#ovibos

A pair of musk ox bulls (Ovibos moschatus) headbutting in Alaska, USA

Muskoxen (Ovibos moschatus), family Bovidae, Alaska

Muskox Ovibos moschatus

In historic times, muskoxen primarily lived in Greenland and the Canadian Arctic. They were formerly present in Eurasia, with their youngest natural records in the region dating to around 2,700 years ago. There are reintroduced populations in Alaska, Yukon, Siberia, and Norway.

Its Inuktitut name "umingmak" translates to "the bearded one". Its Woods Cree names "mâthi-môs" and "mâthi-mostos" translate to "ugly moose" and "ugly bison", respectively.

Muskox (Ovibos moschatus) male Dovrefjell

Muskox (Ovibos moschatus)

Muskox and other Arctic mammals are feeling the heat of climate change

As part of a broader attempt to develop an ecological baseline for Arctic wildlife, researchers have recently focused on muskox, the least studied mammal in North America. “Across a range of species, we’re seeing direct and indirect effects of warming which affect a lot of different parameters of animals’ biology,” said Joel Berger, a senior scientist at the Wildlife Conservation Society.

In a recent study presented in Scientific Reports, Berger and his co-authors found that the head size of juvenile muskox in Russia and Alaska was smaller, and negatively impacted after extremely dry winter conditions and rain-on-snow events during gestation.

The likely cause: warming temperatures have altered air velocity and how long sea ice stays in the Arctic, which in turn has modified oceans currents and the timing and intensity of precipitation. More rain is now reaching some inland areas than snow in the winter months. If temperatures drop below freezing, the ground can ice over, requiring muskox to exert more energy to access food. Conversely, rain without freezing temperatures can make it easier for the animals to reach plants by reducing the snowpack. But without insulation, plant productivity can decline during the next growing season. If mothers are unable to meet the nutritional needs of their gestating babies, muskox young will suffer the consequences.

Over seven years, researchers examined the head size of muskox at three different study sites in the Russian and Alaskan Arctic using telephoto lenses and rangefinders. Marci Johnson, then a biologist with the U.S. National Park Service based in Kotzebue, Alaksa, assisted with radio tracking collared animals, while other research parties traveled by snowmachine for hundreds of miles across drifted snow. “Sometimes it would take them a day to travel between two groups of muskoxen,” Johnson said, describing the difficulties of doing such a study.

Ultimately, the researchers found that the smallest one- to two-year-old muskox in the dataset occurred after the winter of 2007-2008 when no precipitation occurred between October and April. The largest head sizes followed the wettest winter in their data. (On the Tibetan Plateau, endangered wild yaks, a family relative of muskox, have been shown to have less lactation when snow is scarce.) For three-year-old muskox, the largest animals were those that experienced no rain-on-snow events during gestation.

The East Asian sector of Bergingia on Wrangell Island experienced two times more frequent rain-on-snow events, colder temperatures and shorter growing seasons than conditions at Alaskan study sites. As a result, Wrangell Island muskox were smaller than their Alaskan relatives.

“The broader issue dealing with juvenile sizes is that smaller animals have poor survivorship,” says Berger. “We know that [to be true] for a wide range of species. For muskox, we’re using head size as an index to understand questions about population health and population trajectories.”

Muskox (Ovibos moschatus), family Bovidae, Norway