Loss of elk calves puzzles state biologists

Elk cow:calf ratios

This graph from Colorado Parks and Wildlife shows the trend in cow/calf ratios across the state. Biologists says at least 40 calves are needed to build an elk herd. Story by Dave Buchanan

The continuing drop in elk-calf survival rates in southern Colorado continues to trouble biologists from Colorado Parks and Wildlife. There as yet is no known or recognized cause for the loss of calf elk across the southern half of western Colorado, a trend that appears to expanding north.

Research shows the calves are being born but fail to survive into the next summer.

Andy Holland, state big-game manager for Parks and Wildlife, said biologist aren’t sure what’s causing the decline in calf numbers. During a presentation earlier this month to the Colorado Wildlife Commission, Holland showed a graph illuminating a distinct north-to-south trend in declining cow/calf ratios.

“Typically northern Colorado elk herds have 10 calves per 100 cows higher than southern Colorado,” Holland said. “The gap in the last five years grew to about 20 calves per 100 cows, something that really concerned us.”

The graph seen elsewhere on this page illustrates the gap between southern elk herds, which may have fewer than 32 calves per 100 cows, and northern herds, where some areas are seeing upwards of 52 calves per 100 cows. Biologists say it takes a least 40 calves each year provide enough production to grow an elk herd.

“Below 40 it starts to get hit or miss,” Brad Petch, CPW’s senior terrestrial wildlife biologist for the Northwest Region, said. “Below 30 you get to the point where you are not getting enough production and not growing an elk herd.”

The loss of calves isn’t spread evenly across the state. Some mid-state elk herds, such as the Fryingpan River and Eagle Valley herds, are showing drops in calf post-hunt survival lower than farther south.

Because of this, the Fryingpan River herd had cow licenses this year reduced to the allowable minimum of 10 licenses per hunt code. This is the first time any unit has seen licenses cut to the bone.

“This herd has just not responded to our license reductions,” Holland said. “If you would have talked to most of us 10 or 15 years ago, we would never have thought we’d see that in Colorado.”

The agency currently is in the second year of research in what may be causing the drop in calf numbers.



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