TNB Night Owl – Urchin Headgear

Purple sea urchin. Photo by Diego Delso, license cc-by-sa

The internet has a long history with animals wearing things. From to the ever-popular bunny with a pancake on its head, animals wearing odd things have grabbed the interest of millions.

This now extends to sea urchins.

Various species of prickly, rounded urchin are known by marine biologists to adhere to various objects and move the objects to the top of their spines. It’s called “covering behavior” in relation to the initial suspicions about the items: that they were being used as natural camouflage against predators.

Scientists test hypotheses. The predator one was extensively tested, with the expectation of success; instead, the results demonstrated that urchins’ likelihood of putting shells (including ones containing the occasional dead, or more rarely live, hermit crab) is completely independent of the number of predators which are nearby.

Still, even when hypotheses are disproven, names and inertia carry their own weight, and the tendency remains “covering behavior”. The term gained a little validity when further studies determined that urchins would be more likely to put shells upon them when UV light levels were increased. The shells acted as hats, to protect them from harmful radiation.

Other scientists noticed a discrepancy, though. Off of the coast of Canada, researchers discovered that the behavior was far more prevalent in areas of strong tides. Further investigation demonstrated that, while UV radiation is a factor, the most likely impetus for holding onto a shell is the local tidal motion. The stronger the tides and the smaller the urchin, the more likely the urchin is to be holding onto a shell.

The reason seems to be survival. Small urchins can be tossed around by violent waves, and as they are buffeted they are more likely to be injured or killed. Adding the weight of a shell or two can provide a measure of protection from being pushed around by ocean waves.

A nice summation of the situation can be found at, a site for a Canadian organization dedicated to the creation and promotion of community aquariums and ocean life.

That’s a brief rundown of the scientific history of shells being worn by sea urchins. But this post isn’t just about that, it’s about the internet.

Once people started to hear about sea urchins wearing hats, it was only a matter of time… especially as people gained access to 3-D printers to make plastic headwear of just the right size for their aquarium pet.

Viking helmets, wizard hats, cowboy hats, top hats… these and many more have been shared on various styles of social media in recent weeks as the trend ramps up. At least the hermit crabs are finally getting a break.

Question of the night: Do you wear hats? If so, what is your preferred type?

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About AlienMotives 1901 Articles
Ex-Navy Reactor Operator turned bookseller. Father of an amazing girl and husband to an amazing wife. Tired of willful political blindness, but never tired of politics. Hopeful for the future.