Poulsbo, WA – A trip to the shore in Kitsap County would not be complete without an encounter with some of our resident crabs, hopefully not the shore front property owners, but rather the tough crustaceans that roam the intertidal zone as if they hold title. Much like people, crabs are a diverse bunch who come in all shapes and sizes with interesting personalities and habits. I once feared all marine claws, large and small, but have come to love this particular society of beach dwellers.
All crustaceans molt. They have a sturdy exoskeleton that starts to feel like a pair of tight pants as they grow. They must move out and let a larger skin harden into a new shell. In the case of crabs, the process can take weeks. The crab begins to reabsorb calcium carbonate from the old shell to be recycled into the new. Enzymes are secreted not only to separate the old from the new, but also to coat their body with a soft papery shell right under the old one.
The day before they move out, they pull in water, swelling up like a water balloon, which helps to loosen the old shell. Next, they methodically back out of their old shell, carefully pulling their soft claws through narrow joints. They remain swollen with water as muscle begins to replace fluid and are vulnerable as their shells harden, so tend to stay in the safety of the sand and hidden shadows. Quite an elaborate process to endure for a new outfit, and some crabs will molt up to 20 times!
The extended Crab family is much too large to cover in just one post, so consider this gallery of images an appetizer, a visual overview of some of the most common clans found in these parts. From the gentle little shore crabs to the cantankerous red rock crab, there are lots of crabby friends to go around. Watch Pacific Wonder Tracker for more posts about different species of crabs, but for now, scan the beach and shallow water for these amazing little creatures as well as their discarded molts left all over the beach.
Study size, color, pattern and even texture as you track wonder in Crab Country.
Cultivate Wonder… Discover Design
Where and When – Crabs are plentiful in the Puget Sound region. Find lots of little shore crabs just by carefully turning over a rock no larger than the size of your head. Be sure to replace the rock just as you found it. To see scads of crabs in action, wade into areas with sandy bottoms and lots of kelp or eel grass. Tide pools are another great place to watch small crabs go about their business. Be very careful when handling crabs as some, like the Red Rock Crab, can pinch with great strength. Shore Crabs (also called Hairy Shore Crab Yellow or Green Shore Crab) are perfect for children to handle, but be sure to model and teach caution and care as these little creatures are fragile.
Wonder Triggers for Young Trackers
- Watch a crab move. How does it move? How many legs does it have? Do they use all their legs for walking? They are members of the Decapoda order, meaning “ten legs.”
- Try walking like a crab. Position yourself belly up on your arms and legs and try walking sideways? How do you think walking sideways helps the crab?
- Search the beach for crabs that aren’t moving. As you approach, look at the eyes. They will tell you if you are looking at a molt or a dead crab. How? If they look clear like there is nothing there, it is a crab molt. If the eyes seem to be looking back at you, then it is a dead crab and may be very smelly. Count the number of molts versus dead crabs you can find in a section of the beach.
- Find a complete crab molt that looks to be in good shape. Study the carapace (shell) Scientists use the little jagged teeth on the edges to help them identify species. You may find a smaller carapace that has interesting designs on it, which belonged to a young Red Rock Crab. Some designs look like mazes or zebra stripes. Start a collection of unusual crab carapaces.
- Did you know that you can tell if you are looking at a male or female crab? Carefully turn the crab over and study the pattern of the shell plates on its belly. If you see what looks like a long narrow lighthouse, it is a male. If you see a wide pot with a lid, it is a female.
- Shore crabs are so much fun to watch. Carefully turn over a rock (size no larger than your head) in the intertidal zone. Remember where and how it was resting because it is important to put it back exactly where you found it. Why do you think that is important to return the rocks to the exact spot you found them?
- Look at all the colors and patterns of the shore crabs. They are all considered one species, but have different colors and markings on their carapaces. If you find a purplish crab that has a square looking carapace with no hair or spines on its legs, it is known as the Purple Shore Crab.
References and Resources
Images – Sharon Pegany – Copyright 2018