The end of May and early June is the height of Horseshoe Crab spawning. Soon after the herring have migrated upstream to release their eggs, adult Horseshoe Crabs begin to magically appear out of the water at their favorite beaches or mud flats to produce another generation. The spawning season tends to peak at night around the new and full moons; and when water temperatures first rise above 55 degrees. These conditions let know the Horseshoe Crab that it's time to lay eggs.
For at least 350 million years, instinct takes over in the spring for the Horseshoe Crab. They travel on the bottom of the water, sometimes over hundreds of miles from the Continental Shelf, to arrive to coastal beaches to satisfy their need to breed.
Single females swim inshore around the tip of Sandy Hook or Breezy Point. They are followed by males. Wandering females stay unattached for only a short time. Males, which outnumber females by at least 5 to 1, will compete for a female's attention. The winner will latch onto the back-end of the female with their hook-like arms. As the female moves around the shallow waters of the bay making circular tracks in the sand, she will drag the male along. Once a nesting site has been settled on by the female Horseshoe crab, she will burrow into the wet sand and lay up to 1,000 eggs, which the male will fertilize. A single female Horseshoe Crab will lay eggs in three to ten nests sites within the inter-tidal zone.
So if you plan on walking around the bay beaches and mud flats around Lower New York Bay over the next few weeks, watch out! As the Horseshoe Crabs spawn, they are sometimes hardly visible. All you might see is a large lump of sand or some strange marks on the beach. Look closely, though, as part of the male will show. You will see the crab's unmistakable body - a spiny long tail and even perhaps a horseshoe helmet-like shell. Brush away some sand and you might even feel the shell of the female too.
Empty sand holes or depressions in the sand could indicate places where these bay creatures have laid their pale-green clusters of eggs. Leave them alone as well! If exposed to the air or the sun, the eggs will dry up and wither away. If all goes well, in about two weeks, the eggs will hatch will tiny newly born Horseshoe Crabs that will bring fresh life to Lower New York Bay.
Watch where you step and if you see a mating pair of Horseshoe Crabs, please do not pick them up. If you handle a single Horseshoe crab, please do not pick up the crab by its fragile tail. The delicate hinge connecting the tail to the body will not support the crab's weight and the tail will break off. A Horseshoe Crab will then lose an important tool to navigate in the water and on the beach.
It is best to just let the crabs be for the next few weeks. Let them get on with their job of laying eggs and propagating new life, as they have been doing for over 350 million years. This is an important occasion for Horseshoe Crabs. Spring spawning time is the very backbone of their survival.