Researchers used surveys and camera traps to track whether freshwater turtles in North America, the Caribbean, Europe, Asia, Africa, the Seychelles and Australia engaged in the behavior. Over 873,000 photographs later, they were able to document night basking in 13 species of freshwater turtle in tropical and subtropical locales.

The global project was an effort to fill in a research gap. After watching freshwater turtles in Townsville, Australia, emerge from water at night to bask, researchers couldn’t find documentation about the practice. So they set up a team to look at 29 species of freshwater turtles.

“They were coming up at night and sitting on logs exhibiting very much the same behavior they do during the day; when we looked into it, it wasn’t something that turtles reportedly did,” Donald McKnight, a postdoctoral researcher at La Trobe University and a co-author of the study, said in a news release.

Scientists have long documented daytime basking in coldblooded animals such as turtles, and posited that sunning helps the creatures regulate their body temperatures. Other studies suggest basking helps turtles dry out their shells and reduce harmful parasites, and can possibly help them ward off viral infections.

When the researchers analyzed data on night basking behavior, they found the nighttime baskers were clustered around the equator. The nocturnal basking sessions lasted anywhere from two minutes to nearly 11 hours.

The cluster of behavior around the tropics led the researchers to conclude that the practice has at least something to do with environmental temperature. But they write that more information is needed to better understand why the animals take moon baths and how animals’ individual personalities, sex and other factors could contribute.

The research was published in the journal Global Ecology and Conservation.

Nocturnal basking in freshwater turtles: A global assessment

Global Ecology and Conservation