Respiratory cooling enhances infrared sensing in the South American rattlesnake, Crotalus durissus

Abstract

Snakes possess a profound degree of respiratory evaporation, which can impart significant cooling to the face and head. As pit vipers, rattlesnakes also utilize their forward facing facial pit organs for sensing thermal fluctuations associated with their prey. The greater the difference in temperature between the prey and the pit organ, the greater the thermal flux; cooler pit organs may provide greater infrared detection. We examined the potential for respiratory cooling to enhance the rattlesnake's ability to sense their endothermic prey by exposing two group of snakes to different humidities to manipulate the degree of respiratory cooling, while simultaneously assessing their capacity to track and find murine prey. The latency for snakes to find and eat their prey was significantly longer at high than at low humidity, suggesting cooling increases thermal detection. These differences were accompanied by significant respiratory and facial cooling at low humidity compared to high humidity. Upon initial detection of mice, snakes exhibit a dramatic, slow, respiratory cooling associated, further suggesting that respiratory cooling plays a vital role in thermal detection.