Horseshoe crabs, often called “living fossils,” have an ancient lineage extending over 300 million years. These arthropods are more closely related to spiders and scorpions than to true crabs, possessing a distinctive helmet-shaped shell, ten eyes, and a long, pointed tail called a telson. Their long history highlights their adaptability and ecological significance in coastal environments.
Primary Viewing Locations
Horseshoe crabs are most concentrated along the Atlantic coast of North America, especially during their annual spawning migrations. The Delaware Bay, shared by Delaware and New Jersey, hosts the world’s largest concentration of spawning horseshoe crabs. In Delaware, popular viewing spots include Slaughter Beach, the DuPont Nature Center, Bowers Beach, Pickering Beach, and Kitts Hummock. Along New Jersey’s Delaware Bay coastline, in Cumberland and Cape May counties, numerous sandy beaches offer prime viewing opportunities.
Moving north, horseshoe crabs can be observed along the northern Jersey Shore and at sites like Plumb Beach within Gateway National Recreation Area in New York. Further north, in New England, Massachusetts’ Cape Cod area is a viewing location. Along the mid-Atlantic, Maryland’s Chesapeake Bay and Assateague Island in Virginia also experience significant spawning activity. These creatures prefer calm, protected environments like sandy or muddy intertidal zones, coves, and bays for their reproductive gatherings.
When to Spot Them
Observing horseshoe crabs is most productive during their spawning season. In the mid-Atlantic region, this period generally runs from May through June, though activity can begin in late April and extend into early July. Spawning peaks are linked to tidal cycles and lunar phases.
The highest numbers of crabs come ashore during high tides, especially around the full and new moons. These lunar-driven high tides provide optimal conditions for females to dig nests and lay eggs, often accompanied by multiple males. Nighttime high tides during these lunar phases offer excellent viewing opportunities for large aggregations along the shoreline. In some southern regions, like Florida, the breeding season is more extended, running from March to November, with peaks in March and April.
Observing Responsibly
When observing horseshoe crabs, prioritize their well-being and habitat health. Always maintain a respectful distance and avoid disturbing mating pairs or spawning individuals. Their long, pointed tail (telson) is not a weapon; it is used for steering and righting themselves if they flip over. Never pick a horseshoe crab up by its tail.
If you encounter a stranded, upside-down horseshoe crab, gently assist it by carefully picking it up by both sides of its shell and flipping it back over. Horseshoe crab eggs are a food source for numerous migratory shorebirds (like red knots and sandpipers), finfish, and loggerhead sea turtles. Leaving eggs undisturbed ensures this food supply remains available for dependent species.