Winter distribution of the Porcupine Caribou Herd (PCH) was determined quite early in the fall of 2007. By mid September, those satellite collared PCH north of the Old Crow Flats began to move west into Alaska, while the satellite collared caribou in the northern Richardsons slowly began to move south into the central Yukon. On October 10th, Tara Wertz with the U.S. Fish and Wildlife Service flew the Alaskan portion of the winter range and located 68 of 108 radio collars, indicating that over two-thirds of the Porcupine Caribou were set to winter in Alaska. This distribution correlated well with what we were seeing of the satellite collars as by the middle of October two-thirds (10 of 15) satellite collared cows were in Alaska, while only 5 remained in the Yukon.
Of the caribou that did winter in the Yukon, very few got close to the Dempster Highway. Harvest was the lowest that we have seen. Within a few weeks, the migration began to slow. Very few Porcupine Caribou migrated south of the Ogilvie / Peel Rivers.
It's interesting to note that during the winter 2005 / 2006 the majority of the Porcupine Caribou wintered further south than they have been recorded in the last 20 years. Last winter (2006 / 2007) they remained further north than we've seen in the past 10 years. During the winter of 2007/ 2008, the majority of the herd stayed in Alaska. This hasn't happened since 1990.
Movements of Satellite collared cow caribou during winter months, December 1, 2007 to March 31, 2008
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From about the middle of November 2007 until late March 2008, the caribou in the Yukon tended to drift north, ending up in Fishing Branch area. In Alaska, the caribou that were concentrated around Arctic Village moved slightly east.
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Late Winter Telemetry relocations
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Locations of radio and satellite collared caribou, February 27 and 28, March 16, 17, 27 and 28, 2008
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As in past years, Tara Wertz and Dave Sowards with the U.S. Fish and Wildlife Service (Arctic National Wildlife Refuge) conducted the telemetry flights to relocate radio and satellite collared caribou.
In late February, a flight in Alaska located 57 active radio collars near Arctic Village. At that time it was not possible to fly the Yukon portion of the range. Additional telemetry flights in March located 15 additional live collared caribou in Alaska, and 14 in the Yukon. 20 collars were not located. 6 collared caribou were heard on mortality mode during the telemetry flights. These caribou died some time between October 2007 and late February 2008.
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Capture locations
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Locations of caribou captured March 2008 for deployment of radio and satellite collars
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The goal this March was to replace "Catherine's" satellite collar which is due to go off the air this spring and to add more radio collars to adult cows, short-yearling cows and bulls in preparation for a census July 2008. Each spring since 2003, 10 of the past years female calves (known as short yearlings, as they are just short of one year old) have been collared to gather information on the survival of yearling caribou to 3 years of age.
Radio collars were provided by the Government of the Northwest Territories, Canadian Wildlife Service and Ivvavik National Park. Satellite collars were provided by the U.S. Fish and Wildlife Service, the Alaska Department of Fish and Game, and Yukon Government.
On March 16th, a Yukon capture crew including Dorian Amos (Parks Branch) and Shawn Hughes (CO Services) mobilized to Eagle Plains, and on the 17th flew out to the Fishing Branch River from where the satellite collar had last transmitted. Karl Scholz with Fireweed Helicopters flew the captures. The USF&WS was flying aerial support, but we could not locate "Catherine" as it appeared that her VHF transmitter had stopped functioning. Instead, we deployed 4 radio collars (2 on short-yearlings, and 2 on adult cows).
PCH captures in Alaska were combined with Central Arctic Caribou Herd fieldwork. Martin Kienzler flew to Fairbanks to assist Beth Lenart and Jason Caikoski. Rick Swisher with Quicksilver Aviation was hired to fly the captures in his R-44 helicopter. Captures were based from Coldfoot Camp on the Dalton Highway. 11 Central Arctic short-yearlings were collared on the 26th and 27th. On the 27th and 28th, 8 Porcupine Caribou short-yearlings, 4 adult cows and 5 bulls were captured and fitted with radio collars. 1 adult cow was collared with a new satellite transmitter.
During the handling, biologists took seven standard body measurements and recorded body condition. Samples of blood and hair were also taken for later testing.
In total, 21 radio and 1 satellite collar were deployed in March 2008 on Porcupine Caribou. This increases the number of active collars on Porcupine Caribou to 125, including 16 active satellite collars. The new satellite collared cow will be receiving a name soon.
Composition count data
During composition counts, caribou are classified as Cows, Calves, Mature bulls, and Immature bulls. Comp counts are useful in obtaining an estimate of overwinter survival of calves. To obtain an accurate representation of survival for a herd, it is necessary to classify caribou in as many wintering areas as possible as there can be differences between ranges.
Due to the long times required to ferry by helicopter to where the caribou were wintering in both Yukon and Alaska, biologists decided that it was not possible to do a thorough composition count this year.
Dempster Snow Stations
In 1991, YTG set up 8 stations along the Yukon portion of the Dempster Highway in Porcupine Caribou range to monitor late winter snow accumulation and density over the long term. These stations were established in treed and open tundra terrain. The Dempster Highway passes through 3 of these regions (Richardson, Eagle and Ogilvie). There are 4 stations in the Ogilvie region, and 2 each in the Eagle and Richardson regions.
The 6 stations established on the Yukon North Slope were set up in 1999 to monitor snow depth as part of a muskox study. These stations have been measured by staff from YTG, Ivvavik National Park and Herschel Island Territorial Park. Since the muskox project ended in 2005, future measurements will be done opportunistically.
Snow measurements at 5 of the 8 snow stations were collected on the 16th and 18th of March. As we did not have the proper snow kit with us, we could only measure depth but not density. The highway north of Eagle Plains was closed due to high winds and blowing snow at that time which prevented us from measuring the other 3 sites. Snow depths for the Ogilvie section were slightly above average. With the incomplete data, averages could not be obtained for the Eagle or Richardson sections.
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