CREDITS: (PHOTO NICK GARBUTT/NPL/MINDEN PICTURES; (GRAPHIC C. BICKEL/SCIENCE; (DATA NATIONAL PARK SERVICE482 4 FEBRUARY 2022 • VOL 375 ISSUE 6580 science.org SCIENCEH
unters are killing gray wolves in
the northern Rocky Mountains in
numbers not seen since the animals
were nearly driven to extinction in
the continental United States in the
20th century. The recent killing of
some 500 wolves in Montana, Idaho, and
Wyoming—including nearly 20% of the
wolves that use Yellowstone National
Park—threatens to undermine a decades-
old effort to restore the predators to the
landscape and disrupt a long-term Yellow-
stone research project that has produced
influential findings on how wolves help
shape ecosystems. Researchers and environ-
mentalists are calling on officials to rethink
the hunts, which have eliminated more
than 15% of the wolves in the three states.
The loss of the Yellowstone wolves
“is a huge setback,” says biologist Doug
Smith of the National Park Service,
who leads the park’s wolf study, which
began in 1995. “We had in Yellowstone
one of the best models for understand-
ing the behaviors and dynamics of a
wolf population unexploited by hu-
mans.” Now, he says, researchers will
“do what we can to keep the science
going—what we have left of it.”
For decades, wolves were strictly
protected under the federal Endan-
gered Species Act (ESA), but 10 years
ago successful restoration efforts
prompted federal officials to ease pro-
tections and give state governments a
greater say in managing the species.
With wolf numbers in the northern
Rockies reaching about 3100 in late2020, several states have legalized or ex-
panded wolf hunts. Legislators in Montana,
for example, last year set a goal of shrink-
ing the state’s wolf population to “at least
15 breeding pairs,” the minimum required by
the ESA; state rules allow a person to kill up
to 20 wolves each season. Idaho also aims to
shrink its wolf population and has no kill lim-
its. Wyoming has nearly achieved its goal of
maintaining just 100 wolves and 10 breeding
pairs outside of Yellowstone (where hunting is
not allowed).
Biologists say the killings won’t cause the
regional extinction of wolves, although the
U.S. Fish and Wildlife Service announced
in fall of 2021 that it would review whether
“potential increases in human-caused mor-
tality” threaten the species. The losses will,
however, alter the social structure of wolf
packs—and reshape the Yellowstone study,which has produced high-profile findings on
how the return of wolves has affected willow,
aspen, and cottonwood stands as well as elk,
songbird, and scavenger populations. As of
31 January, hunters had killed 24 of the
roughly 125 wolves that use the park, includ-
ing five that carried tracking collars placed
by scientists. Hunters killed 19 in Montana
outside the park’s northern borders, where
officials had recently lifted quotas, and five in
Idaho and Wyoming.
Hunters have previously killed park wolves,
up to seven each year from 2009 to 2020 in
Montana. But the big new kill “complicates
the research as we will now have to account
for the confounding effects of hunting,” says
ecologist Dan MacNulty of Utah State Univer-
sity, who studies how wolves affect food webs.
Smith believes it will take 4 or 5 years for
the park’s packs to rebound from the losses,
and is now planning to study how hunt-
ing affects the wolves. Last week, he placed
tracking collars on wolves in the north-
ern part of the park, hoping to “compare
the persistence and reproductive rates” of
packs that have lost members with those
that haven’t. Studies have found packs
with more than eight members “are more
resilient” to diseases such as mange, Smith
notes, and can “have greater prey kill rates
and are better at territorial defense.”
Smith expects the park’s wolves, which
are a favorite attraction of visitors, to be-
come warier and more difficult to see.
Yellowstone superintendent Cam Sholly
has said he wants “to make the case” to
Montana officials “for reinstating quotas
that would protect the [park’s] core wolf
population.” But state leaders have shown
little interest, and Montana’s wildlife com-
mission recently declined to end hunting
in certain areas near the park. “We
don’t manage for individual wolves
or packs. We manage wolves across
landscape and population scales,”
says Greg Lemon, a spokesperson for
Montana’s wildlife department.
Wolf advocates fear such stances
will mean fewer wolves available to
start new packs elsewhere. (Still, one
nearby state, Colorado, is advancing
a plan to restore the canids.) And
they argue states are pursuing con-
tradictory policies. Montana and Wy-
oming, for example, want to reduce
elk populations that officials say have
grown too large. But they’ve also em-
braced killing a predator that could
help them reach that goal. “Their
management objectives,” MacNulty
says, “are at cross purposes.” jWolves feed on a bison carcass in
Yellowstone National Park.2016–Number of YNP wolves killed0510152025MontanaIdahoWyoming17–18 18–19 19–20 20–21 21–Nowhere to hide
Hunters have killed many more wolves that use Yellowstone National
Park (YNP) during the 2021–22 hunting season than in past seasons.Massive wolf kill disrupts long-
running Yellowstone park study
Hunters kill more than 500 wolves in surrounding states
CONSERVATION BIOLOGYBy Virginia Morell