|MadSci Network: Zoology|
Yes, frogs and toads sleep with their eyes closed. They are equipped with moveable lids that protect their eyes from dust and dirt.
Snakes, like all reptiles do sleep. They are capable of doing this quite soundly despite the fact that they have no moveable eyelids. Moving your hand in front of the face of a sleeping snake will often not cause it wake up for several seconds.
Snakes are perfectly capable of recognizing non-moving prey. Their eyesight is rather poor, but other senses help them to recognize prey. The most important sense is their sense of smell. They may use it to recognize stationary food items. They pick up particles in the air on their tongues and an organ beyond the roof of the mouth analyzes these particles. Some snakes are capable of detecting body heat of prey items. Pitvipers, many boas and pythons have "pits", which are organs that detect heat. These pits are very sensitive. Also, even true vipers are capable of detecting heat well through nerves in the face. In other words, even though snakes are not capable of recognizing prey simply by sight alone, they use other senses to supplement vision.
Well, snakes go under the frostline, of course. But this depends on the climate. It may be a matter of inches or feet, depending upon how cold it gets in their particular region. Many snakes hibernate in burrows dug by other animals. Some hibernate in rock crevices. Most do not dig their own burrows.
The length of their fangs varies tremendously. They may be only one or two millimeters long, in the case of rear-fanged snakes. However, the snake with the longest fangs is the Gaboon Viper (Bitis gabonica). This african viper has fangs that may approach 2 inches in length. Most rattlesnakes have fangs that range between 6-16 mm (roughly). However, there is a report of an Eastern Diamondback Rattlesnake that had fangs that were 27 mm long.
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