May 01, 2012D espite their inherent behavioral differences, gray wolves and coyotes share one common dietary interest: venison. Where they coexist, white-tailed deer serve as the primary winter food for both predators.
Generally speaking, wolves are more adept at capturing adult deer whereas coyotes are more proficient at killing newborn fawns. Coyotes also tend to be more omnivorous -- meaning they eat vegetable as well as animal materials -- and tend to rely on scavenging deer remains, whereas wolves are more inclined to seek live prey. Even so, under the right conditions coyotes certainly can kill adult deer. In fact, some biologists contend that coyotes are doing a good job of replacing wolves in certain areas of the Northeast.
Needless to say, if they could share the same range, wolves and coyotes would make a deadly deer-killer team. The important question is, of course, since wolves also kill coyotes when given the chance (just as coyotes kill foxes), can the two canids coexist? Or, on the other hand, as wolves re-establish themselves, and become more socially organized, as they appear to be doing, will they gradually crowd-out coyotes?
The coyote was originally an animal of the western prairie, before the white man arrived with ax and plow. Since then, it has greatly extended its range in spite of man's traps, guns, and poisons. Indeed, man's past failed efforts to control coyotes seems to have resulted in a "super coyote."
In fact, pioneer ecologist Stanley P. Young suggested it may have been man's persecution that encouraged the coyote's spread through the centuries. In his famous book, The Clever Coyote, Young wrote: "Even among the human races may be found cases where persecution has encouraged the constant seeking of newer and greener pastures."
Today, coyotes can be found from well into Central America to near Point Barrow Alaska, eastward to Hudson Bay, New Brunswick, Maine, across most of the western and Midwestern U.S. Most recently (probably in the last 20 to 30 years), coyotes also have invaded the Southeast, where they are now abundant and highly controversial (see "Party Crashers" in the March 2011 Deer & Deer Hunting).
Gray wolves, on the other hand, have not fared so well in the presence of man. This canid occurs throughout the arctic and formerly occurred southward throughout the United States (except for the Southeast) and into Mexico. However, man extirpated wolves from almost all of the southern part of its North American range by the early to mid-1900s.
Due largely to improving habitat, human tolerance, reintroductions, and a number of contributing factors we don't fully understand, wolves have made an impressive comeback in the past couple of decades across portions of their former southern range. For example, according to Michigan DNR wildlife biologist Craig Albright, only three wolves called the Upper Peninsula (UP) of Michigan home in 1989. Today, there are nearly 700 wolves in the UP. About the same numbers have been tallied in northern Wisconsin and they are doing even better in northern Minnesota. In addition, wolves recently reintroduced to such areas as Yellowstone National Park seem to be thriving.
As wolves disappeared in the past, coyotes quickly moved in to occupy the vacated range. Now, the reverse seems to be taking place; wolves are moving into reclaim range coyotes have occupied for the past 100 years or more.
COVER STORY: Can wolves and coyotes coexist? As wolves disappeared in the past, coyotes quickly moved into occupy the vacated range. Now, the reverse seems to be taking place; wolves are moving into reclaim range coyotes have occupied. Rick Baetsen photos
Some biologists support the view that wolves will replace coyotes in certain areas. Others suggest the "clever coyote" will learn to coexist with wolves. There is scientific evidence to support both views.
The Isle Royale Story
Historically, wolves may have played an important role in replacing coyotes on Isle Royale, located at the west end of Lake Superior. In less than 60 short years, the coyote arrived on Isle Royale, prospered for a time, declined, then disappeared altogether.
According to the late Laurits Krefting, a long-time wildlife research biologist with the U.S. Bureau of Sport Fisheries and Wildlife, coyotes probably reached Isle Royale by traveling over the ice from the Sibley Peninsula region of Ontario, a distance of 15 miles, about 1906. (This is about the same time coyotes were first observed in Michigan's UP.) Despite the less than favorable habitat for them, coyotes flourished on the island, reaching peak numbers of about 150 animals, in 1948.
Krefting noticed that coyote numbers began to decline, starting in 1949, about the time wolves reached the island. The decrease in coyote numbers also came with a crash decline in the beaver population, a die-off of moose, and a low snowshoe hare population. Coyotes disappeared from Isle Royale in 1957 or 1958.
"Even at its best," says Krefting, "the habitat on Isle Royale was marginal for coyotes. When strict fire protection was put into effect, the changes in plant succession gradually produced an even less favorable habitat. A reduced food supply and direct killing by wolves are the factors that probably contributed most to the coyote's disappearance. A combination of these and other factors plus the fact that it was an island situation probably was necessary to cause coyote extinction."
Hence, this may have been a rather unique situation. Certainly, the ecological nature of the island (i.e., dense conifers and lack of openings) is not what one would picture as coyote country. And, given its insular condition, the island undoubtedly lacks the diversity in flora and fauna characteristic of the adjacent mainland. This means there are few alternate prey for coyotes.
In Manitoba, Canada, researcher Ludwig Carbyn observed that wolves frequently killed coyotes but did not eat them. He found no evidence that coyotes avoided wolves during most of the year, but definitely did so from mid- to late-winter.
Carbyn theorized that differences in snow conditions, and learning on the coyote's part, may be involved in the coyotes changing response to wolves as the winter progressed. When snow is deep and soft, coyotes are hindered more than wolves. However, since coyotes often trailed wolves through deep soft snow, Carbyn rationalized although coyotes may avoid wolves after a "refractory period," they may actually trail them at a safe distance in search of food.
Since wolves are territorial and may even kill their own kind when boundaries are trespassed, buffer zones exist between wolf territories where few wolves travel. Coyotes sometimes find these buffer zones safe havens. In Carbyn's study, coyotes were not always safe from wolves while in the buffer zone when wolf density was high. However, overall coyote survival appeared to be greater there during years of only moderate wolf density.
In another Manitoba study, Paul Paquet found coyotes scavenging wolf-killed deer within 24 hours after abandonment by wolves. Although wolves occasionally killed coyotes, Paquet saw no evidence of wolves actively searching for coyotes. Neither was there any evidence that coyotes adjusted their movements to avoid wolves.
In the area where Paquet conducted his study, elk served as the major winter food for both wolves and coyotes wolves killed elk while coyotes scavenged the remains. In this regard, coyotes weren't dumb. As Paquet notes, "Because predation on [large prey] involves considerable risk of injury and is likely energetically expensive owing to a low rate of success, there is no apparent advantage in killing prey if good quality food can be scavenged."
This wolf-coyote relationship is interesting because the primary source of food was large prey, leaving enough food for both wolves and coyotes. However, it may be a different story when both predators must exist primarily upon smaller prey such as deer.
"If deer are the preferred prey," notes Paquet, "then coyotes lose the opportunity to scavenge wolf kills because wolves preying on deer leave few remains."
Findings from studies conducted by Minnesota researcher Glen DelGuidice add a new twist to this story. Apparently, during especially severe winters (i.e., deep snow for four to eight weeks), wolves exhibit surplus killing of deer with no or low consumption of the carcass. Under such conditions wolves may kill many more deer than normal and benefit coyotes by leaving more for them to scavenge.
Recolonizing Wolves in Montana
One of the more recent investigations into coyote-wolf interactions was by Todd Atwood and Eric Gese. They conducted their work during the winters of 2003-04 and 2004-05, in northern Montana. This was shortly after wolves recolonized the region, presenting a unique opportunity to determine how naive coyotes adjust to the sudden presence of a competitively dominant canid that might threaten coyote survival in the region.
Atwood and Gese followed the activities of 29 radio-collared coyotes, belonging to 11 packs living within the 187 square mile home range of the Bear Trap wolf pack. Before pups were born, coyote pack size averaged 4 adults. Wolf pack size varied from 2 to 8 and averaged 5 individuals. In addition, the researchers followed nearly 1000 miles of coyote tracks and over 300 miles of wolf tracks in the snow.
Atwood and Gese located 92 wolf kills (presumably elk and deer), 77 (85 percent) of which were visited by coyotes. They witnessed 36 conflicts, involving 6 different coyote packs and the Bear Trap wolf pack, at wolf-kill sites. Although coyotes gained possession of the contested carcass on 17 occasions, all such carcasses were already nearly depleted. During the course of study, wolves killed one adult coyote and 2 pups, whereas 3 adult coyotes were killed by cougars; all such mortalities occurred within 200 meters of a wolf-killed deer or elk.
In most cases, wolves were able to drive coyotes away from deer or elk kill sites until they had their fill. Generally, coyotes gained access to wolf killed prey only when coyotes outnumbered wolves and only after wolves had already consumed most of their kill.
Interestingly, coyotes were able to spend more time at wolf-kill sites during the second winter of study, as compared to the first. As a result, formerly naive coyotes might have learned, through previous experience, to exploit carcasses in the latter stages of consumption when wolves were more inclined to back off.
Atwood and Gese concluded the following: "Coyotes do not perceive wolves as a threat requiring generalized spatial avoidance. Rather, the threat of aggressive interactions with wolves is spatially discrete and primarily contained to areas adjacent to carrion resources."
Although the researchers don't dwell on the point, these findings imply that coyotes in northern Montana are learning to cope with wolves, and may even benefit from the larger canid's presence.
The gray wolf is definitely coming back to re-claim historic range it lost to coyotes decades ago. What will happen to coyotes in the meantime is anyone's guess. Some predict the demise of coyotes, whereas others believe coyotes will adjust, and maybe even prosper, in the presence of a more dominant canid. I suspect
the outcome will vary from one area to the next, depending upon a host of environmental circumstances.
Ironically, at least across the whitetail's northern range, both predators will benefit from man's mismanagement of deer wintering habitat. Resultant poor quality winter habitat, when coupled with the presence of two capable deer predators, will undoubtedly lead to excessive deer mortality during and following severe winters -- and ultimately contribute to declining deer numbers.
Just remember, coyotes are survivors. They are the clever predator that humans couldn't eradicate with all their traps, poisons, and guns. I don't expect wolves to be any more successful. In fact, here in Michigan's UP, deer hunter sighting rates of coyotes have doubled, while that of wolves have tripled, in the past 10 years.