Jackson Hole moose numbers looking up
Counts show animals may be bouncing back after long declines.
POSTED: WEDNESDAY, MARCH 12, 2014 12:15 AM
Although Jackson Hole’s moose population has declined by perhaps 85 percent since the 1980s, habitat specialists and biologists are encouraged about the herd’s future.
For one, moose numbers appear to be on the rise. Wyoming Game and Fish Department biologist Aly Courtemanch, colleagues and volunteer citizen scientists counted 275 moose in the valley this winter, an increase of almost 40 animals from the year before.
The number takes into account observations from Moose Day volunteers, who on March 1 counted 74 moose.
“Our moose are pretty interesting this year,” Courtemanch said. “We had a higher cow-calf ratio.”
The relative abundance of young moose in the Jackson herd — 37 calves for every 100 cows — is up considerably compared with recent years. The ratio is used as an indication of population growth.
There were just 15 calves for every 100 cows in the herd as recently as 2008, Courtemanch said.
By 2012 the cow-calf ratio grew to 24 per 100, before jumping to 33 per 100 last winter.
“It’s been slowly chunking up every year,” she said. “That’s really promising. It kind of is a preliminary indication that the herd may be starting to rebound.”
Moose habitat in the valley also looks like it’s in relatively good shape.
Brett Jesmer, a University of Wyoming zoology doctoral student, is undertaking a statewide moose habitat and health assessment to help Game and Fish predict where and when moose declines are likely to occur. Courtemanch is collaborating with Jesmer on the research.
In Jackson Hole, “the willow habitat is as good or better than many of the other areas around the state,” Jesmer said Tuesday.
Results are preliminary, as moose scat analysis — a portion of his multiyear assessment — is still not complete, he said. Tests that would further gauge the health of valley’s willows were also forthcoming, he said.
“The goal is to develop some understanding of the interplay between climate, habitat and calf production,” Jesmer said.
Based on Courtemanch’s recent population assessment, moose are doing better in some areas where the species has struggled most.
The cow-calf ratios in the Buffalo Valley this year were 44 young for every 100 adult females. In the Gros Ventre drainage, the ratio was 33 calves for every 100 cows.
“Both areas looked good,” Courtemanch said. “The Buffalo Valley’s population has definitely gone down the most. The Gros Ventre has also decreased, but not to the same extent.
“As you move further and further south, it gets increasingly better,” she said. “But they were still in decline.”
Jackson’s moose population has proven cyclical over the years, as the large ungulate tends to exhaust its productive habitat when numbers are high.
Douglas Houston, a moose researcher in the valley in the 1960s, predicted that the population was going to decline based on poor habitat quality and overabundance, Jesmer said.
The warning proved correct. By the late 1980s — before the transplant of gray wolves — cow-calf ratios were dropping.
“Those calf-cow ratios that are now ticking back up, they started declining just before the 1988 Yellowstone fires,” Jesmer said,
Jesmer’s study also assesses the fat content of moose kidneys, donated by hunters, to determine animals’ health. He will use the moose feces to determine what moose are eating, their diet quality and pregnancy rates.
Besides Jackson Hole, Jesmer is studying herds in the Wyoming Range, Uinta Mountains, Big Horn Mountains, the Snowy Range and Colorado’s North Park. He hopes to expand the research into Colorado’s Flat Top Wilderness.
Results from the project are expected to be published in peer-reviewed scientific journals in about a year and a half, Jesmer said.
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