Kayla Pringle
As someone who considers themselves a bird person, I’m aware of the many different examples of courtship displays between male and female birds. Courtship displays can include special movements, songs, calls, or physical postures that one or both sexes perform to attract a mate and signal readiness to breed. I previously believed that birds were the only animal group that went to great extremes to impress a mate, but I was wrong.
A perfect example is the white-spotted pufferfish, which has a spectacular courtship display of its own. Males of this species create a large circle on the seafloor using their bodies. This is done to attract females for breeding and usually takes more than a week to complete. As the male shapes the circle, he uses his fins to carve evenly spaced divots in the sand around the entire perimeter. He then gathers shells and pieces of coral to decorate each divot and crafts an intricate maze-like pattern in the center. His hope is that a female will be impressed enough to lay her eggs in the middle of his circle.
In 1995, a photographer discovered one of these mysterious sand circles underwater but had no idea what—or who—created them. After years of observation, scientists finally identified the artist in 2011: the male white-spotted pufferfish.
These sand sculptures are found 10 – 30 meters deep, off the coast of Amami Ōshima Island near Japan. Each circle is about 2 meters wide and usually takes the male 7 – 9 days to finish. Scientists believe this may be the most orderly structure ever built by any fish.
What influences a female’s choice of mate remains somewhat of a mystery. Possible factors include sand composition and color, the size of the circle, and the number of divots and peaks. Some scientists hypothesize that females can gauge a male’s size based on the scale of the circle and the divots—potentially favoring larger males for their strength and ability to provide better protection.
Once a female chooses a mate, they spawn, and she releases her eggs into the nest. Afterward, she departs, leaving the male to guard the nest until the eggs hatch, usually about 5 days later. Once the young have hatched, the male abandons the site and does not reuse the nest.
The courtship behavior of the white-spotted pufferfish is a striking reminder that the animal kingdom is full of creativity and complexity, far beyond what we might expect. Just as birds use songs and dances to woo a partner, these small fish transform the seafloor into a masterpiece for love. It’s a great example of how the drive to reproduce can result in breathtaking creations, even on the ocean floor.
Photo: The White-spotted Pufferfish, Torquigener albomaculosus
Credit: タウナギ, CC0, via Wikimedia Commons
