon by numerous predators including black bears and grizzly bears. Due to their high digestibility, and protein and lipid content, spawning cutthroat trout are one of the highest sources of net digestible energy for grizzly bears in the Yellowstone ecosystem. Cutthroat trout are an important late-spring and early-summer food source for bears, providing them the opportunity to regain body mass after den emergence, and assisting females with cubs meet the energetic demands of lactation. The average lifespan of a grizzly bear is about 22 years, and the average lifespan of a black bear is about 17 years.