Counting Horseshoes For Science

The annual horseshoe crab count by the Anne Arundel County Dept. of Recreation and Parks will go on this year but without the help of its usual eager volunteers. 

The COVID-19 pandemic prompted the county not to invite the multitude of volunteers who usually head out to local beaches to investigate the spawning of the arthropods. The count will be held between now and the end of July when the crabs deposit eggs on sandy shores. 

The horseshoe crabs at Beverly Triton Nature Park and Mayo Beach Park in Edgewater are counted to ensure the health of the crabs and make any needed adjustments to the management of their habitat. The crabs have been counted every year since 2017. 

“We usually utilize volunteers or park staff to stroll the beaches and count during peak hours,” says Karen Jarboe, park superintendent for Mayo Peninsula Parks. “We typically stick to a morning count as the afternoon counts are less productive. It seems the crabs prefer the morning hours to spawn.” 

With no volunteers being accepted it will be up to park staff to tally the numbers. 

Keeping track of the crabs tells the county valuable information. “Horseshoe crab eggs are pretty durable if they are left buried in the sand,” Jarboe says. “So, people walking on horseshoe spawning grounds isn’t a big deal. However, digging can be problematic.”  

The county implemented No Dig Zones this year on a small portion of the beach to mitigate some of that impact. “The new zones seem to be working out pretty well and it helps people realize that they aren’t the only ones who enjoy the beach,” Jarboe says. 

Thanks to the count, researchers have learned that spawning occurs at different times in different locations. 

“We are finding that the horseshoe crabs at Beverly Triton spawn later than the horseshoe crabs that spawn on the Delaware seashore,” Jarboe says.  

Plans are already being made for the 2021 count. 

“Some years they arrive earlier, some years, later,” Jarboe says “I think it has to do with water temperature. We will begin including water temperature in our data collection next year to see if that thesis is correct.” 

If you’d like to help count horseshoe crabs in the years to come, there may be even more opportunities. “In the future we may be looking at expanding our count area, and potentially using more volunteers,” Jarboe says. 

Learn more about horseshoe crabs—and their surprising intersection with the medical industry—in Wayne Bierbaum’s Creature Feature