According to Wyoming's Game and Fish Department, there has been a 70 percent decline in migratory elk calf production in Yellowstone since 1992. For years, researchers suspected predatory wolves were to blame. Now, a new study details a more complex set of circumstances that account for the low calf numbers.
Yale School of Forestry and Environmental Studies post doctoral fellow Arthur Middleton led the study. "Wolves aren't the most important predatror of calves. Grizzly bears are," he said. "We also found that Grizzly numbers are. And Grizzly numbers have grown really dramatically." "We also found a strong drought effect that reduced elk pregnancy rates. So, that basically means that fewer calves are born in the first place." Middleton says the reintroduction of cutthroat trout into Yellowstone, a fish Grizzlies are particularly fond of, could cause bears to prey less on elk calves.