Bear Update: Whistler’s mother bears
By Michael Allen
Black Bear Researcher
The Oct. 25 Bear Update will describe the demographics of the Whistler black bear population, but before that I would like to provide an introduction to the "producers" of the population — the mothers.
Adult females 4 years and older mate with adult males from May through July. The reproductive rate or breeding interval for adult females in the Whistler population is at best every second year. The first year is spent nursing, weaning and denning with their cubs. They typically don not mate in their first year. The second year is spent with their now one year old yearlings, until May or June when the family break-up occurs. The mother’s urge to mate initiates family break-up. Break-up is usually slow, occurring over the summer or sometimes into the following year. Daughters are allowed to remain in the mother’s territory while sons are forced to disperse.
From 1993 through 1996 the minimum number of bear families identified in the Whistler ecosystem (from the Whistler Interpretive Forest to Green Lake) was 23. The minimum number of cubs identified was 52. Mean cub litter size for the four-year period was 2.2 cubs per litter. This is considered highly productive for a Western North American black bear population.
Bear mothers with names were used for more detailed observations, providing information on food habits, behaviour, territory size, and habitat use. Three mothers were destroyed and are not on the list. Two of the three mothers were destroyed after returning from relocation. The remaining mother was destroyed after suffering injuries from a motor vehicle accident.
Use caution when viewing the table data. In 1996, more censuses and observations were conducted than in the previous three years. However, patterns in bear family distribution with the higher levels of food (berries) in 1995 tend to support the higher cub production in 1996.
Mothers listed with a letter only were identified and counted for census purposes.
Six mothers (Sadie, Kathy, Suse, Marisa, Molly and Hazel) provided the largest amount of information. Sadie was first identified in the Whistler Interpretive Forest with two cubs in 1994. Her cubs were destroyed as two year olds at the Whistler landfill in the spring of 1996. Sadie has one cub this year and frequents the landfill less often due to its partial closure.
I first identified Kathy in 1994, when she was with one female cub. She spent the majority of her time in the logged areas along the Cheakamus River. This year she again has one cub and has provided information on bear family use of forests in successional stages.
Suse has revealed the greatest information on general bear family ecology. This is her first time as a mother. She and her three cubs have occupied the smallest of the family territories. She has remained within a 1.5 kilometre square area in the interpretive forest. This was due partly to the cubs’ small size, the high quality habitat and her knowledge of her mother’s territory. Suse’s family has provided excellent data on mother-offspring relationships, behaviour toward other bears and cub development.
The remaining three mothers, Molly, Marisa and Hazel, have revealed information on bear family use in ski areas. Molly and Marisa have two and one cubs respectively. Hazel is a large brown mother with one black and one brown cub. All families utilized the ski trails heavily in spring and summer. Their use of berries has established habitat enhancement guidelines for new glade ski trails on Blackcomb. Gladed ski trail development promotes the production of huckleberries and other biodiversity in the understory.