Water Anoles – a type of semi-aquatic lizard that lives in the forests of Costa Rica – have found a way to escape predators by jumping into the water and producing a special bubble around their nostrils. Lindsey Swierk, a professor at Binghamton University, New York, first saw these lizards when she was walking near streams in the mountains of Costa Rica.

Many small invertebrates, such as some species of beetles and spiders, have evolved to use bubbles to extend the amount of time they can spend underwater. These bubbles allow them to inhale previously exhaled air, which still contains some oxygen in it.  This behaviour is called rebreathing, a term used in scuba technology where divers inhale their exhaled air. But until recent times there were no known vertebrates that had been observed using bubbles of air in a similar way—that is, until 2021.

That year, Lindsey Swierk and her colleagues recorded rebreathing in many species of Anolis lizards. “Anoles are kind of like the chicken nugget of the forest. Birds eat them, snakes eat them. So, by jumping into the water, they can escape a lot of predators,” Swierk says, “We know that they can stay underwater for at least about twenty minutes, but probably longer.” Swierk noticed the lizards also used a bubble to rebreathe. One of those species was the water anole.

Though, one of Swierk’s questions still remained unanswered: Did the bubble over the water anole’s nostrils actually extend the amount of time they could spend underwater?

To test this, Swierk put together two groups: one group had a bubble-impairing substance put on their skin and another group did not.

Swierk and her colleagues then timed how long the group with the emollient stayed underwater compared to the group without the emollient.  “Lizard skin is hydrophobic,” Professor Swierk explains, which means a property of molecules that don’t mix with water. “Typically, that allows air to stick very tightly to the skin and permits bubbles to form,” she added. “But when you cover the skin with an emollient, air no longer sticks to the skin surface, so the bubbles can’t form.” They found that the group without the bubble-impairing substance stayed underwater 32% longer than the group with the bubble-impairing substance. So, the bubble did contribute to how long the lizard could stay underwater.

Swierk’s team also noticed that the lizards were eating something while they were in the water. The team hadn’t seen the lizards eating under the water but they had analyzed the lizards’ stomachs. Swierk then bought an underwater camera to see what they were up to. She has not yet recorded the lizards eating underwater.