Horseshoe Crab Mating Season

Be a CITIZEN SCIENTIST: report horseshoe crabs mating on the beach.

Horseshoe crab mating season is here! In a ritual dating back millions of years – ever since they first appeared 450 million years ago in the fossil record, horseshoe crabs converge on beaches just before, during or after a new or full moon.

Your job is to find them, note how many you see and whether or not they are mating. If possible, count how many are mating adults and how many are juveniles (4 inches wide or smaller). Then, add the date, time, location, habitat type and environmental conditions – such as tides and moon phase – when a sighting occurs, and you've got it! You're a CITIZEN SCIENTIST!

Why do we care? Because horseshoe crabs are important to marine ecosystems and their continued existence is important. Their eggs are a vital food source for animals and birds, such as the red knot whose population decline is linked to bait use of horseshoe crabs (read about that here: Their blood is used by pharmaceutical companies to ensure that intravenous drugs and vaccine injections are bacteria-free. Scientists have found that no other test is quite as reliable as that using horseshoe crab blood, which clots in the presence of infectious bacteria. Also, research into horseshoe crab eyes has given scientists a greater knowledge of the functioning of human eyes.

Report your horseshoe crab mating sightings here.