Horseshoe crabs love a full moon


-Horseshoe crabs, one of the Bay’s links to prehistory, hear the call of summer’s new and full moon and crawl out of the water to mate. They arrive at high tide, when the greenish clumps of eggs deposited by the female are farthest from the churning waves.

This is not a sight for the puritanical; the ancient creatures are polygamous, with as many males as possible clinging to a larger, fertile female. The male fertilizes the eggs as they are dug into the sand. Her golf-ball sized clutches contain thousands of eggs; still, she repeatedly returns to lay more, depositing some 90,000 eggs in a season.

Only a fraction of the horseshoe crab eggs will develop to maturity. But that fraction has been large enough to sustain the species for some 350 million years.

You can have a night of crab voyeurism at any sheltered stretch of beach on the Bay or one of its broad rivers. Your next chance will be the new-moon cycle on the weekend of June 12. Bay Weekly prints daily tide times.

If you return after the orgy, gently right any upturned horseshoe so it can return to the life-giving water to hear the next call of the moon.

–Sandra Olivetti Martin