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Bear Update: Cub attacked by another mother bear

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Black Bear Researcher

On the evening of July 3 rd I witnessed a mother black bear physically attacking another mother bear’s cub. This is the first such observation in my 22 years of black bear study.

I have seen adult males attempt and successfully kill cubs and coyotes attempt to kill cubs, but never any physical (contact) aggression by a mother to another mother’s cub-of-the-year.

Adult females in Whistler do not maintain exclusive territories and rarely fight but rather, maintain hierarchies of social ranking by age (size and experience) and dominance. Females will chase females and communicate using body language/posturing, vocalization, and scent-marking on mature trees and sign-posts, etc. While I have observed adult females chasing each other from feeding patches and breeding ranges and less frequently with short bursts of paw-swats or biting, I have never observed a mother attacking another mother’s offspring (cub or yearling).

During an evening (6-9 p.m.) bear viewing tour, I came upon a situation near Crabapple Creek at the top of the Fitzsimmons Chair where Kayley, a resident mother, and her 18-month-old yearling son were grazing 30 metres from the edge of the ski trail. Another resident mother, Jeanie, was treed nearby with her 5.5-month-old son in a mature cottonwood tree. Jeanie’s daughter was treed separately in another cottonwood tree 20-metres upslope. A bike patroller nearby reported that Kayley charged and chased Jeanie to the ski trail edge and, possibly in confusion, Jeanie’s cubs became separated, or they may have climbed the trees before she treed. From 20:17 hours when I arrived, the following events unfolded that led to two physical attacks by Kayley on Jeanie’s 5.5-month-old daughter:

20:17 hrs. Kayley and yearling son grazing 30 metres from Jeanie treed, 20 metres up cottonwood with her son 5 metres above in same tree and her daughter 20 metres upslope and 20 metres high in another cottonwood.

20:21 hrs. Kayley approaches Jeanie’s tree — son climbs higher vocalizing stress — Jeanie snorting and blowing while slapping branches. Kayley backs off and paces with yearling at her side.

20:40 hrs. At this point I left to return clients to valley at end of tour.

21:11 hrs. I returned to find Jeanie and single cub as before treed but now Kayley treed with yearling 1 metre above her on a branch and Jeanie’s daughter on the same branch as the yearling only 1 metre apart. Cub was bawling distress.

21:15-21:46 hrs. Jeanie climbing down tree and pacing around base stressed. Son remains treed above her and is vocally stressed. Daughter extremely stressed vocalizing loud, drawn out bawling. Kayley and yearling remain where they are in tree 1 metre below Jeanie’s daughter.

21:47 hrs. Jeanie charges base of Kayley’s tree. Kayley’s yearling jumps up on branch that Jeanie’s daughter is on. Kayley remains 1 metre below yearling and cub watching Jeanie. Yearling and cub are nose to nose — 30 cm apart. Both distressed with backs arched and hissing (that’s also something I have never seen: offspring of different families on the same branch).

From my point at 60 metres, Jeanie’s cub either slid off branch or jumped. Kayley immediately slid down tree and Jeanie charged into base of tree cover. Kayley’s yearling remained on branch watching downward. Jeanie’s aggression seems to have no affect on Kayley.

21:56 hrs. Jeanie’s cub climbs quickly in second growth cedar with Kayley pursuing. Kayley reaches cub and with no hesitation, swats bawling cub, pulling the small body into her chest and immediately sliding (together) down tree. I can hear branches breaking.

Glimpse of Jeanie charging into base of cedar tree.

21:57 hrs. Jeanie’s cub climbs quickly in mature cottonwood (where she was previously treed; yearling gone) with Kayley following. Cub struggling at upper limit of branches. Kayley bites and swats at branch 1 metre below cub. Cub falls into Kayley’s reach and Kayley swats bawling cub, connecting with cub’s body and catapulting cub from at least 25 metre height back into second growth forest canopy.

At this point, it is too dark to see into the lower forest but, I can hear oscillating vocalization (stand-off aggression) between (likely) Jeanie and Kayley. Kayley’s yearling is not seen nor is Jeanie’s other cub. Kayley then seen climbing cottonwood and sniffing branches then climbing cedar and sniffing branches where attacks took place (as if she was trying to find the cub).

22:00 hrs. No further sounds of aggression or distress. Jeanie walking away with one cub 50 metres upslope. Kayley’s yearling walking away from cottonwood where attack took place. No sign of Kayley.

22:26 hrs. Kayley’s yearling loping away scenting ground and looking around. No sign of Kayley.

22:28 hrs. Last sighting of Jeanie and single cub 200 metres away.

The next day at 04:46 hours, I found Jeanie and single cub grazing 20 metres from attack site. There were no signs of the second cub. At 05:38 hours, I heard two long-winded calls of distress from a cub somewhere back in the second growth forest. Jeanie stood alert with one cub at her side, looking in that direction.

When I arrived with the morning bear tour at 06:00, no bears were seen in area until 07:37, when Jeanie and single cub were seen again grazing 10 metres from area of attack. Kayley and her yearling son were located 600 metres away.

Over the next two days I searched the area for the second cub but only found broken branches and hair.

On July 6, Jeanie was located in the mountain bike park with both cubs. No apparent injuries were observed on either cub. The cub’s survival is a testament to its durability and instinctive effort to flee and climb from danger.

I did not see the initial encounter between the two neighboring mothers (earlier that evening) that would likely help me fully understand why Kayley became so aggressive to target the cub. I can only surmise that at the time Kayley was without her daughter (possibly confrontation with adult male to engage family break-up and breeding) and possibly stressed when she ran into Jeanie. Even though Jeanie is the larger, dominant bear, Kayley can afford to become more aggressive because she has large offspring that are not as dependent in their second year as Jeanie’s cubs are in their first year.

If you want to learn more about the long-term study of mother black bear behavior in Whistler come to Lost Lake Park at 9 p.m. on Saturday, July 28 for a free outdoor, large screen presentation sponsored by the Whistler Museum and Archives Society.

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