05/10/2025
Male pufferfish craft massive, geometric circles in the sand to impress potential mates.
On the sandy seafloor of Japan’s Ryukyu Islands, the male white-spotted pufferfish – just 5 inches (12 centimeters) long – spends over a week sculpting a circular nest nearly 7 feet (2 meters) wide. Using only the beats of his fins, he carves radiating ridges and valleys with astonishing precision, creating what looks like an underwater crop circle.
Every detail is designed to impress a female. The symmetry, the ridges, even the way the structure channels currents to sweep fine sand into the center – all of it becomes a signal of fitness and dedication.
The more intricate the design, the better his chances of attracting a mate.
If a female approves, she lays her eggs in the center of the circle. The male fertilizes and guards them until they hatch. Then, the carefully crafted masterpiece is left behind, slowly erased by the ocean.
These sand circles were first spotted in 1995 but remained a mystery until researchers confirmed the artist in 2011. The species itself, Torquigener albomaculosus, was only officially described in 2014, and it’s still known only from these southern Japanese waters.
What makes the display remarkable is that the fish doesn’t measure or plan; he relies only on instinct.
His geometry is built grain by grain, with repeated fin beats at specific positions and speeds, in hopes that one female will see and choose him.
Learn more:
"Simple rules for construction of a geometric nest structure by pufferfish." Scientific Reports, 17 August 2018.
