Going to the beach before the end of summer? Keep an eye out for sand crabs!
These cute little crustaceans hang out in large groups, right on the shore line, in the “swash zone” or area of breaking waves. They burrow under the sand a little ways and poke their antennae out to munch on plankton… And the best thing about sand crabs (as far as summer activities go): they don’t have claws on their front legs, so you and your kids can have a great time catching them… and learning at the same time! Just remember, sand crabs need a constant fresh supply of plankton to survive, so be sure to throw them back, and don’t let them get too dry!
How to Find a Sand Crab
Since sand crab larvae drift as plankton for several months, they get carried all over the place by currents, and can be found on many beaches. To spot them, just walk along the wet sand where the waves wash up (sandy beaches are better than rocky ones), and keep your eye on the ground. As a wave recedes, you’ll see hundreds of little V shapes in the sand, made by the crabs’ antennae as they poke them out to shovel in plankton.
How to Catch a Sand Crab
Simply scoop up the wet sand around the V shapes as the water recedes. If you’ve caught some, you’ll probably feel them burrow against your hands. Then carefully wash the sand away, and you’ll see some oval-shaped little critters scuttling around in your palm. They range in size from almost as big as a thumb to smaller than a dime. Oh, and a side note when digging for sand crabs: be sure to wear a bathing suit, ‘cause you’re gonna get wet!
Learning with Sand Crabs
Sand crabs are a great lesson in the food chain and the eco-system. They play a very important role as a major source of food for many sea birds (along with those sandwiches you packed specially for the beach outing) and fish. You can show your kids how these little crabs eat microscopic plankton, and then the birds eat the sand crabs!
You can also teach your kids about camouflage. You’ll notice, sand crabs are the same color and texture as – you guessed it – sand. It’s a great way to hide from those pesky sea birds we just talked about… Too bad you can’t camouflage your sandwiches!
Other Fun Facts
Sand crabs have two sets of antennae – one main one, and another that they use to shovel plankton into their mouths.
Sand crabs, unlike most crabs, can swim by kicking their back legs. If you drop one in a clear wave near the shore, you can watch it paddle its way back to the sand.
While most crabs can move in all directions, a sand crab can only move one way… backwards!
For more information and fun facts, check out this great little article from the Monterey Bay Aquarium!
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Filed under: Just for Fun! Tagged: | education, learning, nature, science
