Minnesota moose die from wolves, ticks, abandonment and disease
- joseph marcoty, , Star Tribune.com
The first year of a landmark study found higher mortality rates than normal and listed several causes. Researchers say more work is needed.
A bull moose, sprouting the bumps of new antler growth on its head, grazed in a swamp off the Gunflint Trail in northeastern Minnesota — possibly one of the lucky ones in a declining population. One season of a high-tech study showed that the adult death rate was 18 percent; for calves, it was 71 percent.
It's tough to be a moose in Minnesota.
The deaths of 54 that were tracked as part of the
biggest and most high-tech research study ever
conducted on moose provide a rare glimpse into
the harsh life they face in the wild and help explain
why they are rapidly disappearing from
Minnesota's
North Woods.
biggest and most high-tech research study ever
conducted on moose provide a rare glimpse into
the harsh life they face in the wild and help explain
why they are rapidly disappearing from
Minnesota's
North Woods.
By far the greatest number, primarily calves,
were killed by bears and wolves. A number
were abandoned by their mothers; one drowned.
Three adults died from massive infestations of
winter ticks, and others succumbed to deer-
related
parasites and infections.
were killed by bears and wolves. A number
were abandoned by their mothers; one drowned.
Three adults died from massive infestations of
winter ticks, and others succumbed to deer-
related
parasites and infections.
Researchers said one season's worth of data
from
about 150 collared moose is not enough to
illuminate
trends or to provide solutions in how to help
them
rebound. But it's clear, they said, that more
are dying
than is normal.
from
about 150 collared moose is not enough to
illuminate
trends or to provide solutions in how to help
them
rebound. But it's clear, they said, that more
are dying
than is normal.
Calves suffered a 71 percent mortality rate
after only
one summer, said Glenn DelGiudice, the
wildlife
researcher for the Minnesota Department
of Natural Resources who is running the calf
research portion
of the study.
after only
one summer, said Glenn DelGiudice, the
wildlife
researcher for the Minnesota Department
of Natural Resources who is running the calf
research portion
of the study.
And the ones that made it so far still have to
survive
their first winter.
survive
their first winter.
Moose need a mortality rate of 50 or 55
percent in the
first year of life to maintain their population,
DelGiudice
said.
percent in the
first year of life to maintain their population,
DelGiudice
said.
The adult death rate was 18 percent, said
Michelle
Carstensen, who is running the adult research
for DNR
. If that rises to 30 percent in the winter, as
expected,
"that's not sustainable," she said.
Michelle
Carstensen, who is running the adult research
for DNR
. If that rises to 30 percent in the winter, as
expected,
"that's not sustainable," she said.
The number of moose in Minnesota plummeted
by
one-third last year, double the rate of previous
years.
by
one-third last year, double the rate of previous
years.
Results of the annual aerial moose survey
conducted
in January indicated that 2,760 moose were
left, down
from 4,230 in 2012.
conducted
in January indicated that 2,760 moose were
left, down
from 4,230 in 2012.
In 2006, the population in the northeastern
corner of the
state peaked at 8,840, but by then moose
had alread
y largely disappeared from the northwestern
corner of Minnesota, where they had long
beenpart of thelandscape.
corner of the
state peaked at 8,840, but by then moose
had alread
y largely disappeared from the northwestern
corner of Minnesota, where they had long
beenpart of thelandscape.
The sharp decline adds new urgency to the
effort to
understand why moose are dying in such
numbers.
So far, the project has been funded for two
years
with $1.2 million from the state, tribes and
the
University of Minnesota Duluth.
effort to
understand why moose are dying in such
numbers.
So far, the project has been funded for two
years
with $1.2 million from the state, tribes and
the
University of Minnesota Duluth.
Now researchers are hoping for another
$750,000
from the state in part to determine how
much of
an impact global warming may have
on the moose population.
$750,000
from the state in part to determine how
much of
an impact global warming may have
on the moose population.
Researchers want to attach devices on 30
moose that
measure ambient and body temperatures
to determine
whether heat stress from higher average
summer temperatures is playing a role
in their demise.
moose that
measure ambient and body temperatures
to determine
whether heat stress from higher average
summer temperatures is playing a role
in their demise.
A number of other studies have shown a
connection,
but none actually have provided the biological
evidence, DelGiudice said.
connection,
but none actually have provided the biological
evidence, DelGiudice said.
103 adult moose collared
In the first year of the study, wildlife crews
found and
collared 103 adult moose with GPS devices
that track
their every movement.
found and
collared 103 adult moose with GPS devices
that track
their every movement.
When they die, in a wilderness version of the
television
show "CSI," a signal alerts crews who rush
in and recover
the carcass to determine its cause of death.
The crews
include staff from the DNR, the U.S. Forest
Service,
and the Fond du Lac and Grand Portage
bands of Ojibwe.
television
show "CSI," a signal alerts crews who rush
in and recover
the carcass to determine its cause of death.
The crews
include staff from the DNR, the U.S. Forest
Service,
and the Fond du Lac and Grand Portage
bands of Ojibwe.
In springtime, when the GPS signals alerted
the crews that
the females were bedding down to give birth,
specially
trained crews that do the same work in western
states and Alaska carefully moved in to collar
50 newborn calves.
the crews that
the females were bedding down to give birth,
specially
trained crews that do the same work in western
states and Alaska carefully moved in to collar
50 newborn calves.
Despite taking all the precautions they could
think of, one frustrating and unexpected result
of the calf collaring is that
11 died, said DelGiudice.
think of, one frustrating and unexpected result
of the calf collaring is that
11 died, said DelGiudice.
Nine of them were abandoned by their mothers
One died
when a mother stepped on it during the attempt
to collar it
and one died for unknown reasons.
One died
when a mother stepped on it during the attempt
to collar it
and one died for unknown reasons.
The timidity of the mothers surprised the wildlife
experts who have done such collaring elsewhere,
DelGiudice said.
experts who have done such collaring elsewhere,
DelGiudice said.
In Alaska, the helicopters had to hover directly
above the handlers on the ground to keep the
mothers at bay. In one
case, the pilot had to nudge a mother moose
away with the helicopter strut.
above the handlers on the ground to keep the
mothers at bay. In one
case, the pilot had to nudge a mother moose
away with the helicopter strut.
"Here the mothers were skittish and would bolt
for distances," DelGiudice said.
for distances," DelGiudice said.
In addition to those 11 deaths, four calves slipped
their collars, leaving a total of 34 for the researchers
to follow. By the end
of the summer, 24 of them had died. Four were
eaten by
bears and another 16 most likely were killed by
wolves, though researchers aren't positive about
four of those. One drowned, two were abandoned
by their mothers well after being collared and one
died for unknown reasons.
their collars, leaving a total of 34 for the researchers
to follow. By the end
of the summer, 24 of them had died. Four were
eaten by
bears and another 16 most likely were killed by
wolves, though researchers aren't positive about
four of those. One drowned, two were abandoned
by their mothers well after being collared and one
died for unknown reasons.
If the 10 that are left survive the winter, their chances
are good, DelGiudice said.
are good, DelGiudice said.
Easy prey for wolves
Wolves also took about half of the 19 adults —
eight were direct kills and two died from infections
that developed from wounds, Carstensen said.
Three apparently healthy moose died for unknown
reasons.
eight were direct kills and two died from infections
that developed from wounds, Carstensen said.
Three apparently healthy moose died for unknown
reasons.
That raises tantalizing questions about the predator
deaths. Moose that are sickened or weak are
easy prey for wolves, which then eat the
evidence of what caused the decline in the
first place, she said.
deaths. Moose that are sickened or weak are
easy prey for wolves, which then eat the
evidence of what caused the decline in the
first place, she said.
That may be what happened to one moose whose
demise, by sheer chance, was witnessed by Amanda
McGraw and others in a group of graduate students
who were doing moose
habitat research near Isabella, Minn., during the first
week of September.
demise, by sheer chance, was witnessed by Amanda
McGraw and others in a group of graduate students
who were doing moose
habitat research near Isabella, Minn., during the first
week of September.
They saw an adult moose near the edge of a pond,
and
moved in to get a closer look and take photos. They
crawled through the long grass on their bellies, and
only as they got close did they realize that the moose
was sick and injured.
and
moved in to get a closer look and take photos. They
crawled through the long grass on their bellies, and
only as they got close did they realize that the moose
was sick and injured.
It ignored them, and then stumbled into the water,
where it couldn't get up.
where it couldn't get up.
They called in the moose wildlife crew and left to
finish their work. When the crew arrive two hours
later, the moose
already had been eaten by wolves that most likely
were
lurking in a nearby patch of poplars waiting for its
collapse.
finish their work. When the crew arrive two hours
later, the moose
already had been eaten by wolves that most likely
were
lurking in a nearby patch of poplars waiting for its
collapse.
She realized only later, McGraw said, that while
crawling through the grass she might have come
nose to nose with
a wolf.
crawling through the grass she might have come
nose to nose with
a wolf.