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  • Horseshoe Crabs on Slaughter Beach 5

The First Beach Bums

Horseshoe crabs have been lounging on beaches in the Delaware Bay long before the first human settlers landed on Cape Island. Every spring, volunteers with the Annual Horseshoe Crab Spawning Survey gather to count these ancient arthropods as they come ashore at the height of the mating season. The horseshoe crab counts are held on twelve nights coinciding with the new and full moon phases. Surveyors made up of experts and volunteers alike gather on the beach in New Jersey and Delaware at or near darkness and high tides.  Hundreds of thousands of horseshoe crabs come to the Delaware Bay to Breed in the months of May and June. 

Horseshoe crabs have been around for over 300 million years, making them older than the dinosaurs and North America itself. They become adults around ten years of age. In the spring, they come ashore to deposit eggs and mate. Horseshoe crab eggs are an integral part of the migratory birds that visit Cape May each year. Those fertilized eggs that survive hatch after about two weeks as larval horseshoe crabs. They travel into the ocean to mature over the next decade. 

Horseshoe crabs have a hard exoskeleton, ten walking legs, spines on the abdomen and a long tail. The large head of a horseshoe crab protects its largest set of eyes; they have nine eyes throughout their body.  A horseshoe crab’s tail is called a telson, and is many times mistakenly thought to be dangerous. The purpose of the telson is for a horseshoe crab to flip over if it happens to get stuck on its back.

Not only do horseshoe crabs serve as food for migratory birds, but also they are bled, with no harmful effects, to extract a compound to use in the pharmaceutical industry to test intravenous drugs for dangerous bacteria. The survey along the Delaware Bay is open to volunteers, with training sessions for any one who is interested. Click here to learn how you can volunteer.