Porcupine Caribou satellite collar program
by Darcie Matthiessen
Johnny Charlie Scholarship Recipient
The Porcupine Caribou Herd can be described as being in a constant state of motion. No matter how you look at it, a migration consisting of 123,000 caribou is not a small thing. The PCH have succeeded at dealing with life in the north by undergoing seasonal migrations that take them far across their 260,000 square kilometre range in parts of the northern Yukon, Northwest Territories, and Alaska.
In the spring pregnant cow caribou migrate north to reach the calving grounds in time for calving. Their fall migration south typically begins in September when the caribou make their way towards winter ranges.
 Determining the whereabouts of the PCH has become considerably easier with inventions such as satellite technology. Since 1997, a satellite collar program has been in place to help track these nomad-like creatures. To date, there are 10 satellite collars that have been deployed on caribou cows. Satellite data allows biologists to determine seasonal range use and migration patterns.
Porcupine Caribou reach reproductive age at 3 years and the average life span is 7 years. The average lifespan of a satellite collar is 3 years but some may last for longer periods of time. Often before the collars stop transmitting, the caribou are located and the collars are replaced with new or refurbished collars.
Since the beginning of the satellite collar program, biologists have collected satellite information on a total of 18 caribou cows. Through an Adopt-A-Caribou program, students from a number of schools in northern communities have had the opportunity to name some of these collared caribou as well as use the location data for school projects. In March of 2003, three new satellite collars were deployed on Helen, Arnaq, and Tundra. Biologists monitoring the PCH try to maintain a minimum of 100 radio collars on cow caribou. By locating collared cows, a calf-to-cow ratio may be estimated. This information allows for a determination of new recruits into the herd, which is important as the herd has been in decline for over a decade.
The PCH has been observed to fluctuate according to surveys conducted by biologists since 1972. The peak caribou population occurred in 1989 at 178,000 and been declining 4% each year since. Photo census surveys are attempted every 3 years but can be done only if the caribou aggregate. This phenomenon is referred to as 'post-calving aggregation', and tends to happen in early July when the biting insects are most fierce. Biologists hope to conduct the next photo census this summer 2004.
By watching the movements of the satellite-collared caribou, it is possible to observe several trends. For example, in the spring, the pregnant cows lead the herd to their calving grounds in Alaska's Arctic National Wildlife Refuge (Arctic Refuge) and Northern Yukon. Bulls and non-pregnant females also migrate to the coastal plains but sometimes lag behind the cows.
Second, spring migration tends to be more directed then fall migration. This is because pregnant cows are on a limited time schedule to reach the calving grounds before they give birth to the calves during the peak calving period of June 4th to the 8th. Also, the area where the PCH calve is relatively small and used consistently year after year, whereas their winter range in any one year can cover a vast area.
Third, timing of the migration may vary from year to year. Factors such as weather and snow cover influence the time it takes for the PCH to move to their calving grounds, the date the herd begins moving, as well as the route that the herd may take. Under poor weather conditions, travel is arduous and energetically demanding. In 2000 and 2001, the weather conditions made for difficult travel north. Some of the calves were born along migration routes (NOT inside the calving grounds of the Arctic Refuge), which lowered calf survival. This affects the number of reproductive animals in future years and ultimately the overall population of the Porcupine Caribou. Calving information is not yet available for 2003.
Fourth, fall migration routes and winter ranges may differ from year to year. Fall migration tends to follow terrain features such as valley bottoms and ridge systems. The route itself is largely unpredictable. Winter ranges in north-central Yukon and Alaska may change from year to year depending on factors such as snow depth.
Information that can also be collected using collars (radio or satellite) is calving information. Satellite information provides biologists with technical information that may be of assistance in determining the crucial activities and habitats of the Porcupine Caribou herd that require special management consideration for the future.
Now, if only we could find out exactly what they are thinking, we'd be even closer to understanding these unique creatures!
For more information on the Porcupine Caribou Satellite Collar Program, visit www.taiga.net/satellite.
UPDATES MENU
|