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Pit-viperPit vipers, along with several of their snake cousins, marry two senses to better locate prey at night: sight and a heat-detecting ability. Deep pits, which lie on each side of the snake's face between the nostril and the eye, are capable of sensing the warmth given off by a human hand held a foot away. Each pit has its own "field of vision" which overlaps slightly with the other, so that the pair work stereoscopically in the same way that eyes do. Heat and visual data are sent, via the optic nerve, to the pit-viper's brain, where the two types of data are transposed into a single image. What's different about the nocturnal eye? (back) Photo: Alan H. Savitzky/Old Dominion University. Night Vision | Zoology After Dark Resources | Guide | Transcript | Night Creatures Home Editor's Picks | Previous Sites | Join Us/E-mail | TV/Web Schedule About NOVA | Teachers | Site Map | Shop | Jobs | Search | To print PBS Online | NOVA Online | WGBH © | Updated November 2000 |