KITCHIN AND HURST/ALL CANADA PHOTOS/CORBIS
Wolf genes make the coyotes of northeastern North America bigger and stronger than those elsewhere.
Near the dawn of time, the story goes,
Coyote saved the creatures of Earth. According to the mythology of
Idaho's Nez Perce people, the monster Kamiah had stalked into the region
and was gobbling up the animals one by one.
The crafty Coyote evaded
Kamiah but didn't want to lose his friends, so he let himself be
swallowed. From inside the beast, Coyote severed Kamiah's heart and
freed his fellow animals. Then he chopped up Kamiah and threw the pieces
to the winds, where they gave birth to the peoples of the planet.
European colonists took a very different view of the coyote (
Canis latrans)
and other predators native to North America. The settlers hunted wolves
to extinction across most of the southerly 48 states. They devastated
cougar and bobcat populations and attacked coyotes. But unlike the other
predators, coyotes have thrived in the past 150 years. Once restricted
to the western plains, they now occupy most of the continent and have
invaded farms and cities, where they have expanded their diet to include
squirrels, household pets and discarded fast food.
Researchers
have long known the coyote as a master of adaptation, but studies over
the past few years are now revealing how these unimposing relatives of
wolves and dogs have managed to succeed where many other creatures have
suffered. Coyotes have flourished in part by exploiting the changes that
people have made to the environment, and their opportunism goes back
thousands of years. In the past two centuries, coyotes have taken over
part of the wolf's former ecological niche by preying on deer and even
on an endangered group of caribou. Genetic studies reveal that the
coyotes of northeastern America — which are bigger than their cousins
elsewhere — carry wolf genes that their ancestors picked up through
interbreeding. This lupine inheritance has given northeastern coyotes
the ability to bring down adult deer — a feat seldom attempted by the
smaller coyotes of the west.
The lessons
learned from coyotes can help researchers to understand how other
mid-sized predators respond when larger carnivores are wiped out. In
sub-Saharan Africa, for example, intense hunting of lions and leopards
has led to a population explosion of olive baboons, which are now
preying on smaller primates and antelope, causing a steep decline in
their numbers.
Yet even among such
opportunists, coyotes stand out as the champions of change. “We need to
stop looking at these animals as static entities,” says mammalogist
Roland Kays of the North Carolina Museum of Natural Sciences in Raleigh.
“They're evolving”.
At a fast rate, too. Two
centuries ago, coyotes led a very different life, hunting rabbits, mice
and insects in the grasslands of the Great Plains. Weighing only 10 to
12 kilograms on average, they could not compete in the forests with the
much larger grey wolves (
Canis lupus), which are quick to dispatch coyotes that try to scavenge their kills.
SOURCE: COOK COUNTY, ILL., COYOTE PROJ. & S. GEHRT, OHIO STATE UNIV.
The big break for coyotes came when
settlers pushed west, wiping out the resident wolves. Coyotes could
thrive because they breed more quickly than wolves and have a more
varied diet. Since then, their menu has grown and so has their range;
they have invaded all the mainland United States (with the exception of
northern Alaska) and Mexico, as well as large parts of southern Canada
(see
'On the move').
The
animals that arrived in the northeastern United States and Canada in
the 1940s and 50s were significantly larger on average than those on the
Great Plains, sometimes topping 16 kilograms. Kays and his colleagues
studied the rapid changes in coyote physique by analysing mitochondrial
DNA and skull measurements of more than 100 individuals collected in New
York state and throughout New England. They found
1
that these northeastern coyotes carried genes from Great Lakes wolves,
showing that the two species had interbred as the coyotes passed through
that region. “Coyotes mated with wolves in the 1800s, when wolf
populations were at low density because of human persecution,” says
Kays. In those circumstances, wolves had a hard time finding wolf mates,
so they settled for coyotes.
Compared with
the ancestral coyotes from the plains, the northeastern coyote–wolf
hybrids have larger skulls, with more substantial anchoring points for
their jaw muscles. Thanks in part to those changes, these beefy coyotes
can take down larger prey; they even killed a 19-year-old female hiker
in Nova Scotia in 2009. The northeastern coyotes have expanded their
range five times faster than coyote populations in the southeastern
United States, the members of which encountered no wolves as they
journeyed east.
New to the city
Coyotes
have even moved into Washington DC, appearing in Rock Creek Park in
2004, just a few miles from the White House. Christine Bozarth, a
conservation geneticist at the Smithsonian Institution in Washington,
has tracked their arrival and has shown that some of them are descended
from the larger northeastern strain and carry wolf DNA
2.
Bozarth says the coyotes are there to stay. “They can adapt to any
urban landscape; they'll raise their pups in drainage ditches and old
pipes,” she says. She hopes that the coyotes will help to control the
deer, whose numbers are booming. But Kays says that coyotes have not
made a significant dent in the northeast's deer population. “Coyotes
fill part of the empty niche, but they don't completely replace wolves,”
he says.
Oddly enough, it is the smaller
coyotes in the southeastern United States that seem to be having a real
impact on deer. About the same size as western coyotes, the southeastern
ones have begun to exploit a niche left empty by the red wolves (
Canis lupus rufus) that once roamed the southeast and specialized in hunting the region's deer, which are smaller than those in the northeast.
John
Kilgo, a wildlife biologist with the US Forest Service in New Ellenton,
South Carolina, and his colleagues found in a 2010 study
3
that South Carolina's deer population started to decline when coyotes
arrived in the late 1980s. More recently, he and his colleagues have
studied deaths among fawns, using forensic techniques right out of a
murder investigation
4.
They analysed bite wounds on the carcasses and sequenced DNA in saliva
left on the wounds. They also searched for scat and tracks left by the
killers and noted how they had stashed uneaten remains. More than
one-third of the fawn deaths were clearly caused by coyotes, and
circumstantial evidence suggests that the true number might be closer to
80%. “Coyotes are acting as top predators on deer, and controlling
their numbers,” says Kilgo.
At first, many
researchers had a hard time accepting that conclusion because they
thought that coyotes were too small to affect deer populations, Kilgo
says. He hopes to study how the newly arrived coyotes will affect other
members of the southeastern ecosystem, including wild turkeys and
predators such as raccoons, foxes and opossums.
There
is no danger that the southeastern coyotes will drive the abundant deer
in that region to extinction. But at the northern extreme of their
range, coyotes are threatening a highly endangered band of woodland
caribou (
Rangifer tarandus caribou) in the mature forests of
Quebec's Gaspésie National Park. Logging and other changes there had
taken a toll on the caribou even before coyotes arrived in the region in
1973 and settled into newly cleared parts of the forest. But then
coyotes started hunting caribou calves and the population dropped even
further.
A 2010 study
5
found that coyotes accounted for 60% of the predation on these caribou,
which now number only 140. Dominic Boisjoly, a wildlife biologist with
Quebec's Ministry of Sustainable Development, Environment and Parks in
Quebec City, says that the best way to protect the caribou would be to
cease clear-cutting of the forest, thereby denying the predators a home.
Coyotes
have been taking advantage of the changes wrought by humans for many
thousands of years, according to a study of coyote fossils published
this year
6.
Evolutionary biologist Julie Meachen at the National Evolutionary
Synthesis Center in Durham, North Carolina, and Joshua Samuels at the
John Day Fossil Beds National Monument in Kimberly, Oregon, made that
discovery by measuring the size of coyote fossils dating back over the
past 25,000 years. During the last ice age, coyotes were significantly
larger than most of their modern counterparts and resembled the biggest
of the present-day coyote–wolf hybrids in the northeast. They probably
scavenged meat from kills made by dire wolves and sabre-toothed cats,
and preyed on the young of the large herbivores, such as giant ground
sloths, wild camels and horses, that thronged North America at that
time.
But at the close of the ice age, about
13,000 years ago, most of the megafauna vanished — an extinction
attributed to both climate change and the appearance of efficient Stone
Age hunters. With them went the largest predators, allowing the smaller
grey wolves to fill the vacant niche, which put them in competition with
the largest coyotes. That conflict, as well as the loss of large
herbivores, caused coyotes to shrink in stature. Within 1,000 years of
the Pleistocene extinctions, coyotes had reached the same size as in
most present-day populations.
Now, they're going through a whole new set of changes as they adapt to the modern landscape of North America. Genetic studies
7
show that some coyotes are even interbreeding with dogs, which could
lead to a different sort of hybrid animal. Researchers are struggling to
keep up with the animals and their impacts as they lope into more new
regions.
“Invading a landscape emptied of
wolves may trigger a whole new pathway in terms of the coyote's
evolution,” says Bill Ripple, an ecologist at Oregon State University in
Corvallis. “And the coyote's arrival will have unpredictable effects on
other species in the ecosystem.”
