Can You Tell If a Sand Dollar Is Alive Before Taking It Off the Beach?

Waliking along the beach and finding a perfect, unbroken sand dollar is one of those indescribable, small joys in life that you may not fully appreciate until you've experienced it.

Most of us think of sand dollars as round, flat seashells, but that's a completely inaccurate picture of sand dollars in their natural habitat. In fact, sand dollars aren't shells at all, but living creatures!

Yes, a sand dollar is alive to begin with. During their average lifespan of about 10 years, a sand dollar is actually a living organism, and sand dollars are also cousins of sorts to other echinoderms like sea cucumbers, sea stars (sea stars are also known as starfish) and sea urchins.

"Just like their more recognizable sea star cousins, sand dollars typically have five-part radial symmetry which means that their body could be split into five identical 'slices,'" explained Jessica Brasher, husbandry manager at the Ocean Institute in Dana Point, California, when we spoke to her by email in 2019.

But that symmetry isn't what lands sand dollars in the echinoderm group that includes sea urchins and sea cucumbers.

Indeed, live sand dollars (unlike their deceased, relatively smooth counterparts) feature an endoskeleton that's covered by a layer of spiny skin, according to Leah Biery, who was director of communications at Sanibel Sea School in Sanibel, Florida, when we spoke to her in 2019. "The skeleton, or test, is composed of bony plates of calcium carbonate called ossicles, held together by connective tissue," she emailed. "They have no brain, just a simple nerve ring."

But what is it that makes a sand dollar alive? While we're used to living things sporting legs, wings or some other obvious transportation method, live sand dollars have a far more subtle way of getting around — a water vascular system.

This system not only helps sand dollars move, but is also responsible for pumping filtered seawater so that they can eat, Biery said, noting that the preferred sand dollar diet, for both young sand dollars and old, is microscopic algae food particles scraped from hard surfaces by the teeth in the sand dollar's mouth. Sand dollars also dine on plankton and other food floating freely in the water.

Sand dollars are surprisingly social, preferring to lie flat on the sandy seafloor where lots of other sand dollars live and away from the thrashing water created by storms.

This is especially vital during reproduction season, since being in a large group of sand dollars yields better odds of success.

"Sand dollars reproduce by spawning, which means that males and females release eggs and sperm into the water column respectively," Brasher explained. "If fertilized, the sand dollar eggs will hatch into microscopic, free-floating larvae that hardly resemble their parents." The larvae then undergo a series of developmental changes until it grows its test and settles on the ocean floor.

Is That Sand Dollar Alive or Dead?

So, with all the complexity of sand dollar makeup and life in mind, is it all right to scoop a sand dollar up from the beach and take it home as a treasured souvenir? Well, that depends.

"As live animals, sand dollars filter detritus and debris from the sandy seafloor while also providing a tasty food source to many benthic [bottom of the ocean] natural predators including sea stars, crabs, fish and the occasional octopus," Brasher said.

"Even after their death, the shells of sand dollars still provide a source of calcium carbonate for our oceans. As it can sometimes be difficult to determine whether or not a sand dollar still lives, it's always best to leave them where they were found," he said.

But if one is found and simply must be kept, be 100 percent sure that it is no longer a living being and the sand dollar's body is actually dead. In most states taking a live sand dollar is illegal, but laws vary about collecting a deceased sand dollar, so check for signs at the beach or ask an employee. We spoke to John Rader, marine science educator at Sanibel Sea School, in 2019 and he offered the following tips for performing a sand dollar test to determine whether it is living, or not:

Gently hold the sand dollar and watch the tiny spines. If they move, it is living. The small spines will fall off quickly after the animal dies.
Check the color. Sand dollars are grey, brown or purplish when they are living. When a sand dollar dies, the color fades and the skeleton becomes very white. Sand dollars that are bleached white are no longer alive.
When they are alive, sand dollars secrete echinochrome, a harmless substance that will turn your skin yellow. Hold a sand dollar in your hand for a minute. If the sand dollar leaves a yellow spot behind, it is living.

If by chance you do stumble upon a living sand dollar, take action quickly. "Sand dollars will not survive out of the water for very long," Rader said. "If you find a live individual on the beach, you can carefully return it the ocean."

Sand Dollar FAQ

How can you tell if a sand dollar is alive?

There are a few ways to tell if a sand dollar is a living being or dead sand dollar fossil. If the tiny spines on it are moving, itâ€™s alive. When alive, a sand dollar is usually grey, brown or purplish in color, so if itâ€™s white, the sand dollar is dead. Sand dollars also secrete echinochrome, a harmless substance that turns your skin yellow, so if holding a sand dollar for a minute leaves a yellow spot behind, the sand dollar is alive.

Can you take a sand dollar from the beach?

In most states, taking a living sand dollar from the beach is illegal. However, laws vary about collecting a dead sand dollar. Itâ€™s best to check for signs at the beach, look at your state laws online or ask a lifeguard or warden working at the beach.

Can you touch a live sand dollar?

You can touch a live sand dollar, but their long spines can cause puncture wounds that may become infected and result in a burning sensation. If you have picked a sand dollar up and it seems to move, it's best to gently return the sand dollar to the water.