Hibernation Patterns of Various Frogs – Literature Review on Homeostatis
This article is centrally concerned with the hibernation patterns of the various types of frogs in the world. Frogs live in all parts of the world. They live in dry, wet, hot and cold climates—from the Arctic Circle to the tropical rainforests and all the climates in between. They have extremely incredible survival techniques
allowing them to live in these extreme climates. Two main strategies are hibernation and estivation.
Hibernation is the central response to cold temperatures. The animal’s metabolism slows down extremely, so the body does not use energy moving around. It then goes to “sleep” so it can utilize the stores of energy already in the body. It first must find a place to hibernate—called a hibernaculum—which will protect it from predators and extreme winter weather. After the winter is over, the frog “wakes up,” leaves the hibernaculum, and gets back to its normal activities of breeding and feeding.
The hibernaculum depends of course on the type of frog. Many frogs are terrestrial, and either dig into the ground or find deep crevices in rocks or logs. These cracks sometimes freeze, however, along with the frog. However, these frogs do not die—ice crystals may form in the body of the frog, but a high concentration of glucose in the frogs organs act as antifreeze and prevent the untimely demise of the frog. When the hibernaculum is graced by spring, the organs warm up and the frog wakes again.
Frogs also hibernate underwater—however, they cannot do it deep in the mud like many turtles—they need more oxygen than is provided by the mud. They are usually partially buried or floating on top of the water, and may even swim around slowly during the period of hibernation.
The second general method of survival for a frog is estivation. In tropical regions, often a dry season will ensue. When this happens, a frog in these climates will burrow into the ground and become dormant, just like in hibernation. Estivation, however, is to prevent loss of water during this dry season. This is accomplished by shedding multiple layers of skin after dormancy, providing a near watertight skin, leaving a hole only to breathe. The water is then kept within the frog’s body. When the dry season ends, the frog emerges and resumes normal activity.
Hibernation and estivation are direct examples of homeostasis. They both represent forms of torpor, which is a decrease in metabolism to deal with external change. Homeostasis consists of an organism controlling its internal environment to cope with change in the external environment. In the case of hibernation, the cold weather initiates a change in the body of the frog. Its metabolism slows to a rate where it only needs the energy from matter only on the body, and in extreme cases, when the frog freezes, the heart and lungs even stop operating, only to resume again when the temperature gets warmer.
Estivation is another form of torpor, a homeostatic mechanism. It decreases the metabolism, but not to survive cold temperatures. When a frog gets hot in a dry climate, it can lose too much water and die. Thus frogs that live in a climate that varies dramatically in precipitation use this mechanism to preserve their water until the humidity returns to a favorable state.
Emmer, Rick. “How Do Frogs Survive Winter?” Scientific American. Nov. 24 1997. Associated Press.