Lets talk about bears
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Lets talk about bears *
The current estimate of the black bear population in British Columbia is 120,000–160,000. This is about one quarter of all black bears in Canada.
Black bears have low reproductive rates compared to many other mammals. Females usually don’t reach sexual maturity until four years of age and breed only every two to three years after that. In areas of abundant food, they may reach maturity sooner. Where food is scarce females might not bear their first litter until they are six or seven years old. In most populations males don’t mature sexually until age five or six. Black bears can live for 25 to 30 years in captivity, but their life-span in the wild is usually much shorter.
Black bears in British Columbia usually mate from early June to mid-July. However, in a phenomenon called delayed implantation, the embryo does not implant in the uterus and begin developing until October or November. Cubs are born in January or February, during hibernation. Black bears usually have two cubs, but litter sizes vary from one to five. At birth, cubs are hairless, blind, and weigh about 400 g. They nurse while the mother continues hibernating and weigh 3 to 5 kg when they leave the den in spring. Cubs stay with their mother their entire first year and sometimes longer. During that time, she protects them and teaches them how to survive. They are weaned between July and September and hibernate with their mother the first winter. In coastal British Columbia, almost all black bear dens are in or under large-diameter trees, snags, logs or stumps, and may be up to 25 m above the ground.
Ten thousand-year-old skeletons in caves on Vancouver Island indicate that black bears arrived soon after glaciation.
The black bear (Ursus americanus) is the smallest and most widely distributed member of the bear family found in North America. In British Columbia, black bears inhabit all areas of the province except most urban cores. They are relatively numerous and tolerant of human activities and as a result are the most commonly encountered large carnivore in the province.
Black bears have a chunky body, small black eyes, a broad head, rounded ears, a short tail, and a fine, long pelage. Typically, they have uniformly black fur, except for a tan muzzle and a white V on the chest. The feet are flat-soled (plantigrade), with naked pads and five toes with relatively short curved claws. Adult size, and particularly weight, varies greatly according to sex, season, food supply, and geographic area. Adult males measure about 60 to 90 cm in shoulder height and 130 to 190 cm in length and weigh 80 to 300 kg. Females are smaller, weighing 40 to 140 kg.
Hibernation is an important survival strategy for bears in regions such as British Columbia where their main foods – green vegetation, berries, salmon, and insects – are not available in winter
Black bears typically hibernate for three to five months on Vancouver Island. Females, particularly the pregnant ones, hibernate longer than males.
When cold weather arrives, bears become increasingly lethargic and enter their dens. During hibernation their heart rate drops from about 50 beats per minute to around 10. Oxygen intake decreases by half, and body temperature drops by about 3ºC. In a most remarkable biochemical feat, hibernating black bears do not eat, drink, urinate, or defecate. They have a unique process for recycling metabolic wastes into nutrients. Black bears may lose up to a quarter of their body weight during hibernation. With only about six months to build up fat reserves for hibernation, black bears must eat a lot of food. They are particularly attracted to foods that are abundant and high in protein and energy and that they can get with little energy expenditure. Although this strategy helps them survive, it can also bring them into contact with human beings.
The area that a specific bear uses throughout the year for food, water, breeding, and shelter is called its home range. Home ranges of adult males, typically 25 to 150 km2, are larger than those of females, which vary from 5 to 25 km2. Home ranges are usually made up of several feeding areas connected by travel routes. This is why we see bears on the same trails and roads we use. They travel to the lake or river for food and water. The trees along the way may provide a babysitter tree for a mom with clubs or a safe refuge to hide in when people come by.
A bear’s nutritional state is important because it influences reproductive success, survival, and hence the abundance of bears. Black bears are classified as carnivores (meat eaters), but they are omnivorous (“everything-eaters”) and consume a variety of plant and animal foods. Black bears use different foods in different reasons and seek out low-fibre, easily digestible foods. Vegetable matter forms the bulk of their diet, particularly in spring and summer. In spring, black bears forage for succulent vegetation in meadows, estuaries, riparian habitats, skunk cabbage swamps, avalanche chutes, grassy south-facing slopes, and burned areas. Also in spring, they prey on newborn deer, elk, moose, and caribou. In summer, black bears feed on insects and larvae, fruits, berries, salmon, and carrion. Come autumn, they often forage on berries and on spawning fish. Bears kill and eat small mammals opportunistically throughout the year. Rarely, they have been reported to kill adult moose and elk. To conserve energy, black bears seek out concentrated food sources such as spawning fish and dense berry patches, an important thing to remember when you are in the backcountry. The habitats they use are as varied as the food they eat – forests, wetlands, subalpine meadows, avalanche chutes, riparian habitats, and beaches.
The Bear Necessities: Why Our Forests Need Bears
What comes to mind when you think of bears? Many rural Canadians often think of them as intimidating nuisances that prowl our forests, mountains, and dumps. But bears play a vital role in our ecosystems.
ENRICHING THE FOREST SOIL
Bears are known for their love of fish, but did you know that dragging caught salmon through the forest helps soil? Animal carcasses enrich the soil and forest cover vegetation, adding the nitrogen required for healthy plant growth. These processes are so interconnected that scientists say you can actually use the health of a forest to gauge the health of the nearby river’s salmon run.
SEED DISPERSION
The help offered by bears continues after digestion. Following their meals, bears drop their scat in the forest, which is an effective means of disbursing seeds from the fruits and berries they eat. Bears, particularly brown and black bears that eat a lot of fruit and other vegetation, process the nutrients and digest the seeds, which re-enter the ecosystem in the form of scat. Bears are always on the move, and so too is their inadvertent planting project. Brown and black bears can disperse more than 200,000 seeds an hour per square kilometre!
Each pile of bear droppings contains an impressive concentration of seeds: one pile of scat collected in Rocky Mountain National Park in Colorado yielded 1,200 seedlings after it was replanted in a local greenhouse.
ECOSYSTEM BALANCE
Finally, bears keep populations of deer in check. Like wolves and other carnivorous mammals, bears invoke fear among their prey, meaning animals like deer are always on the move.
This has two positive ecosystem implications: it prevents deer from leisurely grazing and overeating vegetation in a single spot and also upturns the soil when they run. Without bears and wolves, none of this would happen.
Important as they are, Canada’s bear species face numerous threats, including loss of habitat, hunting, poaching, capture, and climate change. Expanding protected areas is the most effective way to ensure natural habitats can sustain populations and prevent population collapse.
Canada’s federal government has committed to protecting 30 percent of our land and ocean by 2030. As we inch closer to the deadline, it’s more imperative than ever that we keep decision-makers accountable. (information copied from Nature Canada)
