Musk Oxen Live to Tell a Survivors’ Tale

by Rebecca on December 18, 2010

in Animal Stories,Animals in the News

Arctic National Wildlife Refuge

A holdover from the Pleistocene era, the musk ox has managed to hang on while most of its brethren disappeared at the end of the last ice age.

 

From the New York Times: http://www.nytimes.com/yr/mo/day/science/ 
By NATALIE ANGIER

 According to Arctic biologists, the quintessential example of megafaunal fortitude in the face of really bad weather is the musk ox, or Ovibos moschatus, a blocky, short-legged, highly social ungulate with distinctively curved horns and long hair that looks like shag carpeting circa 1975.

The ox that is not an ox;  Ovibos’s common name is only partly justified. The males do emit a musky cologne during mating season, but the animal is not an ox. Nor, despite its back-of-the-nickel silhouette, is it a type of buffalo either. Its closest living relations are thought to be goats and sheep, but taxonomically and metaphorically, the musk ox is in an icy cubicle of its own. Once abundant throughout the northern latitudes worldwide, today they are found only in Arctic North America, Greenland and pockets of Siberia and Scandinavia. The musk ox is a holdover from the Pleistocene, the age of the giant mammals memorialized in natural history murals everywhere — the mammoths and mastodons, the saber-toothed cats, the giant ground sloths, the 400-pound beavers. Yet while a vast majority of the frost-fitted bigfoots disappeared at the end of the last ice age, 10,000 years ago, Ovibos hung on, as stubbornly.

Scientists are now seeking to understand how, exactly, the animal has managed to persist through repeated climate shifts and habitat upheavals. Researchers see in the musk ox’s story clues to help guide efforts to conserve other large land mammals now at risk of extinction. They also hope to raise the profile of a species they consider magnificent, at once stalwart and supple, a page of living prehistory whose social and behavioral complexities they have just begun to decode.

“There’s evidence that they have an elephant like social structure, and even some form of culture,” said Joel Berger, a researcher with the Wildlife Conservation Society and a professor at the University of Montana. So why is everybody flying to Africa to see elephants when we’ve got this marvelous species living in our own backyard?

In a presentation last week at the Bronx Zoo, where the wildlife society is based, Dr. Berger described preliminary results from field studies of the musk ox that he has performed with Layne Adams of the U.S. Geological Survey and other collaborators. He talked about the challenges of catching animals to weigh and measure them, check their teeth, take their blood and furnish them with G.P.S. collars. One group of musk ox in Cape Krusenstern National Monument in Alaska had such bad, broken teeth you’d think they were subsisting on a diet of Pepsi and Snickers bars, said Dr. Berger, and the researchers worried that the population was unhealthy and on its way out.

Yet after suffering several seasons of declining numbers, the brown-toothers rebounded this year to match in fecundity and offspring survival a group living in the Bering Land Bridge National Preserve that had exemplary teeth. The cause of their rotten dentition remains a mystery, but the Krusenstern clan clearly was not biting the dust.

For all their storied past as co-prancers with mastodons, musk oxen are not huge animals. Adult males stand only about four feet high and weigh around 600 to 700 pounds, less than half the weight of the average draft horse. Yet they look hulky as a result of their spectacular double-layered fur coat. The long, shaggy outer layer they keep year round, not only to help shield them against the brutal cold of an Arctic winter, when temperatures can plunge 40 degrees or more below zero, but also to deter the insect pests of an Arctic summer.

“You’ll see caribou in summertime trotting across the countryside trying to get away from all the mosquitoes and biting flies,” said Jim Lawler, a biologist with the National Park Service’s Arctic Network in Fairbanks. “But the musk ox just stand there with clouds of mosquitoes hovering above them. It’s hard to penetrate that fur.” For added insulation, musk oxen grow a second fur layer each winter, an undercoat called qiviut that is said to be many times warmer than wool and softer than cashmere — and how obliging of the animals to shed that qiviut in spring for use in scarves.

With their stubby legs, musk oxen are not migratory like caribou or great dashers like reindeer. Their basic approach to winter management is: Don’t just do something — stand there. “You’ll see them in a big storm, drifted over, covered with snow,” said Dr. Lawler. “They’re almost part of the scenery.” They lapse into a state of what might be called hibernation al fresco, as their oxygen consumption and carbon dioxide production drop and their metabolic rate slows by about a third. “They’re basically shutting down some of their machinery so they can survive on less food,” said Dr. Lawler, who has studied musk ox energetics.

Whatever their occasional resemblance to the scenery, musk oxen are by no means as dumb as a post. “They live in loosely knit family-bonded societies,” said Dr. Berger, and they keep track of who’s who. The group is, after all, essential to their survival. When confronted with predators like wolves, a herd of musk oxen will famously circle the wagons, the adults forming a wall of horns facing outward, the vulnerable young safely shielded behind them. They also seem to have a keen memory for where the best foraging grounds may be found in the spring, the optimal mix of grasses and willow twigs to maximize the performance of the microbes at work in their ruminant gut. Musk oxen turn out to be very efficient at extracting calories to put on the fat they need to survive the long winter fast.

Historical records and genetic evidence alike suggest that the musk ox is a Rasputin, “the comeback kid of the Quaternary,” said Ross MacPhee, curator of vertebrate zoology at the American Museum of Natural History. “They undergo periods where they really bolster their numbers for a few years, then they go down to an almost complete collapse, then later they come back like gangbusters.”

As a result of passing through repeated population bottlenecks, in which only a handful of individuals survived to spawn subsequent generations, today’s 100,000 musk oxen are thought to be notably homogenous, lacking in the sort of genetic diversity once thought critical to a species’ long-term prospects. “It would be hard to argue that musk ox are on their way out the door,” said Dr. MacPhee. “They are not weak sisters.”


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