Growing Up Grizzly

April, 11 2017  |  by kevin Back »

Built on instinct, driven by hunger, honed by imitation, a grizzly cub’s first year is nothing short of incredible

Story and Photos by Tim Christie

Grizzly bear moms fiercely protect cubs from any perceived or real threat. As with most wildlife, newly born additions are highly susceptible to multiple risks. Approximately half of cubs die in the first year, falling to disease, starvation and predation. Photo by Tim Christie.

 

The movement is subtle, unfelt by the sow immersed in groggy, hibernating slumber. Little feet of a blind, hairless and toothless cub inch their way through thick hair, innately knowing the way to life-nurturing milk. A second coffee-cup-sized cub finds its way to its mother’s nipple. Ensconced in a deep hole dug last fall under the giant root well of a fallen tree, the three nestle together, insulated from subzero temperatures by a heavy layer of snow.

There is little to worry about right now, unless Mom doesn’t have enough fat reserves to make it to spring. But since she gave birth, that worry is unlikely. Grizzly bears (Ursus arctos horribilis) possess special adaptive characteristics that ensure mothers and cubs a chance at survival.

This midwinter miracle of life is repeated thousands of times each year. It extends throughout the grizzly bear’s range which runs through the Greater Yellowstone Ecosystem at the corners of Wyoming, Idaho and Montana, up into the Lewis, Swan, Cabinet and Selkirk ranges that sprawl from northwestern Montana across the Idaho border, and on up through northwestern Canada into Alaska.

Though their species spans thousands of miles across the continent, this furry family buried under the snow will likely keep to themselves when they awake, relying on instinct and centuries of instruction passed from sow to cub as their tools. Spring is coming. Adventure awaits. Soon the cubs will begin their life journey, the journey of growing up grizzly.

LIFE, SUSPENDED

The story of the birth of these cubs is incomplete without explanation of the incredible process of conception.

Grizzlies breed between May and July. Once bred, what happens is virtually magic. Instead of developing immediately in the uterus, fertilized eggs are held, suspended until October or November as the sow approaches hibernation. After a good summer, rich with food sources that have added vital fat reserves to sustain her winter sojourn, the eggs implant in the uterus. If she is nutritionally lacking or otherwise unhealthy as fall comes on, the sow’s body reabsorbs the eggs. Consuming adequate fat-generating food from spring to fall determines both her health and reproductive ability.

It’s part of a check-and-balance system ursines employ. Adulthood comes quickly to many other mammals. Some species, like rabbits, breed and reproduce within a year of birth. Female elk calves can breed at one year of age. But female grizzlies aren’t mature enough to breed until they are 4 years old, and often wait until their fifth spring. While males, called boars, sexually mature after about three and a half years, few breed until they are 5 or 6. Older, larger males don’t take kindly to young competitors.

AWAKING HUNGER

Despite a sow’s fierce protective nature against all threats, grizzly cub mortality can be high. Couple that with the fact that females only breed every three years on average, and it means grizzly bears have one of the lowest population growth rates of all North American mammals. Photo by Tim Christie.

Spring sunshine bathes snowy hillsides with warmth, stirring life in the high country. Inside the den, the sow has nursed the cubs now for months, depleting her reserves and rousing her from her winter-long nap. Clawing through the snowy blanket that had protected her and the cubs, she steps into the brilliant sunshine. Furry bundles follow, seeing for the first time the landscape they’ll spend their lives exploring.

Leading her two cubs off the snowy mountain to greening grass, the sow finds a meadow replete with blooming dandelions. She’ll eat grass, but prefers nipping the yellow flowers; they offer more protein than the greens.

Sows with newborns are late leaving winter dens. Boars exit their own dens first, followed by cub-less females and sows with older cubs. For all, hunger drives every movement. Snow-covered landscapes offer little nourishment, so grizzlies follow paths that memory or their sense of smell tells them lead to food.

People often find it surprising to see alpha predators in a snow-dotted meadow grazing on newly exposed green grass like cattle. But grizzlies are omnivores, eating nutritional foods including nuts, leaves, roots, tubers, insects and any animal life they can find. They prey on animals; but unlike true carnivores, their diet doesn’t depend solely on meat.

Never far from her sight, the cubs sniff, scratch, run, climb, explore, play and wrestle with one another. Just out of the den, their only attention to a blade of grass is testing its texture with their mouth, still unaware it’s edible. Mom’s their grocery store for now. Several times a day she’ll sit or lie down to nurse the cubs as they make sounds somewhere between purring and a puttering motorboat. Meals are not long affairs. When Mom gets up, she frequently rolls still-nursing cubs to the ground.

 A MOTHER’S MISSION

The sow has three charges: protect her cubs; find food to sustain them all; and teach her cubs to survive.

Lessons are modeled to unsuspecting cubs that are in the process of developing life-sustaining skill sets. Learning Mom’s habits is crucial to survival.

I once photographed a female brown bear with triplet cubs of the year in Alaska digging for clams. At those northernmost reaches of their populations, geography makes a difference as to what these bears are called. In coastal areas, they are known as brown bears. When found further inland, they are known as grizzlies. Initially this brown bear would dig up a clam, crack the shell and give it to a cub. After doing that several times for each cub, she’d dig up a clam and give it unopened to the cub. Understanding good stuff was in there, it had to figure out how to unwrap it. Frustration was obvious, yet the little ones soon unraveled that piece of the food puzzle.

Sows fiercely protect cubs from any perceived or real threat. As with most wildlife, newly born additions are highly susceptible to multiple risks. Approximately half of cubs die in the first year, falling to disease, starvation and predation. In the wild, boars pose a sow’s biggest worry, but wolves, mountain lions, even coyotes also prey on cubs. Humans blundering into close proximity of a female with cubs also can expect her wrath, commonly resulting in physical injury, even death.

While photographing a white-tailed buck several years ago, a sow with a cub crossed my path. Seeing me, the cub bawled, then disappeared. Dropping my camera, I climbed a tree, all the while hearing the sow rushing for me. Her anger was palpable, like a junkyard dog. Halfway up the tree, she caught me. She grabbed my heel; I kicked at her, and my running shoe slipped off. Losing her balance, she fell to the ground, shearing the branches from the tree as she went. Obviously she was offended I’d scared her baby, despite me being at least 75 yards from the cub when it bawled.

A friend had a much more serious encounter while hiking in Yellowstone National Park when he stumbled onto a sow with two cubs in their daybed. The sow severely bit him in the shoulder and ripped his scalp. He played dead, prompting her to leave. He survived but wears scars of the encounter.

Despite a sow’s fierce protective nature against all threats, grizzly cub mortality can be high. Couple that with the fact that females only breed every three years on average, and it means grizzly bears have one of the lowest population growth rates of all North American mammals.

MOTHERING VS. SURVIVING

By late fall, what began as hairless, blind, pound-sized cubs are now miniature replicas of Mom, weighing 60-75 pounds each.

And so is introduced one of nature’s greatest struggles: the sow’s mothering instinct versus survival. Driven by a maniacal feeding frenzy, fall is the final push to put on all the fat possible before hibernation. Cubs are still nursing, so the sow needs to have enough fat reserves to survive hibernation. She is searching for as much food as she can find.

Grizzlies in Greater Yellowstone can strike it rich on dining options during hunting seasons — when elk, moose and deer gut piles are left on the ground. But those treats come with possible consequences. An edgy, potentially deadly human-bear conflict can be created in the backcountry when grizzlies take possession of wild game quarters that haven’t yet been retrieved by hunters. Fortunately for all involved, hunters have worked hard to reduce these conflicts.

Sows that teach cubs to tolerate or invade human domains — both in the wild and in suburban areas — promise generational problems of conflict. As bears expand into more human-dominated landscapes, these occurrences are on the rise. But good moms steer clear of humans, modeling the wisdom of maintaining appropriate distances.

Cubs are sponges, soaking up everything Mom does. And Mom is the ultimate authority, the sage on what her young should or shouldn’t do. She rules with an iron will.

Photographing a sow with two cubs a year ago, I witnessed this disciplinary wrath firsthand. I don’t know what one cub did, but she whirled around, grabbing its neck in her mouth, shaking it and pinning it to the ground. The cub’s ear-piercing bawl only spurred the sow to shake it harder. Releasing him, he slinked off a couple yards. Twenty minutes later, the sow and cubs were playfully wrestling together in the grass.

Discipline hones survival. The cubs have mere years to learn it all before they live alone. Grizzlies eke out life in solitude, gathering together only for romance or forced into close quarters by concentrated food sources like berries, fish, whitebark pine nuts or army cutworm moths (also known as miller moths) along high country rockslides.

At the cub’s elevation, summer yields to autumn once again. Retreating into hibernation, the sow must be healthy and fat. Now much larger, the cubs continue to nurse, relying on the sow to survive the long winter nap.

Flakes of snow the size of wood chips slowly twist and float to the ground, piling deep over their winter quarters. In five to six months, they’ll leave hibernation for another summer of tutoring.

The sow has done all she can to protect, nurse and teach what began early this year as helpless beings. They’re not yet ready to live on their own; more lessons await next year. It takes time to grow up in grizzly country. Time, it seems, well spent.

 

—Tim Christie, a full-time freelance writer and nature photographer, has hunted and photographed throughout North America and Africa. View and purchase his images on his website. This article is reprinted from Wyoming Wildlife magazine.