crabs

The Ancient Ritual of the Horseshoe Crabs

For more than 300 million years, horseshoe crabs (Limulus polyphemus) have left the ocean depths to crawl onshore to breed. In New York, these ancient animals — more related to scorpions and spiders than to crustaceans, and older than the dinosaurs — come to our many shores at full moons, new moons, and high tides beginning in May and continuing into June and early summer. On May 29, 2018, we went to Plumb Beach in Brooklyn close to high tide on a night with a full moon, and were rewarded as the female horseshoe crabs came onshore, with the males grasping onto them. The females dug a nest in the sand and laid their eggs, which the males then fertilized. 

Breeding horseshoe crabs, Plumb Beach, Brooklyn, May 29, 2018

Breeding horseshoe crabs, Plumb Beach, Brooklyn, May 29, 2018

The video showing the horseshoe crabs coming to shore was filmed on May 29 at Plumb Beach, using the soundtrack of the waves. Also in the video are some clips from other beaches throughout the city where I've seen the shells of dead horseshoe crabs, which are beautiful in their own right. Our trip to Plumb Beach was led by Keith Michael of New York City WILD!

Horseshoe crabs have 10 legs, which they use to walk along the ocean floor. They have hard exoskeletons, and nine eyes spread throughout their bodies, plus light receptors near their tails, or telsons. These long, pointed telsons are not used to sting or poison, but to help the horseshoe crabs right themselves if waves push them on their backs.

Horseshoe crab at Marine Park, Brooklyn, May 24, 2018

Horseshoe crab at Marine Park, Brooklyn, May 24, 2018

When the horseshoe crabs were on their backs, rocking back and forth and using their tails to turn themselves over, we watched until we were sure they could right themselves. There were some times when the male and female crabs were both shell down, their legs moving in the air and seemingly without the ability to turn back over. At that point I gently turned the two over and they were able to move again.

Horseshoe crab, Plumb Beach. May 29

Horseshoe crab, Plumb Beach. May 29

A horseshoe crab attempts to right himself.

A horseshoe crab attempts to right himself.

The horseshoe crab eggs, tens of thousands of them, are a food source for fish, reptiles, and birds. About two weeks after the eggs are laid and fertilized, those that survive hatch into larval horseshoe crabs, which are tiny versions of the adults but without tails. These youngsters settle on the sandy bottom of tidal flats, where they grow and molt, shedding their exoskeletons and growing larger ones, as they move farther into the ocean depths. Once they become adults, roughly 10 years old, they begin the breeding process.

Watching the horseshoe crabs on Plumb Beach, May 29, with the New York City WILD! group

Watching the horseshoe crabs on Plumb Beach, May 29, with the New York City WILD! group

Horseshoe crab shell on the beach, 2017

Horseshoe crab shell on the beach, 2017

Fiddler Crab Beachcombers

Fiddler crabs, beetle-sized crustaceans of the genus Uca, scurry sideways along some of the beaches and intertidal mudflats of New York City. I've seen them in beach parks in Queens, Brooklyn and the Bronx. They climb in and out of small holes after the tide goes out, the males dragging their extra-large claws along with them (the females have equal-sized claws, the males have one large claw and a smaller claw). These crabs eat by using their smaller claws to shovel food in their mouths, capturing algae, microbes, fungus and other decaying detritus and returning what's left in small balls on the ground. Their beachcombing habits are thought to help preserve the wetlands by aerating the substrate.

Male fiddler crab, Hunter Island, Pelham Bay Park, near Orchard Beach, Sept. 20, 2017

Male fiddler crab, Hunter Island, Pelham Bay Park, near Orchard Beach, Sept. 20, 2017

The Fiddler Crab video is set to a violin sonata by Jan Brandts Buys, performed by Steve's Bedroom Band and obtained from MusOpen.org, a royalty-free music source. It shows these small crabs at Marine Park in Brooklyn, Broad Channel Park on Jamaica Bay in Queens, and Pelham Bay Park (Hunter Island, near Orchard Beach) in the Bronx on July 25, 2015, and August 22 and 31, and September 20 and 23, 2017.

More fiddler crab shots below. These are fascinating, though slightly creepy, animals. They do molt, shedding their shells as they grow. If a male loses the big claw, a new claw will grow on the opposite side after the next molt. You often see these reclusive crabs go hurrying into their holes, where they will stay after molting until the new shells harden.