All About Bears
It starts out quietly. A few bald eagles fly over the pristine heights of the Alaskan peninsula. A small number of brown bears—also called grizzlies—roam through and feed on lush green sedge growing near the mouth of the McNeil River. Then it happens. Escalating numbers of fish start to swim into the shallows in June and, almost suddenly, birds and bears move in on them. “It’s an amazing thing to see,” says bear biologist John Hechtel. “With an estimated 35,000 brown bears, Alaska is probably one of the last best places for grizzlies in the United States.”
And McNeil River Falls, located within the protective borders of McNeil River State Game Sanctuary, is probably one of the best places to observe the behavior of these mighty—and highly intelligent—creatures. As chum and coho salmon, as well as a fish called Dolly Varden, make their spawning runs through McNeil River, the rocks and boulders that form McNeil River Falls slow them down. Over time, brown bears (Ursus arctos) have learned that this is an ideal fishing spot, so they converge in great numbers, vie for the best positions in the shallow water, and begin the fishing party. The falls’ roiling currents pick up turbulence as bears pounce, strike their paws, dunk, and slam their bodies against large rocks, all in an effort to capture and feast on a primary diet of protein-rich fish that will fatten them up for winter hibernation.
But all is not peaceful in this idyllic setting. The season brings ferocious fights between competing bears of similar rank. Subadults that have already left the den and the watchful eyes of their mothers can die of drowning and other accidents. And adult bears even kill some cubs. If it can happen in the course of a brown bear’s day—and a significant part of its life cycle—it’s likely to be seen at McNeil River Falls.
Photograph by Lynn M. Stone,
Nature Picture Library
Pecking Order
Brown bears aren’t territorial, but altercations can occur over fishing spots and females in estrus. Grizzlies live according to a complex social hierarchy that places large adult males in the most dominant position. Next come females with cubs, followed by single females. But, like so much in bear culture, variables abound. A mother bear with small cubs may first tend to avoid other bears for the safety of her litter. But as the cubs grow, a protective mother with enough size and attitude may assert dominance over an adult male with less fight. The same goes for a single female, who may, in turn, dominate a mother with cubs.
Recently weaned cubs, or subadults, rank lowest. Averaging two and a half years old when their mothers kick them out of the den, these juveniles must make their own way. “They’re pretty confused after being taken care of by their mothers the first few years of their lives,” says regional refuge manager Hechtel. “When they go to eat, they’re forced aside by other bears. They have to figure out where they fit in.”
Many such bears just skulk around, a bit skittish as they pair up and travel together. In some of the sanctuary’s viewing areas, younger bears tend to linger closer to humans as a way of avoiding bigger bears. “The difficulties they suffer because of rank can affect their survivability,” Hechtel says. “Young female bears tend to stay in areas where they were raised, but males are more likely to disperse in search of new places to live. That puts them at more risk of getting into trouble, particularly when they encounter frightened people. They’re not as big as the adult bears and not as savvy about hunting and foraging.”
Getting the Message
Grizzlies maintain their sophisticated social structure through subtle—and not so subtle—displays that communicate their intentions. Using vocalizations, scenting, posturing, and body contact, brown bears carry on a life cycle of feeding, mating, hibernating, and caring for cubs. Although no visitor to McNeil River Falls has ever been harmed by a brown bear since the sanctuary was established, understanding bear signals can be a safeguard against disaster. Here’s a quick overview of brown bear sign language:
- When one bear sits or lies down in front of another, it may be sending the message to the second bear that it’s comfortable and perceives no threat from the other bear.
- Bears of similar rank often take turns at fishing. When one bear lies down and waits, it’s holding out for an opportunity to move into the spot.
- Bears of similar rank may also exhibit a medium-intensity display called jawing, most often used to diffuse conflict. Jawing includes vocalizations and head movement and can sometimes lead to a more aggressive encounter.
- Following a fight, the losing bear may straddle, urinate, and rub against bushes to relieve stress.
- Adult male bears display a slow, deliberate, stiff-legged gait toward competing males in what researchers believe may be a show of strength. Reminiscent of actor John Wayne’s famous walk, cowboy-walking almost always includes urination and often happens at a point in an interaction where the resolution can go either way.
- Head and body movement communicate a bear’s intentions. When one bear stands and turns its side toward the other bear during an aggressive encounter, it may be conveying an unwillingness to attack. But the slow, delicate movement may actually promote an attack by the other bear.
- A grizzly displays extreme aggression when it flattens its ears, lowers its head and body toward the ground, and charges.
The Mating Game
Courtship and mating take place from around mid-May through early July, when male bears can be seen vocalizing, roaring, and hop-charging toward potential mates. Males tend to follow females that are coming into estrus. If she’s not quite receptive, she may whirl around, sit down, growl, squat, or even run away. But if she’s willing, she may allow the male to mount her briefly. However, copulation does not necessarily take place immediately. The act of mating can be more drawn out, with the female facing the male, displaying open-mouth jawing, and playing for a while. “Sometimes a male will try to keep a female confined to a certain area,” Hechtel says. “Or a mating pair may stay together for a week or ten days.” Male bears will mate with more than one female during breeding season. A female bear, it turns out, may also mate with a couple of different bears in the same day, making it possible for cubs in a single litter to be sired by more than one father.
Impregnated females go through delayed implantation, when fertilized eggs divide until they form blastocysts but then go dormant until the fattened bears go into their dens to hibernate in the fall. Around the time of hibernation, the blastocysts are implanted, and the pregnant female feeds her growing fetuses from her fat reserves. “It’s a little tricky to pin down the exact gestation period because brown bears cubs are born inside the den,” Hechtel says. “There are things that take place in the den that we don’t know about.”
Cub Care
A female bear starts reproducing at about six years old and may have a litter every three or four years until her 20s. Around early February, an average of two cubs are born in a litter. They are still nursing when they emerge from the den with their mother in the spring. During the active season, the mother bear will show her cubs around their home range, continuing to nurse them, feed them fish she catches, and keeping a watchful eye on them. Despite fierce protectiveness, cubs do die from accidental drowning or other mishaps at this stage of development.
Cubs return to the den with their mothers for an average of two more winters. But mothers begin forcing them into independence by the time they emerge from the den in their third summer at two and a half years old. It’s touch and go for young cubs, but those that adapt without incident find their place in this rich environment under the fascinated gaze of conservation-minded humans. “When people say a visit to McNeil was one of the coolest things they’ve ever done, I offer them a challenge,” says Hechtel. “I tell them that being conscious of such things as simply not feeding the bears—doing so can lure them into populated areas or dangerous encounters with humans—can ensure that their kids and grandkids have the same opportunity.”