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GPS collars show the hidden lives of deer and
elk |
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December 8, 2017 |
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Story and photos by Roger Phillips
IDFG Public Information Specialist
The whup, whup, whup of a helicopter grows
louder as a herd of deer flees toward a trap. A
small army of Fish and Game staff and volunteers
hide as the animals run into a hidden net and
become entangled.
People rush to the thrashing animals, and within
seconds, untangle and calm them by placing a
mask over their eyes and carefully pin their
legs to their bodies. Then a quick, efficient
routine begins as the animals are measured,
weighed, health tested, and finally, fitted with
a collar.
That scene is repeated dozens of times every
winter for deer and elk, and it’s one of several
ways Fish and Game captures big game animals and
places collars on them to track their
whereabouts and learn more about their seasonal
movements and habits.
F&G does most of its capture-and-collar work
during winter because animals tend to be
congregated, easier to spot, and it’s typically
gentler on the animals to capture them in cooler
weather. It’s labor-intensive, and at times
dangerous, but important work for managing big
game herds.
Fish and Game crews will capture and collar
about 400 deer and 400 elk this winter. Most
collars go on fawns and calves to track their
survival over winter, then those collars fall
off after a few months as the animals grow.
F&G is adding more adults to the mix this year,
which also provide valuable information,
including migration routes, location of fawning
and calving areas, important winter and summer
range, and whether animals are loyal to certain
areas during winter or summer, or if they
wander.
The data also plugs into Fish and Game’s
“integrated population model,” which is a method
of analyzing data from collars, harvest
statistics and aerial surveys to determine
overall game populations and whether they're
increasing or decreasing.
Radio collars have been used for decades to
track animals, but advancements in GPS collars
that link with satellites give Fish and Game
biologists a better opportunity to learn about
animals without having to track them in the
field, which they have to do with VHF radio
collars. A biologist can track an animal with a
GPS collar in real time from any computer and
know exactly where they are, where they’ve been,
and night or day in any weather for up to four
years.
When an animal dies, the collar also emits a
mortality signal when it remains stationary for
a prolonged period. That triggers biologists to
go into the field, find the carcass and
determine the cause of death by performing a
“necropsy,” which is an animal version of an
autopsy. If it was killed by a predator, they
can usually determine whether it was a bear,
mountain lion or wolf based on how it was killed
and how the animal, or animals, fed on it.
“We have a better handle on what’s causing
mortality, and that’s a big benefit of GPS
collars over radio collars,” said Mike Elmer,
F&G’s data coordinator.
Aside from providing lots of important data, GPS
collars also provide some interesting (and
entertaining) insights and head-scratching
moments when animals do the unexpected, and here
are some examples.
White-tailed deer are known for being home
bodies, and unlike their mule deer cousins, they
don’t typically make seasonal migrations. But
one did, and University of Idaho graduate
student Kayte Groth explains the unexpected
travels of a whitetail doe:
In spring of 2017, we captured 40 white-tailed
does by helicopter and placed GPS collars on
them, which allows me to track locations every
15 minutes. I noticed a particular doe was
captured in April in Middle Potlatch Creek
canyon just southeast of Moscow.
The doe remained there for about two months
until about 4 a.m. on June 12, when she left the
canyon. Two days and 20 miles later, she arrived
at a new destination and settled on a canyon rim
overlooking the Snake River.
She remained there until July 25, then traveled
20 miles back to her original capture location
in Middle Potlatch Creek.
“Although we aren’t certain why this particular
doe embarked on such a journey, we speculate it
was due to fawning,” Groth said.
She may have felt safer on the canyon rim, and
once she felt that her fawn was big enough to
avoid predators, she returned. Traveling back
with a newborn fawn likely slowed her travels
and might explain why it only took her two days
to reach the fawning area, but six days to
return home to Middle Potlatch Creek.
We often think we know how and why big game
animals migrate. They typically follow the
family or herd as it travels from winter range
to summer range and back again. It’s a fairly
predictable migration as animals often use the
same, or similar, winter and summer ranges
throughout their lives.
Or do they?
Senior Wildlife Technician Clint Rasmussen
tracked two cow elk that seemed to have
first-class cases of wanderlust.
One was captured and collared in 2015 about 6
miles east of Fairfield in January 2015 while on
winter range. She then migrated about 40 miles
almost due north and summered near Alturas Lake.
Nothing out of the ordinary there, but in the
2016 winter, she overshot Fairfield and
proceeded nearly 75 miles south from Alturas
Lake and wintered in the Hammett area near the
Snake River. Maybe winter conditions forced her
farther south that year, or something else, it’s
difficult to know. But she returned to Alturas
Lake again for the summer of 2016.
Clearly she enjoys summers at Alturas Lake, and
if you’ve ever seen this sparkling mountain lake
in the Sawtooths, it’s easy to see why. But
apparently, she isn’t as faithful to her winter
range because, in 2017, instead of following the
geese south, she headed northeast about 45 miles
to Antelope Flat near Clayton.
Where did she go for summer, 2017? You guessed
it. Alturas Lake.
Another cow elk was captured in January 2015 on
the east side of Magic Reservoir about 25 miles
north of Shoshone. Then it migrated about 80
miles west during the following spring and
summered south of Arrowrock Reservoir, which is
east of Boise. In winter of 2016, it took a
relatively short hop southwest about 25 miles
and wintered near Mountain Home.
Her wanderlust kicked in again the following
winter, and she traveled northwest about 65
miles and summered north of Banks above the
North Fork of the Payette River, then wintered
about 30 miles south in the Boise Foothills.
Her travels ended on May 13, 2017 just south of
Arrowrock Reservoir when her collar registered a
mortality signal. Biologists found the dead elk
and determined she was killed by a mountain
lion.
Biologist Josh Rydalch shares a story about a
wandering mule deer, and how GPS collars have
changed what he jokingly refers to as “collar
and foller” biology.
Rydalch had a mule deer fawn GPS collared in in
the Birch Creek area west of Dubois in hunting
Unit 59A in December 2015.
In April 2016, it started traveling north as
green up occurred, which is like “surfing the
green wave to summer range,” Rydalch said.
The deer took a long jaunt north near Bozeman,
Montana, and by late July/early August, it
reached the Belgrade area. It lived on
media-mogul Ted Turner’s ranch that summer, a
distance of about 120 miles from where it was
collared. But the unusual thing about this deer
is it didn’t return in the fall like most mule
deer.
If the deer had a traditional VHF radio collar,
biologists would have to physically travel to
the general proximity of the animal to determine
its exact location, and it's highly unlikely
they would have traveled to Belgrade, Montana,
to look for it.
“This is an example of what these GPS collars
are showing us,” Rydalch said. “In the past, we
likely would have lost track of this deer and
probably dismissed it as having a malfunctioning
VHF collar and wrote it off.”
The doe died about a year after it was collared,
and with permission from the Turners, biologists
ventured onto the ranch, found the doe and
determined a mountain lion killed it.
“I am grateful they let us on to investigate the
scene and recover the GPS collar,” Rydalch said.
“We wouldn’t have known the animal’s location or
cause of death without it.”
GPS collars provide an interesting glimpse into
the lives of bighorn sheep. Biologist Rachel
Curtis has been part of team of biologists
tracking animals in the Owyhee Desert, where
they captured and collared rams and ewes in 2016
and 2017.
It’s an important time for bighorns because
prior to collaring the animals, there was a
deadly pneumonia outbreak in Oregon’s adjacent
bighorn herds, and biologists needed to know if
it affected Idaho’s sheep.
But the collars showed Curtis much more than
whether an animal was alive or dead. It showed
seasonal movements, or lack thereof, and how
rams behavior differs from ewes.
“It's been interesting to watch their movements
for the last two years because the ewes have
been very loyal to their home range and stay
close to the canyon, particularly when their
lambs are young,” she said.
Rams, on the other hand, are prone to wandering.
“Sometimes we can tell what's motivating them to
move, and other times, we can only guess,”
Curtis said.
As soon as hunting season starts, rams move if
they are spooked. They’re often bumped out of
their typical home range and travel miles away
and on the opposite side of a ridge. One
traveled about six miles after being disturbed.
While six miles might be an afternoon jaunt for
deer or elk in sagebrush country, in the Owyhee
Canyonlands, it means navigating steep canyons,
crossing rivers and finding a notch through
vertical bluffs on the other side, and often
repeating that sequence several times.
But that’s their home turf, and as Curtis
observed, rams aren’t shy about roaming,
especially when the rut starts.
One went on a walkabout looking for ewes that
took him five miles to the rim of a plateau
overlooking Duck Valley. Not finding any ewes
there, he stayed one night and returned home the
next day.
And sometimes rams roam for unknown reasons. One
ram was very faithful to his home range in a
particular stretch of the Owyhee River, or up
one small side canyon. But in April 2017, he
spent a week walking 15 miles upriver, then
turned around and went back.
One of the key facets of bighorn management is
disease control, so it’s important that
biologists know if bighorns leave one herd and
intermingle with others, and information
provided by GPS collars assist biologists in
knowing if that occurs.
It’s not always individual animals that surprise
biologists. F&G’s Elmer sees certain deer herds
that migrate seasonally, regardless of the
weather. Unit 39’s mule deer in the Boise River
drainage are a prime example. Rain, shine or
snow, they start migrating downhill during the
third week of October.
“It’s like clockwork,” Elmer said. “For this
particular group of animals, it seems to be a
time-frame thing more than weather.”
He said they’ve learned other herds in
south/central Idaho have similar time-based
migrations regardless of the weather.
GPS collars have changed the game for biologists
and technicians by providing and cataloging an
animal's location, rather than F&G staff driving
several times a month to track animals via radio
signals, or flying in aircraft to locate them.
When an animal with a radio collar died, unless
the timing was perfect, it might take days or
weeks to discover it died and find the carcass.
By then, a necropsy was difficult, not to
mention smelly, and getting good information on
what killed the animal was often a challenge. |
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