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• Thermal pits of vipers, pythons and boas detect infrared radiation emitted from prey using protein channels activated by heat. Not sure if this shows the heat sensors. Click/tap images for attribution and license information.

• While the molecular precursors of this mechanism are found in other snakes, the protein is both expressed to a much lower degree and is much less sensitive to heat. Infrared sensing snakes use pit organs extensively to detect and target warm-blooded prey such as rodents and birds.

• These findings illustrate the broad evolutionary tuning of transient receptor potential (TRP) channels as thermosensors in the vertebrate nervous system.” (Gracheva et al. 2010:1006) “Although not as well known for infrared vision as the crotalids, another group of snakes, the boas and pythons, also have heat sensors.

That includes venomous snakes from the subfamily Crotalinae, commonly known as pit vipers—so-called for the pair of heat-sensing organs located in “pits” between their eyes and nostrils.

What is commonly called a Pit Organ allows these animals to essentially "see" radiant heat at wavelengths between 5 and 30 μm. The more advanced infrared sense of pit vipers allows these animals to strike prey accurately even in the absence of light, and detect warm objects from several meters away.

Thermal pits of vipers, pythons and boas detect infrared radiation emitted from prey using protein channels activated by heat. Not sure if this shows the heat sensors. Click/tap images for attribution and license information.

Infrared sensing in snakes. Essentially, it allows these animals to "see" radiant heat at wavelengths between 5 and 30 μm to a degree of accuracy such that a blind rattlesnake can target vulnerable body parts of the prey at which it strikes, and other snakes with the organ may detect warm bodies from a metre away.