The Baffling Mystery of Our Dying Lambs

An entire community faces a tyranny of options.

SheepRidgeThey call it Sheep Ridge, the one you can see from the main street in Dubois, but no bighorn sheep have grazed there for a long time.  The herd is still around, but its population is plummeting. Why?

Back in the 1870s, I’ve heard, hunters could find a bighorn sheep in these mountains any time they wanted. Most bighorn sheep in the West came from that original herd as transplants, moved out by the hundreds to other regions of the Rockies during the last century.

Some of those relocated herds have been threatened by the same basic problem, but have bounced back. Not so the bighorns that stayed here.

It’s not that there isn’t any explanation. There are too many. That’s the problem.

Our high school sports teams are called the Rams, and you see their image on logos all over town, but the rams themselves are fragile.  Local taxidermists say some of their skulls are too light to hold screws, and the curly horns are no longer as big as before.

Unlike the herds in Cody and Jackson, Whiskey Mountain sheep keep their weight stable in the winter, but lose weight when they move up to summer range. Is there something wrong with the local wild grasses, forbs, and brush that are central to their summer diet?

Predators like wolves or eagles might play some role in the animals’ deaths. But in those cases they may be only the final blow — not the root cause.

Sheep060816_3The greatest concern is that these bighorns are extraordinarily prey to respiratory infections common among sheep. They harbor a half-dozen strains of the relevant bacteria, while wild sheep elsewhere in the West seem to be hosts to only two or three. Enough lambs are born to this herd each year, but only a handful reach maturity. Many of the ewes live on, chronically ill, to infect again and again.

The infection traces to domestic sheep, which were raised here for four decades starting in 1890, but dwindled as the cattle ranchers prevailed. In 2015, the US Forest Service formally banned domestic sheep from the local bighorns’ range—decades after their decimation began.

It can’t go on. But what to do?

About a year ago Sara Domek, executive director or the National Bighorn Sheep Center in town, approached two experts (wildlife biologist Daryl Lutz of Game & Fish and Steve Kilpatrick, head of the Wyoming Wild Sheep Foundation) to plan a strategy. The outcome is a series of summits now under way in Dubois, where absolutely anyone who is interested is welcome. I didn’t take an actual count, but scores of my friends and neighbors, have turned up, bringing with them an astonishing wealth and depth of knowledge on the subject.

The biggest challenge is the complexity of the problem. “You came up with 170 issues, so we had a lot of fun categorizing them all,” said Jessica Western of the University of Wyoming at the last session. A soft-spoken, genial person, she is shepherding a large flock of biologists, land managers, outfitters, hunters, environmentalists, ranchers, and other interested residents, toward recommendations to help the Wyoming Game & Fish Department decide what it can and should do next.

BighornDrawing_croppedThe Wyoming Game and Fish Department has won grants from four organizations to support the summits, and commitments of time and expertise from bighorn sheep specialists all over the West. One of the grants brought a panel of eight specialists on the bighorns to Dubois last month, where they shared their knowledge, listened to ours,  and brainstormed.

They brought insights about  bighorn sheep and their habitats in Alaska, California, Idaho, Montana, Nevada, Oregon, Washington (the state) and, of course, Wyoming. The scientists truly seemed to enjoy themselves, having a rare opportunity to hide away in the wilderness as a select team asked to learn from each other and contribute to a poignantly good cause.

It’s not that nothing has been tried. At the latest summit, held early this month, Game & Fish habitat biologist Amy Anderson described many  efforts to improve the forage in the wilderness, including fertilizers, herbicides, selective cropping, and “range pitting” (dragging an implement across the ground to disturb the ground and encourage growth of new grasses).

Follow-up studies analyzing the forage (quantity, species composition, protein content, and relative food value) found that these tactics didn’t seem to make any great difference, compared to untreated areas, “so I don’t know what we bought with these treatments,” Anderson said. “We’re not necessarily seeing improvement” in the varieties of grass the sheep prefer.

So what’s the problem? Is it the climate? Minerals in the soil or the salt licks? Air pollution coming from Utah or even farther west?

Prescribed burns have been tried in parts of the forest, not only to encourage growth of grasses but also to deny hiding places to predators. Local hunter and taxidermist Lynn Stewart pointed out that Sheep Ridge itself, visible from the middle of town, was bald a century ago. Today it is blanketed with evergreens and sheep won’t go there.  Another prescribed burn is planned for this summer in a spot where conifers now cover a bighorn migration route between winter and summer ranges.

beckiart
Painting by Becki Neidens

Immense interest centers around University of Wyoming biologist Kevin Monteith, who has been pursuing an intensive three-year research project on this herd. His team has implanted monitors like IUDs in ewes, which  send a signal when they give birth. A member of the team will spend this summer camping in the remote, rocky Whiskey Mountain region, waiting. After a signal, she will race over the treacherous ground to find its source, hoping to reach the lamb and attach a motion sensor. This should allow her and others to locate some of the lambs that die and  learn what happened.

At the latest summit, the facilitator Jessica Western assigned us into breakout groups. Our task was to arrive at a consensus about which of those 170 issues she compiled after the previous session deserve the most attention for the future. Inevitably, we also pondered some recommendations. Some of them are controversial, and some unrealistic.

Why not cull the entire herd and start again with healthy bighorns, descendants of the transplants from the original herd? (They’d inevitably get infected too, because the microorganisms do persist in the soil for some time, and anyway, what about the forage issue? Besides, the transplanted sheep wouldn’t know the local migration routes. Studies elsewhere show that sheep lacking this knowledge tend to stay in the winter range all year round.)

BighornStatue2No solution will emerge quickly. We’ll remain in the dark about the root cause of the die-off for at least three years, while Montieth’s team completes its research.

Meanwhile, in June after the workshops are over, the Game & Fish Department will sort through all the recommendations and decide what it can try, what it can’t, and why not. Whatever it eventually does will also take time, as well as funds and personnel. And the clock is ticking for the herd.

Sara Domek of the Sheep Center closed the last summit with a plea for help from all those people with furrowed brows who were sitting on the folding chairs in the audience.

“This is the time for citizen science,” she said. “People want to help. Let’s do it.”

© Lois Wingerson, 2019

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