Star-Tribune Staff writer
CASPER, Wyo. — A drop in migratory elk calf numbers in and around Yellowstone National Park may be linked to a loss of cutthroat trout in Yellowstone Lake.
As cutthroat trout numbers declined, some grizzly bears began switching from eating trout to preying more on elk calves, said researcher Arthur Middleton.
Middleton was the lead author on a paper called “Grizzly bear predation links the loss of native trout to the demography of migratory elk in Yellowstone,” which was published in a science journal called Proceedings of the Royal Society B.
“We perhaps shouldn’t be so quick to departmentalize fisheries management and wildlife management because even though they seem like separate parts of an ecosystem they can turn out to be more closely linked that we thought,” Middleton said.
Drought still plays a role in declining elk calf production by reducing pregnancy rates, and increasing numbers of bears and wolves are also a factor. However, research suggests some bears are eating more elk calves while elk are still on their summer range near Yellowstone Lake, said Middleton, who worked with nearly a dozen other biologists on the paper.
Elk/calf ratios in migratory herds around the park have decreased in varying degrees since the mid-1990s, and have been low since 2002.