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Do snakes have ears?

A photo of an emerald tree boa on a branch
Does this emerald tree boa have ears? (Image credit: Joe McDonald via Getty Images)

Snakes are unique animals, with their limbless bodies, flicking tongues and the ability to devour prey whole. They mostly rely on their sense of smell to hunt prey, although they do use sight and sound too. But do snakes have ears?

Yes and no, Sara Ruane, a herpetologist at Rutgers University in New Jersey, told Live Science. Like many reptiles, snakes don't have an external ear structure. However, they do have ear bones in their heads that they use to hear.

"When you think about animals, whether it's a dog or a jack rabbit, they hear a noise in a different direction and shift their external ear in order to better capture that sound in case it happens again," Ruane said. "An internal ear is the part where the actual nuts and bolts of hearing happen." Snakes only have the nuts and bolts part of the ear.

Related: What's the biggest animal that a snake can swallow?

Ears are typically made up of three major parts. The outer ear focuses sound on the eardrum, which separates the outer ear from the middle ear. The middle ear contains three bones that transmit sound from the eardrum to the inner ear via vibrations. The inner ear turns these vibrations into nerve impulses that travel to the brain.

Snakes lack both an outer ear and middle ear, according to a 2012 study in the Journal of Experimental Biology. However, they have one middle ear bone that connects the inner ear to the jaw. This enables snakes to hear vibrations, such as a predator creeping closer on the forest floor. However, they're not as proficient at hearing sounds transmitted through the air.

Due to this ear setup, snakes hear only a narrow range of frequencies. They can hear low frequencies but not high frequencies, because those sounds are mostly transmitted through the air. For example, royal pythons are best at hearing frequencies between 80 and160 Hertz, according to the 2012 study. For comparison, the normal human frequency range is 20 Hz to 20,000 Hz, according to "Neuroscience" (Sinauer Associates, Inc. 2001).

"If you were swimming and went underwater, and somebody standing next to the pool shouted to you, you would hear them," Ruane said. "You might not be able to make out the details ... That's sort of what snakes are hearing at higher frequencies."

This narrow range of hearing isn't a problem for snakes, partly because they don't use vocalizations to communicate with each other. The vocalizations they make, such as hissing or growling, are at higher frequencies than they hear at and are probably intended for bird and mammal predators, according to the study.

The bigger reason why snakes don't need sensitive hearing is because they rely on other senses. Their sense of smell is particularly useful. "Snakes are flicking their tongues out, picking up all the odor molecules that are in the air in the vicinity, bringing that back into a specialized organ they have for processing that, and to their brain," Ruane said. So although they don't have a chance at out-hearing most other animals, "snakes are the chemosensory kings."

Originally published on Live Science.