Contents:
Spring 2003 and pre-calving movements
Calving Update 2003
*data and maps provided by Steve Arthur, Alaska Department of Fish and Game*
How many of the satellite collared cows had calves?
Spring and pre-calving movements
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Migration routes from winter ranges by satellite collared Porcupine Caribou, April 1 to May 31, 2003
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During the winter of 2002 - 03, the majority of the Porcupine Caribou Herd started the winter in the Ogilvie and Hart River basins northeast of Dawson City, Yukon. Beginning in late January, some of the caribou left this wintering grounds in the southern portion of the range and moved north about 150 miles to the Whitefish Lakes area between Old Crow and Fort McPherson. Spring migration, however, did not begin until early May. As in past years, caribou migrated generally northwards to the British Mountains, then followed the Babbage River north to the edge of the Arctic coastal plain, then westward into Alaska.
Much of the snow on the migration trail had disappeared by late May, and many of the caribou had reached the coastal plain of the northern Yukon by May 27th.
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Calving Update 2003
Click on map to enlarge
Location of parturitient and non-parturitient Porcupine caribou cows, June 1 - 4, 2003
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On May 27th, and between June 1 - 4, radio-tracking flights were conducted by Alaskan Biologists to locate radio-collared Porcupine Caribou Herd cows, and to observe whether they had produced calves. Follow-up flights were conducted on June 24th and 25th to determine calf survival and to locate bulls and non-pregnant cows that had not been located previously.
According to Steve Arthur, there are 3 indices used to measure reproductive success. They are:
- parturition rate (# of cows that are pregnant or have given birth - early June),
- calf survival within the first month of life (late June),
- and calf:cow ratio at the end of the first month (late June)
Calving began around May 27th, and probably peaked around June 1st. The birth rate for the herd this year was 87%, determined from the 61 of 70 radio-collared adult cows that were observed to be pregnant or accompanied by a calf in early June. Forty caribou were observed with calves, 21 were judged to be pregnant or to have produced and lost a calf, and 9 were judged not parturient.
At the end of June, 67 radiocollared adult cows were observed. 34 of the 40 calves observed in early June were still alive, which represents a post calving survival of 85%.
Additionally, 12 of the 21 cows judged to be pregnant were found with calves. This combined for a total of 46 adult cows with calves after one month, and a cow:calf ratio of 69%.
In summary, parturition rate and post-calving survival of calves in 2003 were identical to rates from 2002, but the late June calf:cow ratio increased, and was the largest since 1999.
Click here here to view a table showing Porcupine Caribou Herd calving ground surveys and population estimates between 1987 and 2003.
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How many of the satellite collared cows had calves?
During early winter 2002 - 2003, 7 caribou cows were being monitored by satellite radio collars. Then, in March, we captured 4 new caribou and fitted them with satellite collars, and removed one of the existing collars. Unfortunately, one of the newly collared caribou, (Carmen) died shortly after capture. For more information, see the April 2003 update .
This leaves 10 satellite collared caribou, which we have been monitoring since. Three of them (Lynetta, Lucky, and Blixen) could not be observed during the calving flights because of malfunctioning VHF transmitters. These 3 cows traveled to the calving grounds and may have been pregnant. Of the remaining 7 cows, Arnaq, Catherine, Donner, Helen, and Isabella produced calves that survived through June 25th. Tundra and Lupine were judged not pregnant in early June, and neither was seen with a calf during the late June flight.
Below is a list of all caribou followed by this project, and information on whether or not they produced calves during the past six years.
Note: -- means that the caribou was not located
For more information on the history of the caribou involved in this program, click here.
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