Horseshoe Crabs are Frequent Visitors to Cape Beaches

Posted by Mark Washburn on Wednesday, March 11th, 2015 at 3:44pm



While the summer months bring a lot of extra visitors to Cape Cod beaches, it’s not just people swarming to enjoy the surroundings.  While extra visitors are often lured to the area by its scenery, serenity and countless options in outdoor recreation, another frequent visitor has an entirely differently plan in place.

Every year the horseshoe crab takes over several of the Cape beaches for a few select early summer nights.  The same thing has happened for millions of years.  Typically, when you visit the Cape beaches around May or June, you may just stumble upon a large number of horseshoe crabs.  This is because this time of year is peak spawning season for the crabs.

Usually the horseshoe crab will wait for a full moon.  While you may catch some horseshoe crabs emerging from the water during daylight, typically they don’t come out until its dark.  It’s truly an amazing site, watching countless numbers of them scurry up on the beach in search of some sand in which to lay their eggs.  The female crabs will dig the nest, drop off thousands of eggs and then head back to the water as the males fertilize the eggs.

The horseshoe crab is just as commonplace as other marine life in Cape Cod, and there’s a good reason why.  The horseshoe crab plays an important part in the area’s ecosystem, as well as serves as a natural resource.  The horseshoe crab preys upon things like worms and mollusks, while sharks and loggerhead sea turtles actually feast on the crab.  Migrating shorebirds also include horseshoe crab eggs as part of their necessary diet.

As for people, the horseshoe crab serves an important role in everything from commercial fishing to pharmaceuticals.  The horseshoe crab is commonly used as bait to help catch whelk and eel.  In addition, the horseshoe crab’s blood is used in making vaccines and certain medical devices.  Horseshoe crabs cannot be harvested from Cape Cod National Seashore, rather this particular area is working to help tag the creatures and learn more about them for the future.

If you do want to glimpse the horseshoe crabs as they migrate onto the shore, you can see them, among other places, at Cape Cod National Seashore.  You’ll likely encounter the horseshoe crab ritual at Nauset Marsh, Pleasant Bay, Great Island and Lt. Island.  Again, you’ll have to time it right, by the new or the full moon.

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