How to Tell if a Sand Dollar Is Dead

A living sand dollar is covered in a velvety coat of short, dark spines and looks nothing like the bleached white souvenirs sold in coastal gift shops. The quickest way to tell if one is dead is to look at its color and feel for movement: a live sand dollar is dark purple, brown, or reddish and its spines shift perceptibly when you touch it, while a dead one is pale, stiff, and smooth. The distinction matters more than most beachgoers realize, because many of the sand dollars people pick up on the shore are still alive.

Color and Texture Tell You Almost Immediately

The single easiest indicator is the sand dollar’s color. Living sand dollars are covered in thousands of tiny, flexible spines that give them a fuzzy or velvety texture. These spines are pigmented, and depending on the species and region, a healthy sand dollar can appear deep purple, chocolate brown, reddish-brown, or dark gray-green. The Pacific sand dollar found along the west coast of North America tends toward a purplish hue, while species in the Caribbean and Gulf of Mexico lean more toward brown or gray.

A dead sand dollar loses its spines over time. Once the animal dies, the organic tissue that anchors each spine to the hard internal skeleton deteriorates, and the spines fall off. What remains is the calcified endoskeleton, called the test, which bleaches white or gray-white in the sun and surf. If the sand dollar you found is stark white and smooth to the touch, it has been dead for a while. If it still has a few loose spines clinging to it and looks pale but not yet white, it likely died recently, perhaps within the past few days.

The Spine Movement Test

Color alone can occasionally mislead you. A sand dollar that has been out of the water for a short time may look faded but still be alive. The definitive check is to watch the spines. Pick the sand dollar up gently and hold it flat on your palm. On a living animal, the tiny spines will visibly move, waving slowly or bending in one direction like grass in a breeze. The movement can be subtle, so look closely, especially around the edges and on the underside. If you hold it for ten to fifteen seconds and see no movement at all, try placing it back in shallow water. Sometimes a sand dollar that appears motionless on land will resume spine movement once rehydrated.

The spines serve the animal in life by helping it burrow into sandy substrate, move food particles toward its mouth, and maintain respiratory flow across its body surface. When the nervous system shuts down at death, the spines stop responding to stimuli almost immediately, though residual muscle contractions can cause brief twitching for a short period after the animal dies. If spines are actively and persistently moving, the animal is alive. If they are completely rigid and do not react to your touch, it is dead.

Checking the Underside

Flip the sand dollar over and look at the flat bottom. On a living sand dollar, you will see hundreds of tiny tube feet, which look like miniature translucent tentacles poking out between the spines. These tube feet are part of the water vascular system that all echinoderms use for locomotion and gas exchange. On a live specimen, some of the tube feet will be moving, curling, or retracting when exposed to air. The mouth is at the center of the underside, and in many species you can see the small jaws, part of a chewing structure sometimes called Aristotle’s lantern, an intricate set of calcified plates and tiny teeth the animal uses to grind food particles from sand.

Sand dollars in the genus Scaphechinus, for example, have a lantern composed of paired pyramid-like structures with teeth that are only a few millimeters long, shaped as elongated trapezoids with one pointed end.¹ You will not see these internal parts unless the animal is dead and the test has broken open, but on a live sand dollar the mouth area will show active movement. On a dead one, the underside will be inert, and the tube feet will be absent or dried up.

The Stain Test and the Smell Test

Many beachgoers discover a useful trick by accident: a living sand dollar leaves a yellowish or greenish stain on your skin when you handle it. This dye, called echinochrome, is a natural pigment found in the animal’s spines and surface tissue. If you pick up a sand dollar and your palm turns a harmless brownish-yellow color within a few seconds, the animal is alive. A dead sand dollar whose organic tissue has already broken down will not leave any stain.

Smell is another reliable indicator, though admittedly a less pleasant one. A freshly dead sand dollar will begin to smell foul within hours, especially in warm weather. The odor is unmistakable, a strong rotting-fish scent produced by decomposing tissue. A fully bleached, long-dead test will have no smell at all. A live sand dollar has a mild, briny ocean smell but nothing offensive. So if it looks dark but smells terrible, it probably died recently but is no longer alive. And if it is white and odorless, it has been dead long enough to be a clean skeleton.

Why So Many Sand Dollars Wash Up Alive

People are often surprised to find living sand dollars on beaches because they assume the animals live far offshore. In reality, many species occupy the shallow subtidal zone, sometimes in enormous concentrations called beds or aggregations, just a short distance from the wave line. Storm surges, strong tides, and heavy wave action can dislodge sand dollars from their buried positions and carry them onto the beach. During particularly low tides in some regions, you can wade out ankle-deep and find sand dollars half-buried in the sand, very much alive.

Sand dollars grow slowly, and their populations depend on recruitment of juveniles into these beds over many years. Growth rates increase with body size up to a point, peaking at a test diameter around 20 to 40 millimeters before slowing sharply.² This means many of the larger sand dollars you encounter on a beach may be several years old. Removing live individuals, especially adults, can meaningfully reduce a local population’s breeding stock.

What to Do if It Is Alive

If your inspection reveals a living sand dollar, the best course of action is to return it to the water as quickly as possible. Sand dollars can survive brief exposure to air, but prolonged time out of the ocean causes them to desiccate and suffocate. Their gas exchange depends on water flowing over the tube feet and through small pores in the test called petaloids, the flower-shaped grooves on the upper surface. Without water, this system fails.

Place the sand dollar gently back in shallow water, ideally in a sandy area rather than on rocks. Lay it flat with the darker or more convex side facing up. Do not throw it like a frisbee, as the impact can crack the fragile test. In calm conditions, a sand dollar returned to shallow water will typically rebury itself within minutes, using its spines to work downward into the substrate until only its upper surface is exposed.

In many coastal U.S. states, collecting live sand dollars is illegal or regulated. Florida, South Carolina, and Oregon, among others, include sand dollars under marine-life harvesting rules. Fines for taking live specimens can range from modest to substantial, and enforcement does happen in popular beach areas. Even in places without specific sand dollar regulations, general marine collecting permits may apply. If you are not sure about local rules, treat living sand dollars as protected and leave them in the water.

Cleaning and Preserving a Dead Sand Dollar

Once you have confirmed a sand dollar is dead, you can bring it home and preserve it. Freshly dead specimens still carrying some organic tissue will need cleaning to prevent odor and to achieve the classic white appearance. The traditional home method involves soaking the test in a dilute bleach solution, roughly one part household bleach to three parts water, for several hours or overnight. This breaks down residual tissue and lightens the test. After soaking, rinse the sand dollar thoroughly with fresh water and let it dry in the sun.

Researchers studying sand dollar spines at the microstructural level have used enzymatic treatments and hydrogen peroxide to carefully remove organic material while preserving the nanostructure of the calcified spines.³ For casual collectors, though, the bleach method works well. Once dry, the test is fragile. A thin coat of white glue diluted with water, brushed over the surface and allowed to dry, will harden the test and help prevent it from crumbling. Some collectors use a spray-on clear acrylic sealant instead, which adds a slight sheen but gives more structural support.

Avoid using boiling water to clean a sand dollar. Rapid temperature change can crack the test. Also avoid scrubbing with a brush while the test is still soft from soaking, as this can break through the thin upper plates. Patience and gentle handling are the key to ending up with an intact specimen.

Reading the Marks on a Dead Sand Dollar’s Test

If you look closely at a bleached sand dollar test, you might notice small circular or oval holes that are not part of the natural body plan. These are often drill holes left by predatory snails, particularly cassid gastropods, which are specialized predators of sea urchins and their flat relatives. The snail uses a combination of acid secretion and mechanical rasping to bore through the test, then feeds on the soft tissue inside.

A detailed study of drill holes in the Caribbean sand dollar Leodia sexiesperforata found that the holes left by the predatory snail Cassis tuberosa have distinctive characteristics: subcircular to elliptical outlines with irregular margins, sometimes featuring small notches produced by the predator’s drilling apparatus. Researchers compared freshly drilled holes to those found on empty tests collected from beaches in the Bahamas and found them identical in shape and dimension.⁴ So if your beach-found test has a neat, beveled hole through it, a snail likely killed the animal. Other damage marks, like jagged cracks or large chunks missing, are more often caused by fish, crabs, or wave impact against rocks.

These marks are worth noticing because they tell you something about why the sand dollar ended up on the beach. A test with a predation drill hole was killed by a snail and the remains eventually washed ashore. A test with no holes and no cracks might have died of old age, disease, or environmental stress. And a test that is broken into fragments was probably already dead when waves battered it against hard substrate.

Commensal Organisms as a Sign of Life

One less-discussed clue is the presence of other small organisms living on the sand dollar. Several species of pea crabs, which are tiny crabs only a few millimeters across, are obligate commensals of sand dollars, meaning they live exclusively on living hosts. Researchers studying sand dollar beds off the coast of Brazil documented pea crabs of the species Dissodactylus crinitichelis that actively selected among sand dollar hosts, favoring occupied patches where they could find mates and reproduce.⁵ If you flip a sand dollar over and see a tiny crab clinging to its underside, the sand dollar is almost certainly alive, because these crabs abandon dead hosts quickly once water flow and food supply cease.

Similarly, small barnacles, worm tubes, or algal growth on a sand dollar test can indicate the animal has been dead long enough for fouling organisms to colonize the skeleton. A living sand dollar’s spine movement and mucus secretion typically prevent encrusting organisms from settling on it. So heavy fouling on a test is evidence it has been a dead surface in the ocean for weeks or months before washing ashore.

Situations That Create Confusion

A few scenarios regularly trick beachgoers into misjudging whether a sand dollar is alive or dead.

The first is the partially dried specimen. A sand dollar that washed up during high tide and has been sitting in the sun for an hour may look pale and feel stiff, but its internal organs can still be functioning. The spines may appear motionless because they have dried out. Placing it back in water often revives visible spine movement within a minute or two. When in doubt, give the water test before concluding the animal is dead.

The second is the juvenile sand dollar. Very young sand dollars can be quite small, sometimes the size of a coin, and their spines are proportionally shorter and harder to see. Their coloring is also lighter than that of adults in some species, appearing grayish rather than dark purple. A tiny, pale, flat disc on the beach might look like a dead test fragment when it is actually a live juvenile. Examine it closely and look for spine motion before tossing it in your pocket.

The third situation involves mass die-offs. Occasionally, large numbers of sand dollars wash ashore simultaneously after a storm, a sudden temperature change, or an algal bloom that depletes oxygen in shallow water. In these events, the sand dollars on the beach are genuinely dead, but their sheer numbers can make it seem as though the beach is covered in living animals. You can usually tell a mass die-off because the specimens are all roughly the same stage of decay: slightly faded, still retaining some spines, and uniformly unresponsive. Within a day, the smell will confirm the situation beyond any doubt.

The Five “Doves” Inside

A common piece of beach lore says that if you break open a sand dollar, you will find five small white objects inside that look like tiny doves or birds. This is true, but only for dead, dried specimens. The “doves” are the teeth of the Aristotle’s lantern, the chewing apparatus mentioned earlier, which loosens from its supporting structures as the internal tissue decomposes. In a fully dried test, the five tiny V-shaped pieces rattle around inside like loose seeds. Their presence tells you the sand dollar is dead and has been dry long enough for the internal ligaments to break down completely. On a living sand dollar, these teeth are firmly embedded in the jaw structure and could not be shaken loose without destroying the animal.

This bit of folklore has been passed along so enthusiastically on social media that some people break open sand dollars specifically to find the “doves,” not realizing that doing so to a live specimen kills it. If the test you are holding is white, dry, odorless, and the loose pieces rattle inside when you shake it gently, you are holding a long-dead specimen and no harm is done. If the test is dark, heavy with moisture, and nothing rattles, put it back in the water.