May
18

A Rising Hope for Our Bighorn Sheep

Bighorn sheep are often described as the “icons of the Mountain West.” The three primary species, or subspecies, of bighorns are the Rocky Mountain bighorns (most of the West), the desert bighorns (desert mountains of our southwest and down into Mexico) and the California bighorns (occupying the mountains and steep country of our West Coast states). Our local sheep are Californias, with a few Rocky Mountain sheep in the easternmost wild places of Washington. There are 18 herds of bighorns in Washington, adding up to around 1,500 wild sheep – more than half of which are along the Yakima River.

Icons? Think about it. When was the last time you drove down the Yakima River Canyon – or anywhere else in the West – and spotted wild sheep? And when didn’t you see others already there, or stopping, to admire the beauty, grace and strength of these animals?

As you are well aware, I have long loved bighorn sheep. I was a founding board member of the Rocky Mountain Bighorn Society in the 1970s and involved with writing bighorn sheep viewing guides for the Colorado Division of Wildlife. Some weeks back, I put together a phone conference involving biologists and sheep nuts from around the West. I wanted to share the latest work with sheep and get a handle on where we are headed. This is the first of my efforts to bring you up to speed.

There are fair numbers of bighorns from Mexico to Canada, but they live a rather precarious existence. While there have likely been bighorn die-offs through history, regular die-offs in wild sheep herds became a fact of life when European settlers moved into their various habitats.

You recall that we’ve been here before. The issues with our local sheep are a mirror image of problems across bighorn habitat, so an understanding of efforts focused on our Washington sheep will inform us about sheep work happening across most of bighorn country. In the major die-off of 2009-10, we lost a significant number of our regional California lambs and adults to pneumonia. Hard to see – but not surprising – it happened again in 2015. Research and experience tells us now that, for up to a decade, surviving ewes may not produce lambs that live more than a year. Thus, herd recovery can take decades, if it even happens.

Obviously, biologists at universities and game departments in each of the states with wild sheep have been researching die-off issues. Through a growing body of work we are all learning more about the various forms of pneumonia and the range of bacteria involved. A great deal is now known about how, specifically, the illnesses spread through a sheep herd. This informs not only medical responses, it also gives wildlife managers a better handle on just how much – or little – patience needs to be practiced when wild sheep start dying. There is also a major looming move to keep domestic sheep from sharing any given habitat with bighorn herds.

Over the last three decades, alone, pneumonia has almost wiped out wild bighorn herds in the Blue Mountains and others in the Hell’s Canyon area of Idaho and Oregon along the Snake River. The pneumonia outbreaks are all apparently related to various Mycoplasma and Pasteurella bacteria.

Genetic analysis of bacteria over the past few years has shed some light. It appears that the Mycoplasma bacteria sufficiently weaken immune defenses for Pasteurella (and now a variety of other genetically-identified related bacteria) to trigger the pneumonia. Each of the various bacteria-caused pneumonias may lead to different outcomes. (For example, sheep may survive one type, develop antibodies which last for only a year or two, and be re-infected. Or, some strains may kill so quickly that little evidence remains of the bacteria responsible.) Some ewes are “shedders,” not unlike human “carriers” (unaffected by something like a strep throat they carry, but infecting others). Then, too, it seems possible that lambs which survived pneumonia are carrying the bacteria and infecting other lambs. Answers are slowly coming.

Through much of bighorn country, the various pneumonia bacteria are transmitted from unaffected domestic sheep to wild sheep, where they spread rapidly. Much research has centered on antibiotics and vaccines (and ways to get them into bighorns). Researchers are developing domestic sheep which are free of the Mycoplasma bacteria – much of this work is being done at the Washington State Prison in Walla Walla. It is unlikely that enough bacteria-free sheep can be developed to be viable in the large flocks of sheep in the vast sheep grazing allotments spread across bighorn country, but these sheep will be highly prized in some smaller areas.

Many western states have developed strict rules about the intermingling of domestic and wild sheep. The risk of disease to wild herds is so great that some states have given carte blanche to the killing of any bighorn (ram, ewe or lamb) found near domestic sheep. Almost any nose contact (a common greeting) will infect a wild sheep with enough bacteria to spread like wildfire through a bighorn herd. Washington and western biologists have worked with both public and private land managers to avoid interactions between bighorns and domestic sheep.

There is now a push among conservation groups (such as the Wild Sheep Foundation and the National Wildlife Federation) to reallocate some wild sheep research and other funds to actually pay sheep grazers to not use allotments that pose a risk to bighorn herds. Some sheepmen have switched to cattle in those sorts of allotments. In addition, current state and federal environmental impact studies performed prior to bidding on grazing allotments are putting increasing value on the presence of, or proximity to, wild sheep.

There is growing hope for wild sheep. Take a drive down The Yakima River Canyon – or into any sheep country – and say hello.

Written by Jim Huckabay. Posted in Uncategorized

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