The last two winters have hit Wyoming mule deer hard, especially those within the Wyoming Range herd. Recently, the Wyoming Game and Fish Department (WGFD) released its aerial population survey results, reporting that the current 2024 estimated number of mule deer in the renowned herd to be around only 11,000 animals – a serious drop from February 2023’s estimate of 30,000, according to a news release. 

“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,” said Doug Brimeyer, WGFD deputy chief of wildlife. “However, given the unprecedented winter of 2022-23, regional managers decided it was important to obtain an accurate and full picture of this herd’s population.”

Additional data collected this winter found that, among the Wyoming Range deer herd, the fawn ratio had fallen with 34 fawns for every 100 does, making it the lowest on record since the herd was designated in 1982 – a direct result of the “intense energy demands of a harsh winter.”

“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 Gary Fralick, WGFD South Jackson wildlife biologist. “The lost fawns will result in a shift in the age structure of the population.”

Buck ratios were also the lowest on record with 24 bucks for every 100 does. This herd is managed with a buck ratio objective of 30 to 45 bucks per 100 does.

Those that did survive last year’s winter had less competition and more forage because of this. Deer captured by University of Wyoming researchers as part of a study led by Dr. Kevin Monteith had the highest fat levels since 2013.

“The high fat levels are a result of increased forage production, fewer deer on the landscape and many does being liberated from rearing fawns — all of which contribute to allowing deer to store more fat coming into winter,” said Fralick. “This year the winter ranges have received below-average snow, allowing animals to easily access abundant forage.”

The Wyoming Range mule deer herd will need some favorable weather patterns to recover from the last couple of winters. In contrast (and better news), the Sublette mule deer herd wasn’t as negatively affected by severe winter weather and currently has a buck-doe ratio of 34:100 and a fawn-doe ratio of 60:100.

“Investing in quality habitat is key and allows us to build resilient ecosystems. 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,” said Brimeyer. “The Wyoming Game and Fish Department and partners are committed to the recovery of the Wyoming Range mule deer herd and support projects that reduce deer-vehicle collisions, control cheatgrass, manage predators and facilitate movement across important habitats.”