'Explosion' of research on Yellowstone bison

YELLOWSTONE NATIONAL PARK: The public — and policymakers — tend to be "behind the curve" when it comes to bison science. Meanwhile there's been an "explosion of research" into brucellosis and bison in the past 20 years, said Ryan Clarke, USDA epidemiologist.

In 1990, harsh winters pushed bison out of Yellowstone, and Montana began using lethal means against bison at the park boundary. After the state sued the federal government in the mid-1990s, the parties settled in 2000 on an interagency bison management plan with the goal of preventing the transmission of brucellosis to cattle while still protecting bison.

Competing values, histories, emotion and politics will go into crafting a management plan this year, but so, too, will two decades of science from the pastures to the labs.

Taking complex science and translating it into something people can grasp "is absolutely critical to success devising some way to go forward in the greater Yellowstone area," said Keith Aune, researcher with the Wildlife Conservation Society. "We need to engage people in this from all aspects."

Brucellosis causes abortion and is transmitted via oral contact with birthing fluids. The greater Yellowstone area is an island of infection in a nation that's otherwise brucellosis-free.

Chris Geremia, a Yellowstone bison researcher, said the new management plan will include more science on how bison live in the ecosystem and how brucellosis spreads.

"We took the best available knowledge in 2000 and came up with a best practice," Geremia said. Negotiation shaped the plan, and so did the next 15 years.

"We've learned movements are different than how we envisioned them," Geremia said.

Bison have more nuanced lives than the plan allowed. Managers thought they could remove 100-200 animals a year and keep the herd at 3,000 animals. They thought that would be a population without pressure driving animals outside the park.

Well, it turns out spring rains and the grass they bring and the severity of winter are key factors in migration, and now those things are modeled to help determine when bison who have left will naturally return to the park.

The park has two bison populations, a northern herd that has members exiting through Gardiner and a central herd that follows the Madison River into West Yellowstone and, managers have found, join the northern population.

"It's complicated how animals exit the park," Geremia said. "We have years when very few leave outside of West Yellowstone."

The park's bison population grows 12-15 percent a year, with no noticeable demographic impact from wolf or bear predation, Geremia said.

"There's high female, high calf survival," he said.

That leaves culling the herd to the humans, with about 700 bison killed every winter.

Calving time, when the brucella bacteria is shed onto the landscape, is when bison seek the richer pastures at lower elevations, such as at the park boundaries.

May 16 was the date set in 2000 for bison to be back in the park but now "that's a moving target, based on weather conditions and snow level," he said.

"If it's not time, the animals just go back," Geremia said. "The timing of green-up and calving may not perfectly align with a specific Julian date."

This year, like the last several years, the park had about 500-600 bison along the border.

"We had an early green-up and some of the calving was early," Geremia said.

Scientists use tracking collars to track movement and fecal and grass clippings to analyze the quality of food in forage areas.

Hazing has changed in time as managers learned from the bison. Now managers move 50-100 animals at a time — natural group sizes. Movement is slower and more likely to involve horses than helicopters.

"It seems like trying to almost simulate migration," Geremia said. "The bison will tell you when it's time to stop moving. We're trying to use low-stress livestock handling techniques."

Rick Wallen, NPS bison team leader, said the dates of hazing back into the park have tended to relate more to the capacity of neighboring communities to tolerate bison than to science.

"What we've learned is bison would function better on the landscape if they're allowed to follow natural patterns of movement, so we negotiate for more time and space at lower elevations. We've been successful in conveying that some years the conditions are just not ready for migration back into the park. Our efforts to understand bison migration patterns have gained the animals a week or two outside the park in some years," he said. "You can burn up manpower and time or you can accept how the ecological processes naturally play out and work with those to achieve the objects of separation from livestock. It saves the taxpayers money, too."

A gentler approach also has eased conflict with environmental groups.

The plan originally called for almost daily hazing with a very limited number of bison allowed outside the park into a small area. However, now hazing focuses on the end of the season and giving bison more room to roam, said Christian Mackay, director of the Montana Department of Livestock.

Bison crossing the border have been a safety concern (they don't do much for cars in collisions), he said, and they compete with cattle for grass.

Also, bison hunting on the park boundary has been controversial for drawing predators to gut piles and horrifying tourists, though it's also allowed tribes to exercise treaty rights.

On the lab side of research, one of the most interesting advances in bison research has been mapping of the Brucella abortus genome.

Pauline Kamath, disease ecologist with the U.S. Geological Survey in Bozeman, said researchers found five lineages of brucella bacteria in the Yellowstone region, suggesting five separate introductions into the area. The family trees of the lineages merge with a common ancestor in 1764 to disease in cattle introduced to North America.

Three of the lineages are centered in specific parts of the Yellowstone region, but two are widespread. Most transmissions are within species but every lineage crossed species.

The brucella family tree showed 13 times the brucella spread from bison to elk, five times from elk to bison and 17 jumps from elk to cattle through time. None showed bison to livestock transmission.

"Targeting Yellowstone bison may be unlikely to affect B. abortus dynamics in other regions of greater Yellowstone ecosystem," she said.

For four of the five lineages, the spread of brucella centered around Wyoming elk feeding grounds, but now the elk population outside the feeding grounds is a reservoir for the disease.

"There's evidence to support management focus on minimizing elk-to-livestock contact," Kamath said.

The research shows the median rate of spread of the lineages of brucellosis is 4 kilometers a year, she said.

Wallen said the research points toward the importance of elk transmitting disease.

"That's definitely a change in the way of thinking," he said. "Just 20 years ago, bison were considered the primary threat. That time of science, taking a look at how this small bacteria has moved around the greater Yellowstone area, has opened the eyes of managers that elk are a lot more significant influence than they were once considered to be. If there's ever a hope to eliminate the disease or manage it appropriately to prevent that risk, you have to acknowledge elk, and up until recently we didn't."

The genome mapping is an example of new technology and research identifying what is reality and what is not in the brucellosis debate, he said.

Aune's research with the Wildlife Conservation Society looked at how bison fetuses moved and disappeared on the landscape — illuminating how long potentially infectious tissue remained.

In Yellowstone, fetuses lasted about 30-31 days, while outside the park the fetuses averaged 56-59 days thanks to lower predation, he found.

A long list of predators dragged the aborted fetuses around on the landscape. Some fetuses were cached in trees, in soil and in dens.

Predators help cleanup the landscape so "the more coyotes, the more scavengers we have, the faster these infected tissues disappear," he said. "Scavenging is a huge part of this when you think of the risk of transmission."

Brucella disappeared more quickly in sunnier spots and later in the calving season, the difference of 100 days from February or 30-some from May.

Aune also looked at birth/abortion sites with aid of vaginal implants. Then researchers swabbed tissue, soil and plants. Out of 152 sites, 14 had brucella detected.

Separation of wildlife and cattle seems to be the most effective policy for now, barring advances in vaccination and other technologies.

"I think we're going to be living with brucellosis for a long time," Aune said.

Aune and Kamath were among those addressing a group of scientists working to tie together new brucellosis research into a guide for policy.

The effort will help science inform the future course of any actions used to address brucellosis in the Greater Yellowstone Area, Clarke told the scientists gathered at Montana State University for presentations on the disease from the Montana Fish, Wildlife and Parks, the USDA's Animal and Plant Health Inspection Service, the National Park Service, Inter Tribal Bison Council and Montana Department of Livestock and others on Wednesday and Thursday.

The committee of scientists, appointed by the National Research Council, will prepare a report on brucellosis and the feasibility of suppressing the disease, updating the committee's 1998 report "brucellosis in the Greater Yellowstone Area."

"We figure this is a good venue for us to get some, I guess you would say, future look at how we want to address this problem as our agency moves forward," Clarke said.

The USDA's objective is to eradicate brucellosis to safeguard the health of livestock, maintain the viability of trade and protect human health, he said.

In 1934, 11.5 percent of cattle were infected nationally, with half the herds infected.

Testing, vaccination and quarantines combated the disease with the federal government, state governments and producers working together.

"It's been successful with those three groups being invested in trying to get rid of the disease," Clarke said.

In 2008, after 74 years of fighting the disease, the USDA was able to announce all the country's livestock were brucellosis free. The designation lasted a few months, until elk transmitted the disease to cattle in Montana and Wyoming.

"Even though we reached brucellosis-free status nationally, we keep running into transmission from wildlife," Clarke said. "Our goal isn't going to be reached when we continue to get transmission from wildlife."

Losing the status in 2008 cost Montana between $5 million and $12 million, and that would be even more today, said Eric Liska, Montana Department of Livestock veterinarian.

The state focuses testing for infection on a designated surveillance area around the park into Beaverhead, Madison, Gallatin and Park counties, containing about 60,000 head of cattle on some of Montana's most valuable land.

Montana spends $1.3 million to manage the area, home to elk that can spread the disease. A lot of costs of preventing brucellosis fall on producers. One producer calculated a six-month quarantine on one pregnant cow is $88.

"Then you start talking about 2,300 animals," Liska said. "People could lose jobs."

The USDA has authority over wildlife only in emergencies — the last instance coming in the 1920s. Otherwise, it's the purview of states and, in national parks, the National Parks Service.

From 1990-2001, the GYA had zero cases of transmission from wildlife to cattle. In the next seven years, the area averaged one case of transmission a year. From 2009-2015, it's been 1.9 cases a year, Clarke said.

"The rate has doubled in this last seven-year period," he said. "That is a bad thing."

"Livestock in three states are under the persistent threat of exposure because of the disease that's endemic in GYA wild elk and bison," he said. "The goal is still eradication. We want all our livestock to be free of disease. We want to make that statement to all the international markets that buy cattle from the United States.

"We can see where we need to be but we need advice on how to get there," he said. "All the risk of transmission is with wildlife. How do we address that?"

The 25,000 to 30,000 elk in the state's surveillance area use 22 core winter ranges, said Kelly Proffitt, Montana Fish, Wildlife and Parks biologist. About half that land is privately owned, generally ranch land.

Eradicating the disease might be impossible and is unlikely to meet anything but a furious public backlash if it means killing large numbers of wild bison and elk. It also could lead to bison being added to the endangered species list, which would have significant ramifications when it comes to management, said P.J. White, presenting the NPS perspective to the scientists. White is chief of wildlife and aquatic resources in Yellowstone.

"We'd have to take all the exposed bison and elk, kill them and replace them," he said. "There would be furious public reaction. The public would not accept this."

It wouldn't be in keeping with the NPS's mission since the founding of the park to protect wildlife, either, he said.

As per the 2000 plan, the NPS launched a vaccination effort — and found that vaccinating wild bison is much different than livestock.

For 10 years, the NPS used compressed air rifles to fire vaccine "biobullets" into animals.

White said managers found they had a short range — about 65-100 feet — and the biobullets often fragmented.

"We never knew what dose was delivered or if it was the intended dose," he said.

The biobullets caused injuries and bleeding. Marking animals that had been vaccinated was difficult. And, bison behavior changed as managers kept shooting at them.

The best time to vaccinate bison is in autumn, but that's during rut when animals are in large groups. Revaccination was probably necessary.

"It would take decades and decades to reduce the prevalence, and the best we could do is probably 50 percent," White said. "We question whether it would change management" to have an exposure rate drop from 60 percent to, say, 30 percent.

Vaccination would be difficult, cause unintended effects to wildlife and visitors and need to be perpetual. And then elk would reinfect the bison anyway, White said.

An expert science panel reviewed the vaccination program and concluded it wasn't worthwhile. In 2014, the NPS decided to end remote vaccination.

Mackay said the Montana Department of Livestock would like to see more vaccinations inside and out of the park. He's also interested in immuno-contraceptives, which prevent pregnancy while a bison is infected.

If the immuno-contraceptives are successful, it could mean a higher tolerance for bison outside the park, he said.

White said the 2000 plan considered bison a "reservoir for brucellosis, even though there hadn't been a detected transmission from bison to cattle. Cattle were given precedence over bison on public lands outside the park."

The odds of brucellosis transmitting to cattle are 99 times more likely from elk than from bison, White said. There's been 20 transmissions from elk to cattle in the last 15 years. Elk in 22 million acres around Yellowstone don't have the habitat restrictions bison face.

Since 1985, 8,000 bison have been killed to keep the herd at 3,000-5,000. Most culled bison are sent to slaughterhouses, though some are killed by hunters.

"The public doesn't like it, and we don't like it," White said.

The elk herd has been reduced from 20,000 in 1995 to 5,000 today, mostly through wolf predation. Wolves prefer elk to bison.

"Management of bison is not going to solve the disease," White said.

"Zero risk of transmission to cattle is unrealistic," he said. "Current suppression tools are inadequate."

Separation of bison and cattle has been effective, however.

"This is about elk," White said.

"We prefer (brucellosis) not to be there, but at what cost to these populations?" he said. "We don't want to decimate these populations to reach a level of infection that means it's still there."

Yellowstone Superintendent Dan Wenk said the park's 3.5 million annual visitors mean a $550 million impact to the local economies and "most of these visitors come to view the iconic wildlife we are tasked with preserving for future generations."

He noted the disease was likely introduced to Yellowstone's wildlife from cattle in the first place.

The fact Montana and Yellowstone can debate bison and how to live with them is something to treasure and something that almost didn't happen.

In 1902, Yellowstone had 23 bison, the last of the wild plains population. Now the park has a genetically diverse herd numbering 5,000.

"We still have a wildlife legacy to protect, unlike other states that are 100 percent urban and agricultural," Wallen said. "Montana still has the opportunity for debate."

White said bison conservation is a great success story.

The animals are "important in defining the American experience," he said. "They're the last link to the vast herds that once roamed across the western United States."

Congress could make bison America's national mammal

The National Bison Legacy Act aims to name the bison as the country's national mammal.

The bill has been introduced in the U.S. House for the second consecutive Congress. It's sponsored by Reps. William Lacy Clay (D-Mo.), Jeff Fortenberry (R-Neb.), Kristi Noem (R-S.D.), José Serrano (D-N.Y.) and other co-sponsors.

House Resolution 2908 aims to recognize the cultural, historical, economic and ecological role of bison.

"No other indigenous species tells America's story better than this noble creature. The American bison is an enduring symbol of strength, native American culture and the boundless western wildness," Clay said.

Kristen Inbody covers state government at the Great Falls Tribune Helena Bureau. She can be reached at kinbody@greatfallstribune.com. Follow her on Twitter at @GFTrib_KInbody.