Saturday, June 25, 2022

Horseshoe Crabs could be on a beach near you



The Horseshoe Crab (Limulus polyphemus), a species that has existed for hundreds of millions of years and is likely the closest living relative to the ancient trilobite (an extinct marine arthropod,) is unmistakable to identify: chestnut brown in color, with domed, U-shaped head, spiny edged abdomen with eight crab-like legs, and a stiff pointy tail. These crabs can grow up to 24 inches and are found on the coast from Maine to Florida. They may look a bit creepy or a hover-craft to some – related to spiders more than crabs – but they are gentle and safe to handle with care. They have a long life span: horseshoe crabs can live 20 to 40 years and females take a decade to mature to reproduce.

Once abundant, their numbers are declining throughout their range. The decline is related to a variety of factors, including intense fishing, but it’s mostly due to loss of reproductive habitat – they need low-energy beaches that allow the adults to mate in the tidal area then nestle their eggs in the upper limits of the high tide zone, or what is called the “swash zone.” Their eggs are a vital food source for migratory shorebirds, many relying on these eggs as the primary energy source for their long, sometimes global, migration. Due to this reason, scientists relate decline in horseshoe crab populations to the decline in many species of shorebird populations. They also have been noted as a valuable species in pharmaceutical and biomedical research.

The horseshoe crab needs your help! As the Gulf waters get warmer, these crabs are moving in from deeper waters to mate and nest their eggs on the Marco Island beaches and nearby sandbars. If you are out boating or taking a beach walk and you observe horseshoe crabs mating and nesting (two or more crabs connected together,) please report this to Florida Fish and Wildlife Research Institute (FWRI.) This agency has been conducting statewide surveys of nesting beaches for horseshoe crabs and is interested in the date, time, location and environmental conditions (such as moon and/or tide phase.) Remember, if you do see them, it is a sign of a healthy ecosystem.

To report your observations please contact FWRI by email:, by phone 1-866-252-9326 or report your information in an online survey at


One response to “Horseshoe Crabs could be on a beach near you”

  1. Izadora Gil says:

    Hello today I saved a seahorse crab and I’m only 12 years old! And I saw a sea horse crab glued to each other’s back but I thought the one that was in his back was his daughter

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