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.

Like all pit vipers, the rattlesnake’s sixth sense depends on two innocuous pits located between their eyes and their nostrils. With two pits on either side of its head, the snake can even ‘see’ heat in stereo. Each pit is a hollow chamber with