Northern elk herd in Yellowstone has big drop in cow-calf ratio

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YELLOWSTONE NATIONAL PARK, Wyo. (AP) - Wildlife managers are preparing to launch a three-year study to determine why the cow-calf ratio in the park's northern herd has dropped dramatically in recent years.

The ratio is a key indicator about the reproductive rate of the herd, and generally 30 calves per 100 cows is thought to be enough to sustain a herd, officials said.

A survey on March 24, focusing on a herd sample of about 4,200 elk, found only 12 calves to every 100 cows, either the lowest or second-lowest ratio recorded since the surveys began n 1968, said P.J. White, ungulate biologist at Yellowstone.

The 2002 survey showed the ratio for the northern herd was 14 for every 100 cows, compared with a 2001 ratio of 29 to 100.

''It's low and certainly is a concern that it's that low,'' White said. ''If it bounces back, then these two years aren't going to hurt things. But if the trend continues in the future, we'll almost certainly see a decrease in the growth rate of the population,'' he said in an interview with the Billings Gazette.

About 15 age classes remain productive within the herd, White said, so two years of low calf-cow ratios may not be a problem if things turn around.

The northern elk herd typically spends summers in Yellowstone and winters between the park's northeast entrance near Gardiner, Mont., and Dailey Lake in the Paradise Valley

There are a number of factors that wildlife officials think is affecting the population.

''The (wolf) predation certainly is contributing and I think the drought is too,'' White said.

Calf-cow ratios in other herds in Montana and Wyoming, including those who don't live around wolves, have also dipped recently, White said.

''So I think there is a region-wide effect from the drought,'' he said.

Last fall, biologists estimated there were about 20 calves per 100 cows, which is still relatively low, White said, and the drop to 12 by the end of March is unexplained.

Starting next month, researchers plan to begin an intensive three-year study on elk calves in the northern herd, tracking newborn calves for their first year and examining each death that occurs.

''The idea is to assess what's happening in this early neonatal period,'' White said. ''Hopefully we'll get a better idea about what's going on.''

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