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Spy on Horseshoe Crabs

July’s two full moons are prime viewing times

Does a full or new moon woo you? Perhaps draw you to follow its reflection in warm, shallow waters of the Chesapeake?
    Homo sapiens are not alone in lunar motivation. It’s shared by that most antique of species, the horseshoe crab, which chooses spring and summer high tides during those moon phases to mate along many Bay beaches
    The horseshoe crab is misnamed. More closely related to spiders and scorpions than to other crabs, it has changed little in 360 million years. Its hard brownish-green shell, which can grow to about two feet long, is shaped like a horseshoe. Its spikes and spines may look dangerous, but horseshoe crabs are harmless, indeed helpful. Their eggs feed many migrating birds, and their blood helps medical research.
    You can have a productive night of crab voyeurism at stretch of beach on the Bay or one of its broad rivers as horseshoe crabs continue their mating in this month’s two full moons: July 2 and 30, each followed by the new moon. Adults come up on sandy beaches to mate and lay eggs. This ritual usually corresponds with full moons and evening high tides. The green eggs are laid in nests or clusters in the sand at the high tide mark. After about a month, the eggs hatch. A high tide will break open the shells and carry the newly hatched horseshoe crabs to the water.
    The Maryland Department of Natural Resources wants to know about any shoreline used by horseshoe crabs for spawning. GPS coordinates are best, but also helpful are approximate locations on map or chart. Contact DNR’s Marek Topolski: 410-260-8263; marek.topolski@maryland.gov.