When Mother Bears Collide (Again)

Last summer, 128 Grazer and 409 Beadnose found themselves face to face in defense of their cubs . Recently on bearcam, they had another dustup. This one was unique and included elements I had never observed before.

When we ask, “Why did that bear behave like that?” we should ask two additional questions.

  • Was the bear motivated by food or potential access to food?
  • Was the bear motivated by sex or reproductive success?

Biology can be distilled simplistically into two categories: food and sex. Adequate nutrition is necessary for survival of the individual, and since bears hibernate throughout much of the year they are particularly motivated by food. Reproduction also drives bears to behave in particular ways. We should also consider how each bear’s disposition influences their behavior.

128 Grazer
As a young adult bear, 128 Grazer became very skilled at fishing the lip of the falls. She’d compete for access to that spot with several other adult males and females. As a single bear (i.e. no cubs), she was fairly tolerant of other bears in close proximity. After 128 became a mother in 2016 though, her behavior became increasingly defensive. She didn’t shy away from confronting larger adult males in order to protect her cubs .

Still caring for three yearlings in 2017, she seems to be just as protective and wary as last year.

409 Beadnose
In contrast to Grazer, 409 Beadnose is an experienced mother who has weaned three litters (her current batch of yearlings is her fourth known litter). Beadnose can be defensive too, but tends to avoid confrontation more often than 128. While Grazer visited the falls with her spring cubs last summer, 409 did not. This is a clear behavioral change for Beadnose, because she visits the falls frequently when she’s not caring for cubs.

two bears standing in shallow water

128 Grazer (left) and 409 Beadnose are familiar with each other and often use the same areas to fish.

Now both of these mothers are raising yearlings, both have returned to Brooks Falls, and both tend to fish the same places (the lip or the far pool). Most importantly, both are competing for the same resources in order to successfully raise their cubs—leading to situations like this.

Can this apparent snafu be explained by a motivation for food or reproductive success? When the video begins, 409 Beadnose is ascending the hill. 128 Grazer is the blonder bear standing under the spruce tree. Grazer refuses to yield to Beadnose’s approach. The bears jaw and growl at each other, while 128’s yearlings remain in the spruce tree above their mom.

screen shot of bears beneath spruce tree

Beadnose seems compelled to get up the hill and skirts Grazer. There are other routes available, but she sticks with this one.

screen shot of brown bear on hill near spruce tree

Grazer’s cubs eventually come down from the tree while Beadnose lingers in the forest nearby. Something keeps Beadnose from moving farther away, but at this point we can’t see her.

bears standing on his near river

With 409 still on the hill, Grazer and cubs move down to the river. Shortly afterward her yearlings react to something in the same tree they had just climbed down from. Grazer begins to jaw pop, a loud and distinctive warning noise. We can see movement in the spruce tree above.

four bears standing in river near a steep embankment

It’s one of Beadnose’s cubs.

four bears standing in river. Yellow circle surrounds bear in tree. Text reads, "409 yearling"

Grazer and her yearlings scramble up the hill just 409’s yearling tries to climb down. Now we understand why Beadnose didn’t give Grazer more space previously and why Beadnose remained in the forest near spruce tree—one of her cubs was in the same tree as Grazer’s cubs! This is something I never witnessed before, cubs from two litters in the same tree at the same time.

409 is mostly out of sight as 128 and cubs run up the hill. 409’s yearling though, is unable to get out of the tree.

Two bears climbing a hill. Yellow circle highlights a bear in a spruce tree. Text reads, "409 Yearling"

A short stand-off ensues. 409’s yearling remains in the tree, 409 stands not far up the hill, and 128 Grazer and yearlings remain close by.

Screen shot of bears on hill in vegetation. Yellow circles highlight location of bears. Text reads, from top to bottom, "409 yearling" "409 Beadnose" "128 Grazer"

When 409’s cub tries to climb down again, Grazer reacts and charges to the base of the tree.

screen shot of bear standing on hill near river

Grazer then climbs the tree, forcing Beadnose’s yearling back up. About ninety seconds later, 128 has moved farther away, which allows 409’s cub to climb out of the tree and rejoin its mother.

This interaction between Grazer and Beadnose was unique because cubs from two different litters were in the same tree at the same time, greatly complicating a situation where the families could’ve avoided each other. The interaction was ordinary however, because both Beadnose’s and Grazer’s behavior seemed to be motivated by an urge to protect their cubs. Grazer’s defensiveness is easily triggered and she must’ve viewed the 409 yearling as a threat, which in my opinion led her to chase it back up the tree. Beadnose may have realized Grazer was willing to physically fight in this situation. This could’ve deterred Beadnose from standing next to the tree under her cub. At the beginning of the video, Beadnose also couldn’t get her cub out of the tree with Grazer’s cubs still in it. Stuck in a Catch-22, Beadnose seemed to choose a more cautious tactic: move slightly away and wait.

Motivation for food or reproductive success explains quite a lot in biology, but not all bear behavior can be explained so simplistically (why would a bear play with her foot? ). The prolonged interaction between these families however, does fit one of the biological motivators. This interaction probably wasn’t hierarchical; that is, it wasn’t about asserting dominance for access to food and mates. It was about protecting offspring. In other words, it was about reproduction.

Bear Courtship

Bearcam is back! While brown bears fishing at Brooks Falls are the cam’s main attraction, bears also engage in another important event—courtship. Bears make new cubs at this time of year.

Courtship is a conspicuous part of bear life in spring and early summer. Sometimes a male bear encounters a female bear at the right time and they copulate immediately, but more often bear courtship is a prolonged affair. From an ursine perspective, courtship is a process in which a male follows a female in estrus, habituating her to his presence until she is ready to mate.

large bear (right) follows smaller bear through grass

A large adult male, 856 (right), follows 708 Amelia while she was in estrus in 2013.

Courting pairs are easy to recognize by the male’s conspicuous and persistent behavior. A male bear recognizes an estrous female by her scent. He then walks behind her, shadowing her movements like he has a laser sight affixed to her rump (hormonally, the simile may not be far from the truth). However, bear courtship contains neither romance nor effort from the male to attract the female. He’s simply biding his time.

Copulation takes place only when the female is ready, which may not be for days. (The longest courtship I ever noted at Brooks River was 10 days.) It’s certainly not uncommon to see a male following a female for hours and hours.

Over those hours and days, the male follows her, guarding his access for the opportunity to mate. If another male of equal or greater dominance catches the female’s scent, then the two males may engage in a violent fight. Male testosterone levels peak, not coincidentally, in June as well. In late spring and early summer, fresh wounds on dominant adult males may be battle scars from a fight for access to a female bear. Bigger can be better in the bear world.

large bear with wound on cheek sitting in water

In June 2015, 814 Lurch returned to Brooks Falls missing an ear and with a large wound in his right cheek. These wounds could have been received during a fight with another male over access to a female.]

The victor continues his slow pursuit until the female decides the time is right. Outside of the mating season, male bears pose real threats to smaller females (sometimes, albeit very rarely, killing them) so the close, persistent proximity of a large male must be alarming at first. Eventually, hormones and habituation to the male overcome her initial trepidation.

Even then, the female may not be ready.

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Copulation lasts upwards of twenty minutes. Brown bear females are promiscuous and may mate with more than one male. Her estrus cycle isn’t a single event. She can have several over the mating season, which generally runs May through July. Female black bears may be induced ovulators, so brown bears could be too, and while no evidence of multiple paternities has yet been confirmed at Brooks River, a single litter of cubs could have multiple fathers.

mating bears

218 Ugly mates with 402 at Brooks Falls in 2010.

If mating is successful, the fertilized egg divides only a few times before entering a state of arrested development in the mother’s uterus. Only after she enters the den in the fall will the blastocyst begin to grow again. Through this delayed implantation, female bears can focus the rest of their summer efforts gaining enough fat reserves to survive hibernation. This allows cubs to be born in mid-winter when they are most protected in their mother’s den.

Over the next few weeks on bearcam, watch for male bears to doggedly follow single females. This is the most conspicuous sign of bear courtship, a season is marked by competition, conflict, persistence, and the promise of another generation of bears at Brooks River.