Friday, March 12, 2010

Musk Ox Historic Decline

The musk ox exists across the barren lands of the Arctic.  A breeding population has been reintroduced into northern Siberia and is prospering.  They will not disappear anytime soon.

However, they were evolved to prosper on tundra and its vegetation in the face of difficult chilling weather.  Their real problem is that their original niche disappeared with the Ice Age itself.  The tundra zone was adjacent to the ice’s edge and perhaps somewhat further south geographically but not in terms of climate and latitude if one accepts the premise of the Pleistocene nonconformity. The presence of Mastodons surely affected access to grazing possibly in a positive manner.

Expanding the herds throughout Siberia is desirable as is active herd management.  This may justify the provision of a winter fodder supplement and modest shelter to assist in surviving the worst.  They too get killed in the worst cold when their food energy simply cannot keep up.

Without such support, the herds are stable and suffer little predation at all as far as has been reported.  They do not run from predators and reportedly give a good account of themselves when confronted. 

The prospect for commercial wool industry also exists and should be combined with husbandry. A winter fodder drawn from cattails from not far south would be possible.

I keep thinking that fodder for the wooly elephants must have been difficult but perhaps not.  We do not have a handle on the quantity of available fodder on the tundra, but it is obviously quite plentiful and active grazing would allow an annual replenishment.  My assumption is to keep it low, yet grasses only need a few weeks of warmth and sunlight to produce a heavy crop and that is possible.  Actual ripening is more of a challenge and would constrain an annual.  So we hear about shrubs that avoid the problem.

I suspect that the tundra is quite competitive in fodder production during the days of the midnight sun.

Musk Ox Population Decline Due to Climate Not Humans

by Staff Writers

University Park PA (SPX) Mar 10, 2010

Musk Ox (Ovibos moschatus). Musk oxen once were plentiful across the entire Northern Hemisphere, but they now exist almost solely in Greenland and number only about 80,000 to 125,000. Credit: Tim Bowman, U.S. Fish and Wildlife Service

A team of scientists has discovered that the drastic decline in Arctic musk ox populations that began roughly 12,000 years ago was due to a warming climate rather than to human hunting. "This is the first study to use ancient musk ox DNA collected from across the animal's former geographic range to test for human impacts on musk ox populations," said Beth Shapiro, the Shaffer Career Development assistant professor of biology at Penn State University and one of the team's leaders.
"We found that, although human and musk ox populations overlapped in many regions across the globe, humans probably were not responsible for the decline and eventual extinction of musk oxen across much of their former range." The team's findings will be published in the 8 March 2010 issue of the journal Proceedings of the National Academy of Sciences.
Musk oxen once were plentiful across the entire Northern Hemisphere, but they now exist almost solely in Greenland and number only about 80,000 to 125,000. According to the researchers, musk oxen are not the only animals to suffer during the late Pleistocene Epoch. "The late Pleistocene was marked by rapid environmental change as well as the beginning of the spread of humans across the Northern Hemisphere," said Shapiro.
"During that time several animals became extinct, including mammoths and woolly rhinoceroses, while others, including horses, caribou, and bison, survived into the present. The reasons for these drastically different survival patterns have been debated widely, with some scientists claiming that the extinctions were due largely to human hunting.
Musk oxen provide a unique opportunity to study this question because they suffered from a decline in their population that coincided with the Pleistocene extinctions, yet they still exist today, which allows us to compare the genetic diversity of today's individuals with those individuals that lived up to 60,000 years ago."
To conduct their research, the team collected musk ox bones and other remains from animals that lived during different times - up to 60,000 years ago - and from animals that lived across the species' former range. From these remains, the scientists isolated and analyzed the mitochondrial DNA, which is useful for studying ancient population dynamics due to its rapid rate of evolutionary change.
The scientists also isolated and analyzed the mitochondrial DNA of musk oxen that are alive today. They then used a Bayesian statistical approach to estimate how the amount of genetic diversity of the musk oxen populations changed through time.
"Over the past decade, ancient DNA studies have matured, moving away from simply identifying animals to actually giving us insights into the population size and dynamics of animals, stretching back over the last 100,000 years," said Tom Gilbert, an associate professor at the University of Copenhagen in Denmark and another of the team's leaders.
"Thanks to significant computational developments made by colleagues of ours, we have the fantastic opportunity to watch what happened to the ancient populations. When did they increase, or decrease, and at what rate?" he said.
Scientists believe that a reduction in genetic diversity of an animal's population can reflect a decrease in the size of the population. By estimating when the genetic diversity of musk oxen began to decline, the team was able to test whether the decline was due to the arrival of humans in a particular region or to some other effect.
The scientists found that the genetic diversity of the musk ox was much higher during the Pleistocene than it is today. They also found that the genetic diversity of the species increased and decreased frequently over the past 65,000 years.
"The periods of growth and decline observed in the musk ox populations in this study are considerably different from those that have been reconstructed previously for musk oxen or for other species, such as bison and mammoths," said Shapiro.
"While musk oxen experienced a significant population decline nearly 65,000 years ago, mammoths first began to decline only around 48,000 years ago. Bison populations remained stable until around 35,000 years ago - a period during which musk ox populations actually were growing.
"As we get a better idea of the overall picture of megafaunal dynamics in the Arctic, it is becoming clear that each species is following its own population trajectory. This is a strong argument that it is changes in habitat that are driving these population dynamics, and not a single factor such as the introduction of human hunters."
Shapiro continued, "We know from historical data that musk oxen are sensitive to changes in the Arctic environment. While we cannot confirm exactly what climate factors are driving the changes we observe in musk oxen over the last 65,000 years, we can say with confidence that humans are not causing local extinctions. In Greenland, for example, humans and musk oxen arrived and began their expansion at the same time."
According to Gilbert, "We wonder how the current climatic instability will effect the survival of musk oxen in the near future. There's a lot in the news about the plight of polar bears, but musk ox may be similarly at risk."
Muskox, (Ovibos moschatus)
Muskoxen have historically been associated with the hunting cultures of early mankind. Their meat and hides were used for food, clothing, and shelter, while the horns and bones were carved to make tools and crafts.
During the Ice Age, muskoxen were found as far south as Kansas, but as the ice and tundra receded northward, so did the muskox. They currently roam the arctic tundra of northern Canada and Greenland and have been successfully returned to Alaska and Russia. A small introduced population also exists in Scandinavia.
The muskox and the caribou are the only two arctic ungulates, or hoofed mammals, that survived the end of the Pleistocene Era (10,000 years ago).
The muskox is a member of the bovine, or cattle, family. Other wild North American bovines include mountain sheep, Dall sheep, mountain goats, and American buffalo. An identifying characteristic of bovines is their horns, which are carried by both males and females and are not shed. In contrast, only male members of the deer family have antlers (with the exception of caribou), and they are shed each year.
The long, thick coat of the muskox makes the animal look larger than it really is. Male muskoxen, called bulls, weigh between 400 and 900 pounds, while females, or cows, normally weigh from 350 to 500 pounds.
The muskox's coat ranges in color from dark brown to almost black, with the lower legs, faces, and backs light brown to white. The coat consists of two parts: long, coarse outer hairs, called guard hairs, that reach almost to the ground and shed rain and snow; and a soft, dense undercoat called qiviut. Qiviut is the warmest, lightest wool in the world. The heavy guard hairs and insulating qiviut protect the muskox from the severe cold and high winds of the Arctic.
The muskox's short, stocky legs and large, rounded hooves enable the animal to move through shallow snow and to be an agile climber on snow and rock. From the humped shoulders, the muskox's back slopes slightly toward its narrow hindquarters.
Muskoxen have sharp horns with rounded bases on the forehead which curve down and outward, and then upward like large hooks. The bull's horns are much larger than the cow's and are used during fights over females. Both males and females use their horns to dominate other muskoxen and to fight off predators.
Muskoxen are plant eaters, feeding primarily on sedges, grasses, and willows. Since green plants are available for only a few weeks during the arctic summer, for most of the year, muskoxen must paw through snow to feed on dried plants.
Muskoxen have a low reproductive rate with single calves born annually or every 2 to 3 years. At 3 years of age, cows normally bear their first calf. Environmental factors such as availability of food and severity of weather affect the age of first breeding and whether calves are born annually or at longer intervals. Mating takes place in August and September with most calves born in late April or May. Within a few hours of birth, calves are able to follow their mothers back to the protection of the herd.
Wolves, bears, and man are the primary predators of muskoxen. They are also vulnerable to accidents, such as falling from cliffs or drowning, and starvation if deep snow or ice covers their food. Cows may live more than 20 years, but the average lifespan is much less. On the average, bulls probably die at a younger age than cows due to the increased risks during fights over females.
Pictures of muskoxen often portray one of their most unique behaviors: group defense. When disturbed, muskoxen run together to form a tight circle, or crescent-shaped line, with their rumps to the center and sharp horns facing outward. Adults may dart out of the circle or line with heads lowered to pursue an approaching predator.
Muskox populations were extirpated from Alaska in the late 1800s, and apparently declined in Canada and Greenland by the early 20th Century. Although scientists are not sure about the exact causes of the decline, hunting and climatic changes may have been factors. Concerns that the muskox could become extinct resulted in efforts to reintroduce the species into areas of its former range.
A small number of muskoxen originally from Greenland was reintroduced on Alaska's Nunivak Island in 1935-1936. The population grew over the years and supplied animals for other reintroduction efforts in northern Alaska from 1968 to 1981. Today, a population of about 2,300 muskoxen resides in Alaska. Muskox hunting is permitted in Alaska, but strictly controlled to keep population numbers stable or increasing.
Muskoxen also have been reintroduced in Russia, to Wrangell Island and on the Tamayr Peninsula. Worldwide, muskoxen now number about 125,000.
The muskox is one of the few large mammals capable of living year-round in the severe arctic environment. Wildlife managers are working to identify and carry out management practices that will maintain a proper balance between muskoxen and human activities in the Arctic.
revised March 1995

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