High Tech Hobby Sheds Light on Prehistoric Creature

Photo courtesy of Perry Smith, UNH Photographic Services

A horseshoe crab leaves a trail of pits in the mudflats of the Great Bay, NH looking for shellfish and other invertebrate to eat.

After a summer of tromping around in New Hampshire’s Great Bay National Estuarine Research Reserve to study pits dug by horseshoe crabs, a Fellow in the NERRS’s Graduate Research Fellowship Program Wan-Jean Lee realized that her own feet were getting in the way of her research. A chance encounter with another scientist whose hobby is remote control airplanes helped Lee solve her dilemma and led to a novel way to show the importance of the Great Bay estuary to the horseshoe crab. Wan-Jean Lee works with the Great Bay NERR and University of New Hampshire faculty to learn where and when horseshoe crabs feed and the impacts of their feeding on the Bay’s ecology.

With the population of the prehistoric horseshoe crab declining on the east coast, Lee wants to see if their decline will significantly affect invertebrates like shellfish that live in Great Bay’s muddy bottom. “Knowing where and when they like to eat is important if we want to know where to look for them as the population declines,” Lee says. “We also need to understand how that decline might affect other parts of the ecosystem.”


Photo courtesy of Perry Smith/UNH Photographic Services

Graduate Research Fellow Wan-Jean Lee took to the air with a remote controlled airplane to study horseshoe crabs in the Great Bay, NH, National Estuarine Research Reserve.

The Venerable Horseshoe
Horseshoe crabs move up with the flood tides in the Great Bay estuary every spring to spawn
on the water's edge. Throughout the summer, they return to the Bay’s mudflats with the incoming tide, where they dig pits to find shellfish and other invertebrates to feed on. When the tide goes out, it takes the crabs with it, leaving a pocked mudscape that looks like the surface of the moon.

Lee began monitoring the locations and cycle of the crabs’ digging and the holes filling by walking in the mud herself. But after her first summer, she realized her footsteps were adding holes that skewed the big picture. 


The Old College Try
Lee‘s advisors suggested some creative solutions. After ruling out using a small prop plane because it would fly too high to pick up the detail she needed, Lee mounted a camera on a pole on a boogie board. But that could cover only a small area, not giving an accurate perspective of how the crabs use the entire mudflat. 

Next, Lee strung a clothesline between two points of a small bay and pulled a camera along the line over the mud. Better, but still limited by the distance the line could be strung.

Then, at a professional conference, Lee ran into a post-doctoral researcher  at the New England Aquarium whose hobby happens to be remote control airplanes. When Lee explained her research problem, Joshua Idjadi, now an Assistant Professor at Eastern Connecticut State University, got excited and offered to help. Why not mount a video camera to one of his airplanes and fly over it the estuary?


Photo courtesy of Perry Smith, UNH Photographic Services

The Horseshoe Crab

  • Not technically a crab, which is a crustacean, but an arthropod, more closely related spiders and scorpions

  • Commercially important as bait

  • Blue blood is used in biomedical research.

  • Eggs are important food for migrating birds.

  • Been around about 250 million years

  • Found in western Atlantic, from Maine to the Yucatan

  • Uses its long barbed tail as a rudder to move through mud

Bird's Eye View
Idjadi brought his airplane to Great Bay, and, sure enough, it could fly low enough to show the details of the crab holes and high enough to reveal the spatial coverage Lee needed to understand the importance of the crab’s feeding disturbances throughout the Bay. With some computer manipulation of the images, Lee was able to create a complete map of some Great Bay mudflats.

Crabs Need the Bay
The results of Lee’s research show that the Great Bay mudflats are important foraging grounds for horseshoe crabs between spring and fall. Says Lee, “The study shows that the estuary should be managed as essential habitat for horseshoe crabs in Great Bay.”

Lee, who will soon complete her PhD, says “I tell people I study horseshoe crabs and everyone has a story about how they used to find them on the beach when they were a kid. Everyone seems to love them. I love that I am studying something that is so important to the local culture, something that is so closely affiliated with what people think about when they think of Great Bay.”

As for the remote control airplane, Lee calls the collaboration with Idjadi  “an unexpected synergy of research and personal interests. It was a great enhancement to the original objectives of the research project and it could turn out to be a useful, low-cost survey method for other researchers.”


For more information, contact Cory Riley