If you live near the coast, no doubt you have encountered a horseshoe crab, or at least their shells, once or twice. Inconspicuos as they may seem, these creatures are critical to the red knot, a shore bird that migrate annually from the tip of South America to the Canadian Artic to rear their young.
The red knots have a lay-over along the Atlantic shoreline in their migration north so they can feast on the literally millions of eggs that are deposited by horseshoe crabs during the spring mating season. A serious decline in the horseshoe crab population in the 1990s, attributed to over-harvesting for bait and medical purposes, has diminished the food source for the red knot so seriously that the red knot population is at risk of crashing. States have imposed harvest limits, but enforcing them is difficult because the prime time for collecting the crabs is in the dark of night when they come ashore to mate and lay their eggs in the sand.
We don’t have enforcement authority, but concerned citizens can help. The crabs prefer to mate in the new moon to full moon period of March, April, and May, with May being the most active month. If you find yourself on the beach on a May night, you may come upon what is literally an orgy for the crabs. Multiple males, attach to a female who has burrowed in the sand at the water’s edge. And there can be hundreds of crabs mating at a single beach. Often the breaking waves of a choppy bay will turn the crabs over, leaving them helpless and facing certain death. If you find one like that, just turn it over and put it back in the water so it can live to mate again. They are completely harmless, so there is nothing to fear from picking them up.
The other day I was walking the beach to monitor piping plover breeding activity and came across a site recently used by the mating horseshoe crabs, along with an overturned fellow who was close to becoming seagull food. We picked him up, put him in the water and watched him collect himself and swim away.
Score one for the horseshoe crabs and red knots.
Horseshoe Crab mating site-five pairs in one place.