May 2012, Week 4


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Sun, 27 May 2012 22:12:28 -0400
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Coyotes Are the New Top Dogs
Coyotes are champions of change and have evolved in 
clever ways to take advantage of a human-dominated 
By Sharon Levy of Nature magazine
Scientific American
May 17, 2012

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

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.

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

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 analyzing mitochondrial DNA and skull measurements of
more than 100 individuals collected in New York state
and throughout New England. They found 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. 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

John Kilgo, a wildlife biologist with the US Forest
Service in New Ellenton, South Carolina, and his
colleagues found in a 2010 study 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. They
analyzed 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

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

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 Gasp├ęsie 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 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.
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 saber-
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

Now, they're going through a whole new set of changes as
they adapt to the modern landscape of North America.
Genetic studies 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

This article was first published on May 16, 2012 in
Nature magazine.


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