Learn a lot about horseshoe crabs
When I was growing up my family would go to Ocean City every summer for a funfilled vacation at the beach.
Even after a whole week of surf and sun, we were never quite ready to go home when it was time, so my dad would drive us up to Rehoboth Beach on the way out of town and we’d check out their beach and boardwalk for some last minute fun and lunch at Grotto Pizza.
One year, on the morning of our last day at the beach, my sister and I found a trove of dead horseshoe crabs washed up on shore. Thinking it was a good idea to bring them home with us, we collected as many as possible in our beach towels and stowed them in the back of my mom’s car. As we drove to Rehoboth for lunch that day, the mercury started rising. It was going to be a hot one.
The horseshoe crabs baked for several hours in the blistering sun in the back of my mom’s car while we explored the beach and ate lunch. When we were finally ready to drive home and opened up the car, the stench that greeted us was too foul for words. My dad dispatched of the offensive carcasses immediately and we drove home with the windows down, trying not to gag too much. Our great idea probably cost my mom a few hundred dollars when she traded in her car a couple years later. The smell lingered.
Since then, I’ve never had too much of an interest in horseshoe crabs. My family and I have seen them on occasion at the beach and had the chance to handle the specimens at the Calvert Marine Museum in Solomons. We are aware they are living fossils, relatively unchanged since before the time of the dinosaurs. And that long spiked tail? It’s not a stinger. Horseshoe crabs are harmless and the tail is used by the crab to flip itself upright if it gets turned over.
But horseshoe crabs have quite an interesting story. Earlier this month, the Southern Maryland Audubon Society sponsored a field trip to Flag Ponds Nature Park in Lusby and I tagged along to learn more about this funny looking creature.
This wasn’t just any field trip either, it was a nighttime adventure that started at 9 p.m. on a Sunday night. I wasn’t really thinking things through when I invited my 5-year-old daughter to accompany me on this outing that started just after her bedtime.
We met up with naturalist Andy Brown who knows a lot about horseshoe crabs, and a lot about birds and nature in general. He started off the night by asking the audience if anyone knew what an arachnid is. A lot of hands shot up and some people shouted out “spider,” but there were some confused looks from a few people who wondered if they were in the right place.
As it turns out, horseshoe crabs aren’t crabs at all. They are part of a group of animals closely related to the arachnid family. Therefore their cousins are more likely to be spiders and scorpions rather than lobsters and true crabs. That’s something I didn’t know. But just like Mar yland’s most famous crabs, horseshoe crabs have to molt to grow bigger.
Horseshoe crabs have blue blood. And, no, I don’t mean they are related to Prince William and Princess Kate. Their blood is actually bright blue. Brown handed around a vial of the blue stuff and asked us to be very careful. Horseshoe crab blood has a lot of medical properties that make it quite valuable, with a price tag of about $15,000 for just one quart. That little vial probably contained a few hundred dollars worth of horseshoe crab blood.
We were curious just how horseshoe crab blood is collected. There are no farm-grown horseshoe crabs to do the job, so wild ones are caught and about 30 percent of their blood is harvested. Then they are released back into the ocean. Each year about a quarter of a million horseshoe crabs donate their blood so medical devices and vaccines
are safe for human use.
Lately, scientists are wondering if this practice is harming the horseshoe crab population. It is estimated that up to 30 percent of crabs don’t survive after being bled, and the harvesters release the horseshoe crabs far from where they were captured to avoid recapturing and bleeding them again.
I can’t imagine being forcibly moved to a new territory is very good for a crab’s survival.
A tagging program is now in place to keep track of exactly where the crabs live and spawn. While their natural range spans the entire east coast, the tagging program has shown that some crabs return to the same beaches year after year to spawn. That’s pretty incredible.
And the reason the Audubon Society takes
an interest in horseshoe crabs? Their eggs provide the fuel for thousands of migrating birds each year. The red knot, a bird that migrates 10,000 miles from Argentina to the high arctic to breed, stops off in Delaware Bay to gorge on eggs at the peak of the horseshoe crab spawn. Without the
horseshoe crab eggs to feast upon, these birds wouldn’t have the energy reserves to make such a long and arduous trip. It’s amazing how nature is interconnected.
After talking about horseshoe crabs for a few minutes, the group walked about a mile down to the edge of the Chesapeake
Bay. The moon wasn’t full, but there was enough light so we could see our way on the beach without flashlights, which is a good thing because horseshoe crabs have 10 eyes that are light sensitive.
The wind was whipping that night which made the surf rougher than ideal, but we still found a few female
horseshoe crabs burrowing in the sand to deposit their eggs. The male crabs, which are significantly smaller than the females, will congregate around a female in hopes of fathering some of the offspring. But we only saw pairs of crabs that night.