Contents:
Spring 2002 and pre-calving movements
Calving Update 2002
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, 2002
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The herd wintered in 2 groups of approximately equal size: one in the Ogilve Mountains north of Dawson, YT and the other in the vicinity of Arctic Village, AK. Another small group wintered in the upper Sagavanirktok River, in an area occupied by Central Arctic caribou. Snow cover in all areas was relatively light and caribou captured during March seemed to be in very good condition (ADFG and Yukon Environment unpublished data). Caribou began moving toward the calving grounds during early May. As in past years, caribou that wintered in Yukon migrated generally northwards to the British Mountains, then followed the Babbage River north to the edge of the Arctic coastal plain. Caribou that wintered in Alaska moved east of Arctic Village during March and April, then northward to the upper Kongakut River, then northeastward along the Firth and Malcolm Rivers to the Canadian Arctic coast. After reaching the coast, most caribou moved westward into Alaska.
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Calving Update 2002
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Location of parturitient and non-parturitient Porcupine caribou cows, June 1 - 7, 2002
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Between May 30th and June 7th, 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 25th and 26th 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),
*calf survival within the first month of life (June),
*and calf:cow ratio at the end of the first month (late June)
The peak of calving this year appeared to be around the 5th of June, which was several days later than most years but earlier than during 2000 or 2001. The birth rate for the herd this year was 87%, determined from the 59 of 68 radio-collared cows that were observed to be pregnant or accompanied by a calf in early June. At the end of June, 85 % of the calves born were still alive, which represents a ratio of 56 calves per 100 cows.
Overall, calf production in 2002 was greater than during 2000 and 2001. However, the calf:cow ratio was lower than the average between 1994-1999, and it is feared that the current levels of reproduction may not be great enough to stop or reverse the decline in herd size that has occurred since 1989.
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How many of the satellite collared cows had calves?
During winter 2001-2002, 9 caribou cows were monitored by satellite radio collars, including 1 that was first captured during March 2002. One cow (Trudy) died during late winter. Three others (Lynetta, Lucky, and Blixen) could not be observed during the calving period because of malfunctioning VHF transmitters. These 3 cows traveled to the calving grounds and likely were pregnant. Of the remaining 5 cows, Cupid, Donner, and Lupine produced calves that survived through 25 June, Isabella was judged to be pregnant on 7 June but was not accompanied by a calf on 25 June, and Catherine (classed as young when captured in March) was judged not pregnant and was not seen with a calf.
Below is a list of all caribou followed by this project, and information on whether or not they produced calves during the past five 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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