Why This Philippine Sea Turtle Sleeps Head-Down in a Sponge

Quick Take

• A turtle wedged upside-down in a sponge looks like a rescue situation, though the diver who filmed it says something completely different is going on. See what's really happening →
• Giant barrel sponges host tiny shrimp and microorganisms, yet one green sea turtle keeps choosing the same sponge as its personal bedroom. Discover the turtle's sponge habit →
• Sea turtles breathe air, yet they can sleep submerged far longer than you'd expect, and their biology has a surprising trick that makes it possible. Explore their underwater sleep trick →
• Rest isn't just downtime for sea turtles. A study found it has a dramatic effect on their survival that most people would never guess. See how rest affects survival →

Sea turtles have been found resting in the strangest places. Recently, a diving instructor in Moalboal, Philippines, shot the above video featuring a green sea turtle upside down inside a giant barrel sponge. Some social media commenters were concerned the turtle was stuck. However, the diver, Oliver Richardson, responded, “I can assure you they[‘re] perfectly fine,” he said. “They just love this spot for a nap.”

Why This Sea Turtle Keeps Returning to a Giant Sponge?

Moalboal is a popular diving spot where people come to witness the famous daily sardine run. It’s also a great area for finding sea turtles. The green sea turtle (Chelonia mydas) seen in the video and the hawksbill (Eretmochelys imbricata) are the two most abundant species in the region.

But why does this sea turtle find himself upside down in a barrel sponge? The Indo-Pacific giant barrel sponge (Xestospongia testudinaria) can grow to be over 6 feet tall. They live on tropical reefs, are barrel-shaped, and have a large opening at the top. Many marine organisms use the sponge as a home and shelter, making it a thriving micro-habitat.

While it may not be a surprise to see a tiny shrimp swimming in and out of a barrel sponge, it sounds unusual to come across a large sea turtle wedged tightly in the opening, with only its back end and legs sticking out. However, Richardson told a commenter, “This is the 5th time I have seen this one sleep like this.”

How Sea Turtles Sleep Beneath the Waves

We don’t know why this turtle chose this particular sponge, but sea turtles are known to anchor themselves under rocks to keep from drifting in their sleep. It could be that this turtle found the perfect resting place to keep itself from drifting away in the ocean currents.

Although turtles need to breathe air, they can stay underwater for extended periods while resting or sleeping. Their heart rate slows, allowing them to stay underwater for four to seven hours at a time.

How Long Can Sea Turtles Sleep?

Turtles need different amounts of sleep depending on their species and age. What is important is that sea turtles have access to undisturbed resting habitats. A 2016 study found that some sea turtles may sleep for up to 11 hours per day. This study also showed how important rest is for sea turtles, as they can cut their daily energy costs nearly in half.