A century and a half ago, muskoxen roamed the North Slope of the Yukon from Alaska to the Mackenzie Delta. Then they disappeared.

Their disappearance, between 1858 and 1865, was probably the result of overharvesting. The demand for muskox meat came from whalers and explorers, commercial hunters and fur traders. Until recently, the only remaining evidence of muskoxen on the North Slope was skeletal remains and traditional knowledge among the peoples of the Mackenzie Delta.

Then they came back. In 1969, there were reports that a muskox was shot near Aklavik. The first sighting of a muskox in the Yukon happened in the early 1970s. By the 1990s, aerial surveys usually spotted over a hundred muskoxen on the North Slope.

The muskoxen now living in the Yukon are not descended from the nineteenth-century Yukon muskox population. Modern muskoxen are immigrants from Greenland, by way of the United States.

The Yukon muskoxen are descendants of a small herd that was reintroduced to the Alaskan North Slope in 1969, says Dorothy Cooley, Yukon Renewable Resources biologist in Dawson. The original animals used for the reintroduction of muskoxen to Alaska came from the Greenland muskox population.

The Alaskan North Slope muskoxen had a hard time in their first couple of years, but after 1972 the herd grew rapidly. In the early 1970s it spread into the Yukon.

Now there are believed to be about 700 muskoxen on the Alaskan and Yukon North Slope combined. How many of them spend part or most of their time in the Yukon is still unclear.

A survey in the Yukon in the summer of 1993 located 157 muskox, Cooley says, but surveys in later years have found fewer. The most recent survey found only 96 animals.

"The drop in numbers might be because they move back and forth across the Alaska border," Cooley says, "or it might mean that we have to improve our survey techniques."

Whatever the actual numbers are, the muskoxen seem to have re-established themselves firmly on the North Slope. They're frequently seen along the Firth River and on the Beaufort Coast in Ivvavik National Park, and in Herschel Island Territorial Park. In the past few years, they've been sighted occasionally further south, along the Dempster Highway and the Porcupine River.

Muskoxen are odd-looking animals, with long coarse outer coats and a helmet-like arrangement of horns. Their closest genetic relatives are goats.

Their long hair, shoulder humps, and sloping backs make muskoxen appear larger than they really are. In fact, muskoxen are smaller in stature than caribou, although they weigh more. The bulls stand about a metre and a half at the shoulder and are more than two metres long. They weigh about 340 kilograms. Cows are smaller and lighter.

Most muskoxen are dark-coloured, with lighter-coloured horns, lower legs and faces. The long, coarse outer hair hides a soft underfur called quiviut that is shed in the spring and early summer. Quiviut is highly prized for yarn-making.

Apart from their differing sizes, you can tell a bull muskox from a cow by its horns, Cooley says. On bulls, the horns come together into a massive plate that covers the forehead. Cow horns don't meet in the middle, and usually there's a tuft of hair on the forehead between the horns.

Muskoxen generally spend their time in herds. Most herds contain about 8 to 25 animals, although they can be smaller or much larger. A bull leads the herd and signals when it's time for the herd to form its famous defensive circle, adults facing outwards and the calves safely in the centre. The formation works well as protection against the muskox's chief predator, the wolf.

Currently, the muskox is designated as Specially Protected Wildlife under the Yukon Wildlife Act, and hunting is not permitted.

For more information about muskoxen, contact the Yukon Department of Renewable Resources.