Sick bighorn sheep herd in North Dakota might be improving

(U.S. Fish and Wildlife Service)

BISMARCK, N.D. — An outbreak of deadly bacterial pneumonia that has plagued western North Dakota’s bighorn sheep population for years is showing signs of waning, though it might still be a few years before the herd is out of the woods.

Game and Fish Department biologists counted 283 bighorns in a population survey that began last fall and was completed in March to see how many lambs survived the winter. The total number is up 7% from the previous year’s count of 265, which was the lowest in a dozen years.

“The increase in the 2018 count reflects lessening effects of bacterial pneumonia that was detected in 2014,” big game biologist Brett Wiedmann said.

The outbreak five years ago killed about three dozen sheep, leading Game and Fish to cancel the fall hunting season in 2015 for the first time in more than three decades. The agency reinstated hunting the following year but reduced licenses in 2017 after a summer survey documented a significant drop in the number of rams, which hunters seek for their trophy horns.

The number of rams dropped again in the latest count. However, adult ewes improved and there was a significant increase in lambs.

“Fortunately, annual survival rates of adult bighorns are similar to those prior to the die-off and lamb survival is improving, which could indicate the population is becoming somewhat resilient to the deadly pathogens first observed in 2014,” Wiedmann said.

It can take up to 15 years for bacterial pneumonia to work its way out of a herd, according to Game and Fish Wildlife Chief Jeb Williams. Wiedmann said the next few years will be important in determining “if the pathogens are likely to persist and cause a long-term population decline.”

Bighorn hunting is popular in North Dakota. This year, more than 15,000 people have applied for a license. Fewer than 10 licenses are issued in a typical year. Last year, only three were given out , down from five the previous year and eight the year before that.

A decision on this year’s hunting season will be made in September, following a summer survey of the sheep population.

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