Long Winter, Cold Spring Hard on Mule Deer Fawns

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Most adult female mule deer being monitored by Idaho Fish and Game biologists survived, but less than one third of fawns survived.

Fish and Game biologists have been monitoring nearly 800 radio-collared mule deer through the winter of 2007-08. Of 263 mule deer fawns monitored, only 30 percent – 78 fawns – survived to May 15. Overall survival for the 528 adult females monitored was 90 percent.

That means mule deer numbers are expected to remain the same or drop slightly this fall, but yearling buck number will drop significantly in most of southern Idaho, which in turn means a lower buck harvest.

“That’s not surprising, given the weather we’ve had,” big game manager Brad Compton told Fish and Game commissioners during their meeting May 22. But with the good female survival, and expected good forage this summer, biologists expect mule deer numbers to rebound quickly, he said.

At 30 percent, statewide fawn survival tied 2005-06 as the poorest survival rate since Idaho began monitoring fawns in 1998-99. A dry summer, followed by deep snow and delayed spring greenup contributed to higher than normal April and May fawn mortality.

Fawn survival in most of Idaho was in the 20-30 percent range, but varied from a low of 8 percent in the Palisades area to a high of 70 percent in the Boise River population management unit.

Statewide adult female survival was in the low-normal range, except for the Weiser-McCall area where it was 84 percent and the Middle Fork area where it was 80 percent.