Bother over Yukon’s burgeoning bison herd

Over the past six years, Tom Jung shipped 438 piles of ungulate poop to the U.S. "It's not the most glamorous job," says the Yukon government's senior wildlife biologist.

Over the past six years, Tom Jung shipped 438 piles of ungulate poop to the U.S.

“It’s not the most glamorous job,” says the Yukon government’s senior wildlife biologist.

The scat stockpiling, like most investigative science, started with a straightforward question: What impact is the Yukon’s burgeoning bison herd having on the territory’s other ungulates?

There were concerns North America’s largest land mammal might be munching up all the food. There were also worries bison might be pushing caribou, moose and sheep out of their natural habitats.

Bison were here before. They used to roam the Beringian steppe with wooly mammoths some 8,000 years ago. Caribou and sheep shared the terrain back then too, but not moose. These waterlogged, knobby-kneed mammals came later.

Bison stuck around until 300 years ago, then disappeared.

Jung isn’t sure exactly why. It might have had to do with the landscape changing from cold prairie grassland to mossy forest, drastically altering food supplies. Or it could have been that the bison were hunted to death. “I suspect it is somewhere in the middle,” says Jung. As the landscape changed, the bison were concentrated in the remaining grassy patches, where they were easier to hunt and more susceptible to disease.

Biologists assumed Canada’s wood bison were extinct until the 1950s, when a small herd was discovered in the N.W.T. To maintain their genetic purity, and protect them from possible predation and environmental threats, the bison were shipped to Elk Island, Alberta where they bred like rabbits.

“So many reintroduction programs fail quite badly,” says Jung. “But bison do really well.”

The Elk Island bison do so well, they’re being shipped all over the world. Siberia started a reintroduction program in 2006, and Alaska, after 23 years of red tape and permitting problems, just started flying bison into some remote regions this year.

The Yukon was way ahead of them. It adopted 142 Elk Island bison from 1986 through 1992, reintroducing them in the Aishihik Lake area.

It took a while for the beasts to settle into their new digs. At first, they hung out in nearby towns and villages, wandering through backyards proving a nuisance, or standing in the road, staring down cars. People heading out to pick berries were worried the huge, hairy herd might charge them.

Today, reintroducing a giant mammal to the Yukon would not be so easy. “In the 1980s, consultation, bureaucracy, permitting and paperwork are not what they are now,” says Jung. Had they been, Jung wouldn’t have had to send all those piles of poop to the U.S., because the research would have been done first, before the reintroduction.

The first big surprise was bison breeding.

Yukon biologists figured the reintroduced herd would grow to 200 or 400 animals, then level off. But the bison kept birthing – and birthing, until there was close to 1,500 of them tramping the hills around Aishihik.

As concern grew that bison were eating the other ungulates out of house and home, the Yukon government created a 2012 bison management plan, and hunters started taking down the massive mammals.

But Jung wanted answers. Were bison really competing with sheep, caribou and moose for food and habitat?

That’s where the poo collecting comes in. There is a lab at the University of Washington that dissects an animals diet by prodding through its poo.

For the past six years, Jung and his colleagues collected piles of sheep, caribou, moose and bison poop and shipped it to Washington State.

The findings were surprising.

Though moose and bison are closest in size, it is sheep that share bison’s diet. Moose are browsers eating twigs and shrubs in winter and aquatic plants in summer, while bison and sheep both eat a lot of grass.

The caribou were also a surprise. It was generally believed these nomadic ungulates eat mostly lichen. But their poo told a different story. At least in the Aishihik area, the caribou had the most diverse and flexible diet of all the ungulates.

Examining poo piles eliminated Jung’s concern that bison might be competing with moose and caribou for food. But habitat competition remained a worry.

To look at this overlap, Jung and his colleagues perused past aerial surveys and tracked the movement of their radio-collared ungulates.

In the 8,000 square kilometres they surveyed, moose and bison overlapped in less than seven percent of the region. It was similar with caribou. “They weren’t using the same habitat,” says Jung. With the sheep, it was another story.

Bison, it turns out, have no problem hauling their huge, heavy bodies up mountains. “Initially we thought they’d stay in big wide open spaces, looking for prairie environments,” says Jung. “But they go right up to the high alpine, climbing up to 1,500 metres. These animals frequently surprise us. They are more flexible than we first thought, both here and in Siberia.”

Although sheep and bison favour similar alpine environments, they use them at different times, the bison eating in summer where the sheep feast in winter. As a result, there remains little habitat overlap between bison and the other ungulates.

Finally, Jung wanted to confirm that the bison were not pushing other ungulates from certain areas, or attracting them.

One winter of aerial surveys, conducted when the animals are most stressed in terms of finding food and habitat, confirmed there was neither attraction nor disruption. “The animals were randomly distributed and not associating positively or negatively,” says Jung. “And there is so much food available, it is inconceivable there would be a food shortage.”

Jung isn’t that surprised by the bison study findings. Bison, caribou and sheep evolved together over thousands of years, he says. So it is no wonder these big ungulates co-exist so comfortably. And moose, the latecomers, eat a different diet.

Evolutionarily speaking, there was only a small blip without bison. This reintroduction is simply “filling a niche that has been vacant for 300 years,” says Jung.

Following this year’s hunting season, the Yukon’s bison population has dropped to roughly 1,300 animals. Alaska’s fledgling herd, flown in from Elk Island this year, is starting with 100, while Canada has shipped more than 120 Elk Island bison to Siberia since 2006.

“This kind of conservation effort you seldom see,” says Jung, who can count North America’s successful reintroduction programs on one hand – peregrine falcons in the North, Californian condors, wolves in Yellowstone, and now bison.

“These are once in a lifetime experiences,” he says.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at research/publications/ newsletters_articles