Its spring on Nantucket and as we return to the island’s beaches, there are many treasures to find! This year, the really low tides around our full and new moons, one of the most common things on the beach seems to be horseshoe crabs – left high and partially dry by retreating tides.

Why are there so many crabs on the beaches? April-June is horseshoe crab mating season in New England. The larger female crabs make their way to the beaches, pursued by eager males. The females dig into the beaches at the highest tides of the month, depositing eggs within the sand. The males come by after and inseminate the eggs which are left to develop and hatch on their own. Because those crabs are coming up into the shallowest of water to reproduces, they often don’t finish their tasks before the tide goes back out again. Then they are left waiting until the next tide comes in.

Our first instinct is that these prehistoric sea creatures are suffering, stranded away from the ocean and likely trapped. The most important thing to know is that, as long as you pick them up carefully, you cannot hurt horseshoe crabs by picking them and returning them to the water’s edge. But maybe the other important thing to know is that you don’t have to move them if you are hesitant. Horseshoe crabs can actually live out of the water for about 4 days! The crabs will bury themselves into the sand or fold their bodies up to hold on to water until the tide rises again and they can swim free!

The other risk to being stranding on the beach is possible predation by gulls and other birds. For these birds, an exposed horseshoe crab is a tasty meal. So if you can confidently lift the crabs and if they aren’t buried deep in the beach laying eggs, feel free to get them gently back into the water to safety.

To Move a Horseshoe Crab

Place your hands under the top lid of the largest part of the crabs shell, one hand on both sides and lift gently. Carry the crab back to the water’s edge and place it gently, shell UP into the water. NEVER grab a crab by the tail. Horseshoe crabs need these tails to swim and flip themselves over.

Save This Animal's Life With a Simple Act -- It May Help Save Your Own —  SOUTH CAROLINA COASTAL RESOURCES
Beach Chair Scientist — Marine & Freshwater Environmental Education