In the last week of September, Whistler black bears are now working on the downside of summers bumper huckleberry and blueberry ( Vaccinium spp.) crop. Bears have been foraging Vaccinium berries during the last 80 days from valley to sub-alpine elevations. In a good summer-fall berry season, bears should have 80-120 days of berry feeding at valley to alpine elevations from July through November. Berry use and availability is quantified each year by the number of "berry days."
Berry days are defined as the number of days bears have access to Vaccinium and Sitka mountain ash ( Sorbus sitchensis ) berries. Berry availability begins when the first 25 per cent of berries are ripe in surveyed plots throughout select shrub-dominated habitats in the Resort Municipality of Whistler. This years high berry availability is attributed to high pollination during spring bloom (May and June) followed by a balance in precipitation (June to mid-July) and sunny, hot weather (mid-July to August).
A well-balanced "seasonal" climate prevents stress in plants allowing optimal berry yield in fruit and size (swell diameter). The draught of 2004 forced berries into ripening synchrony across a low to high elevation gradient (valley to alpine), allowing bears to consume the summer and fall berry crop in two months (summer) instead of 3.5 months (summer-fall). The consequence was low to non-existent fall berry availability (starting early September) forcing bears into valley urban habitats to search for domestic berries and fruits and opportunistic human foods.
Berry size was also lower in 2004 due to stressed plants in drought conditions. Smaller berry size reduces the bears foraging efficiency (berry bite rate) and increases berry shriveling.
As of Sept. 23, 2005, bears have consumed an estimated 75 per cent of the Vaccinium crop in ski area shrub-fields and are beginning to rely heavily on the clusters of bright red Sitka mountain ash berries while consuming the scattered remains of huckleberry and blueberry. The mountain ash berries did experience a drop in abundance above mid-mountain due to last winters low snow pack that may not have insulated shrub dormancy. Many of the 1-2 metre high shrubs were sticking out of the snow in January and February and did not produce berries this summer.
In October, bears will continue to seek Sorbus berries in the mountains and then, depending on weight gain and onset of early winter snowfall, could move to valley elevations to continue berry feeding.
Other late fall berries secondary to Vaccinuim are the clusters of dogwood berries (white), rosehips (orange-red), Oregon grape (blue), currant (blue), and high-bush cranberry (bright red). If scattered Vaccinium and Sorbus crops can keep bears foraging at higher elevations through mid-October followed by early winter snowfall, bear activity in urban habitats should be low.<