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Winter Solstice and hibernators

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Winter begins on the Winter Solstice and ends on the Vernal Equinox. Winter is the season with the shortest days and the lowest temperatures.

In the Northern Hemisphere, the Winter Solstice occurs either December 21 or 22, when the sun shines directly over the tropic of Capricorn. This year the Winter Solstice is on December 21, at 12:11 PM EST.

Because of the Earth’s tilt at this time of the year, the Northern Hemisphere receives less direct sunlight creating winter, while the Southern Hemisphere receives more direct sunlight creating summer. As the Earth continues its orbit the hemisphere that is angled closest to the sun changes and the seasons are reversed.

The Winter Solstice marks the shortest day and the longest night of the year. The sun appears at its lowest point in the sky, and its noontime elevation appears to be the same for several days before and after the solstice. Hence the origin of the word solstice, which comes from Latin solstitium, sol or "sun" and stitium, which means "a stoppage." Following the winter solstice, the days begin to grow longer and the nights shorter.

Trees and plants stop growing in winter and many animals hibernate or migrate away from cold weather.

As winter and cold weather approach many mammals eat and add layers of fat to hold them over to spring. Some wild critters have the ability to shut down or hibernate for the winter. No food or water for extended periods of time waiting for spring.

Creatures like frogs, snakes and insects have this ability, but what is truly amazing is that larger animals like bears, raccoons and groundhogs can go without the basic necessities of life for long periods of time.

Some of these mammals; groundhogs, marmots, jumping mice and some bats are true hibernators. Meaning they lower their body temperature to almost freezing and lower their body functions. While the list for hibernating mammals is relatively small, the body temperatures of these animals will plummet until only a few degrees above the cold climate, their breathing will drop from several hundred times a minute, to one in five minutes, their heartbeat will go from several hundred a minute to one or two beats a minute, they will move only slightly every few hours, although their muscles will retain their tone and their digestive and excretory systems will continue to work. So deep is this sleep, that often times the hibernating animal is insensible to sound or touch!

False hibernators (also known as torpor) maintain a normal body temperature but have a reduced metabolism. If the weather warms a bit, they may become active and meander around outside their den.

Bears and chipmunks are examples of false hibernators. The so-called hibernation pattern of many bears is only a series of naps.

Since the body temperature of bears remains high (which burns an estimated 4,000 food calories a day) and their breathing remains at a normal rate, their winter sleep can easily be disturbed. Some bears even wake up during their winter nap and prowl around for hours, sometimes days.

Fish are ectothermic and cannot hibernate because they cannot actively down-regulate their body temperature or their metabolic rate. However, they can experience decreased metabolic rates associated with colder environments and/or low oxygen availability and can experience dormancy.

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