Do you remember what it was like 450 million years ago? Neither do I. But horseshoe crabs, somewhere in their DNA, remember. They were around in some form over 200 million years before dinosaurs first appeared, and 300 million years before birds. What do horseshoe crabs call birds? Whippersnappers. The entire glacial history of Cape Cod wouldn’t qualify as even a rounding error in the estimated age of horseshoe crabs.
So what does this have to do with birds? Here in Massachusetts, the answer, sadly, is not much these days. But down in Delaware Bay, now that it’s May, an old ritual is beginning, a natural spectacle we can only dream of up here. For some debatable portion of evolutionary time, certain shorebirds have routed their northwards migration in accordance with horseshoe crab spawning in places like New Jersey and South Carolina, where millions of horseshoe crabs crowd shorelines to spawn each May.
The crabs are so abundant they dig up each other’s nests, leaving eggs piling up in the wash zone, where hungry birds eat their fill. Semipalmated Sandpipers, Ruddy Turnstones, Sanderlings, and especially Red Knots depend on the tiny green eggs to fatten up for breeding season. The knots, who are federally Threatened, have just arrived from the south end of South America, and boy are they hungry. They will need to as much as double their weight, then fly straight from Delaware Bay to the high Arctic in hopes of successfully breeding during an impossibly tight window in June.
Concern over Red Knots drives management decisions around the horseshoe crab harvest in that region – they’re used as bait in whelk traps, an obscure export fishery and a not so noble use of the species. New Jersey allows no harvest at all to make sure there are enough crabs for the Red Knots, and the other Delaware Bay states have banned the harvest of females. With recent changes in New York and Connecticut, Massachusetts stands alone with the least restrictive horseshoe crab regulations on the Atlantic coast. Protections in other states include either much lower harvest quotas, or some combination of no bait harvest, no female harvest, or no harvest during spawning. Massachusetts allows all of that, along with one of the bigger biomedical harvests.
Something like half-a-million Horseshoe Crabs are also bled and returned to the water in an important biomedical fishery – their blood is used to make the only FDA approved test for bacterial contamination of drugs, medical equipment, and, yes, vaccines. Mortality in this biomedical fishery is around 15-30%. Charles River Labs, a $16 billion company and the world’s biggest producer of the crab-based test, has just opened up shop in Harwich and will begin to bleed Massachusetts crabs. They likely came north for our less restrictive regulations after burning some bridges and facing new restrictions down in South Carolina. Time will tell what this will means for already stressed populations of crabs here on Cape Cod.
There is still a place in Massachusetts where some small vestige of the old connections between horseshoe crabs and birds remains. On remote beaches of Monomoy National Wildlife Refuge, where no bait or biomedical harvest of horseshoe crabs is allowed, there are still enough crabs to entice a few Red Knots to stop by in May. It’s still nothing like Delaware Bay, it’s just a taste of what we’ve likely lost, here in what is now a flyover state for Red Knots.
I’ve still not witnessed the incredible horseshoe crab and shorebird frenzies down in Delaware Bay, but I recommend you check it out if you have the time and the means. If you go, you should lean down real close and listen. You might hear this ancient species saying something to those more recently evolved birds, these whippersnappers eating their eggs: “get off my lawn!”
