Help us document the distribution and abundance of horseshoe crabs during their annual mating season along the shores of the Chesapeake Bay in Calvert County and beyond!
Use iNaturalist to photograph and map your observations in a few easy steps.
You can also help verify other people's observations to improve our data quality, come to a scheduled horseshoe crab survey, or even hold your own event. You can also explore on your own.
Spread the word—it's a big area! The area includes the entire Chesapeake Bay Shoreline in Maryland, Virginia and Delaware. We are really interested in Calvert County sightings, but any observations along the Chesapeake are important.
There are many questions about this “living fossils.”
• Where are horseshoe crabs coming ashore and laying eggs?
• Will they be found mating during the daytime?
• Are they in the water if they aren’t on the shore?
• Does the moon need to be full for them to mate?
• How many horseshoe crabs are found on any one survey?
Did You Know...
How You can Help
Become a Calvert Steward and learn how to:
Horseshoe Crab Survey
Atlantic Horseshoe Crab
Horseshoe Crabs have been nick named “living fossils:”
Their scientific name, Limulus polyphemus, is from the Greek one-eyed monster, are one of 4 species worldwide.
They occur along east coast from Maine to Florida and Yucatan Peninsula.
Horseshoe crabs today don’t look a whole lot different from the fossils of their ancestors – hence the nickname – living fossils. They have been relatively unchanged for about 350 million years