How Rattlesnakes See at Night

To hunt at night, rattlesnakes use which kind of sense?

And the answer: infrared vision.

Snakes that are known as pit vipers, like rattlesnakes and moccasins, have that description not because they live in pits, but because they have special heat-sensing organs, located in pits between their eyes and nostrils. This allows them to notice a slight rise in temperature nearby.

For predators whose primary prey are small, warm-blooded mammals, pit vipers are perhaps almost too evolutionarily prepared. These snakes are able to sense movement and heat in complete darkness, and can strike their prey dead-on without a moment's hesitation.

However, while scientists originally believed that these infrared pits were solely for hunting, recent evidence points to its function as a means of thermoregulation. In an experiment where scientists placed pit vipers and true vipers (snakes without infrared abilities) in a dark, warm maze, true vipers struggled to find refuge while pit vipers had no problem. This suggests that heat sensors help the pit vipers make decisions like seeking refuge, and fleeing prey. Now, scientists have begun to theorize that pit vipers' infrared vision originally evolved as a defense mechanism.

Regardless of its evolutionary origins, pit vipers' infrared abilities combined with their deadly venom work to create some of the most dangerous predators in the world. Check out this video to see the top cut of deadly snakes in action:

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