Monday, November 18, 2019

How Wolves Arrived in North America

At least 130,000 years ago Canis lupus, the essential predator we call the gray wolf, entered North America from Eurasia. After it turned and travelled far south, it probably encountered dire wolves (Canis dirus), the dominant wolf in North America at the time. Dire wolves had appeared abruptly and fully evolved across North America thousands of years earlier, according to Ronald Nowak, writing in Wolves: Behavior, Ecology, and Conservation. He speculates that dire wolves may have travelled north from South America. 

While we tend to picture dire wolves as huge, Nowak contends they varied in size. Some were the biggest wolves ever; others were smaller, about the size of a large gray wolf. Dire wolves had massive heads, huge teeth, and short legs relative to their body size. Fossilized remains of these wolves have been found across the Lower 48. Dire wolves seemed to prefer warmer climates; they never migrated to the northern reaches of North America, leaving that territory to Canis lupus.

Map by William Harris. (CC BY-SA 4.0)

The dire wolf disappeared about 8,000 years ago along with some of its large prey, the mastadons, wooly mammoths, and camels that had been plentiful during the Ice Age. Not all ancient herbivores perished, writes James Bailey in American Plains Bison: Rewilding an Icon. Ancestors of Yellowstone’s bison survived this mass extinction, as did elk and moose, caribou and musk ox, bighorn sheep and mountain goats.

The dire wolf’s disappearance may have been caused, says Nowak, by increasing numbers of humans taking the wolf’s prey. Or dire wolves may have been outcompeted by gray wolves and red wolves (Canis rufus), both better suited to hunting the relatively smaller and faster prey that was becoming prevalent.

Whatever the cause, the dire wolf’s extinction left gray wolves as the dominant wolf. With plenty of game to dine upon, Canis lupus flourished. “Its range,” writes Nowak, “was more extensive than that of any other terrestrial mammal.” Except humans.

Early gray wolves first entered North America across the Bering Land Bridge during the last Ice Age. When the climate was coldest, glaciers formed at points around the globe and locked up water. This caused sea level to fall in the Bering Strait. As cold persisted, more water froze, sea level fell further, and the Bering Land Bridge appeared, a land route connecting Siberia with Alaska. (On the NPS map below, the land bridge is the yellow area.) 

The name “bridge” misleads. This land bridge was not long and thin like a highway bridge. It was more of a dry subcontinent, called Beringia, that was about five times the size of present day Alaska. Beringia’s cold-hardy vegetation drew many grazers. Hungry wolves followed.

Once pioneering gray wolves crossed Beringia into North America, the species began to divide. Eventually there would be five subspecies of Canis lupus. Each type of wolf adapted to its specific habitat, prey, and climate. This led to the development of the different sizes and behaviors seen in these wolves. 

1. The arctic wolf (Canis lupus arctos) inhabited the cold far north. 

2. The northwestern wolf (Canis lupus occidentalis) roamed Alaska and western Canada. 

3. The plains wolf (Canis lupus nubilus) claimed the largest territory, a wide swath from Oregon to Newfoundland and from Hudson Bay to Texas. 

4. The eastern wolf (Canis lupus lycaon) had the smallest range, prowling a compact, football-shaped portion of the northeastern US and southeastern Canada. 

5. The Mexican wolf (Canis lupus baileyi) stalked its prey in Mexico and the deep southwestern US.

The red wolf (Canis rufus)—a different species—crossed the Bering Land Bridge long before the gray wolf and howled in the eastern and southeastern US.

This North American suite of wolves would remain complete until we humans decided to conquer the continent and get rid of wolves. 

We killed off the plains wolf by 1926.

We drove the red wolf to near extinction by the mid-1900s and it remains critically endangered. 

photo by Dave Pape, public domain

We killed off the Mexican wolf in New Mexico by 1927. It remains endangered with more wolves living in captive breeding programs than in the wild. 

photo by Jim Clark, public domain

The remaining eastern wolves are protected in both the US and Canada. According to the International Wolf Center, there is a scientific debate that some or all the wolves in Minnesota, Wisconsin, and Michigan are eastern wolves. 

Photo by Michael Runtz. (CC BY 4.0)

The arctic wolf survives in Canada’s Queen Elizabeth Islands. 

Photo by Ralf Schmode. (Copyright free)

The northwestern wolf ranges from Canada into the northwestern US, including Montana, Wyoming, Idaho, Oregon, Washington, and California and is protected in some states by the Endangered Species Act.

Photo by Ellie Atteberry (CC BY 2.0)

Award-winning Indie author Rick Lamplugh writes, speaks, and photographs to protect wildlife and wild lands. 

His bestselling In the Temple of Wolves; its sequel, Deep into Yellowstone; and its prequel, The Wilds of Aging are available signed. His books are also available unsigned or as eBook or audiobook on Amazon.

Photo at top of post of Wapiti Lake Pack wolves by Mary Strickroth