The Sea Turtle Patrol stays busy monitoring nests every morning in the Lowcountry.
Island visitors quickly become accustomed to the beach, the tide and their sunrise coffee, but the wildlife is often a mystery to them.
They have seen the green vehicle motoring up and down the beach every morning searching for sea turtle tracks. Usually a polite wave is exchanged but, without fail, there will be at least one mystery solved each morning. Visitors have questions and who more qualified to ask than someone operating a motorized vehicle on the beach? The “stop hand” replaces the casual wave and, wait for it…
“Excuse me, what’s up with all the dead turtles?” he asks.
I glance at my patrol partner, as I hide my expression. “Dawn, why don’t you take this one.”
“Horseshoe crabs! Those are horseshoe crabs.”
These fascinating animals have been around for about 445 million years.
Yet they are still a very foreign and confusing creature to many people. They are often misidentified by beachgoers as stingrays or turtles. Many visitors just have no idea what to make of this alien creature and they keep their distance as they curiously poke them with a stick…a long stick.
Yes, they might look a little frightening, but they are completely harmless. The telson (tail) is not used as a weapon, it is not a poisonous stinger and it will not hurt you. It is actually used to steer and to help the crab right itself if it gets flipped over.
Horseshoe crabs spend most of their time moving along the ocean floor like a small tank.
They plow along and eat shellfish, worms, and dead and decaying matter. They visit our beaches each spring during the new moon and the full moon high tides (called spring high tides). Female horseshoe crabs will crawl out of the ocean, often already dragging a male who is attached to her using his hook-like front legs. Once the female is on the beach, she will dig a hole in the sand underneath her body with her legs. As she lays her eggs, the attached male, and possibly several other satellite males, release sperm to fertilize those eggs.
A female horseshoe crab will lay about 2,000-4,000 eggs per nest.
She will lay several nests per visit, and possibly as many as 80,000 eggs per season. The eggs develop under the sand for 2-4 weeks until they hatch just in time to hitch a ride on the next spring high tide.
During spawning season, many horseshoe crabs will get flipped over by the waves and stranded by the receding tide. If you see a stranded horseshoe crab, just grab it by its sides and flip it back over. Remember, it will not hurt you, but please be careful that you do not hurt the horseshoe crab. Always pick up a horseshoe crab by its sides and not by its telson.
Flipping stranded horseshoe crabs is an easy and important way to help this species.
You can also help protect this species by doing simple things like picking up trash off the beach and reporting tagged crabs. If you see a horseshoe crab with a tag on it, please call the number on the tag and report the tag number (take a picture or write it down before the crab crawls away). Reporting tags will help organizations like the South Carolina Department of Natural Resources learn more about these incredible creatures.
Historically, horseshoe crabs have been harvested and used as eel bait and fertilizer but, more recently, several important reasons for protecting this species have been discovered.
Currently, in South Carolina, horseshoe crabs may only be harvested for biomedical use by those who are permitted by the state to do so. Horseshoe crab blood contains a clotting agent called Limulus amebocyte lysate (LAL) that can be used to detect bacteria in pharmaceutical drugs and medical supplies. Chances are you have used something or had something used on you that has been tested using LAL. Horseshoe crabs do not have to give their lives to keep us safe. After about 1/3 of their blood is drained, they are returned to the coastal waters where they were collected.
In addition to saving our lives, horseshoe crabs play many other important roles.
They are a critical part of the food web. They also help to feed animals like those loggerhead sea turtles that nest on our beaches. Their eggs also help fuel a variety of migratory bird species, including the Red Knot which is a threatened species.
Story and photos by Dawn Brut, curator of education at the Coastal Discovery Museum.