Wyoming’s mule deer population was seriously affected by recent winter weather, especially its fawns. Recruitment took a major hit as countless young-of-the-year died, with survival rates dismally low compared to other, more moderate winters.

The Wyoming Range Mule Deer Project annually conducts surveys of the local mule deer herd. Fawns are trapped and collared each summer, allowing researchers to monitor them throughout the following year. While much of the country saw unusually high temperatures this winter, Wyoming seemed to find itself in a perfect storm of frigid conditions.

“Winter ranges for mule deer in the Wyoming Range have experienced exceptional winter weather in 2017,” the project said in a recent newsletter. “With snowpack levels at roughly 200 percent of normal and numerous days of sub-zero weather, this winter has tested the resilience of wildlife populations in western Wyoming.”

Tried them . . . and found them wanting. Of the 70 fawns monitored during the 2016-17 winter, only one survived until March 5, 2017.

The project noted that a less than 50 percent survivability is common, with its first year of fawn data—2015-16—showing only 45 percent of fawns survived the winter. Still, the loss of 99 percent of an age class means a great deal for a species that is facing steep declines across its entire range.

Adult deer also suffered this winter, although not to the same extent as fawns. A typical year has a survival rate of 92 percent; in 2016-17 only 75 percent of the monitored animals lived to see another spring.

The good news? The subsequent age class will likely be high. Researchers found most of the adult does were pregnant going into the spring of 2017, with many carrying twins. The data shows that this year’s fetal rate is 1.6 fawns per doe, just slightly off the surveys’ average of 1.7.




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