Colorado wildlife officials say elk herd numbers may not be sustainable over the next 20 years

There are places in Eagle County where there seem to be plenty of elk. But the long-term survival of those herds is in question.

Colorado Parks and Wildlife is currently working on a 10-year herd management plan, and Eagle County contains portions of four “Data Analysis Units” in the study. The Eagle County Board of Commissioners heard a report Tuesday about the study so far from a trio of CPW officials.

Wildlife biologist Julie Mao told the commissioners that there’s only so much officials can do to try to manage herds. The most significant of those tools is issuing hunting licenses in order to manage herd populations and the ratio of bulls to cows. But there’s no real way to manage cow/calf ratios in those herds. Those ratios are a long-term indicator of the health of a particular herd.

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The cow/calf ratios — the number of healthy calves in a herd — have declined significantly since the 1980s.

Mao said the ratio 40 years ago was roughly 60 calves for every 100 cows. That ratio today is in the mid- to upper 30s. That means herds today are less resilient.

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Matt Yamashita, the area wildlife manager for CPW, told the commissioners that the ratio to maintain a herd is 44 or 45 calves per hundred cows. While there are animals “on the landscape,” Yamashita said current populations probably aren’t sustainable over the next 20 years or so.

Habitat loss is among the biggest problems. District wildlife manager Brian Woodrich noted that’s something out of the agency’s control.

Mao showed the commissioners a series of maps — spanning the decades between 1970 and 2020 — demonstrating how development and population density have affected habitat in much of Eagle County. Most of those areas are along highways and near towns.

Marcia Gilles, the county’s director of its Open Space and Natural Resources department, said those maps tell a “compelling” story of human impact on habitat, adding that the county government could help habitat efforts either through funding or with land-use regulations and policy.

County Manager Jeff Shroll noted that migration corridors in the study area that includes the Roaring Fork Valley are blocked on two sides, one side by Interstate 70 and the other by Colorado Highway 82. Both highways need better ways for wildlife to cross those corridors, Shroll said.

Areas around towns also pose problems for wildlife managers. Woodrich said agency representatives will attend a Nov. 7 meeting of Eagle’s Open Space and Recreation Advisory Committee.

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Wolves may also play a role in herd sizes, but that impact won’t be studied until those predators have been introduced to the areas.

In addition to development and roads, Woodrich said fencing can also play a role in herd survival. The area has “miles” of tangled old fencing on the ground, Woodrich noted. That leads to a lot of animal mortality.

Three of the four study areas have had a good deal of impact from human development, the fourth, encompassing the Flat Tops area, is the most remote. It’s also the largest in terms of land area and herd sizes, and has the best cow-calf ratio.

That herd is estimated at around 40,000 animals, but populations and cow-calf ratios have declined since the 1980s in all four study areas.

A draft herd management plan is expected in December.