Take a look at the below footage out of Yellowstone National Park, taken by wildlife photographer Evan Watts and posted to his Watts Wildlife Photography Facebook page in early October of this year. What kind of bear do you reckon is beelining for this expired bull elk?

If you guessed black bear – and more than a few commenters to the Facebook post appeared confident in that ID – you’d be wrong. This is, as Watts notes in his caption, a grizzly bear. A notably dark-coloured grizzly, to be sure, but a grizzly nonetheless.

Comparison of grizzly bear and black bear body shapes, faces, claws, and tracks. Image © NPS

The giveaways? For one thing, that big shoulder hump (or “roach”). The muscle-slabbed hump – which helps power a grizzly’s impressive digging abilities – and the raised rump give the griz a sort of saddleback appearance. The back of a black bear, by contrast, typically slopes fairly smoothly from a rump-ward high point down toward the head. (Mind you, black bears can definitely show a bulge over their shoulders, but even with such a “false hump,” if you will, the bear’s rear end tends to be notably taller.)

Sharp-eyed viewers will also catch a few fleeting glimpses of the large, light-coloured claws on the bear’s front paws. Their prominence points to a grizzly, whose long, straightish foreclaws – another adaptation for digging (to munch roots, bulbs, invertebrates, and burrowing rodents, and to excavate winter dens) – contrast dramatically with the shorter, tightly curved ones of a black bear. (The claw differences are one key reason why black bears are much better at scrabbling up tree trunks than grizzlies. They also aren’t too shabby when it comes to rock-climbing, turns out.)

The general massiveness and blockiness of the bear’s head is another griz trademark. (To some extent, so is its “dished” profile compared to the typical “Roman” or straight-face line of a black bear, though this distinction isn’t cut-and-dried.)

Finally, the bear’s hefty size is evident from the reference of the dead elk; Rocky Mountain elk bulls in the Greater Yellowstone Ecosystem typically weigh in the neighbourhood of 318 kilograms (700 pounds). Grizzly bears grow bigger than black bears, although there’s generous overlap between large black bears and small grizzlies.

Some initial confusion over the bear’s pedigree is understandable. Brown bears – of which the grizzly is a North American subspecies – and American black bears are probably the foremost ursids in the pelage-variability department. That makes their common names potentially big-time misleading.

Just as American black bears can be brown as can be (more on that shortly), brown bears can also be black – or nearly so, anyhow. Let’s quickly explore the “50 shades of grizzly,” shall we?

A griz by any other colour is just as grizzly

Grizzlies get their name from their commonly grizzled coats, a result of pale-tipped guard hairs that also explain their historical nickname of “silvertip.” This effect can be extreme enough to explain another early label for the North American grizzly: “white bear” (which is what Captains Meriwether Lewis and William Clark, who introduced the English name “grizzly” during their 1803-1806 expedition across what became the western United States, initially called the fierce beast).

But grizzlies and other bruins come in plenty of other shades and patterns: blonde (as exemplified by the so-called “Toklat” grizzly colour phase of interior and northern Alaska), creamy (see: the famed “white” grizzly of Banff National Park known as Nakoda), caramel-coloured, reddish, chocolate-brown and, yes, almost black. The influential naturalist and field researcher Adolph Murie, who studied grizzly bears in Alaska’s Denali (formerly Mount McKinley) National Park for decades, wrote in The Grizzlies of Mount McKinley, “An old male I examined was black except for dark-brown grizzling over the shoulders and back.”

The "Toklat” grizzly colour phase seen in Alaska's interior and northern regions is distinctly 'blonde'. Image © Gregory Smith

The coastal grizzlies – often simply called brown bears – of southern Alaska and British Columbia are usually more uniformly brown, and sometimes quite dark indeed, compared to the classic paler, more silver-tipped suit of grizzlies in interior North America.

A portrait of Ininkari from the 1700s is one of the earliest known records of brown bears with white fur. Image © Kakizaki Hakyo

The Ussuri brown bear of eastern Russia and the northern Japanese island of Hokkaido, meanwhile, is occasionally called the “black grizzly” due to its often dark tone. But one population of this subspecies, found in the southern Kuril Islands, is uniquely whitish on the head, forelegs, and shoulders. (A 2011 study on this pale-hued island brown bear called it the “Ininkari bear,” after an 18th-century Japanese painting showing Ininkari – a chief of the Ainu people, indigenous to the Kurils – with two bear cubs, one of them white.)

Things get more complicated still when one considers that a brown bear’s coat may change across the seasons. A grizzly, for example, which looks rather dark freshly emerged from its winter den might appear lighter by late summer as its coat gets sun-bleached and worn. And speaking of sunlight, it can play tricks on a bear-watcher: The very same bruin may appear a whole different shade in full sunshine versus shadow.

Back in black (or brown or red or blonde)

American black bears, meantime, are arguably even more all-over-the-place when it comes to fur colour. While most black bears in eastern and central North America as well as on the Pacific Coast are indeed black, a large proportion of black bears in interior western North America – the majority, in some regions – are blonde, reddish, or chestnut-brown. Such brownish black bears, for example, aren’t uncommonly seen in the Greater Yellowstone, where they’re readily mistaken for grizzlies.

These “cinnamon bears,” as they’re sometimes called, owe their unique color to a mutation that, a study published last year in Current Biology suggested, only arose about 9,360 years ago, probably in the American Southwest, and has been spreading since.

Brownish black bears – sometimes called cinnamon bears – aren’t uncommonly seen in the Greater Yellowstone, where they’re readily mistaken for grizzlies. Image © Appalachian Encounters

Biologists have theorised the brown hue may confer some small selective advantage to western black bears, which range into drier, more open habitats than their eastern cousins. The Current Biology paper didn’t find a lot of support for ideas that the colour may provide a thermoregulatory advantage or even mimic the appearance of the more intimidating grizzly bear where the two species overlap. The authors did theorise that it might serve as a mechanism of crypsis, camouflaging a cinnamon bear – vulnerable, especially as a cub, to wolves, cougars, and other bears – against its environment.

And there are some particularly striking, more geographically restricted colour morphs of the black bear found in coastal northwestern North America, including the silvery blueish “glacier bear” of southeastern Alaska. More famous is the so-called “spirit bear,” the white-coated variant of the Kermode bear, a black-bear subspecies found on a section of the British Columbia coast, including within the Great Bear Rainforest. Enjoy some up-close looks at two spirit bears from that magnificent swath of temperate rainforest, Ma’ah and Warrior, in this behind-the-scenes footage from Bears: Ultimate Survivors: