Halloween Urchins

What happens when you try to dress a sea urchin up for Halloween? Apparently, the urchin tries on the outfit but ends up wearing something else. But we had reason to hope our costumes would work.


Urchins primarily eat algae and kelp, often grabbing bits of food out of the water. Then they use their tube feet and spines to convey food from whatever part of the body first contacts it, to their mouth. Animal Caretakers enjoy offering them long strands of kelp just to watch this process.

It’s also common for green sea urchins to have non-food items all over their top and sides. They will hold onto those items for days or longer. It’s hard not to think that they must somehow benefit from doing this. Our green urchins are all carrying something, usually small shells or bits of coral. This behavior has been extensively studied. Possible explanations offered by scientists are refreshingly similar to the reasons anyone else might think of:

♣ To protect themselves from predators
♣ To protect themselves from wave action
♣ To take the brunt of collisions with flotsam and jetsam
♣ To protect themselves from harmful UV radiation
♣ In case there’s something edible on the item, they can eat it later
♣ Holding debris is an inadvertent result of being able to hold useful things like food and substrate

Recently in the Halloween holiday spirit, we offered our sea urchins something small and lightweight to hang onto. In the hopes of illustrating this behavior we offered a Star Wars Imperial Stormtrooper helmet. For a couple of days it worked, but so far the urchins show a strong preference for the shells and bits of debris that would be more natural in their habitat.

We want our animals’ enrichment to fill their needs as well as provide learning opportunities for our guests. The Stormtrooper helmet was fun and offered a good way to open conversations about this behavior, but so far the urchins are having none of it. And they get to decide.