radio-collared caribou and low-altitude photography help biologists
count almost half-a-million caribou in the Western Arctic
Outdoors / Juneau Empire / March 14, 2004
Riley Woodford / Alaska Department of Fish and Game
Alaska's largest caribou herd, the Western Arctic Caribou herd, has grown to
at least 490,000 animals, according to a census completed this week by the Alaska
Department of Fish and Game.
This vast herd ranges over a 140,000-square-mile area bounded by the Arctic Ocean,
the lower Yukon River and the trans-Alaska pipeline. About 40 communities and
13,000 people are located within the range of the herd. For the indigenous people
of these communities, the herd is both a vital link to their cultural heritage
and a staple of their diet.
There is also growing use of the Western Arctic Caribou Herd by resident and
nonresident hunters living outside the herd's range. These caribou are an important
source of income for commercial operators that provide services to hunters.
Because of its tremendous size, the ecological importance of the Western Arctic
Herd to northwestern Alaska is incalculable. Although they are important prey
for wolves and bears, these caribou directly and indirectly impact the entire
food web through nutrient cycling - affecting organisms from bacteria to moose.
Wildlife biologist Jim Dau, Alaska Fish and Game's lead biologist for the Western
Arctic Caribou Herd since the late 1980s, estimates the herd has grown about
1 percent annually for the last 10 years. That's significant for this herd, which
crashed in the mid-1970s from about 242,000 to 75,000 animals.
Counting almost half-a-million caribou is no easy task. Radio-collared caribou
and low-altitude photography are two key components. The census was staged out
of a remote airstrip on the western North Slope last July. A team of 13 biologists
and four planes were involved, including a Beaver fitted with a large format
U.S. Geologic Survey mapping camera. One or more planes radio-tracked the herd
daily to determine whether conditions were right for the photography.
"The sample of radio-collared caribou tells us two things," Dau said. "They obviously
lead us to the groups, but they also indicate what proportion of the herd is
present. Seventy-five percent of a herd this size looks like all the caribou
in world are beneath the plane. But until we are certain at least 90 percent
of all the collared caribou are present, we know we need to keep looking for
During the census the department determined 97 percent of all collared caribou
were present in the various aggregations of caribou. Once suitably aggregated,
the Beaver flew transects over each group and shot photographs at a regular interval
so that each photograph overlapped on all four sides.
While the Beaver photographed large groups of caribou, two Piper Cubs and a Cessna
185 radio-tracked caribou and searched for small groups that did not contain
a radio-collared animal. When a group was found the Beaver was either called
in to photograph it or the animals were counted directly from the plane.
Once back in town the photos were laid out and areas of overlap marked so that
no caribou were double-counted. "It took 11 of us three days to put the overlap
lines on photos," Dau said. "It's a big job and a critical part of getting an
With the overlap lines marked, the tedious task of counting began. The Department
took more than 1,100 9-inch-by-9-inch photographs to capture the herd on film.
Most of the actual photo counting was done by Don Williams, who lives in the
heart of the range of the herd in Ambler, on the Kobuk River. Williams has worked
with Fish and Game for many years radio-collaring caribou and, more recently,
counting census photos.
"He's really into it. He pores over each photo and does a wonderful job on a
task that most people would consider intolerable," Dau said. "Don counted about
85 percent of the photos for this census."
The herd is on a three-year census schedule. The Department attempted a census
during July 2002 but high wind, snow and fog forced a one-year delay. Weather
almost prevented the 2003 attempt as well.
"Weather delayed our start by one week," Dau said. "Then, once we were there,
weather conditions were still marginal for the caribou to aggregate. High wind,
clouds and cool temperatures subdued levels of insect activity. Without intense
harassment by mosquitoes, warble flies and bot flies, caribou don't form the
huge aggregations we need to photograph the entire herd."
Since the Western Arctic Caribou Herd crashed in the mid-70s, biologists and
hunters have been concerned that the herd could experience a similar drop in
coming years. According to Dau, Western Arctic caribou have generally been in
good body condition during fall. Following several recent mild winters caribou
were in relatively good condition even during spring.
"The body condition of caribou is really the ultimate expression of their habitat
in terms of quantity, quality and availability of their food," Dau said.
To determine if diseases are present in the herd, biologists have systematically
collected blood samples from the caribou since 1992. Dau said the data so far
indicate that disease is currently not a problem for this herd.
The next census is planned for 2006.
to Current Events 0304]
Song of Alaska, P.O. Box 671670, Chugiak, Alaska 99567-1670
Wolf Song of Alaska.
The Wolf Song of Alaska
Logo, and Web Site Text is copyrighted, registered,
protected, and cannot be used without permission.
Web design and artwork donated by She-Wolf Works and Alaskan artist Maria Talasz
All rights reserved