HIBERNACULUM

What is a "Hibernaculum"?

A Hibernaculum is a place, where an animal finds refuge in an unfavorable season.

What is "Hibernation"?

Hibernation may be defined as the state of dormancy, which many animals undergo, in unfavorable seasons. Different animals hibernate for different reasons. Some hibernate when their food supply runs short; some hibernate when their habitat dries out; while others hibernate when it is too cold for them to survive.

Why do snakes hibernate?

Snakes are poikilothermic or ectothermic in nature, commonly called cold blooded. In fact their blood is not cold, however, such animals do not have metabolic rates high enough to generate their own body heat. Their body temperature rather depends on the temperature of their surroundings; the higher the temperature of the surroundings, the higher their body temperature will be and vice versa.

However, the snakes regulate their body temperature within an optimum range; when it gets too hot, they find shelter in shady places, and when it gets too cold, they bask in the sun to warm up. Usually the optimum day temperature range is 84-88 degrees F, for tropical species, and 80-84 degrees F, for temperate species. The optimum night temperature is usually 5-20 degrees below the day temperature.

In the winters of temperate regions and northern latitudes, the temperature falls too low for a snake to maintain its optimum temperature and the normal level of activity. Therefore it lowers its metabolic rate as the temperature falls down and falls into a deep sleep (hibernation). In order to stay alive during this state of dormancy, the snake relies on its body reserves of fat, stored under the skin and glycogen, stored in liver and muscles. When the snake has used up all of its stored glycogen and fat, it catabolizes the proteins in its muscles to release energy.

Where do snakes hibernate?

The snakes cannot hibernate in the open, since in winter, the temperature of the air and the ground falls below freezing point (32 degrees F). Therefore, to avoid being frozen, a snake must find a wintering shelter or a hibernaculum, where the temperature stays above freezing throughout the winter.

In the wild, the snakes hibernate in any suitable shelter, which lies below the frost line. The frost line marks the depth (3.3 feet in Toronto) to which the ground freezes solid in winter. The preferred hibernation sites are rock piles, deserted rodent burrows caves & caverns, rock crevices, hollow trees, decaying logs, leaf litter or decaying vegetation, loose bark of trees, and moist loose soil. Although some snakes may hibernate in man made shelters such as among the cracks of building foundations, between the dry walls, in junkyards, in barns and basements etc.

When do snakes hibernate?

The snakes spend most of their spring and summer in their foraging grounds close to a body of water, where the prey is abundant. By mid to late September, they stop feeding, leave the foraging grounds and move towards the nearby woodlands and rocky outcrops to find a suitable hibernaculum (or den) to spend the winter. Most snakes return to the same den year after year. They gather in great numbers at these dens, sometimes travelling many kilometers to reach the site. Later arrivals locate a den by following the trails left by earlier snakes that actually found the site. It is common for different species to share the same hibernaculum.

After arriving at the hibernaculum, the snakes linger nearby for several weeks, basking in the open on warm days and retreating into the den on cold days and nights. Finally, by the late October to early November, they settle into deep recesses of the hibernaculum and fall into deep sleep, not to wake up until the snow thaws in the spring.

What is an artificial hibernaculum?

An artificial hibernaculum is a man made shelter, specially constructed to suite the needs of hibernating snakes. The hibernaculum is usually built at a site with good sun exposure (facing south). It consists of a large pit, dug at least two meters below the ground and loosely packed with rocks, bricks, rubble, wood scrap, stones etc., to create many chambers and crevices at various depths for the snakes to hibernate in. The bottom of the pit is close to water table, so that water vapors arising from below keep the den moist, thus protecting the snakes from dehydration. The den also has several entrances at the top, for the snakes to come and go.

Why there is a need to build artificial hibernacula?

As the towns and cities are expanding, the wilderness areas are shrinking and the natural hibernation sites are becoming rare. Sometimes hibernation sites are also destroyed during excavation & earth moving operations. With fewer hibernation sites, many snakes are forced to migrate long distances from their foraging areas to reach their hibernacula. During these migrations, they often risk being trampled by motor vehicles, when crossing roads and highways that separate their foraging grounds from areas with suitable hibernacula.

To prevent such unnatural losses in snake population, there is a strong need to build artificial hibenacula in isolated pockets of wilderness, so that the resident snakes would not have to migrate over long distances to reach a natural hibernaculum.

Moreover, building artificial hibernacula would also increase public awareness and tolerance for snakes.

How does building artificial hibernacula benefit humans and the overall ecology of an area?

Building artificial hibernacula would help maintain a healthy snake population, which is vital to the local ecosystem. Snakes play a very important role in the ecology of an area, both as a vital link in the food chain, as well as a biological pest control agent.

Garter snakes are one of very few predators, which can feed on poisonous toads, newts and salamanders; thus they facilitate their entry into the food chain.

Smaller snakes like the red-bellied and the brown snake, play their role in the ecosystem by controlling slugs and snails, which feed on the leaves and buds of small plants and young trees and may grow in plague proportions if not kept under control.

On the other hand, larger snakes like the milk snake keep the rodent population under control by preying on mice, rats and voles.