I couldn't say it better Chris, I got this off of a zoological website:
"Heat-seeking missiles of the natural world, ball pythons can easily hone in on prey in utter darkness. Along a ball python's upper jaws, several scales cup inward, each forming a deep pit containing nerves that sense infrared, or body heat. The snake can tell which direction warmth is coming from because the pits open at different angles, like an open fan of folded paper. A temperature change of only 3/1000th of a degree sends a signal to the brain, alerting the snake to the nearby meal. These labial pits, coupled with the ability to see well in darkness, spell doom for its mammalian victim."
Jeff & Starr
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