Turtles live in water bodies across the globe. Many assume that turtles are diurnal, look for food during the day and basking in the sun. But, their sleep patterns are not this simple. Turtles adapt to their surroundings depending on food sources and predators. This flexible behavior means that they must often change their sleep patterns too. Considering these variations, we wanted answers to the question, are turtles nocturnal or diurnal, or something else? So, we did our research, and this is what we learned.
The Sleep Behavior of Turtles Depends on their Species
Some turtle species are nocturnal, some are diurnal, and some turtles are cathemeral. However, most turtle species are diurnal. These species include North American box turtles, cooters, red-eared sliders, painted and sea turtles. Nocturnal turtle species include mud, common musk, alligator, and snapping turtles. But turtles are not always strictly nocturnal or diurnal. Some diurnal species will be awake to forage for food at night, while some nocturnal species swim during the day. This behavior explains why many species of turtles are thought of as cathemeral. Examples of cathemeral turtles are snapping turtles, green turtles, and stinkpots.
Cathemeral animals do not follow a strict pattern of waking and sleeping. Turtles are cathemeral because they adjust their sleeping patterns to their surroundings and situations. For example, a typically diurnal turtle may show nocturnal tendencies if there are more food sources at night. Also, turtles often adjust their sleeping patterns to avoid the danger lurking during the day or night. Captive turtles are generally diurnal, even if their species is known to be nocturnal. This activity pattern occurs when the turtle feels safe and comfortable in its enclosure. Captive turtles also do not need to hunt and may be more interested in human activity during the day.
The Sleep Cycle of a Turtle
Turtles usually sleep with their eyes open and sometimes even move around slightly even though they are asleep. This movement occurs because the turtle stays aware of its surroundings while it sleeps. Turtles do not lose complete consciousness while they sleep. Instead, their brain activity slows down along with their heart rate and breathing. Like many other reptiles, turtles have two sleep stages: slow-wave sleep and REM sleep.
Turtles sleep four to seven hours a day. Some turtles sleep up to 11 hours a day. The length of their slumber relies on their age and takes place during the day or night, depending on if they’re mainly diurnal or nocturnal. Although most baby turtles sleep four to seven hours a day, baby sea turtles are known to sleep only four hours a day.
Where do Turtles Sleep?
Turtles cannot leave their shells which means they sleep in them. But the location of their sleep depends on the habitat. Most turtles bury themselves in the mud to sleep. Whether freshwater or saltwater turtles, they seem to prefer hiding in the substrate to rest. Other turtles find caves, crevices, logs, or the burrows of other animals for protection when sleeping.
What do Nocturnal Turtles do at Night?
Nocturnal turtle species carry out their regular activities just at night. Some species, like mud and musk turtles, are active at night when they forage for food in ponds. Other turtle species, like the common musk, alligator, and snapping turtles, lay their eggs at night.
Nocturnal Turtles can see in the Dark
Sea turtles do not have advanced night vision but can see in the dark once their eyes adjust to the lack of light. During the day, their irises narrow, and their pupils constrict, so less light enters their eyes. This function ensures clear vision in lighter settings. At night, their pupils expand to allow more light into their eyes. Their eyes need a few seconds to adjust to the darkness before their vision becomes clear again.
Some Nocturnal Turtles may be at a Disadvantage
Some turtle species are cathemeral because this behavior is safer and is a better adaptation to their environments. Much of this cathemeral behavior is due to specific physical limitations. As some turtle species do not have peripheral vision, their eyes don’t quickly adjust to the darkness. They also do not have additional sensory advantages like advanced hearing, which is valuable for nocturnal animals. Also, many turtle species do not have the essential eardrum or tympanum, so they do not have good hearing. Having lousy night vision and hearing, in general, increases their risks of becoming prey at night. Turtles also need UVB light exposure for strong, healthy bones, which they can only get during the day.
Sea Turtles are Diurnal
A scientific study of sea turtles in a captive situation found that these reptiles did not sleep. Instead, their behavioral patterns fluctuated between activity (mainly in the late afternoons) and inactivity. They either nap floating on the water’s surface or wedging themselves between a rock or coral reef. Baby sea turtles rest on the water’s surface and fold their front flippers into the back of their shells. However, sea turtles demonstrate nocturnal behavior when laying eggs. Female sea turtles swim out of the ocean to the shore at night to lay their eggs in the sand. They dig a hole where they lay their eggs before covering them with sand to protect them from predators. Some sea turtle species hatch at night and find their way to the ocean. This behavior is probably an evolutionary adaptation so that baby sea turtles can avoid diurnal predators.
Pet Turtles are Generally Diurnal
No matter their species, pet turtles, will generally be diurnal because of their relationship with humans. Pet owners often pay attention to their turtles during the day, providing them with food and play, stimulating interaction. This engagement causes more diurnal activity. Because humans are more diurnal and sleep at night, their pet turtles find it impossible to sleep during the day.
Turtles also need to bask in the sunlight for their health. Owners should create a basking area in their enclosure for their turtles. If the enclosure doesn’t receive direct or indirect sunlight, experts recommend using a UVB light. However, owners should ensure they do not light up the enclosure the entire day. Doing so could lead to overheating and possible health issues for the pet turtle. Instead, owners should provide UVB lighting for a portion of the day, so their pet turtle can choose to bask during daylight hours and sleep at night.
Do Turtles Dream?
Scientists cannot say for certain that turtles dream as we do, but one 2016 study shows that bearded dragons experience REM sleep and slow-wave sleep. Because scientists know that people experience REM sleep when they dream, this suggests that reptiles, and perhaps also turtles, can dream. However, another study suggests the opposite, so the jury is still out about whether nocturnal, diurnal, or cathemeral turtles can dream or not. However, studies seem to indicate that turtles also snore as we do. Their snores often sound like regular snores, a whistle, or even crying sounds. If your pet turtle whistles or cries while sleeping, this may indicate something wrong with it, in which case, you should take it to a vet for an assessment.
Nocturnal vs. Diurnal: What’s The Difference?
Up Next – All About Turtles
- How Old Is the World’s Oldest Turtle? 5 Turtles that Survived for Centuries
- Where Do Turtles Go in the Winter?
- Turtle Predators: What Eats Turtles?
The photo featured at the top of this post is © Steve Byland/Shutterstock.com
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- Reuters, Available here: https://www.reuters.com/article/us-science-sleep-idUSKCN0XP2OE
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