Mystery underwater sand circles are actually puffer fish art

If you thought crop circles were strange, odds are you haven’t seen these:

crop circles

The underwater version of crop circles!  Some of the intrigue with crop circles faded once people stopped thinking they were made by aliens, but these sand circles are even more interesting to behold once you know where they do come from.

So who or what makes these enigmatic sculptures where they are doomed to fade into nonexistence once the ocean erodes them away?  No, not an alien race, nor a group of people from of the legendary Atlantis, but Puffer fish!

Male puffer fish craft their detailed sculptures by using a single fin to push the sand around, working day and night to finish the job, topping it off by cracking shells and placing them along the inner grooves of the circles.  Similar to bower birds, the puffer fish creates these structures to attract females.  However, the marine art serves a greater purpose than to look pretty to impress the ladies.  The puffer fish constructs his art with great care because it will become a nursery ground for his future offspring!  Watch him here:

Once the female has found the grooves, she will follow the ridges to the male in the center, mate with him, and lay her eggs.  The more ridges the circle contains, the more likely it is that the female will mate with the male, because she knows that the ridges will buffer the eggs from currents, thereby protecting the eggs from disturbance and exposure to predators.  Furthermore, the seemingly decorative seashells provide nutrients to the eggs and newborn puffer fish.

The artist at work

The artist at work

Next time you get annoyed by the sand that gets in every orifice after a day at the beach, or think humans are clever for using sand to make glass and concrete, think about how the puffer fish makes art out of sand to attract females, protect its young, and provide sustenance to its offspring just by using the raw stuff-and you might find new appreciation in sand, and the ingenuity of animals, a little more.



This is Colossal:


Dress to impress: bird courtship rituals


Mandarin duck

Birds exhibit some of the most elaborate and bizarre courtship rituals of any animals on earth.  Here are a few of the more beautiful and zany examples:

The marvellous spatuletail hummingbird exhibits one of the most extreme courtship rituals (see video below).  The male bird has two elongated tail feathers that end in a large violet-blue disc, or spatule.  The male bird hovers in the air, waving his spatules in front of the female and making a snapping sound with his beak.  To the hummingbird, which is the size of a ping-pong ball, this display costs a lot of energy.  Spectators of this courtship ritual have reported that after he’s done dancing, the male will have to flop down on a branch, exhausted, and sit still for over an hour to regain his strength.  This species of bird is rare and endangered, and lives in only a few places in Peru.

The bird of paradise is equally stunning:

The frigate bird puffs up a large red balloon on its chest and dances about, calling to the female in question to impress her:

Mandarin ducks, both male and female, bob in and out of the water to seal their partnership, which is for life.  In Chinese culture these monogamous ducks symbolize love, marital fidelity and relationship respect.

Red capped manikins do a sort of funky moonwalk reminiscent of Michael Jackson:

The white-throated bee-eater is a rakishly plumed bird that engages in the “butterfly display,” in which the male and female both hold out their wings while calling to each other.


Mandarin duck:

Marvellous spatuletail hummingbird:

White-throated bee-eater:

Sticks and tricks: Bowerbirds use interior design and optical illusions to attract females

Human men aren’t the only ones to show off for the ladies.  In fact, their stabs at romance seem a bit shabby when compared to the courtship displays bowerbirds put on for females they are trying to charm.

Imagine if a man built you an entire house and put all of your favorite things in it to get you on his good side?  A male bowerbird does just that, building a shelter or “bower” of sticks and elaborately decorating it with anything he can find to impress the female in question:

Bowerbird 1

Bower of a Vogelkop bowerbird (Amblyornis inornata) decorated with natural and man-made objects

But that’s not all – it turns out that bowerbirds are very particular about the type and arrangement of objects they place in and around their bowers.  Apparently, female satin bowerbirds prefer the color blue, which is perhaps why they have evolved such strikingly blue eyes (see picture below) so the males seek out blue objects over those of other colors.


Satin bowerbird (Ptilonorhynchus violaceus)

Furthermore, male bowerbirds construct their bowers to create an optical illusion.  Objects are not randomly placed around their court, but instead placed in a size gradient with smaller objects closer to the entrance of the bachelor pad and larger objects farther away.  This optical illusion is called forced perspective, and causes all of the objects to look the same size while the entrance of the bower appears smaller than it actually is.


Satin bowerbird with female

12713-satin_bowerbird-cswHow does this help the male bowerbird snag a female?  If the bower entrance looks smaller than it is, then the male hopping and dancing around the bower entrance in his courtship display will appear larger than he actually is!  Males are very specific about constructing this optical illusion and will in fact recreate it in three days if it is disturbed.

Perhaps we humans should take a leaf out of the bowerbird’s book – I’m sure the ladies wouldn’t complain!




Photographs from Arkive site:

Bowerbird optical illusions:

Animal romance National Geographic page:

Bowerbird informational video from National Geographic:

Bowerbird information from National Geographic:

Bowerbird stealing man-made objects video from National Geographic:

Satin bowerbird picture from Wikimedia commons is under a Creative Commons license.

Arkive photographs taken by:

© Tim Laman /

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