Disease affects Devil Canyon bighorn sheep herd

Disease affects Devil Canyon bighorn sheep herd

After landowners near Bighorn Canyon National Recreation Area sounded the alarm of the bighorn sheep die-off, responding Wyoming Fish and Game officials found more than three dozen of the iconic species dead and dying in the prized state Devil Canyon herd.

Wildlife biologists immediately collected biological samples, including nasal and tonsil swabs and tissues, from carcasses at the site. They then sent the samples to Laramie for analysis by the department’s Wildlife Health Laboratory. They found that the cause of death is a pathogenic strain of the bacteria Mannheimia haemolytica, known to cause lethal pneumonia in sheep.

Most of the deaths occurred in ewes and lambs, with only a few young rams, aged 1 to 2 years, still succumbing in the group. Adult rams live more solitary lives most of the year, but the rut will set in soon, bringing them into contact with larger groups and worrying wildlife managers.

The Devil Canyon herd has traditionally been one of the healthiest and most disease resistant herds in the state. It is often selected for translocations when other Wyoming herds need to be supplemented, said Corey Class, wildlife management coordinator for the Cody region.

“For the most part it’s a relatively clean pack,” he said.

The herd hasn’t had many cases of ovipneumoniae in the past, a disease that has plagued the species elsewhere in the Rocky Mountain range. Class said the hope is that the Mannheimia haemolytica bacteria won’t live that long and it will be before the rams join the groups.

“We expect this disease to be very different from the standard pneumonia problems we’ve had with other flocks of sheep,” he said. “We have lost many sheep. But in the long run, we might just get out of this. But I don’t have a crystal ball.”

The source of the infection is unknown, the department said in a Monday news release.

Wildlife Health Laboratory Supervisor Hank Edwards said he hopes the outbreak can be contained.

“Our limited experience with this pathogen gives us some hope that the outbreak will run its course quickly, with minimal mortality,” he said.

The 37 that have died so far are more than 10% of the herd, which was estimated to trend around 300 individuals before the outbreak.

“It was one of the worst things I have ever seen in my career to see 37 dead bighorn sheep. It was a bad day, but I hope there is a silver lining,” Class said.

Game and Fish is actively monitoring the population and any future or potential spread of pneumonia. Biologists have GPS transmitters to alert them to future kills.

Currently, 24 bighorn sheep from this herd are equipped with GPS tracking collars to monitor distribution, habitat use, seasonal movement, annual recruitment, and survival rates.

“The collars will now help us monitor bighorn sheep populations from a disease perspective and document additional mortalities,” Class said.

When a collared sheep dies, officials are immediately alerted by text messages and emails sent by the transmitter.

Class said the owners’ cooperation is essential to managing the herd.

“We have been working closely with a local landowner who has been key to controlling and monitoring this disease outbreak,” Class said. “We greatly appreciate your assistance and cooperation.”

All bighorn sheep carcasses were disposed of to decrease the spread of disease. The pod is not in contact with other pods in the area and this is expected to be an isolated case in the species’ primary habitat. The department had a similar outbreak near Laramie Peak, southwest of Douglas.

“Looks like the Laramie Peak herd seems to be doing better now,” Class said. “Our hope is that this disease will burn itself out because it progresses so quickly.”

Game and Fish requests that anyone who sees dead or dying bighorn sheep in the area call the Cody region offices at 307-527-7125.

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