Snakes evolved from their reptilian ancestors to have no limbs. They slither along the surfaces of the earth, sensing the world through reverberations on the ground and smells in the air. They smell through their tongue. They hear through sound reverberations that hit their body and travel to their hearing organs. They move by avoiding normal surfaces. The body of a snake evolved to be composed of curves, designed to detect irregularities in the surface of the earth, allowing them to find and push their way against these friction points on the land. Irregularities along their body create friction with the irregularities on the ground to propel them forward. Clearly snakes evolved to live completely differently than humans. No wonder humans have developed an intense fear of snakes; the world of snakes is too foreign for human comfort.
Humans have organs called eyes that allow us to see by perceiving light reflected on the world around us. Similar to how humans use light to see, some snakes are able to see in the infrared spectrum by perceiving heat that is reflected off of objects. Pit vipers, boa constrictors, and pythons have evolved organs, called pit organs, in their faces that are used to detect the infrared energy of prey. Angela Corkill, an animal keeper at Zoo Montana, is a caregiver to Harry, who is a 21-year-old ball python. Harry is a snake that is able to see in infrared. “He is ectothermic,” said Corkill. “He gets his heat from an outside source. He does not create it on his own. Those little pits can help him determine what’s warm and what’s not.” Humans can also sense heat in the environment, but humans use heat sensitive nerve fibers to do so, not a specialized organ. A ball python receives heat stimuli through the large pits on either side of its head, directing heat to infrared sensitive tissue inside the pit organ.
Over 30 years ago, a breakthrough study was published in Science AASS, on infrared vision in snakes. The study was done by Eric Newman, Professor in the Department of Neroscience at the University of Minnesota, and Peter Hartline, who is currently a researcher at New England Biolabs. They found that a rattlesnake’s pit organ may play an important role in responding to prey and predators. The information received from its heat sense allows the rattlesnake to recognize biological objects and orient itself. The rattlesnake is able to do this because its pit organ receives a crude IR image of the environment around it and sends the signal to the part of the brain involved with the visual system. This makes scientists wonder if the pit organ acts like a camera for infrared light, allowing the snake to see in infrared images. The study showed that the visual part of a rattlesnake’s brain receives inputs from both the visual (eye) and IR systems. The researcher’s observations suggest these systems are working in unison. When a rattlesnake or ball python sees the world it, may look like an IR image overlaid on a map, providing more thermal data to the user.
Recently an article published in Nature, Molecular Basis of Infrared Detection by Snakes, took this information on pit organs to the next level. The study looked at the nerve impulses of the pit organ, and shed light on what it’s like for snakes to feel heat stimuli. They found that the receptor channels on the nerve fibers in the pit organ (TRPA1 channels) are the same as the ones in humans that are activated by wasabi, mustard plants, and other irritants. These channels allow both snakes and humans to feel wounds. A mutation in these channels is what gave certain snake’s the ability to sense heat. Whether a wound and IR might feel the same, we can’t say for sure, leaving the exotic experience of a snake’s world up to our own inferences.