No Longer Top Dog
Studies of coyotes in Yellowstone National Park show that wolf reintroduction is changing the canine social hierarchy
Roger Di Silvestro
Biologist Bob Crabtree and several of his colleagues expected nothing out of the ordinary that June day in 1995. As usual, the researchers were perched at vantage points above the Lamar River Valley in the northeast corner of Yellowstone National Park. As always, the river's clear, cold waters ran in lazy curves through rich meadows flanked by tree-crowned ridges. Elk, bison, deer and pronghorn grazed as expected among the tall grasses. The animals that held the biologists' attention--a group of four coyotes that Crabtree had dubbed the Norris Peak Pack after a local landmark--were where they should be, with their pups at a den on one of the ridges.
But then something occurred that no one had seen in the park in recent memory, if ever. A pack of five wolves moved across the valley floor and caught sight or smell of the coyotes. The wolves immediately moved toward the ridge and the den. The coyotes, bound to the spot by attachment to their young, yelped and howled as the wolves drew near. While their caterwauling might have discouraged the advance of other coyotes, the wolves did not break stride. When they reached the den, they attacked. Outweighed perhaps three to one, the coyotes fought a losing battle for 15 minutes, then fled. The wolves tried to dig out the coyote den. That evening the biologist found a dead pup at the den site.
The incident answered one question that had been preying on Crabtree's mind since the U.S. Fish and Wildlife Service had released 14 gray wolves from Alberta into the park the previous March: Would the wolves kill park coyotes? With that answered, he could go on to other matters: "Coyotes will survive wolf reintroduction," he says, "but the question is, how? Will the coyote's social structure change? Will wolves affect what coyotes prey upon? And how deeply will coyotes decline?"
The extirpation of Yellowstone wolves is an artifact of the earliest era of modern wildlife management. In 1872, Congress made Yellowstone the world's first national park. Before the decade was out, administrators were trying to kill off park predators on the assumption that wiping out wolves, coyotes, cougars and bobcats would protect hoofed animals. The fact that elk, deer, bison and moose had thrived under a full ecological complement of predators seems to have eluded the policy makers.
The control effort continued into the 1930s, but Yellowstone's wolves had been wiped out during the previous decade. All other park predators survived. Now, under an endangered-species recovery plan, the federal government is reintroducing wolves to the park in an effort to restore natural balances. For Crabtree, his coyotes and the Yellowstone ecosystem, the reintroduction signals an ecological revolution that will reverberate through the lives of the many species with which the wolves will coexist, including coyotes, elk, grizzlies and even, Crabtree's studies suggest, rodents.
Crabtree made his first professional visit to Yellowstone National Park in 1974, when he worked as a busboy at Old Faithful Inn. That was also the year he saw his first coyote and got hooked on the animals. "I've always liked dogs," he says, "and after I saw my first coyotes, I knew that was the species I wanted to study."
Crabtree was only a high-school student then, but his interest in animals already went back many years. Born in Astoria, Oregon, he moved to Moscow, Idaho, when he was five. His father had died when he was young, but in Moscow, a university town, he met three biologists who became, he says, "surrogate fathers" and sparked his interest in wildlife research. By the sixth grade, Crabtree knew he wanted to be a biologist. He published his first scientific paper while still an undergraduate. In 1985, he started a four-year study of coyotes at the Hanford Nuclear Reservation in southwestern Washington. There he honed the skills that would serve him at Yellowstone, where, in 1989, he began a long-term coyote study at the invitation of the National Park Service.
Photo By George Harrison
Coyote in Glacier National Park
Yellowstone was the ideal place for his work because park
coyotes are virtually undisturbed by human activities. This is a
rare find in the United States, where the federal Animal Damage
Control program has killed tens of thousands of the animals every
year for decades. "When a wildlife population is under that
kind of pressure, its social and biological character breaks
down," says Crabtree.
The coyote is a smallish, predominately brown canine native
to Mexico and the western United States and Canada. Though
subject to the same control efforts that killed off almost all of
the nation's wolves, the coyote during the past century has
expanded its range into Alaska, Central America and eastern North
America as far as Nova Scotia. This success was a result of the
coyote's adaptability. While gray wolves specialize in hunting
large hoofed animals, coyotes are generalists that feed on
everything from elk to mice and don't turn up their noses at
refuse, eating out of garbage cans in urban settings such as New
York City and Los Angeles. Crabtree estimates that insects make
up 5 to 10 percent of the coyote diet in Yellowstone.
Crabtree's studies are done under the auspices of Yellowstone
Ecosystem Studies (YES), a research group that Crabtree founded
in 1993. He raises funds through YES, then links graduate
students and other scientists with research projects. He also
accepts untrained volunteers, who make a donation to YES and work
under professional guidance. Crabtree and his colleagues have
tallied about 450 coyotes in 65 packs in Yellowstone's northern
range. The largest and, in Crabtree's estimation, most successful
is the Bison Peak Pack.
Although coyote packs generally comprise two to ten animals
led by the most dominant male and female, called the alpha
animals, the Bison Peak Pack, during one bumper-crop breeding
season, included 11 adults with 12 pups. This small army was made
possible, Crabtree believes, because the pack's territory lies on
some of the richest land in the Lamar Valley, a site replete with
rodents and herds of hoofed prey.
Like all coyotes, the Bison Peak animals maintain their
territorial pawhold by leading lives reminiscent of Shakespearean
drama. The alpha male and female rule like a king and queen, and
only they produce pups. The lower-ranking, beta animals exist
mainly to serve the alphas' fiefdom. Likely to be pups from
previous years, the betas help to raise subsequent litters and
protect the territory.
The alpha male decides when and where the pack will hunt and
is almost invariably the first of the pack to attack, going head
to head with animals such as elk, which may outweigh him more
than twentyfold. This leadership role comes with a price: The
face of one former Bison Peak alpha male was heavily scarred by
the travails of predation and intraspecies warfare.
The Bison Peak's territory, like that of all packs, adjoins
the domains of other coyotes. Occasionally, neighboring packs
transgress on one another's land. If caught, a snarling battle
may ensue. However, coyotes are gifted in the art of biological
diplomacy. Inherited behaviors--certain vocalizations and body
postures--indicate submission, surrender and retreat, allowing
interlopers to escape alive. Friendly meetings also occur between
members of different packs. Crabtree has seen the alpha female
from the adjacent Amethyst Pack pay amiable visits to Bison Peak
coyotes. He suspects that her father was once a Bison Peak beta.
In Yellowstone, alphas usually ascend to their positions when
two to five years old and may hold on to them for years. Though
the average coyote lives only six years, Crabtree says, many beat
the odds. The oldest on record was a Colorado animal that lived
16 years. One former alpha female of the Bison Peak Pack was more
than 13 years old when she was killed and eaten by a cougar.
The death of an alpha offers a chance for one of its beta
offspring to advance in coyote society. A younger male in the
Bison Peak group took over after the alpha male was killed by a
snow plow as he crossed the Lamar Valley road one winter day. But
betas do not always wait until an alpha dies. Sometimes, like an
ambitious prince, a beta will make a power play against a
reigning monarch: "In about half of territorial
takeovers," Crabtree says, "betas throw out the alphas.
In the other half, outside loners do the job."
Loners wander a social and biological netherworld in the
unclaimed margins between territories. Mature animals that lack a
home, loners make up about a fifth of the coyote population and
are ever vigilant for signs that an alpha is losing power or has
died, offering a chance to take over. When an alpha is deposed,
it generally takes up residence on the fringes of its old
Alpha males and females mate for life. Courtship begins in
December in Yellowstone as the paired animals work in tandem to
mark territorial boundaries with sprays of urine. The alphas mate
in February, and pups are born in April in underground dens.
A pack may have as many as 10 den sites on its territory and
may move young pups from den to den, perhaps to avoid other
predators or to reduce the chance of insect infestation. Coyotes
use dens handed down from previous generations. The Bison Peak
Pack in 1992 was using a den at which biologist Weldon Robinson
had captured pups in 1946. Crabtree has discovered that at least
75 percent of the dens in the Robinson study are still in use.
Coyotes use dens only for sheltering pups. At 12 weeks of age
the pups begin to travel with the adults, and the pack abandons
den life. Kazia Hatier, one of Crabtree's graduate students,
found that the highest pup mortality occurs from mid June to
early August as the pups enter the world beyond the den.
Generally, only two pups from an average litter of six survive
into adulthood. Much of pup success depends on food availability.
Alphas always eat first. If nothing is left over, pups and betas
Which suggests that the life of a predator, even in a place
like Yellowstone, is not an easy one. Of 6,433 encounters between
coyote and prey that Eric Gese, a doctoral student working on the
coyote project, has tallied, only 1,545 concluded successfully
for the coyote. Nevertheless, Crabtree's research has shown that
coyotes as a species annually kill more elk than any other park
predator. In the northern range, home to 20,000 elk, coyotes
yearly take about 1,350 elk, grizzlies 780 and cougars 612.
Most of the elk that coyotes kill are calves, preyed upon
mainly in early summer. During the warm months, coyotes also take
advantage of the park's rodent smorgasbord. Crabtree was
surprised to find how large a dent coyotes can make in rodent
populations. "In the Lamar Valley," he says, "they
take 23.6 percent of all pocket gophers, 35.2 percent of ground
squirrels and a huge 76.2 percent of all voles."
In winter, a fresh stock of elk calves is months away and
rodents are scarce, so coyotes turn to killing adult deer and
elk. Even ailing elk make impossible quarry for a lone coyote.
But Yellowstone coyotes have numbers on their side, attacking as
packs. They also use patience as a weapon. A park ranger once
reported a pack of coyotes that for seven days besieged an elk
that had taken refuge in a stream. The pack finally killed the
elk when fatigue drove it ashore.
Even when food is readily available, coyotes do not come
easily to their place at the table. Other predators demand a
seat, too. Cougars, Crabtree believes, kill 5 to 10 percent of
the park's coyote population every year. And now the coyotes have
to contend with the gray wolf.
Prior to extinction of the wolf in Yellowstone, the park's
canines lived under a distinctly hierarchical system in which
wolves dominated coyotes and coyotes dominated red foxes. The
extent to which wolves persecuted coyotes in Yellowstone is
unknown, but one of Crabtree's studies found that 71 percent of
interactions between coyotes and foxes in the Lamar Valley are
aggressive, with 40 percent fatal to the fox.
Now it may be the coyote's turn to experience suppression. In
the year following the Yellowstone wolf release, Crabtree
recorded that the newcomers had killed 12 adult coyotes in the
Lamar Valley. He estimates that wolves may have accounted for a
total of 48 dead coyotes since the first release, perhaps 25
percent of the Lamar coyote population. "Wolves will be a
lot more effective at controlling coyotes than the old park
trappers ever hoped to be," Crabtree says.
Crabtree and the park's wolf biologists have discovered that
who beats whom among coyotes and wolves is a matter of numbers.
In the Lamar valley, the dead coyotes were the victims of nine
resident wolves. But in a north-central part of the park called
Blacktail Plateau, where only two wolves have set up shop, it's a
different story. Wolf biologist Michael Phillips discovered last
winter that this duo was killing far more elk than he would have
expected. Subsequent research showed that a pack of six coyotes
was driving the wolves off their kills, forcing them to hunt more
frequently than they ordinarily would.
Such data only hints at things to come. One of Crabtree's
studies suggests that, with wolves in the equation, elk, bison
and moose numbers may be trimmed by 8 to 20 percent. Coyotes are
likely to decline, perhaps steeply. If they do,
pronghorn--heavily hunted as fawns by coyotes but too small to
interest wolves--may increase. And how will a drop in coyotes
affect voles, the rodents of which coyotes devour so many? Will
grasslands, eaten by a growing rodent horde, suffer? Or will red
foxes, freed of coyote suppression, glut on the rodents and
experience a population boom?
The federal government released 17 more Alberta wolves into
the park last April. This will increase pressure on the coyotes,
but perhaps they will be up to it. "Yellowstone coyotes are
bigger and stronger than those elsewhere, perhaps because, in the
absence of wolves, they have turned to hunting big game,"
Crabtree says. "The loss of wolves may have yielded a super
coyote, so maybe they'll hold their own against the wolves. Or
maybe they'll sink back to underdog status. That's one of the big
questions that I hope to answer in the future."
Roger Di Silvestro, a senior editor on this magazine,
sometimes wishes he had been raised by wolves.
Watch Wolves On NWF Television
National Wildlife Productions, NWF's TV and film division, tells
the wolf-reintroduction story in "The Wolves Return to
Yellowstone," airing on TBS Superstation initially at 9 p.m.
E.S.T. Sunday, November 3, and three more times in ensuing weeks.
The program, hosted by Matt Fox of television's "Party of
Five," documents every detail of the highly controversial
recovery effort, from the battles at public hearings to the
release of wolves in Yellowstone.
Restoring the Wolf
The National Wildlife Federation has campaigned for wolf
reintroduction since the early 1980s. Tom Dougherty, NWF's
Western Staff director, served on the federal Wolf Management
Committee, helping to develop the reintroduction proposal. Such
efforts yielded an outpouring of public support and resulted in
release of wolves in Yellowstone and Idaho beginning in 1995.
Recently, NWF helped defeat a lawsuit brought by Montana ranchers
to stop the release of more wolves. "Our efforts would not
have been successful without active public support," says
Dougherty. "Wolf reintroduction demonstrates the flexibility
of the Endangered Species Act and shows that large predators can
coexist with humans."