The Horseshoe Crab
Limulus polyphemus

During the high tides of the new and full moon in early spring, a female horseshoe crab becomes active. Emerging from the muddy bed where it has spent most of the winter, it begins its journey to shore to take part in the spawning ritual that began millions of years before. Females dig several nests to lay their eggs. The males, one-third the size of the females, attach themselves to the rear of the female's carapace and are pulled over the nests to fertilize the eggs.

Horseshoe crabs attempt to protect their eggs by covering the nests with sand. Often wind and waves shift the sand and leave many of the eggs exposed. The eggs are eaten by the many  migratory shorebirds stopping along the Atlantic coastline. Shorebirds almost double their weight from feeding on horseshoe crab eggs which gives them the energy source that enables them to continue their migration north. 

Researchers determined that the blue, copper-based blood contains a chemical substance, hemocyanin, which clots when exposed to bacteria.  To obtain the blood, the horseshoe crabs are collected, a regulated amount of blood is drawn, and the crabs are released back into the wild. 

In an attempt to learn more about horseshoe crabs, biologists for state and federal agencies are participating in a Cooperative Tagging Program. Tag return data will provide information about migration patterns, distribution, abundance, and mortality of horseshoe crabs. This in turn will provide biologists with the  necessary information needed to manage and maintain healthy horseshoe crab populations. 

You can help by reporting any horseshoe crabs caught or found with our tag by calling the toll-free number printed on the tag 1-800-LIMULUS (546-8587).  A certificate of participation  containing  release information  is awarded to those who report our horseshoe crab tags.

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