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Terrestrial Life - Muskoxen


Muskoxen (Ovibos moschatus) were driven to extinction before the 20th century.  They were reintroduced in 1969 and their numbers reached a peak at almost 400 individuals in 1986.  Since then, the muskoxen population has declined to around 200 individuals.  Reasons for this population decline include emigration, increased predation by grizzly bears, and severe winters.  Also, hunting by humans has increased since their reintroduction. (Patricia E. Reynolds, Kenneth J. Wilson, and David R. Klein, 2002)

Muskoxen population
Population dynamics of Muskoxen
Graph:  http://www.absc.usgs.gov/1002/images/Fig07-01.gif.

Muskoxen conserve energy by limiting their movement; they tend to stick to a core area about 50 km2 in the winter and 200 km2 during the calving and summer seasons.  Calving occurs from March to June, so it is especially important for mothers to build up enough reserves during the summer to last the winter and to feed the newborn.  Thus, a prolonged winter would have significant negative impacts on calf survival.  

Muskoxen depend on riparian cover along river corridors, floodplains, and foothills year-round.  During the winter, it seeks out areas of soft shallow snow.  Its winter diet consists mainly of low-quality forage such as sedges, grasses, mosses, and forbs.  In the spring, it feeds on high quality flowering sedges.  Muskoxen tend to be very loyal to a particular spot, returning there year after year.  (Patricia E. Reynolds, Kenneth J. Wilson, and David R. Klein, 2002)

Muskoxen herd
Muskoxen herd
(Photo: http://www.saskschools.ca/%7Egregory/arctic/Amuskox.html)

Any human activity should stay away from the muskoxen habitats, including adjacent uplands.  The areas that muskoxen frequent are places often used for gravel and water extraction for roads and/or platforms.  Muskoxen congregate into larger groups in the winter, and large groups of animals are more likely to be disturbed by human activity because they tend to have more sensitive individuals.  

Muskoxen groups that have moved west tolerate the Trans-Alaskan pipeline and the Dalton highway, but it is due to the wider area of habitable land available to the animals.  Muskoxen remaining in the 1002 coastal plain are in a more geographically constricted habitat, with the Beaufort Sea to the north and the Brooks Range to the south.  Eastern muskoxen populations are likely to suffer if human activities displace their territories and there are few alternative habitats available. (Patricia E. Reynolds, Kenneth J. Wilson, and David R. Klein, 2002)

Muskoxen habitats and vegetation in ANWR: Map

As muskoxen populations in the far west have coexisted peacefully with the Trans-Alaskan pipeline, a similar pipeline through the 1002 region should have little impact as well-- if it is built with the same environmental precautions.  For example, the Trans-Alaskan pipeline has 579 animal crossings over its 800 mile span.

Helicopters and low-flying aircraft have been noted to cause some herds to stampede and abandon their calves.  Some herds have been agitated by 3-D seismic exploration as far as three kilometers away; other herds seem unperturbed as close as 300 m.  Generally, noise produced by traffic, etc will have a negative effect on the animals. (Patricia E. Reynolds, Kenneth J. Wilson, and David R. Klein, 2002)

Little data are available on the interaction between muskoxen and human settlement associated with oil development.  This is because drilling platforms have been built in regions rarely visited by muskoxen.  However, the nature of the muskoxen's normal food source is such that its scavenging among human waste is unlikely.  The major concern is the gravel used for the platforms, which would have to be extracted from muskoxen habitats.

Locations of mixed-sex groups of muskoxen seen during winter and summer surveys in the Arctic National Wildlife Refuge, Alaska, USA, 1982-1999: Map

(Map:  http://www.absc.usgs.gov/1002/images/Fig07-06.gif)


Map on muskoxen and vegetation: "Distribution of Selected Wildlife on Arctic Refuge Coastal Plain".  Conservation GIS Center. February 5, 2003. http://www.conservationgiscenter.org/maps/html/2000_wildlife.html and GIS data from USGS


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