Maryland DNR

During tonight's full moon, horseshoe crabs will return to the shores of Ocean City as part of their annual spawn. This spectacle happens during the full moons and new moons between May and July, because horseshoe crabs wait for these high tides to lay their eggs in the sand. Thousands of horseshoe crabs crawled onto the shores in search of a mate during the new moon this month. The spawn is thought to be the oldest wildlife migration in the world. Horseshoe crabs are not crabs, or even crustaceans, but are a type of arthropod more closely related to spiders and scorpions. These living fossils are part of an ancient lineage of animals that have scuttled the world’s seafloors for 450 million years, long predating the dinosaurs. Horseshoe crabs are very well adapted to their environment and haven’t needed to change much in their long history. The Atlantic horseshoe crabs you can see on the East Coast today are nearly indistinguishable from fossils found in the Jurassic Period, 148 million years ago. Aside from providing yet another generation of this ancient species, this spawn is also important for feeding our migratory birds, many of which depend on horseshoe crab eggs during their stopovers on beaches.