This is the last full moon of the Horseshoe spawning season. Gravid females can lay tens of thousands of eggs during the season, making successive trips to shallowly bury their eggs at the high tide line. Very few of those eggs become adults. I’ve seen one estimate that says only 10 individuals will reach adulthood out of tens of thousands of eggs. Once, where there were millions of Horseshoes up and down the east coast, all these eggs were key to an littoral foodweb, with migratory birds and ocean animals scarfing up the rich bounty of protein. But enough Horseshoes made it to spawning age — it takes 9-12 years — so that, with the usual highs and lows of natural cycles, it all evened out in the long run. And Horseshoe crabs have had a long run; their ancestors go back some 400 million years — that predates the dinosaurs by some 200 million years.
No more: Horseshoe populations are plummeting. Long Island sees less and less of them every year. Why? They were ground up for fertilizer by the ton until the mid-20th century. Right around the time that assault finally stopped, they started being chopped up for bait for the eel and whelk fisheries. Combined with beachfront development, poisons (a.k.a. pollution, the costs fobbed off by corporations onto the world’s biotic, including human, communities), and such assaults on the ocean as dead zones, warming, and acidification, the Horseshoe population has taken a big hit.
Meanwhile, and here’s what really gets me, they’re also bled for our benefit. Anyone who’s ever taken antibiotics, much less had surgery or prosthetics — owes something to Horseshoe crab blood, from which the bacteria-detecting LAL is extracted and used world-wide to test pharmaceuticals and medical devices. (The industry says 3% of these bled Horseshoes die; others say it’s more like 10-15%.) Personally, I think we owe these animals a lot more thanks than the hacking of them into pieces of bait for eel and whelk eaters.
Horseshoe crabs were also instrumental in advances in the science of vision — who’d a-thunk it? — and the understanding of chitin (which is now found in everything from tampons to livestock feed, although it’s not commercially derived from Horseshoes).
Some of you may, in a way, owe your life to this animal, whose ancestors survived two global extinction events but may not get through the present one.
I usually see my Horseshoe crabs at beaches that are part of Gateway National Recreation Area. You can’t harvest Horseshoes there, so I kinda always assumed that it would be the same elsewhere in the state. Wrong! Gateway’s federal. New York shamefully allows licensed commercial exploitation. Additionally, individuals can take a max of five a day in season for “recreational” purposes w/o a license.
UPDATE: Through the magic of the internets, I’m actually not on the long island whose western-most end is Brooklyn at the moment. I’m at the far eastern end of the terminal moraine/outwash plain, on Nantucket, and today I spotted two Red Knots, the increasingly rarer shore bird that migrates up from South America to the Canadian arctic, a bird heavily dependent on Horseshoe crab eggs. I’ve never seen them before.