Spot horseshoe crabs before they go for a year
ALL along the shoreline, slick shells of horseshoe crabs glisten in the fading daylight. Listen closely, and you can hear their subtle clacking and the whisper of water over their carapaces.
It’s horseshoe crab spawning season in Delaware Bay. Every May and June, on nights when the moon is new and the tide is high, they crawl on to the beach to mate and bury their eggs.
The ritual goes back 445 million years. Horseshoe crabs are living fossils that have survived four mass extinctions. They are bizarre creatures with 10 eyes that offer insights into how vision evolved. And their blood has saved countless human lives.
But these creatures are in peril. It’s urgent that biologists understand their life cycles and learn how many there are. Researchers work quickly to take a census of the crabs before they go under the waves.
Elle Gilchrist reaches into a pile of crabs. Each is glossy green-brown and shaped like a shallow combat helmet with a 15cm spine sticking out the back.
Gilchrist, a 20-year-old intern with the Delaware National Estuarine Research Reserve, expertly flips a crab over to reveal 10 segmented legs and a sheaf of sturdy gills. The males’ limbs end in pincers, used to grab prospective mates. The insides of the females’ carapaces are lined with thousands of tiny pale green eggs.
Gilchrist counts the horseshoes in her plot. Then she thrusts her hand among the mass of shells and feels for the huge, smooth carapace of the lady they’re all trying to woo. “One female.” She says the mating ritual is “awe-inspiring.” Conservation ecologist John Tanacredi, director of the Centre for Environmental Research and Coastal Oceans Monitoring at Molloy College in New York, wants the UN to create a new Unesco designation for them: “World Heritage Species.”
“These animals walked below the legs of brontosauruses at some point in time,” Tanacredi says. “They really should be the paradigm for survival and sustainability.”
Horseshoes crabs are not crabs. They’re distantly related to spiders and scorpions.