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BEAR UPDATE: Of clover and mating to delayed pregnancies and berries By Michael Allen Black Bear Researcher The lush, dark green leaflets of clover brush the bottom of the 300-mm lens. Lying flat on my stomach, I peer over the green carpet into the eyes of a brown phase adult female black bear. The large brown head hesitates — her mouth stops chewing — stems of clover spilling out through her protrusible lips. "It's OK, keep feeding," I say out loud. She resumes chewing then bobs her head up and down across a shoulder-width patch of clover. We are surrounded by 30-cm deep, sweet-smelling clover. Two adult males (one black, one brown) are grazing about 2 metres apart 20 metres down slope of the female. Despite the long awaited summer temperatures, the 29 degree Celsius heat does not force these bears to cooler forest cover. They are hungry and with the ripening of the first valley berries still 1-2 weeks away, most bears are forced to grazed (and probably used to it) on new green vegetation through late summer. The female continues grazing. I am so close that I can here the ripping of the clover and horsetail stems: 1, 2, 3... 14 rips before she begins chewing the mouthful of green garnish. Suddenly, her hind end whips around as she responds to the rush of the brown male. Perhaps by feeding too close or starting to advance toward the female, the black male was charged twice by the brown male in the time it took me to re-focus my lens. All three bears re-adjust their spacing and continue grazing, the two males keeping a close eye on one another. Estrus and mating in black bears occurs from late May through late July. Mating activity this year has been high, with 10 different male-female pairs observed since early June. There are a minimum of 12 females available for mating this year, due to low cub production in the last three years. Low cub production is attributed to natural berry crop failures due to extreme weather changes. Adult females can mate successfully with more than one male (cubs in the same litter can have different fathers) during their short estrus of 1-5 days, while the same male may mate with many females in the two-month period. Females may copulate each day with the same or different males. When females are no longer receptive they will move away from approaching males. The male's objective is to sire as many cubs as possible to maintain genetic flow through the population. Females become pregnant in June and July regardless of berry ripening. At fertilization the growth of the zygote stalls and remains free-floating in the uterus. About 20 weeks later, usually mid-October to mid-November, the blastocysts implant and gestation begins — but only if the mother is fat enough. This process is called delayed implantation and occurs to prevent the birth of cubs earlier in the winter when mothers (specifically smaller and/or marginally heavy females) would have a greater burden of nursing a longer period. Most lone pregnant females enter dens from mid-October through mid-November depending on successful weight gain and onset of snowfall. As of mid-July, with no available ripe berries, females have 16 weeks to gain 50-100 pounds to carry a successful pregnancy to term in January 2000. Huckleberries will be the most productive from the valley to 1,300 metre elevations, but rather than ripening in late June they will be available 2-4 weeks later, in late July. High elevation (above 1,300 metres) berry crops will have low, scattered and in some cases no berry production, due to a prolonged snow pack and late flower development. Remaining summer-fall weather patterns will guide ripening success. Weather too hot/dry will shrivel and drop berries. Weather too cold/wet will rot berries. Expect very high bear activity through the Whistler Valley and lower mountain slopes above subdivisions this year, until bears begin entering dens in late October. Residents/visitors to Whistler must accept the responsibility for keeping developed areas clean so that bears passing through to feed on natural food are not attracted to human food. Learning about bears and exercising a higher tolerance for close natural bear activity are the key factors leading to successful co-existence. Whistler black bear research is funded by Coast Mountain Black Bear Resources. Bear ecology displays can be viewed in the valley at the Whistler Museum and on Whistler Mountain at the Roundhouse Lodge. Bear Update columns are sponsored by Pique Newsmagazine. Questions or information about black bears call 935-1176.

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