Horseshoe Crabs: Ancient Survivors Facing Habitat Loss

Horseshoe crabs are arthropods that have existed for roughly 445 million years, predating dinosaurs. Though called “crabs,” they are more closely related to scorpions. Each animal possesses nine eyes, six pairs of legs (five for walking, one for shoveling food), and a harmless tail used to right themselves. Their copper-based blue blood is harvested by the biomedical industry to test vaccines for harmful toxins. In North America, they inhabit shorelines from Maine to Mexico; the related mangrove species *Carcinoscorpius rotundicauda* occurs in India, Bangladesh, and Southeast Asia. Females lay about 4,000 eggs in sand-filled nests during high tides and full moons, providing a critical food source for migratory shorebirds.

The Guardian

Rising sea levels and expanding coastal infrastructure are eroding the sandy beaches that serve as spawning grounds. When these habitats disappear, the crabs lose the nurseries essential for egg deposition and hatchling survival. The loss of beach habitat also threatens the shorebirds that depend on crab eggs for nourishment.

The Guardian

Ecologist Prof Mark Botton, who has studied horseshoe crabs for nearly five decades, acknowledges the species’ resilience but warns that habitat loss could become irreversible if spawning beaches are eliminated. He emphasizes that the crabs can locate small patches of suitable sand even in heavily altered coastlines, suggesting a degree of adaptability.

The Guardian

• “There’s a worry that rising sea levels are eroding sandy beach habitat, and once that spawning area on the beach is gone then it’s gone,” — Prof Mark Botton

The Guardian

• “They are very good at finding small patches of sandy habitat even if a coastline has been almost completely concreted over,” — Prof Mark Botton

The Guardian