Biologists make risky move to save bighorn sheep herd near Gunnison

Rocky Mountain bighorn sheep are curiously delicate for such a brutish animal. The Division of Wildlife is attempting to save a herd near Gunnison that has been in decline due to the prevalence of pneumonia and other respiratory diseases.

The Colorado Division of Wildlife is willing to gamble if it means saving a population of Rocky Mountain bighorn sheep.

A herd of bighorn sheep in the Taylor River area north of Gunnison slowly has been dwindling away to where now it numbers approximately 30 animals, DOW biologists say.

While the habitat seems sufficient to support the herd, biologists point to the prevalence of pneumonia and other respiratory problems, ailments to which bighorn sheep are extremely susceptible.

The typical response to augmenting bighorn sheep populations is moving sheep from healthier herds to the problem areas.

However, the presence of pneumonia makes such a move risky for the Gunnison herd, said Scott Wait, senior terrestrial biologist for the DOW’s southwest region.

“While some adult animals seem able to live with these diseases, most newborn lambs become infected soon after birth and die within a few months,” Wait said.

With few new animals surviving, the herd is slowly dying off, he said.

A transplant of three bighorn adult ewes in late March included first treating the animals with long-lasting antibiotics, which are hoped will prevent infections.

Biologists say blood tests revealed the ewes were pregnant and are expected to give birth in May. Biologists expect to know by early fall if the lambs born to these ewes survive.

“This is just a small trial to see if this type of augmentation might work,” said J Wenum, area wildlife manager for the DOW in Gunnison. “The new ewes might become infected, so we understand that we’re taking a risk with these animals.

“But we can’t determine if it’s a potentially viable approach without taking a small risk.”

The three ewes were fitted with radio-collars to track their movement and survival.

Bighorn sheep herds throughout Colorado have a history of similar problems. Biologists have tried various combinations of vaccination, medication, nutritional supplementation and other approaches attempting to find an effective means of reversing declines in sheep herds.

“To date it is yet unknown if we have been successful with mid-winter treatments and supplementing herds with new animals from other areas of Colorado,” Wait said. “However, with some new tools and treatments we are willing to keep trying. At this point we can only wait and see how this works.”


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