Britannica Sources used in this answer

How sensitive are the heat-detecting pit organs of rattlesnakes?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A painted turtle (Chrysemys picta) with a dark shell and red and yellow markings rests on a rock near water, surrounded by green aquatic plants. — reptile Painted turtle (*Chrysemys picta*).

The heat-detecting pit organs of rattlesnakes and other pit vipers are remarkably sensitive, functioning as highly specialized thermoreceptors that allow these reptiles to strike at warm-blooded prey with precision, even in total darkness.12

These organs are capable of detecting infrared radiation that produces a temperature change as small as 0.003 °C (0.005 °F) at the nerve endings within the pit membrane. This sensitivity triggers a significant dynamic increase in the frequency of nerve impulses sent to the brain. While these receptors are highly responsive to rapid thermal changes, they are notably insensitive to steady, gradual temperature variations, which helps the snake filter out background environmental shifts.1

In behavioral experiments, rattlesnakes have demonstrated the ability to detect prey that is 10 °C (18 °F) warmer than the background environment from a distance of 40 cm (16 inches). While some studies have shown that pit vipers and certain boas can detect temperature differences of less than 0.6 °C (1.1 °F) using controlled heat sources, the physiological threshold for individual receptor activation is significantly more acute.12