Ring-tailed lemurs are famed for their ‘sun-worshipping’ posture, legs and arms outstretched to reveal their pale bellies. Like humans, they do it to save energy and boost health. Sunlight is necessary to many bodily processes.
As a source of vitamin D it’s required to maintain bone and muscle health. It is also related to the production of serotonin, the chemical that regulates mood, sleep and stress response.
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Described by biologists as ‘sunning’ or ‘basking’ behaviour, it is common to many species and most notable among ectotherms who do not produce heat metabolically and rely on the temperature of their surroundings.
Reptiles, amphibians, insects (particularly butterflies) and the ocean sunfish have all been observed purposefully exposing themselves to the sun’s rays.
While lying, sitting or floating in the sun makes an animal vulnerable to attack, studies have revealed that it can also be a defence mechanism.
Humans use fever to fight infections, raising body temperature to create an unfavourable environment for bacteria or parasites to live in. A similar ‘fever’ response has been recorded in lizards that increase basking time when infected.
Likewise, as many as 50 species of bird have been studied adopting a variety of poses that maximise exposure to the sun. With their wings outstretched, vultures are thought to be taking advantage of the sun’s heat to kill bacteria picked up from their carrion meals.
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Scientists are still investigating how sun exposure defends against parasites but it’s thought to be a combination of factors.
UV irradiation can be toxic to tiny insects such as mites, while increased temperatures can result in fatal desiccation – or death by extreme drying.
Sun exposure is found to increase the activity of parasites, making them easier to find and remove, which may explain why grooming behaviour is common following sunbathing sessions.
If the temperature of their surroundings falls, cold-blooded animals seek out sunny spots to maintain critical processes including digestion. An eye-catching example comes from American crocodiles in Florida that have taken to lying on docks, kayaks and even jet skis.
Researchers have recently argued that these basking spots have become essential for the crocodiles’ survival as their natural habitat has been disturbed.
Top image: American crocodile basking on kayaks in Broward County, Florida, in February 2024. This crocodile is being tracked with a satellite transmitter as a component of ongoing research. Credit: Jeannette Marquard via Steen et al (2025) \ Wildlife Society Bulletin
