When you’re a small critter like the water anole (Anolis aquaticus), what better way to evade scary land predators than to spend extended periods underwater? This might seem like mission impossible for most lizards because they don’t have gills like fish, but researchers from Binghamton University now say that the water anole is… ‘different.’
Image Credit: Lindsay Swierk
Although the water anole doesn’t sport gills, it has purportedly evolved to spend extended periods underwater. As it would seem, the reptile can produce an air bubble that clings to its face as it spends time below the surface, enabling it to ‘scuba dive’ for 16 minutes (or possibly longer) at a time. The findings will soon be published in the journal Herpetological Review.
"Diving underwater and remaining there for a long time is an anti-predator strategy for water anoles," elucidated Lindsey Swierk, the biologist who made and documented the discovery.
"These lizards aren't particularly speedy, and taking to the water is a very effective option. It's easy to 'disappear' to a predator's eye once you hide under water for a few minutes. I think that any underwater breathing adaptations in water anoles would have arisen to extend the amount of time they can stay in their underwater refuge."
The air bubble sticks to the water anole’s face, just near its nostrils. It’s thought that the animal can breathe underwater by extracting recycled air from the bubble, and once the air supply runs out, the lizard returns to the surface to rinse and repeat.
One might be inclined to ask whether the water anole developed this technique on its own as an evolutionary defense against predators or as a clever life hack, but the answer isn’t yet clear. Regardless of which direction you sway, you can watch the water anole perform its unique ability in Swierk’s short documentary video below:
"I think it's possible that some additional air pockets are being trapped around the anole's head and throat, and that the inhalation and exhalation of the air bubble allow for some trading of fresh air among these air pockets, allowing the anole to swap air in its current air bubble with 'new' air," Swierk said.
"It's additionally possible that the air bubble plays a role in allowing an anole to get rid of carbon dioxide. I suspect that there might be morphological adaptations, namely the shape of the top of the anole's head, which allows a large bubble of air to cling to it easily."
According to Swierk, collecting evidence of the water anole’s underwater breathing technique wasn’t originally a part of her research plan, but she thought that capturing video footage of it would help in studying the behavior going forward.
Follow-up studies are being planned to investigate why the water anole does this and to learn more about how it works, but regardless of the nitty-gritty details, we have to admit that this is one cool ability.
It should be interesting to learn whether this capability is unique to water anoles or if other anoles can exhibit similar behavior. Furthermore, answering some of the remaining questions about the recycled vs. fresh air debacle will be equally as fascinating.