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A Look at the Black Bears of Kuiu Island
By Riley Woodford
Alaska Department of Fish and Game
Courtesy of Lily Peacock
Group effort: Lily Peacock, front left, and Kim Titus, front
right, teamed up with state and federal biologists and
volunteers to study Kuiu Island's black bears.
A project involving bear hunters, antibiotics and barbed wire has provided
revealing insights into one of the world’s most dense populations of black
bears, on Kuiu Island in Southeast Alaska.
Bear researcher Lily Peacock found that Kuiu Island, about 40 miles west
of Petersburg, has three to five bears per square mile. Peacock also found
that surprisingly high numbers of bears coexist seasonally on salmon streams
on the island. She counted 115 different bears using a one-mile stretch of
stream during a two-month period.
“Using modeling techniques that look at patterns of capture and recapture,
we estimated about 175 bears used that segment of that stream over two
months,” Peacock said. “That surprised me. It was corroborated with other
work that I did, observing bears from tree stands.”
Peacock said it’s difficult for an observer to keep track of that many
different bears. A casual observer might see 20 bears, she said, but you
don’t know if that’s seeing five bears four times or 20 different bears. To
identify individual animals, she used the same genetics techniques forensics
experts use on crime scenes, extracting DNA from hair follicles. Peacock
collected 1,554 hair samples from trails along seven streams in 2000 and
The hair snares are simply a single strand of barbed wire strung between
trees. The barbs snag tufts of hair, and by carefully monitoring and
cleaning the snares, Peacock to identify individuals and their patterns of
“I put hair snares on salmon streams “Did they stay for two weeks, did they
stay for one week, did they stay for the whole season,” she said. “And how
many different bears used the stream over the course of the salmon run.”
Courtesy of Lily Peacock
Bear on a wire: A remote camera snapped this image of a black bear
passing under a strand of barbed wire near a salmon stream on Kuiu
Island. Hair snagged on the wire provided DNA, allowing researchers to
identify individual bears.
The Alaska Department of Fish and Game and the Forest Service’s Petersburg
Ranger District worked with Peacock on the four-year project, which was part
of her Ph.D. dissertation at the University of Nevada, Reno. Wildlife
biologist Kim Titus, now Deputy Director for the Division of Wildlife
Conservation, served as Peacock’s Alaska advisor.
Titus said Fish and Game provided the primary funding for the research, and
initiated the project because of concerns about the high hunter harvest of
Kuiu Island black bears.
The island is renowned among bear hunters, Titus said, and the big game
guiding industry shared wildlife managers concerns about the island’s bears.
The cooperation of guides and hunters was instrumental in the success of the
“We had tremendous support and interest from Petersburg Ranger District -
Tongass National Forest staff,” Titus said. “The project really paid off.
Fish and game needs this information to work with the Board of Game and bear
hunters in setting appropriate harvest levels. The Forest Service issues
permits for big game guides and some transporter operations. This research
helps ADF&G and the Forest Service manage this world-class black bear
Peacock and Titus said there is not much research on black bears in
Southeast Alaska, or how black bears use salmon streams.
“We all know black bears use salmon on Anan Creek,” she said, “but other
than these prize fishing spots, we wanted to know how black bears use the
run-of-the-mill salmon streams, of which there are thousands up and down
Southeast Alaska, the streams that are the backbone of the forest. And one
thing this project did was to demonstrate how many black bears use these
Peacock was surprised by some of the differences in behavior
between black and brown bears. Bears deal with the safety of their cubs in
different ways, she said. Brown bear mothers keep their cubs close at hand,
while black bears often leave their cubs while they fish, usually sending
them up a tree.
Courtesy of Boyd Porter
Crowded isle: Kuiu Island, about 40 miles west of Petersburg, has one
of the world's densest black bear populations - about three to
five bears per square mile.
Despite of the high numbers of bears on the streams, Peacock rarely saw
bears fight. She said the bears practice sexual segregation, with males and
females fishing at different times, and the average stay on a stream for a
bear was two weeks. She said that although bears are solitary animals for
the most part, they are forced to be together on the salmon streams, and
they’ve developed mechanisms to work together in these seasonal high
“They keep their distance from each other,” she said. “With this huge
density you’d expect more conflict, but there wasn’t. They avoid each other.
Brown bears up north can be pretty scarred up from fights. But not these
bears, they look beautiful. Not many scars. They’re behaviorally pretty
mellow. They have this dance - males here, females there.”
Titus said the super abundance of food helps relieve a lot of the potential
stress in the population.
Peacock worked with hunters to estimate the total number of black bears on
Kuiu Island. She used a standard technique called mark-recapture.
“The technique is fairly old fashioned, and it can be used on animals from
salamanders or snails to whales,” Peacock said. “You mark a sample of
population, say 100 animals, and then go back later and catch or resight
another sample. Part of that second sample will be marked from the first
time. If only two of second sample were marked from before, then you
probably have a pretty big population. If you recapture 99, it means you did
a good job getting marks out there, and marked almost every one.”
Tetracycline, a commonly administered antibiotic, was used to mark the
bears. When tetracycline is ingested by a bear or a human, it leaves a mark
on bones and teeth. The mark is visible when a cross section of bone is seen
under a microscope with ultraviolet light.
“Our bones and teeth are constantly growing and remodeling, new material
is being absorbed and created every day,” Peacock said. “If a bear eats
tetracycline, a tiny layer appears. Capturing bears is expensive, so we let
the bears mark themselves.”
Courtesy of Lily Peacock
Nosy islander: A Kuiu Island black bear investigates a wad of material
laced with scent that helped draw the bear to the bait station. The
box on the tree behind the bear contains the tetracycline-laced bait.
Peacock designed bait stations that minimized chances of animals other
than bears taking tetracycline-laced bait. In June of 2000, about 200
stations were set up along roads and beaches in the area that connects
northern and southern Kuiu Island, and about 130 bears were marked. In 2002,
263 bait stations were established, one on every square mile of the island,
and about 195 bears were marked. The number of bears marked was based on the
number of baits consumed by bears.
Bear hunters were asked to submit toe bone from bears they killed, and that
provided the “recapture” data. Titus said cooperation from hunters was
almost 100 percent.
Of 166 bears harvested on Kuiu during the 2000/01 hunting season, 11 (6.6%)
were found to be tetracycline marked. Overall, Peacock found 32 marks in 503
samples taken from Kuiu and nearby Kupreanof Island. Peacock estimated the
population of black bears on Northern Kuiu Island to be 1,019, and the
overall density to be about 4 bears per square mile. The results were
consistent for both rounds of the study.
“It’s a snapshot in time,” she said. “You need several estimates to
determine trends, whether the population is stable, increasing or
decreasing. Some people have said that there used to be more bears on the
island, and the population is decreasing. But this study wasn’t designed to
address that question.”
Titus said Fish and Game will continue will continue to refine the
population estimate with additional samples from bear hunters. The
tetracycline mark will stay in the bones of marked bears for four years.
Hunters have harvested black bears on Kupreanof Island that were marked on
Kuiu, so fish and game is requesting toe bones from all black bears taken on
both Kupreanof and Kuiu islands. This will allow wildlife managers to
evaluate the extent to which bears are moving back and forth between the two
“By combining new and innovative DNA methods in wildlife and conservation
genetics to solve some old-fashioned wildlife management problems of
estimating bear numbers, we are collectively able better manage black bears
for long-term sustainability,” Titus said.