Take a whiff of mustard or wasabi and you'll be hit with a familiar burning sensation. That's the result of chemicals in these pungent foods hitting a protein called TRPA1, a molecular alarm that warns us about irritating substances. The same protein does a similar job in other animals, but rattlesnakes and vipers have put their version of TRPA1 to a more impressive and murderous purpose. They use it to sense the body heat of their prey.
Pit vipers are famed for their ability to detect the infrared radiation given off by warm-blooded prey, and none more so than the western diamondback rattlesnake. Its skills are so accurate that it can detect its prey at distances of up to a metre, and strike at objects just 0.2C warmer than the surrounding temperature. Against such abilities, darkness is no defence.
