Monitoring shows winter fawn survival below average, calf survival average

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Roger Phillips | Idaho Fish and Game

The following is a news release from Idaho Fish and Game.

IDAHO FALLS – The late winter snow took a toll on radio-collared mule deer fawns during March and April, but it had less effect on collared elk calves.

“That record snow pack that we observed in February did not do fawns any favors,” said Daryl Meints, Fish and Game’s deer and elk coordinator. “It will not be like the winter of 2016-17, but we will be below the long-term average. On a brighter note, it appears that elk calf survival is doing just fine, as are adult doe and cow survival.”

Idaho Fish and Game biologists have been monitoring 207 mule deer fawns and 201 elk calves that were captured in early winter and fitted with telemetry collars.

Mortality not as bad as 2016-17 winter

As of April 30, 46 percent of the collared fawns and 77 percent of the calves were still alive. That compares with 61 percent of the fawns and 72 percent of the calves surviving through April in 2017-18, and 34 and 57 percent through April 2016-17.

March and April are often when calf and fawn mortality is highest because the young animals’ fat reserves are rapidly depleting, and their bodies need time to convert to digesting fresh forage.

Through the end of April, mule deer fawn survival was below the 20-year average of 58 percent, which is tracked annually through the end of May. Some additional mortality is expected during May, but wildlife managers expect that 2018-19 mule deer fawn survival will end up being higher than 2016-17, which was the second-lowest survival of fawns (30 percent) in 20 years.

Elk less effected than mule deer

Elk have not been trapped and collared for as many years as mule deer, and elk calves typically survive at a higher rate than mule deer fawns. Adult deer and elk also typically survive at high rates unless it’s an extreme winter.

Of the 548 radio-collared mule deer does being monitored by Fish and Game researchers, 92 percent were alive through April 30, and 98 percent of the 643 collared cows survived. Fish and Game biologists will tally the final survival estimates in June.

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