Every spring and summer, a 200 million year old ritual takes place right here on Monomoy National Wildlife Refuge. Adult horseshoe crabs begin a long trek from the deep ocean bottom to deposit their eggs along the coastline during low tides.

Upon hatching, the larvae spend about a week swimming until they settle to the ocean bottom where they begin to molt a hard shell. Do you see any small horseshoe crab shells along the beach? While these may look like dead horseshoe crabs, they’re actually the molts. The horseshoe crab is still alive but swimming around in a larger shell! Over a period of 9 to 12 years, a horseshoe crab will molt at least 16 to 17 times.

Did you know that horseshoe crabs aren’t actually crabs? They are arachnids, closely related to the spider!