Snakes have good vision especially King Cobra and the tree snakes, but most of them are near-sighted like borrowing snakes and the others. Of course, all are colour-blind. They do not have eye-lid to cover their eye.Snakes can smell pretty well mainly by their sensitive tongue,but not much by their nostrils. The tongue picks up the odours/molecules in the air and the Jacobson's organ above the mouth will make out what the odour is.
Snakes like Pythons & Pit Vipers have heat sensing pits, which helps in detect warm-blooded animals like rodents & birds in absolute darkness.
Venom is a prey-immobilizing substance in snakes that is used secondarily as a defense system. Venom is not composed of a single substance, but is a toxic saliva consisting of a complex mixture of chemicals called enzymes. Almost all venoms are composed of approximately 90% proteins. Two general types of toxins are known, neurotoxins and hemotoxins.
- Hemotoxin (blood toxin) : Hemotoxic venom attacks the circulatory system and muscle tissue causing excessive scarring, gangrene, and sometimes leads to amputation of the affected area. This venom basically destroys tissue and blood cells. In addition to killing the prey, part of the function of a hemotoxic venom for some animals is to aid digestion. The venom breaks down protein in the region of the bite, making prey easier to digest.ex : Vipers
- Neurotoxin (nerve toxin) : Neurotoxic venom attacks the victim's central nervous system and usually result in heart failure and/or breathing difficulties or even total respiratory paralysis. eg: Cobras, Kraits, Coral snakes.
Some snakes have venom that is both hemotoxic and neurotoxic.