Scientists reveal how snakes ‘see’ at night

PARIS, March 14, 2010 (AFP) – Scientists revealed Sunday for the first time how some snakes can detect the faint body heat exuded by a mouse a metre (three feet) away with enough precision and speed to hunt in the dark. It has been known for decades that rattlesnakes, boas and pythons have so-called pit organs between the eye and the nostril that can sense even tiny amounts of infrared radiation — heat — in their surroundings.

Among pit vipers, the western diamondback rattlesnake, native to northern Mexico and southwestern United States, is in a class of its own, its heat-seeking ability up to 10 times keener than any of its cousins.

Even with tiny patches covering its eyes, the snake has shown the ability to track and kill prey blindfolded.

But exactly how these reptiles detect and convert infrared signals into nerve impulses has remained a mystery, and the subject of sharp debate.

One candidate was the photochemical process underlying vision, whereby the eye sees electromagnetic radiation — visible light for humans — in the form of photons that activate receptor cells, which in turn convert the energy into a biochemical signal to the brain.

Some fish, for example, can see into the infrared