Prepared by Laura Thorpe and 10th Grade Biology Students Wainright, Alaska
In this chapter, our class would like to contribute information about the natural processes that affect Alaskan caribou populations - weather, snow conditions, predation, accidents and fire.
But first, a few of our observations here in Wainwright. We have had the luck of observing members of the Tesukpuk Lake Herd outside our doors all winter. They have provided subsistence food and fur for the villagers and are just a beautiful animal to have on our rather desolate winter landscape! And it is still white and cold here, although our temperatures have reached 0 degrees F and the sun sets around midnight! Soon comes mud and birds and mosquitoes!
The focus of the Inupiaq folks right now is on the commencement of the whaling season, the single largest and most important event in the life of a coastal Inupiat community.
NATURAL PROCESS AFFECTING CARIBOU POPULATIONS
WEATHER The first and probably most variable from year to year is weather. Summer temperatures can fluctuate dramatically from below freezing to 70 and even 80 degrees F. At one time, researchers thought that storms, high winds and wet conditions during the calving season caused high mortality rates of calves. However, re-evaluation of the data and more observations indicate that other factors, other than weather, are responsible for calf mortality. Caribou are very well adapted to the various environments they encounter throughout a year, and weather is not as important a factor in terms of mortality.
PREDATION Predation has been found to be an important mortality factor for Alaskan and Canadian caribou (Bergerud 1974). Possible predators include brown bears, black bears, polar bears, wolves, coyotes, foxes, lynx, wolverines, golden eagles, bald eagles and ravens, although most of these predators rarely occur in the same place at the same time.
WOLVES Found to be the most significant predator of caribou in North America (Skkog, 1968), the wolf is been cited as the selective pressure behind the evolution of caribou behavior and adaptations. Such behaviors include migration to areas of low wolf density, synchrony in calving, herding, and alertness to moving stimuli on the tundra. On the Arctic National Wildlife Refuge where the Porcupine Herd resides in the summer, wolf predation is low and here, the caribou are more affected by the presence of brow bears.
BROWN BEARS On the Arctic refuge, brown bears are more numerous than wolves and live close to the coastal plain where caribou have their calves. Some researchers have suggested that bears are more important predators on caribou than wolves (Whitten et al. 1986). Overall brown bear predation, however, has not affected caribou population numbers.
GOLDEN EAGLES Relatively high numbers of golden eagles in the calving area of the Arctic Refuge have been observed over the years. Mauer, 1976 found that golden eagle predation on young-of- the-year calves meets or exceeds that of the brown bear on the refuge. Combined, wolves, brown bears and golden eagles account for 50-80% of calf predation on the refuge.
ACCIDENTS As highly migratory species, caribou are exposed to a number of conditions that lead to mortality. One significant accident occurs while the Porcupine Herd crosses the rivers on its migration routes. If young or weak animals get caught in rapids they can be swept under water and drowned. Another fatal accident, crippling, occurs when the herds stampede due to bug harassment, or when predators are chasing the herds.
FIRE Wildfires are very common throughout the interior regions of Alaska and Canada. With the changing attitudes about natural fires, scientists have found that fire has a crucial role in maintaining healthy plant and animal life in the Arctic. When a fire sweeps through a region, the short term results may seem bad for the life there. However, the fire has removed old, dead biomass that hinders growth of new shoots. The long term results of faster growing and healthier plants far outweighs short- term death and charred landscape.
For those of you with access to the internet, we have found some great WWW pages on the Arctic, Antarctic, and Alaska. Start at: http://www.stud.unit.no:80/~sveinw/arctic/ (don't forget that tilde after the 80/) and cruise from there! Happy hunting! There is a wealth of information on Alaska out there that can be found by cruising from this home page.
Sincerely,
Laura Thorpe and her 10th grade Biology class
Journey North 125 North First Street Minneapolis, Minnesota 55401 Phone: (612)339-6959