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BEAR UPDATE: Claire's Cubs

Black Bear Researcher The odour of damp, rotten wood and the mustiness of a warm-blooded animal fill my nostrils. I can see nothing. I don’t dare shine the halogen light into the blackness of the tree cavity.

Black Bear Researcher

The odour of damp, rotten wood and the mustiness of a warm-blooded animal fill my nostrils. I can see nothing. I don’t dare shine the halogen light into the blackness of the tree cavity.

Instead, I attach a red filter minimizing the intruding illumination. Red light floods the sleeping chamber, revealing an oval-shaped dark mass. I adjust my footing should I have to exit quickly.

Despite the dormant state associated with hibernation, black bears can be alert in seconds to defend themselves. A broken branch is wedged behind my knee. My right hand grips a dangerously thin rhododendron stem uncovered from this winter’s scant snow pack. The sharp branch impales my knee, but prevents me from sliding down the 86 per cent slope and into the talus ravine below. I can feel the blood from the gash behind my knee trickle down my leg. I balance myself against the sharp branch by pulling harder on the shrub while straining to look deeper into the basal cavity of the old growth yellow cedar.

Claire

, an adult female black bear resident to the north-east boundary of Garibaldi Provincial Park occupies this den. A teardrop-shaped opening above the den’s entrance allows me to squeeze my head through and look directly down into her lair. My face is less than 200 cm above her body.

I begin adjusting the strength of the light when I hear faint squeaks from beneath the dark mass. I douse the light and retreat from inside the cavity. I half stand and crouch outside the tree with my ear to the opening.

Squeaks again.

I slowly stick my head inside the opening again while at the same time introducing a small beam of light revealing the mother bear’s position. The squeaks, as far as I could see, belong to at least one black cub. Without disturbing the family a lot, I cannot discern the size of the litter.

Claire

’s den will be monitored through March and April, before the family emerges during May. Litter size will be confirmed either in the den or immediately after during emergence.

During the last six winters (1994-2000) the dates of newborn cub (or COY; cub-of-the-year) vocalizations have been recorded at 16 maternal dens of 10 known and six unknown female black bears in the Whistler Ecosystem. Cub vocalization and visual detection at dens have been recorded from Jan. 5 to March 18. Cubs observed suckling in dens during mid-February through mid-March appeared more active and visually larger than cubs observed in January.

Birth dates of black bear cubs throughout North America are predominantly in January, with occasional reports of later births in early February. Only on two occasions have I observed newborn cubs less than seven days (estimated) after birth. The reason being, at this stage in my research, I do not handle bears. So around maternal dens I give way to bear family security, remaining unobtrusive – which also explains the lack of photographic documentation of newborn bear cubs. Next winter, however, I will use a digital camera to record the size of newborn bear cubs.

At birth, the weight of a 350-gram black bear cub equals two bananas. A 91-kg (200-lb.) female bear will give birth in January to a cub 0.4 per cent of her weight. So why are cubs born tiny, relative to the size of the mother? The answer lies with first, the length of gestation. Black bears mate during June and July. Gestation stops during early August. Delayed implantation takes over to correspond with late summer-fall berry feeding when all bears, especially pregnant females, must gain enough weight to build fat reserves for hibernation and successful reproduction.

In early November the pregnant bear enters her den and by late November if she has not reached peak denning weight, the egg dissolves, and is reabsorbed by her body. If she has gained sufficient weight, gestation resumes, the egg implants, and 6-8 weeks later cubs are born during January.

The small size (350-g; 20-cm in length) of cubs at birth results from this shortened active gestation period. Delayed implantation allows a period of weight gain for the pregnant bear, prevents the birth of unhealthy cubs, and extends the birth date of black bears into the middle of winter, so that after five months of "den development" the cubs may emerge with the new green plant growth during spring.

The second reason why black bear cubs are so small is because of the limited amounts of glucose a pregnant bear can produce during hibernation. The development of mammalian fetuses requires glucose to power metabolic pathways. Black bears do not eat, drink, urinate, nor defecate during hibernation. In this state, the pregnant bear cannot supply the levels of glucose to the fetus without disrupting her lean muscle mass.

In Whistler, an adult female black bear’s annual cycle follows the "2-3-7 pattern" – two months of grazing on new green vegetation, three months of foraging berries and insects, and seven months of hibernation, including five months of cub rearing in the den. Natural foods are unavailable to bears roughly half the year due to colder temperatures and snow cover. Bear food plants enter dormancy and so does the bear.

Whistler black bear research emerges into its eighth season. From 1994 to 2000 field studies on black bear ecology have been conducted as a self-interest project with the purpose of increasing public knowledge of black bears in the Sea to Sky Corridor. Field research is supported by myself through funds received from bear awareness programs sponsored by Whistler-Blackcomb Mountains (1995-2000), Resort Municipality of Whistler (1999-2000), US Web Animal Planet (2000), Natural History Unit of British Broadcasting Corporation (1998) and Jennifer Jones Whistler Bear Foundation (1996-1997). Bear Update columns are sponsored by Pique Newsmagazine . Questions or information about black bears, call me in Whistler at 905-9845 or in Squamish at 898-2713 and by e-mail mallen_coastbear@direct.ca