To: Journey North From: Laura Thorpe and 10th Grade Biology Students Wainwright, Alaska
Looking back at the previous chapters we've provided, I see that we haven't given much information about the migration patterns of the Porcupine herd. So, here goes...First, here are some questions for you to think about before answering. They are all about the adaptations that caribou have evolved for survival. Please send your answers to us at: lthorpe@arctic.nsbsd.k12.ak.us
CHALLENGE QUESTIONS 1. During the spring migration north, why does the herd travel in long, single-file lines? (Think about the conditions under which they must travel.)
2. What are three reasons why the herd uses the coastal plain as a birth and nursery ground?
3. Why are the calves dropped nearly all at the same time? (Think about the dangers to the young - such as predators.)
4. How fast do you think a caribou can run?
AND
5) What is aufeiss? (pronounced "off ice")
Answers to previous CHALLENGE QUESTIONS:
1) Thanks for the answers about oil development vs. preservation from Buck Stroh and his fifth and sixth graders at Lamb Elementary and from Joan Berger and her class at East Hills School! We will post all the responses in a future message and offer some more information to understand the conflict here in the Arctic.
2) The Web URL for the US Fish and Wildlife Service home page that includes some neat stuff on refuges and endangered animals is: http://www.fws.gov/
PORCUPINE HERD - SPRING MIGRATION PATTERNS
The porcupine herd, named after the river that is along its migration route, is comprised of about 165,000 animals and ranges over 250,000 square km (150,000 square miles). The herd winters in both Alaska near Arctic Village (just south of the Brook Range) and east in Canada to the Richardson Mountains or the Peel river basin of the Yukon and Northwest Territories.
In early March, smaller groups drift to the northern limits of their wintering range. When actual migration occurs, pregnant females are the first to head north. A typical bird's eye view of these females reveals that they migrate in long, single-file lines, staying on higher ridges and across windswept frozen lakes. Weeks to a month later, males, barren females, and juveniles will cross the same routes heading north to the coastal plain of Alaska and Canada.
COASTAL PLAIN CALVING Pregnant females will arrive at the core calving areas which range widely from the Babbage River in Canada to the Canning River in Alaska which is the Western boundary of the Arctic National Wildlife Refuge. Females arrive at the core areas from early to late May depending on the stage of snow melt. In years of advanced snow melt they will arrive earlier than in those with late melt. These areas are usually snow free and have already produced small quantities of nutritional grasses such as cotton grass (Eriophorum vaginatum).
The cows spread out along the area and "drop" their calves within two weeks. The Peak period of calving on the Arctic Refuge is June 3-8 and all calving is finished by June 15. The newborn calves are precocious. They can stand within an hour after birth, a very important adaptation because they must stand to nurse. After one day, they can walk with their mothers as they graze and by the first week, they can run with the whole group. Amazing if you think about how helpless the human baby is for months and months after birth.
POST CALVING The cows and calves form nursery bands for the rest of the summer until the whole herd disperses and prepares to head south for the winter in August. These bands seem to move in response to food availability and mosquitoes.
DOG DAYS OF SUMMER
For the caribou in the summer, the greatest harassment is not predators, but bugs. By July and August, mosquitoes fly in incredibly dense clouds and can drive caribou "mad" with the constant buzzing and biting. If you have ever been to northern Maine or northern Minnesota in the summer, you will know about a fraction of what the caribou (and all the other animals, including humans) experience in Alaska during this time.
The caribou have adapted to the mosquitoes in two important ways. First they will form large, dense groups that seem to keep the pests off of the caribou in the center of the group. Secondly, they stay on the coastal plain where winds from the Beaufort Sea provide them with relief - hence another crucial reason to keep those coastal areas open to the caribou. When the herd goes "mad", stampeding is prone to happen and young are often crippled or crushed. Other areas of relief from bugs include snow fields, aufeiss, mud flats, and river deltas.
FALL MIGRATION
By mid-September the whole herd is at some stage of southern movement back toward the Brook Range and into Canada. During some years the Canada component of the herd moves west to winter in Alaska. As part of the yearly southern migration, the herd must swim across the Porcupine River near the international border. It is here where the native groups come to hunt to provide themselves with another year's supply of meat for their communities.
Until next week!
Laura and her 10th grade Biology class in Wainwright, Alaska lthorpe@arctic.nsbsd.k12.ak.us
Journey North 125 North First Street Minneapolis, Minnesota 55401 Phone: (612)339-6959