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Bighorn problems | Domestic sheep pass deadly pathogens to bighorn herds

October 23, 2013

Julie Fought calls herself a backyard sheep raiser. She is ranch operator at De La Cour Ranch, which sits at 5,500 feet in the mountains below Mt.Whitney. They have guest cabins; they grow and sell lavender, vegetables and eggs at farmer’s markets in Lone Pine and Independence; and they produce manure compost.

 

“And,” she said, “scientists and land managers consider us smack dab in the middle of bighorn habitat. That’s how close we are.”

 

The Sierra Nevada bighorn sheep was given emergency endangered status in 1999 after their numbers hit an all-time low of 100 in 1995. The decline coincided with pioneers settling across the west, and is due to diseases transmitted from domestic sheep and hunting.

 

“There have been many documented pneumonia outbreaks, resulting in bighorn die-off across the west, following contact with domestic sheep,” said Alex Few, bighorn sheep biologist.

 

Tom Stephenson, program leader for the Sierra Nevada Bighorn Sheep Recovery Program, said there is debate within the scientific community over which pathogens are involved, but there is no question that nose to nose contact between domestic sheep and bighorn transmits deadly pathogens to bighorn. 

 

“There are usually multiple pathogens involved in a pneumonia epidemic,” Stephenson said, “and the science and technology used to identify them is evolving.”

 

The domestic sheep are “carriers” of these pathogens, Few said, which means they are not harmful to them.

 

But in bighorn, she said, these pathogens are deadly and can lead to a pneumonia outbreak, wiping out most of a herd. 

 

An infected bighorn will shake its head, have a runny nose, develop a cough, and eventually stop moving because it is too hard for it to breathe.

 

In a matter of a few days to a few weeks, an infected bighorn will die, Stephenson said.

 

Since their listing as an endangered species, the Sierra bighorn have grown to 500 animals in 10 herds from Olancha to Virginia Lakes, Few said.

 

The recovery goal, she said, is 305 females distributed across 12 herds in that range. 

 

The historical range went further north, but local stakeholders, including land managers, private land owners, and scientists, got together and decided not to reintroduce the bighorn further north in order to mitigate conflict with domestic sheep operations in that area, Few said.

 

During mating season, male bighorn sheep become much more risk tolerant, Few said, and will venture very far in search of a mate.

 

And, she said, they will head for domestic sheep herds.

 

The best way to prevent the spread of respiratory disease, Few said, is to prevent contact. 

 

Seemingly obvious, in practicality this means one of three things: vacate the grazing allotments shown to be in bighorn range; move domestic sheep earlier from said allotments to avoid riskiest times (the fall mating season); or build a double fence to prevent nose to nose contact, with the outer fence eight feet high. Bighorn can jump over anything smaller. 

 

“When domestic sheep are in or immediately adjacent to bighorn range, domestic sheep grazing is too risky at any time. Eight foot fences should work on smaller parcels,” Stephenson said.

 

Fought has one breeding pair of domestic sheep, and would like to expand to four or five ewes, she said, to produce more meat and participate in local meat shares.

 

“I have a goal of keeping the food dollars local,” she said. “But I can’t, in all fairness to the bighorn sheep, expand. The recovery is a decade-long program and is super successful. To threaten that—I just can’t do it.”

 

Fought is also president of the Lone Pine Lions Club and works closely with other local ranchers.

 

To prevent possible contact with bighorn, Fought said her sheep are confined to a barn area, day and night, year round, with people and dogs around all the time.

 

She also doesn’t send her sheep out to forage, she said. Instead, she harvests native grass and willow as feed for them so their diet is the same as if they were foraging. 

 

“I only have two sheep, so it’s kind of a hobby,” she said, “I enjoy it.”

 

But, she said, this would be difficult with more sheep.

 

Fought said she doesn’t know what the cost would be to build an acceptable double-fence enclosure so she could move her sheep from barn to pasture and keep them enclosed. 

 

But just to build a double fence around the one breeding pair she keeps now, not out on pasture, would be roughly $3,000 to $5,000, she said.

 

“Initially,” Fought said, “I wanted to be a poster child on how to do it right.”

 

“That was two years ago. We haven’t built our double fence because we don’t have the money.”

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