One little bison calf in Yellowstone National Park got another shot at becoming a snorting, swaggering full-grown buffalo a few days back, after a run-in with some hungry predators. On August 7, a guide with Yellowstone Wolf Tracker, Michelle Holihan, filmed several grey wolves of the Junction Butte Pack making a go at a pint-sized buffalo on the park’s wide-open Northern Range.
“We had an exciting morning of wolf watching in Yellowstone today as several members of the Junction Butte Pack tried to take down a bison calf,” Yellowstone Wolf Tracker wrote in a Facebook post introducing Holihan’s video. “After the adults ran them off they gave up the chase and went back to the rest of the pack.”
In the footage, both adult bison cows and bulls take part in the “best-defence-is-an-offence” response to the wolf attack: a running flurry of pounding hooves and loping lobos that almost threatens to bowl over the calf in question.
The event illustrates what’s probably the standard interaction of wolves and American bison, the heftiest land mammals on the North American continent and the so-called “buffalo” of Old West lore. Weighing up to a ton, fleet-footed and agile, possessed of some pretty wicked hooked horns, bison are about the opposite of easy prey, representing the toughest quarry of all for wolves. As comparatively vulnerable youngins, though, they certainly present a tempting target to a wolf pack.
Up in Canada’s Wood Buffalo National Park, bison serve as a major food source for wolves, which selectively target herds with calves during early summer. Yet wood bison (the boreal American-bison subspecies) do plenty to safeguard those wolf-harried calves. A late-‘80s study on wolf predation on bison in Wood Buffalo National Park suggested that wolves are often stymied when buffalo herds simply stand their ground, or when calves are within and toward the front of a fleeing herd. (That research indicated calves become more vulnerable if wolf-hounded bison are driven into woods, where they appear less able to stay ensconced within the herd.)
The 1995-1996 reintroduction of wolves into the Rocky Mountain wilds of Yellowstone presented another rare opportunity to resurrect the age-old predator-prey relationship of Canis lupus and Bison bison. Yellowstone is sanctified buffalo ground, having served as the primary refuge of the plains bison in the face of near-extinction across North America during the latter half of the 19th century.
Bison were, historically, very widely distributed on the continent, but the oceanic prairies of the Great Plains were their grandest stronghold. Grey wolves hunted and scavenged those enormous herds – so associated with them, in fact, that Euro-American observers commonly called them “buffalo wolves.” An 1820 report describing the great bison droves noted, “Large herds are invariably attended by gangs of meagre, famine-pinched wolves, and flights of obscene and ravenous birds […].”
The drawn-out, exhausting effort that Wood Buffalo and Yellowstone wolves often engage in while attacking bison is mirrored by historical accounts from the Great Plains, which include many references to extended affairs involving buffalo wolves wearing down lone bison over hours. In 1859, for instance, on the Saline River in present-day Kansas, Laurens Hawn described seeing “about a dozen brown and white wolves arrayed in a circle around one of the largest buffaloes I had ever seen. The attack, cool and deliberate, displayed wonderful sagacity. They did not rush upon the buffalo in a mass, but calmly waiting until his heels were towards them, several of them sprang like darts from the circle and fastened to his flanks or hams and as the buffalo turned to confront these others would seize upon the vulnerable parts […]” This kept up until the bison ultimately succumbed.
Some 19th-century reports describe bison forming rings around calves to ward off wolves, reminiscent of the choreographed, horns-out “circle defence” muskoxen employ to protect their young from packs.
While it didn’t take very long after the Yellowstone reintroduction for the first wolf attacks on bison to take place, the canids weren’t necessarily proficient for some time. In Canada’s Yukon, where bison were reintroduced in the 1980s, it took about a quarter of a century before local wolves really learned the ropes of buffalo-hunting.
A Yellowstone pack known as the Mollie’s Pack became known for preying on bison in the years following wolf reintroduction, but this was basically borne out of necessity, as the Mollie’s wolves inhabited the Pelican Valley in the park interior, where the preferred prey of elk was unavailable in winter. Hunting the overwintering Pelican Valley bison was still a formidable challenge. Case in point: The Mollie’s Pack was observed bringing down a bull bison in March 2003, but it was an all-day affair that saw one wolf killed and two others wounded.
In general, Yellowstone wolves focus on elk – significantly easier to kill – rather than bison. A 2014 study in the park suggested successful bison-hunting involves a larger number of participating wolves and a greater degree of cooperation among them than elk-hunting. “Whereas improvement in elk capture success leveled off at 2–6 wolves, bison capture success leveled off at 9–13 wolves with evidence that it continued to increase beyond 13 wolves,” the authors of that study wrote. “These results are consistent with the hypothesis that hunters in large groups are more cooperative when hunting more formidable prey.”