A conservation milestone is underfoot in one of the best-known and best-loved protected areas in the world: the restoration of American bison, colloquially called “buffalo," to Alberta’s Banff National Park in the southern Canadian Rockies. This summer, wildlife managers there will release a herd that’s been acclimating in enclosed backcountry pastures since February 2017.

One intriguing element of bringing North America’s heftiest land animal back to Banff’s mountain valleys is how local gray wolves -- the only serious buffalo hunter besides humankind -- will respond.

Plains bison – the more southerly subspecies, or perhaps simply ecotype, of the American bison – once roamed extensively over Alberta's shortgrass prairies. Though mostly associated with that sort of wide-open Great Plains country, ecologists believe the animals also once ranged up into the foothills and higher grassland valleys of the Rocky Mountain Front Ranges, at least seasonally.

By the late 19th century overhunting had decimated American bison all over the continent, and they’d been long gone from the Banff area at the establishment of the national park in 1885. Restoring the ecological influence of this humpbacked beast has been on the table in Banff for decades. A habitat-suitability study published in 2016 suggested the park could support as many as 600 to 1,000 bison, but the current effort is still exploratory.

Early last year -- after being blessed by representatives from several First Nations groups --16 bison from Elk Island National Park were trucked to a ranch just outside Banff, then helicoptered into the roadless Panther Valley within park boundaries. The bison have resided in large paddocks since: A six-hectare winter pasture and a summer one twice that size, where these former flatlanders got their first taste of steep Rocky Mountain slopes and big rivers. This is the “soft-release” phase of the reintroduction program, where the herd, which added 10 rusty-orange calves to its ranks in spring 2017, adjusts to the local environment under close monitoring.

Next up is the “free-roaming” phase: This July the paddock gates will open, and the herd will have about 460 square miles to wander. This bison range -- centered on the grassy Panther and Dormer valleys. but extending into the Red Deer and Cascade drainage areas -- will come hemmed in via mountain terrain as well as stretches of (hopefully) buffalo-proof fencing permeable to other critters. After five years, Parks Canada will assess how well the bison do decide how to proceed in the long-term.

As a CBC News article noted this past December, the free-roaming chapter of the reintroduction program will see bison and wolves interacting in Banff for the first time since the mid-1800s.

“Right now, the bison are in a secure enclosure,” Parks Canada's Jesse Whittington told the CBC, “and we know that wolves are traveling around that enclosure but cannot get in to access the bison. But I’m sure the two are aware of each other.”

That’ll change come this summer, when the bison spread out to occupy their expanded backcountry digs. And this development will be significant, as there are now only a few areas in North America where these age-old enemies, which once crossed paths over essentially the entirety of the bison’s range, overlap. The American bison is the largest prey tackled by wolves anywhere; the canids, in turn, are the only significant non-human predator of the bison, though grizzly bears opportunistically take calves and the occasional adult. Grizzly pawprints were seen outside the Banff bison paddock during last year’s calving season.

Massive, fleet, ornery and well-armed, bison make mighty tough quarry; Wolves preferentially target young animals and injured, ailing or otherwise hampered adults. In Wood Buffalo National Park, where wood bison serve as primary prey, wolves focus in late spring and summer on herds with calves, but even these pose a significant challenge: Calves can evade wolves by fleeing into the middle or ahead of the main herd, while both cows and bulls mount active defenses -- and wolves usually turn tail when confronted with an oncoming full-sized buffalo.

Interesting insight into Banff's forthcoming new-old wolf-bison relationship comes from Yellowstone National Park in the U.S. Rockies, where bison always persisted but where wolves were eradicated in the early 20th century and then reintroduced in the mid-1990s. As in Banff, Yellowstone wolves have other, less-dicey prey species to choose from, elk being their favorite. Nonetheless, biologists suspected reintroduced wolves would try their hand at buffalo-hunting, and they did: Within 25 months of wolf reintroduction, the first bison kills were recorded in Yellowstone, and over time wolves apparently improved their prowess -- mostly aimed, unsurprisingly, at calves and weak or wounded individuals, as well as bison struggling in deep snow.

One Yellowstone pack, the Mollie’s Pack, excelled (relatively speaking) at bison predation -- a skill born of necessity, as these wolves inhabited Pelican Valley in the park's interior, where buffalo were the only reliable suitable prey in winter.

Generally, though, healthy adult bison in Yellowstone don’t have much to worry about wolf-wise. One study suggested the presence of wolves impacted elk habitat selection and diet -- an example of what ecologists call the “landscape of fear” a predator creates -- but didn't find similar effects in bison. Observations from Wood Buffalo and Yellowstone show wolf attacks on bison sometimes drag out over many hours, such is the difficulty of finding and wearing down a vulnerable animal. In March 2003, the Mollie’s Pack managed to kill the toughest quarry of all, a bull bison, but the undertaking required 12 hours and claimed a wolf's life as well.

“Once we open the gates sometime this summer, it’s the ground rules of the wild,” Karsten Heuer, Banff’s bison reintroduction project manager, told CBC News earlier this year. “If a wolf pack decides they want to take [a bison] down, then that’s nature. I think it will take some time though. A bison is a pretty formidable animal, so it will be interesting to see how it evolves.”