Freshwater turtles were discovered relaxing in the moonlight.

At twilight, a freshwater turtle basks. The image was taken for research into nocturnal basking behaviors. Dr. Donald McKnight of La Trobe University


Until recently, nocturnal basking in wild freshwater turtles was not widely reported. However, this study indicates that the behavior is prevalent and occurs across many species. Dr. Donald McKnight, a postdoctoral researcher at La Trobe University, noted that he initially observed freshwater turtles engaging in nocturnal basking at the Ross River in Townsville. Dr. 

McKnight remarked that the turtles were climbing on logs at night and displaying behavior similar to that observed during the day. When the team investigated this, they found that it was an undocumented behavior in turtles.

A global team of researchers has discovered that freshwater turtles engage in nocturnal basking, a previously undocumented behavior. The team placed cameras on basking logs to observe as many freshwater turtle species as possible. The researchers found that the behavior was widespread across the turtle family tree, but it only occurred in the tropics and subtropics. 

Dr. Donald McKnight, a postdoctoral researcher at La Trobe University, noted that the behavior might be related to temperature. He observed that the water is warmer at night than turtles typically prefer, causing them to come out of the water to cool down. Dr. McKnight first noticed the behavior with Dr. Eric Nordberg from the University of New England on the banks of the Ross River in Townsville, Australia.

Freshwater crocodiles and turtles basking in Townsville, Queensland, image from the paper Nocturnal basking in freshwater turtles: a global assessment. Dr. Eric Nordberg of the University of New England

To gather data on 29 species from seven freshwater turtle families, cameras were installed in 25 locations around the world. The cameras took one photograph every two minutes and were set up in Australia, Belize, Germany, India, Seychelles, Senegal, Trinidad and Tobago, the United States, and South Africa.

Reference: Donald T. McKnight et al, Nocturnal basking in freshwater turtles: a global assessment, Global Ecology and Conservation (2023). DOI: 10.1016/j.gecco.2023.e02444


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