Sunday, January 9, 2011

Tweed Wolf, The Eastern Coyote

Many years ago... Across a grassy meadow on the Kaibab Plateau in Arizona, a single hunter loped. I watched this carnivoran from a distance through my spotting scope, and momentarily I thought I was watching a fox. Then I realized the solitary predator was a coyote. I was on the north rim of the Grand Canyon, and I was watching my first western coyote while a sky blue Mountain Bluebird watched me in turn from a nearby perch. Why did I momentarily mistake this creature for a fox? Because it was noticeably smaller and daintier than the coyotes I was familiar with in my native New England. But why would this be?

"The idea of wilderness needs no defense. It only needs more defenders." Edward Abbey

Western Coyote (Canis latrans) Photographed by Jim Zipp in New Mexico
Eastern Coyote In Connecticut by Paul Fusco
Canis latrans. Eastern Coyote. "Tweed Wolf." Now common in New England, this icon of the wild is a relatively new arrival here. There are many people still living who were born before the Coyote came to New England. Before Europeans came to settle northeastern North America, the landscape of the region was mostly forested. This was not the habitat of the Coyote, a species that had evolved to prey on small mammals in the open grasslands and deserts of the west. The forested landscape of New England was the habitat of the White-tailed Deer and the Moose, and it was the home of the Wolf. Wolves once roamed virtually all of what is now the lower 48 states and nearly all of North America. Generally speaking, two species of North American wolf were historically recognized, the Red Wolf (canus rufus) of the southern and southeast United States, and the Gray Wolf (Canus lupus) in the west and northeast. It was long recognized however that the wolves in New England and southeastern Canada were smaller than the Gray Wolves of the west. These eastern wolves were considered a subspecies of Gray Wolf, and as such they were identified as canis lupus lycaon. Now the genetic evidence strongly suggests otherwise, that the eastern "Gray" wolves are a separate species, the Great Lakes Wolf (Canis lycaon.)

Great Lakes Wolf (Canis lycaon) USFW Photo
A predator's evolutionary course and success is based on the prey it hunts. In the northeast, the Great Lakes Wolf evolved to hunt the White-tailed Deer (Odocoileus virginianus). This was a species of the eastern deciduous forest. North of the White-tailed Deer's range, where the larger ungulate the Moose (Alces alces) dominated in coniferous forests, the Great Lakes Wolf range ended and it was replaced by the larger Gray Wolf. The Great Lakes Wolf is not large enough to hunt Moose efficiently. Its head and jaw are too small and lack the musculature to bite and hang onto the larger more powerful ungulate. This predator prey size relationship acts as a biological barrier against a predator species' range expansion. The predator can not expand into areas where reliable prey doesn't exist. So before Europeans came to America, The Great Lakes Wolf roamed the northeast, the Coyote loped across the southwest, the Red Wolf hunted the southeast, and the Gray Wolf howled throughout the west and the far north. The distribution of these carnivorans was determined by prey, habitat, and biological barriers in a natural balance.

White-tailed Deer (Odocoileus virginianus) Prey of the Great Lakes Wolf. Photo by Paul Fusco

Moose (Alces alces) One of the primary prey species of the Gray Wolf in eastern North America.  Photo by Jim Zipp
With the coming of Europeans came great and sweeping changes in the landscape and fauna of the northeast. The forest was felled and replaced by agriculture and grasslands. The wolf was feared and reviled and hunted relentlessly. Eventually no wolves were left alive in the northeast. The numbers of Moose fell as well, and the species' range withdrew northward. The predator prey balance was destroyed and the faunal diversity of New England plummeted. The wolves were gone. The predators that remained, Black Bears in small numbers in rugged mountain retreats, Gray Foxes in declining numbers, adaptive Red Foxes in increasing numbers, and Bobcats in small numbers, were no threat to White-tailed Deer that remained. The ecosystem of the northeast was forever altered.

Bobcat (Lynx rufus) in Connecticut. Photo by Paul Fusco.
The anthropogenic changes wrought on the northeast by the early Europeans were not to last unchanged either however. The open grasslands and agricultural lands slowly gave way to reforestation as farming and herding dwindled as major components of human land use. With the patchwork reforestation, and without a predator of ungulates, the White-tailed Deer flourished and expanded farther north than it had historically existed. Where once Moose fled before Gary Wolf packs, now White-tailed Deer existed untroubled by hungry carnivorans and soon the Deer population was larger than ever. The northeast was ripe for a large predator. But which one could exploit this open niche? By the twentieth century, wolves were greatly diminished or extirpated from much of their former ranges across North America. Not only had the wolves been been subjected to an organized slaughter by man, they had also starved as their prey dwindled. The survival of the Gray Wolf requires large numbers of Bison, Elk, Black-tailed Deer, Moose, and other large ungulates. These species's numbers also crashed as the new "Americans" moved westward. But one North American carnivoran could succeed in the now fractured and battered ecosystems of North America. The stage was set for the great success of the Coyote.

Coyote in Connecticut. Photo by Jim Zipp
 The combination of an altered landscape and the removal of the Wolf allowed the Coyote to expand its range. The Coyote preys primarily on smaller mammals than the Wolf. While large wolves do eat small mammals as well, the species can not survive without large prey animals. The wolf packs were gone, and Coyotes, though persecuted by man as well, moved in. The expansion was rapid. In the late 1800's and early 1900's the species reached Ontario west of the Great Lakes and then continued to rapidly expand eastward north of the lakes. It is believed that the expansion north of the lakes was pioneered by just a few individuals. While this northern route was being pushed rapidly eastward through Ontario, a slower expansion was also occurring south of the Great Lakes in the United States. This was partly due to a greater density of human occupation south of the lakes but there was a more ecologically significant factor in the disparate rates of expansion. The rapidity of the expansion along the northern route was greatly aided by a key factor, the Great Lakes Wolf. This species still existed north of the lakes and the pioneering Coyotes came into contact with them. One result of this contact was crucial to the Coyotes rapid success in the northeast, hybridization. But why should this happen now, why didn't it happen where Coyotes and Gray Wolves were sympatric in the west?

Recent genetic research is painting a clearer taxonomic picture of the canid species in North America. It is now believed that the Great Lakes Wolf and the Red Wolf may be more closely related genetically to the Coyote than to the Gray Wolf. Where the Gray Wolf and Coyote both existed, there appears to have been no successful hybridization. Hybridization often occurs where closely related species exist in contact with one another and one of the species occurs in small numbers while the other species occurs in larger numbers. An example birders will readily recognize is the decline of the scarce Golden-winged Warbler (Vermivora chrysoptera) as it hybridizes with the more numerous Blue-winged Warbler (Vermivora cyanoptera.) But this interbreeding does not seem to happen with Gray Wolves and Coyotes. The reintroduction of Gray Wolves to Yellowstone National Park and the slow natural repopulation of Gray Wolves in the northern Rockies in Idaho and Montana has not led to hybridization but rather seems to highlight the genetic and phenological differences between the species. The story was different with the contact of the few Coyotes among the Great Lakes Wolves in Ontario. Successful hybridization did occur. One result of this was a larger, more powerful Coyote, the Eastern Coyote. A "Tweed Wolf." This new form of Coyote came with new skills and advantages that were to prove very useful in the anthropogenic landscape of the northeast.

Wolf and Coyote in Yellowstone National Park. Photo from the blog Ecobirder.

The Coyote evolved to hunt small mammals in semi-arid and desert habitat. It did not hunt ungulates and it did not enter forests. It's head and the musculature of its jaw were not up to tackling White-tailed Deer. But with the hybridization with Great Lakes Wolf, the Eastern Coyote now is larger, shows sexual dimorphism (males are larger than females), and has proportionally larger and stronger jaws. This new jaw size and strength allows the Eastern Coyote to grasp a White-tailed Deer and hang on while the ungulate fights for its life. New behaviors were exhibited by the hybrid as well, it acted more wolf-like and readily entered the reforested habitat of the northeast. This northern hybrid expansion to the east far out-paced the southern route below the Great lakes, which was being carried out by essentially unaltered Western Coyotes. Eastern Coyotes reached Quebec in 1945, New Brunswick, Canada, in 1958, and Maine in 1970. It continued to expand eastward and then southward eventually wrapping around the Great Lakes and heading back southwestward. This expansion met up with the non-hybrid Western Coyotes moving slowly eastward forming a contact zone in western New York and Pennsylvania. The void had been filled, a large carnivoran had resettled the northeast.

Eastern Coyote in Guilford, CT. Photo by Bob Gundersen.

There remains a distinct fear and loathing of Wolves and Coyotes in some people. This is despite the fact that our most loved pet is the domestic dog (Canis familiaris), which is the descendant of domesticated Wolves. When the Eastern Coyote showed up in the northeast, people recognized they were bigger and acted differently than Western Coyotes. They called them "Coydogs," assuming these Coyotes had hybridized with domestic dogs. Genetic research has proven this to be untrue. While dogs and Coyotes can interbreed, the resulting hybrid has behavioral and biological disadvantages that create an evolutionary dead end. These hybrids (shown by genetic research to be extraordinarily rare) do not reproduce successful young in the wild. It was also thought that it might have been phenological plasticity that caused the larger Coyotes. Phenological plasticity is when an organism develops in different ways in different areas based on environmental conditions, such as Blue Jays being larger in the northern part of their range. Now we know it isn't "Coydogs", it isn't phenological plasticity, it is the Wolf within.

Coyote. Photo by Jim Zipp.

It is paramount that we strive to understand the natural world. Despite what some would have us believe, our survival depends on a healthy functioning environment. I also believe that our natural world has worth beyond any price. The howling of the Wolf once struck fear in us, and there are many who still would kill all the Wolves and Coyotes. This hatred of Wolves and Coyotes seems in some ways primal, and is certainly in no way rational in today's world. Why do humans see such malevolence in these predators, these progenitors of our dearest companions? Is it that some see in the Wolf all that is deplorable in our own nature? I don't know the answer. But I do know that the howling of Wolves and Coyotes is a most welcomed sound to me personally, and if these voices were no longer to be heard in the wilds of North America, it would be an incalculable loss.

"If the wolf is to survive, the wolf haters must be outnumbered. They must be outshouted, out financed, and out voted."     L. David Mech

Truly the call of the wild. Coyote in Connecticut. Photo by Jim Zipp.

References used in preparing for this entry include:

"Rapid Adaptive Evolution of Northeastern Coyotes via Hybridization with Wolves" Keys, Curtis, Kitchman. 2009.

"The Cranial Evidence for Hybridization in New England Canis" Lawrence and Bossert. 1969.

"Hybridization Among Three Native North American Canis Species in a Region of Natural Sympatry" Hailer and Leonard. 2008.

"Genetic Nature of Eastern Wolves: Past, Present, and Future" Kyle, Johnson, Patterson, Wilson, Shami, Grewal, and White. 2005.

"Legacy Lost: Genetic Variability and Population Size of Extirpated US Grey Wolves (Canis lupus)" Leonard, Vila, and Wayne. 2004.

"Widespread Occurrence of a Domestic Dog mitochondrial DNA haplotype in Southeastern US Coyotes" Adams, Leonard, and Waits. 2002.


  1. Really great and informative post.


  2. Great post Dave. I have always found this topic fascinating since hearing about coyotes returning to area when I was a kid and the big debate of their origin. I remember that it was somewhat political as livestock owners would not be compensated for losses if the coyote were completely wild and natural. I also remember some researcher claiming that there was a subspecies of coyote that always lived on Cape Cod, but that didn't seem to make much sense to me.

  3. This is absolutely wonderful! Just what i was looking for to pass on to the coyote and wolf haters here in New Hampshire. My family has just placed a conservation easement on our many acres here and we will protect coyotes (& wolves hopefully) and defend them as long as we can. Whittum family