Unless you're a tardigrade, you need water to survive. For many creatures, this means lapping up or drinking water up through the mouth. Others, like those in desert environments, get it from the food they eat or by relying on other adaptations, like gathering moisture on their bodies.
Snakes have their own particular adaptation as well. They open their mouths and just soak in the H2O.
And it's kind of adorable when they do.
Snakes don't lap up water with their tongues. It'd be pretty difficult to do that, after all, considering that snakes don't open their mouths up wide enough when they flick out their tongues. Additionally, snakes' tongues actually go into sheaths when they're not in use, gathering up scents to give the snake a sense of their environment.
So if the tongue can't help a snake get water, what does? For a while, we believed that snakes simply sucked in water through a small hole in their mouths. Think of it as a sort of built-in straw. This method, called the buccal-pump model, relies on the snakes, particularly boa constrictors, alternating the negative and positive pressure in their oral cavities to make a flow of water. They depress their jaws, creating negative pressure to draw in the water and then seal up their mouths on the side to create positive pressure and push the water into the rest of their bodies.
Except that's not how it works
A 2012 study published in the Journal of Experimental Zoology Part A debunked this particular assumption, at least in regards to some snake species. The mouth sealing process, so important to the buccal-pump model, wasn't always found in snakes, leaving the issue of how the snakes consumed water up in the air. Mouth sealing, it turned out, was incidental to the whole process.
"One thing that didn't fit the model was that these species don't seal the sides of their mouth," David Cundall, a biologist at Lehigh University in Pennsylvania, explained in a 2012 statement released by the university. "From there, it took a long time for me to realize that the anatomy of the system and the lining of the lower jaw suggested a sponge model."
Yes, a sponge model. It turns out that at least four species — the cottonmouth, the Eastern hognose snake, gray rat snake and the diamond-backed watersnake — move water through their mouths thanks to the sponge-like properties of their lower jaw.
Watch Bacon Bit, a western hognose snake, show you how it's done in the video above.
When snakes open their mouths to eat, they "unfold a lot of the soft tissues," according to Cundall, and the folding of this soft tissue creates a number of sponge-like tubes that water flows through. Muscle action then forces the water into the snake's gut.
Cundall and his team used synchronized video and electromyographic recordings of muscle activity in three of those species and pressure recordings in the jaws and esophagus of a fourth to come to this conclusion.
So sip on, snakes. And thanks for the quick lesson in biomechanics.