|Bear in its den - MDC|
The difference between hibernation and torpor is mainly a matter of degree and the terms tend to be used interchangeably in many sources. Hibernation can be thought of as an extended degree of torpor. Hibernating animals will wake up briefly during the winter and may even emerge for a period on occasion. On the other hand, the increased metabolic cost of arousal may be harmful, such as when bats are aroused and fly, burning up their winter metabolic reserves.
Hibernation and torpor may be triggered by decreasing temperatures and day length, or in other species by the lack of metabolic resources. In either case the slowing of metabolic activity is a means of storing energy. Some snakes will hibernate in the extreme heat of summer, a response called aestivation.
During my medical residency in Minnesota there was a research project studying bear metabolism during hibernation. I was "given the opportunity" to perform a liver biopsy on a hibernating bear. The plan was to sneak into the hibernaculum, plunge a large bore needle between the ribs and maintaining suction, extract a core of liver tissue and leave before the bear was fully awake. I was out of town at the appointed time and missed my chance --- I was also young and foolish enough to be disappointed in missing the "opportunity."
Bears should be denning by now unless they are confused by the warm winter weather. I was reminded of this by a recent story in the New York Times. A scout leader in New Jersey was showing his troops a cave he had been checking for many years. He crawled through a tight crevasse at the opening and was attacked by a bear denning inside. You should read the rest before crawling into a winter cave.
Missouri bears can den in hollow trees, root wads, caves or ground nests in brush. A bear den can be a busy place as seen in this MDC Video from Jeff Beringer.
The scout master has been released from the hospital with minor injuries as reported on cnn.com