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EHD Strikes Black Hills Deer

Wyoming Game and Fish biologists have confirmed that epizootic hemorrhagic disease (EHD) has killed a number of white-tailed deer in the Black Hills this summer. Due to the difficulty in locating carcasses and the broad area affected, the exact number of deer succumbing to the disease cannot be determined.

EHD is mostly a disease of white-tailed deer, but also occurs in pronghorn antelope, elk, and mule deer. Variants of the disease can affect species such as bighorn sheep and some domestic animals. EHD is spread by a biting gnat. Symptoms include loss of appetite, extreme weakness, and dribbling of blood-stained urine and feces. Affected animals usually die in late summer and fall. EHD die-offs are a common occurrence in the Black Hills, especially following long, dry summers when the first frost is delayed. Lack of water sources and rapidly drying ponds also tend to concentrate deer in areas where gnat populations are high and facilitate the spread of the disease.

Drought conditions have led to EHD outbreaks and the loss of white-tailed deer across much of the western United States this summer. “It appears the die-off is widespread geographically and significant in some locations,” said Newcastle Wildlife Biologist Joe Sandrini. “However, the disease is endemic in the Black Hills and we experience some level of die-off most years. We’ll be able to get a better handle on this in mid October when we do our deer trend counts in the Black Hills, and hopefully by then we will have had a good hard frost and the disease will have run its course.”

In recent weeks concerned citizens have contacted the Game and Fish Department about dead or dying deer. “I have been fielding a lot of phone calls about sick and dead deer in Crook County,” said Sundance Game Warden Chris Teter. “It seems like there have been more phone calls than with past outbreaks, but we also have a lot more people living on small acreages where deer concentrate in the summer.”

Newcastle Game Warden Troy Achterhof noted that all of the dead deer he has found and those that have been reported are whitetails, and most of the mortality so far seems to be in fawns and bucks, but does are being affected as well. His observations have been similar to what the game wardens in Moorcroft and Sundance have found, and now the die-off appears to be hitting all age classes of bucks and does.

“The current EHD die-off really emphasizes how many factors come together to regulate deer populations in the Black Hills,” Sandrini said. “The weather, disease, insect populations, predators such as mountain lions, and habitat all interact, affecting each other and ultimately acting to increase or decrease deer production and survival. You just cannot point your finger at one thing and say it is solely responsible for trends in deer numbers.” But he also noted, “Something like this current EHD epidemic can have a significant short term effect, the results of which can impact hunting opportunity for several years, and unfortunately, this latest impact follows on the heels of the 2010-11 winter which was most responsible for our current low numbers of deer.”

There is no human health concern from hemorrhagic disease. Humans can’t get it and neither can most other wildlife. Mule deer occasionally get the disease but are generally insulated from the infection because they don’t tend to inhabit the environment of the gnats.

EHD was first identified in Wyoming in the Black Hills in 1957. At that time a significant die-off of deer occurred north of Newcastle on Oil Creek.