JACKSON, Wyo. — The Wyoming Game and Fish Department (WGFD) announced on Thursday, Feb. 29, the results of the Wyoming Range mule deer aerial population survey, which was a more accurate calculation of how the 2022/2023 severe winter impacted the population.
Wildlife biologists estimate the current herd number to be about 11,000 animals — a considerable decline from the February 2023 estimate of 30,000 mule deer.
“Game and Fish biologists and wardens wouldn’t typically conduct intensive aerial surveys two years in a row due to the high costs and flight time involved,” Wyoming Game and Fish Department Deputy Chief of Wildlife Doug Brimeyer said in an announcement. “However, given the unprecedented winter of 2022/2023, regional managers decided it was important to obtain an accurate and full picture of this herd’s population.”
Earlier this winter, biologists and game wardens recorded data for the Wyoming Range deer herd by flying over portions of winter ranges in a helicopter and tallying the number of observed fawns, does, yearling bucks and adult bucks. Results from the survey indicate the fawn ratio for the deer herd was 34 fawns for every 100 does — the lowest on record since the herd was designated in 1982. Low fawn ratios can be attributed to the intense energy demands of a harsh winter, according to the WGFD.
“When doe deer are stressed due to severe winter conditions, they may experience decreased reproductive success that leads to lower conception rates and reduced survival rates of fawns born shortly after the winter,” said Wyoming Game and Fish South Jackson Wildlife Biologist Gary Fralick in a statement. “The lost fawns will result in a shift in the age structure of the population.”
The survey recorded 24 bucks for every 100 does, which also is one of the lowest on record. Wildlife managers observed low yearling buck numbers, which can be attributed to the high mortality of buck fawns last winter. An average of 30 to 45 bucks per 100 does is more typical for the Wyoming Range herd.
For the animals that did survive last year’s hard winter, there was abundant forage and less competition, so the deer were able to put on adequate fat reserves.
The nearby Sublette mule deer herd, that migrates from summer ranges in the foothills of the Wyoming Range, Bondurant and Jackson Hole areas to lower elevation winter ranges near Pinedale, Green River and Rock Springs, was not affected as strongly by last year’s severe winter. WGFD classification flights indicated total buck ratios of 34 for 100 does, and fawn ratios of 60 for 100 does. The buck and doe ratios were lower than average, but expected after a harsh winter.
“Investing in quality habitat is key and allows us to build resilient ecosystems,” Brimeyer said in a statement. “The most important thing we can all do to help wildlife survive and recover from tough winters is to protect and enhance their habitat and connectivity between seasonal ranges.”
WGFD said in the announcement, that the recovery of the Wyoming Range mule deer herd will depend on a multitude of factors, but maintaining healthy ecosystems and enhancing corridors between seasonal ranges will be vital to maintaining and improving the health of the herds. Consecutive years of favorable weather will also be critical for the deer herd’s recovery.
