By Becca Lewis | Published
A species of lizard that lives in the rainforests of Costa Rica, known as the diving anole, can dive underwater like a scuba diver and store oxygen as they breathe. These scuba lizards trap tiny air bubbles in their heads that cover their nostrils and allow them to breathe while remaining hidden from predators underwater. The lizards’ ability to remain underwater for several minutes gives them an advantage in survival and makes them unique in the world of biology.
What’s really interesting about scuba diving lizards is that multiple species in the genus Anolius exhibit this behavior. All of the lizards that exhibit diving behavior live in the same area, and they’re all aquatic, living on land as well as in the water.
The only other animals that exhibit this underwater breathing behavior are arachnids and insects, while scuba lizards are the only vertebrates that exhibit this ability.
Anoles aren’t very fast, so their main defense against predators is their ability to camouflage. If that doesn’t work, hiding in water is the anole’s best defense. This strategy to ambush predators is a mysterious behavior, and researchers are trying to understand its origins.
Hiding underwater is a scuba lizard’s best defense.
Dr. Lindsay Swierk, a researcher at Binghamton University in New York, captured some anoles to better observe their bubble breathing. At the Las Cruces Biological Institute in Costa Rica, she placed the lizards in clear tanks to observe them breathing. One group of lizards had a softening agent applied to their noses to prevent air bubbles from forming, while the other group was left alone.
Control lizards that weren’t given the softening agent produced large air bubbles to breathe underwater, while the softening agents gave them smaller bubbles or no bubbles at all.
The scuba lizards with softening agent on their noses were unable to attach bubbles and therefore could not perform normal scuba behavior – all of the lizards use their throat muscles to pump oxygen to their lungs.
On average, a scuba lizard can stay underwater for three and a half minutes.
The bubble-free lizards had to surface just over a minute faster than the scuba lizards. On average, the scuba lizards were able to stay underwater for three and a half minutes, while the bubble-free lizards lasted just under two and a half minutes.
This bubble breathing technique has the advantage that it allows diving anoles to evade predators for longer periods of time.
The downside to diving to catch lizards is that it can cause a drop in body temperature: the cold water in which scuba lizards hide will cause them to lose body heat faster than they would if they were at the surface. This cooling effect causes the lizards to move slower when emerging from the water, reducing their ability to escape predators.
It’s still unclear how the lizards are able to hold onto the air bubbles, or how this ability developed across multiple species. By studying the video and statistics of recent experiments, the researchers hope to piece together a better explanation for the scuba lizard’s unique behavior.
They hypothesized that oxygen could diffuse through the bubbles, allowing the lizards to breathe through them for longer than previously thought.
