The Early Years of a Horseshoe Crab in NY Harbor

At 3:30 PM on Sunday, the temperature reached 92 degrees. It was another sultry early summer day around Lower New York Bay. 

Trying to cool off, I went wading in the calm waters of Sandy Hook Bay, a small cove connected to the much larger estuarine waters of Lower New York Bay. Walking in the water, though, didn't help much. Even the water was warm with surface temperatures in the shallow part of the bay in the upper 70s to lower 80s. The earliest I can remember the water being so warm. Fortuitously, there was a slight breeze off the bay that kept things a bit more refreshing than inland.
While slowly walking beyond the first few feet of tidewater, I thought how the warm temperatures would help to create an ideal nursery for small juvenile fish and crabs to feed and grow. Estuaries often are important spawning or nursery areas for many diverse species -- birds, fish, crabs, shrimps, and other wildlife. 

Then just like that I spotted something small and tan moving along the sandy bottom of the bay. It was neither fish or crab. Reaching down with bare hands I picked up, to my surprise, a young Horseshoe Crab. The critter was so small it could fit comfortably inside an adult Hard clam shell.
It seemed like an appropriate time to find little Horseshoe Crabs. The tide was coming in and young Horseshoe Crabs have been known to forage during incoming tides for small worms, dead fish, and mollusks. The flow of higher water provides some degree of protection from certain predators. Wading birds fly off to be in ankle-deep water to look for food and larger fish have yet to enter near the edge of the bay to hunt. 


I have not seen a young Horseshoe Crab around the bay for some time. So the sight of this little critter in the palm of my hand was exciting. New life!
Horseshoe Crabs are not technically crabs. They are actually arthropods more closely related to spiders and scorpions. To me, though, this small Horseshoe crab looked like an ancient armored tank. Nothing living quite resembles a Horseshoe Crab. Even when young this unique bay creature had a hard helmet-like shell with a long spiked tail. Around its dorsal shell were several sets of primitive eyes that act like light sensors and two large compound eyes  (much like a fly's eyes) on either side of its shell. Underneath was a prehistoric bushy mouth and seven pairs of appendages including five pairs with claws.
Sounds menacing right? But they are actually a peaceful and quiet animal. Underneath its hard shell is a vulnerable and shy creature. Juvenile Horseshoe Crabs prefer to spend most of its time in shallow estuarine waters buried in the sand or mud to hide from numerous predators, such as gulls, herons, egrets, eels, sea turtles, sharks, and other fish including Summer Flounder, Striped Bass, Weakfish, and drum.  It's a stressful life, always looking around to flee from something that wants to eat you. 


Of course, its largest predator are humans. Some people might take this small crab as a pet, which is illegal. Other people might use it as bait for eels, conches, catfish, or other aquatic species, which is illegal to do in New Jersey and regulated in New York. With millions of people living or visiting near the edge of Lower New York Bay, particularly during the summer, not everyone is going to be kind or caring when finding a little sea creature.

Another stressful event for young Horseshoe Crabs is molting. Imagine losing and growing new skin every few months. No doubt this is a challenging task to say the least.  In order for young Horseshoe Crabs to mature, they must shed or molt its stiff outer shell (also called an exoskeleton) an average of three or four times a year, but less as the crab nears adulthood or sexual maturity. The molting process takes about 12 to 24 hours. During this time the crab has a soft shell  and is exposed to attacks by predators.
The good news is that if the little crab survives , each successive molt increases the size of a Horseshoe Crab an estimated 25 to 30 percent. Males are usually sexually mature after their sixteenth molt or around 9 years. Females need at least 17 molts or 11 years to mature, as they are on average 30 percent larger than males given that they create and carry eggs. 

The crab I found in Sandy Hook Bay was likely one that was 2 to 3 years old. Hatched out from its tiny egg somewhere on a beach in Sandy Hook Bay. The little body from the tip of the tail to the edge of the shell measured about 3.5 inches long. Still a long way to go yet before it would be big enough to swim out in deeper waters with the adults.
As I let the little crab go back into the water where it was found, I wished it well and hoped for the best. Lower New York Bay is not an easy place for any wild animal to live, especially a little Horseshoe Crab that exists alone.  Juvenile Horseshoe Crabs generally do not live in groups or schools with other crabs of their own age. They exist on their own only coming out of their furrow to forage and molt. 

Still, I tend to be an optimist. I believe this little Horseshoe Crab will survive. The species has been around for more than 400 million years. Horseshoe Crabs have been around  on this planet when the first dinosaurs and prehistoric mammals appeared.  Few other living animals on Earth can claim this record.  Juvenile Horseshoe Crabs have been doing the same thing for millions of years. I just hope they can keep it going and find a way to survive within one of the most urban and densely populated estuaries in the world.