The Effects of TORPOR or Lack thereof

There are several definitions of torpor: sluggishness, apathy, suspension of physical powers, or dormancy. ESTAVATION is a summer torpor that occurs with species that live in warm climates. It occurs during the hottest time of the year. HIBERNATION is winter torpor. We, here in Idaho, are most familiar with this type. All species go through some type of torpor. Nocturnal animals sleep during the day, and diurnal species do the opposite.

Torpor is an involuntary thing. The HYPOTHALAMUS is the part of the brain that controls body temperature, hunger, sex drive, moods, and sleep (TORPOR). Changes in the weather or fatigue can stimulate the onset of torpor. When waking from torpor, hibernating animals waken very slowly and are very groggy.

HISTAMINE is an organic, nitrogen compound involved in immune responses and physiological functions. It is believed that the production of this chemical is a natural inducer of hibernation (torpor).

Bears and many rodents are not true hibernators. Their heartbeats and temperatures do not go down to the degree that other hibernators do. This allows them to awake periodically to eat from a food cache, defecate, and drink.

An interesting study with chipmunks has shown that lack of torpor can kill.When winters are warmer than usual, these rodents fail to go into their natural torpor cycle. The results are that about a 90 percent loss of life occurs within a population that doesn’t get the required sleep. This is contrasted against a 90 percent winter survival rate with populations that get the needed sleep.

Estivation and Lizards

Estivation is a condition of dormancy or torpor during very hot or dry seasons. It’s like summer hibernation. Snails, salamanders, frogs, desert tortoises, snakes, and lizards are some animals that estivate. The only known mammal to do so is the Malagasy Fat-Tailed Dwarf Lemur. The snakes, which I kept in my High School classroom, were forced to estivate during the summer when no one was around to feed them.

The most abundant reptiles are lizards (about 3000 species world wide) – most of which live in hot areas. They are some of the more common species that Estivate during the hot times. Lizards usually have four legs, with five toes on each foot. Their skin is dry and scaly, eyelids are moveable, and ears are on the sides of their head. If you’ve ever tried to catch one, you know how fast they can move. I’ve caught them by using a fishing pole with a loop on the end of the line. By reaching the pole as far as I could, I’d carefully drop the noose around their neck and then pull it tight.

Most lizards are carnivorous but some, like iguanas, are vegetarian. For reproduction, the female lays her eggs, covers them, and then lets the warmth of the sun hatch the young – six or seven is the most common number. However, some species give live birth.

Because their body temperature is the same as the air around them (cold blooded), a burrow is extremely important to escape cold or the extreme summer heat of the desert which would cook them. The burrow is also an escape from a predator that ventures too near. Otherwise, they will remain motionless and rely on their camouflage to escape the danger.

Lizards send visual signals by head or body “bobbing” – each species has its own signature method.

A dark phase Western Fence Lizard at attention on a rock

A dark phase Western Fence Lizard at attention on a rock