Sleeping Black Beauties
With the onset of colder temperatures, many of the forests' animals realize that it is time to hibernate. One such forest dweller, the Black Bear (Ursus Americanus) hibernates for several months each winter.
The time of hibernation for the Black Bear as well as other animals is dependent on geographical location. For instance, the further north the bear lives, the earlier in the season the biological alarm will sound, telling the bear to begin to den for winter. Black Bears, like grizzlies, are normally very solitary mammals except around abundant food sources and during courtship and mating when they tend to spend a great deal of time together. Once mating has taken place they begin to drift apart, eventually going then-separate ways. Usually the entire process of courtship, spending time together, copulation (mating) and drifting apart takes approximately 1-2 weeks. A rather short love affair one must admit, although hopefully now with the female impregnated, a fascinating biological phenomenon is already taking place inside her.
The phenomenon is called delayed fetal implantation and because the female must hibernate, while at the same time ensuring that its species procreates by giving birth during such a harsh time of year, it has developed a method whereby it is actually capable of delaying the development of the embryo. Members of the bear family such as the Grizzly Bear, Black Bear, Polar Bear, as well as many of the bear sub-species all possess this adaptation. Besides bears and their subspecies, many other mammals use Embryonic Diapause or D.F.I., Delayed-Fetal-Implantation as an adaptive advantage. The Badger, as well as most other members of the Weasel family, including Kangaroos and Wallabies, Seals, Roe Deer, Bats, Armadillos, Skunks, ...in fact about 100 species of mammal utilize D.F.I. Researchers are getting closer to understanding how it works.
This process begins when an egg is fertilized by the male during mating in summer (around June or July) and will be carried by the female in suspended animation until denning begins in late fall of that year. The embryo will develop during hibernation where, in the warmth and safety of the den, the female gives birth to an average of two cubs. At birth in January, Black Bear cubs are usually 3/4 of a pound, whereas grizzly bear cubs are usually one pound or more. Both a male and female bear's physiological systems slow dramatically while hibernating.
Breathing and heart rate drop to near unbelievably low levels, such as a heart rate of as few as 30 beats per minute. Black bears, as well as other bear species, often wake up in the den and may actually take a stroll outside during the winter months. Rarely do they stray far from the den site. Neither the male or the female eats or eliminates during their entire winter sleep, and instead exist solely on reserves of fat they have hopefully been able to build up over the summer months.
According to scientific data, the Black Bear may lose up to 25 percent of its body weight during the hibernation cycle, A nursing female with cubs may lose as much as 40 percent. Oddly enough, this is the time of year when Black Bear mortality is at its lowest. Bears in hibernation are actually capable of recycling their urine and breaking it down into non-toxic components. If humans were to try this, they would die from urea poisoning. Our bodies are set up in a way that requires us to purge wastes through our urine.
Furthermore, if a human were to be relatively inactive for a six month period, they would undoubtedly suffer from severe muscle loss and would lose the valuable calcium that makes bones healthy and strong (in other words, osteoporosis) and yet hibernating bears don't suffer any of these conditions. If however, the food supply is low in any given year such as that which burdened Black Bears in Ontario only 2 years ago, female Black Bears may only reproduce every 3 or 4 years, and apparently cases exist where females have gone as long as 9 years between births.
The Black Bear is truly a marvel of biology and a large carnivore deserving our respect as well as admiration. It is the king of the forest in many areas of Canada aside from the territories occupied by grizzly and Polar Bears.
Scientists believe that much can be learned from the bear to help cure, or at the very least, relieve the symptoms of various human diseases like osteoporosis. Effective conservation planning and protection will enable the Black Bear, the most common and prolific of bear species, to remain that way in our Canadian forests. Let's help conservation efforts to protect this incredible, majestic and powerful animal.