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Capturing wolverines with pixels and wire
brushes |
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January 13, 2017 |
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By Roger Phillips
IDFG Public Information Specialist
The forest floor has a thick blanket of snow
topped by a layer of bone-chilling air that’s so
still a creaking tree sounds like an airhorn. It
appears all animals have abandoned the forest
for warmer climes, but biologist Diane Evans
Mack’s remote cameras tell a different story.
A handful of hardy animals roam Idaho’s snowy,
mountainous forests, and among them are
wolverines. Only a tiny fraction of the public
has ever encountered one, and it’s difficult to
determine how many are out there, but Idaho Fish
and Game is trying to learn where they live, or
at least, where they are likely to live.
Wolverines are solitary animals that inhabit
large swaths of rugged mountainous terrain in
very small numbers, and Fish and Game biologists
are trying to determine where wolverines live in
Idaho. It’s part of a four-state project with
Wyoming, Montana and Washington that’s trying to
predict the likelihood that wolverine inhabit
certain areas.
Biologists across the four states identified
suitable wolverine habitat and overlaid a grid
onto the map, then randomly selected grid cells
and placed cameras in them during October and
November.
Each camera site is as uniform as possible with
the same model of camera, same bait, and same
array of four wire brushes that jut out from the
trunk at 90 degree angles. The brushes catch
hair as the animals climb the trunk to get the
bait.
Having hair samples gives biologists a genetic
sample so they can tell if more than one
wolverine visited the site, or if it’s a known
individual from a previous study.
Through the research, biologists will generate a
“probability of occupancy map” that predicts the
chances of wolverines being present in a given
area of suitable habitat.
Understanding and managing all of Idaho’s
wildlife is part of the agency’s mission, and at
times, it can be challenging. Knowing where
wolverines are likely to live helps managers
understand their needs and have baseline data
about their habitat and population.
Wildlife technicians Luke Ferguson of McCall and
Peter Ott of Marsing face long winter treks into
Central Idaho’s mountains to check the cameras
and retrieve the memory cards.
They ride snowmobiles and ski into remote sites
that are typically between 7,000 and 9,000 feet
during some of the most inhospitable winter
weather. Short day light hours and up to
66-mile, round-trip snowmobile/ski trips mean
they’re up long before sunrise and making long
drives so they can be at the trailhead at first
light.
“It’s a lot of fun and real rewarding, but it’s
not easy,” Ott said.
Not only do they check the cameras’ memory
cards, they have to replace the bait, which is
road-killed deer or elk quarters (which they
also have to collect). An additional lure is is
a sponge saturated with a viscous blend of skunk
scent and beaver castor, which is a combo that
smells as pungent as it sounds.
After a long day of winter driving and
backcountry trekking, the highlight of their
trip is downloading the card onto a computer to
see what visited their bait sites.
“So far, we’ve had an animal of some variety on
every camera,” Ferguson said.
Aside from wolverines, their cameras have
captured fishers, martens, birds, foxes,
coyotes, wolves and even deer before the snow
got too deep.
Some cameras are placed in areas that are so
remote they can’t feasibly be checked during
winter. Those have a slightly different system
in place. Instead of a deer leg, a cow’s femur
is attached to the tree and a special container
periodically drips scent onto the femur. Those
cameras will be checked and recovered in the
spring after the project wraps up for the
season.
One of the 61 sites in Idaho where cameras are
stationed is about 12 miles northeast of McCall,
an area where wolverines have been known to
inhabit in recent years.
The camera triggered a sequence of five photos
whenever there was movement at the bait site,
and it recorded an intriguing scene in time
lapse where at least one wolverine and American
marten consumed an entire deer leg during a
series of visits.
Through digital images, the scene showed that
the silent, seemingly lifeless forest was
actually a hub of activity for these specialized
predators.
If it was a male wolverine, chances are good it
was the only one in the area. Males are highly
territorial and can claim up to 500 square miles
of exclusive territory while typically allowing
a few females to share that terrain, but they
have an uncanny knack for securing it from other
males.
Previous research in the McCall area showed a
clear demarcation line between two adjacent
males' territories. Data from radio telemetry
collars showed their locations throughout
winter, and the locations of one is represented
by purple dots and the other blue dots. Except
for a few cross overs along the border, each
respected the other's territory. (Story
continues below)
Why would a wolverine remain in the forest
during winter when nearly all of its prey has
migrated to lower elevations or hibernated? The
why part is unknown, but scientists know how
they survive winter conditions that would likely
kill other animals.
During winter, wolverines largely switch from
carnivores to scavengers, and they’re experts at
finding and consuming carrion, which explains
how a frozen deer leg was devoured like a
Thanksgiving turkey.
Wolverines can find food beneath a thick layer
of snow, and they even have a specialized upper
molar in the back of their mouths that helps
them chew meat that’s frozen solid.
That ability to find food in the dead of winter
is key to Fish and Game’s project. Ferguson and
Ott will continue to brave winter weather to
discover secrets that the cold, silent woods
reveal thanks to modern technology, skunk scent,
a frozen deer leg and wolverine’s keen senses. |
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