One cannot spend a summer on Cape Cod enjoying the beaches and islands without running into one of the tiniest and mightiest animals in the area: CRABS! The master of camouflage, most people don’t even realize that they are next to one until they decide to move to a new hiding spot. What people also don’t know is that there are invaders among the crab population, and we want to teach you how to tell the difference between them. The four most common species of crabs that you will find along the cape are the Fiddler crabs, Blue crabs, Green crabs, and the Asian Shore crabs. Fiddler crabs are named so because of the single large claw the males have in order to attract females for mating. Traveling in large groups, they are round and about the size of a large marble with a purple grey or blue carapace. Blue crabs are…well…blue! Fully grown, they are about the size of a teacup saucer. Green crabs as you may have guessed are…NOT all green and can vary in colors like yellow and sometimes orange! They have a very wide carapace and spider-like legs. Lastly, the Asian Shore crabs are known for having a square-like carapace about the size of a silver dollar and also vary in many colors. Have you figured out which ones are invasive? If you guessed Green crabs and Asian Shore crabs then you are correct! As a rule of thumb, there is a good chance an organism is invasive if they can survive in various habitats, eat a wide variety of food, and out compete other similar organisms in the area.