Four Fast Feet
By Wayne Bierbaum
I recently took a couple of days off for a trip to the beaches of Fenwick Island. Of course, I got up early to walk on the beach and watch the sunrise. While walking on the beach, I had to be very careful not to crunch a crab. Early in the morning, there were ghost crabs running around everywhere. As the sun came up, I saw how many crab holes there were.
Fenwick Island is the quiet part of the southern Delaware coast. As I later visited Ocean City, it was much more crowded with people and there were fewer crab holes.
The Atlantic ghost crab (Ocypode quadrata) is common along the Atlantic Coast from Rhode Island to Brazil. They are a land crab that spends only its larval development in seawater, however, they still have gills and require moisture as an interface for gas exchange. On sunny dry days, they stay in a burrow. Overnight and on clouded damp days they will be out.
They are hunter/scavengers that will go after a fly or a newly hatched turtle. They also look for food in the high tide debris.
As everyone that has tried to catch one knows, they run really fast and change direction on a dime. This helps them escape from the many animals that want to eat them.
The crabs live about three years and spend cold winters in their burrows. After the water and sand warms, the crabs spend time scurrying around looking for a mate. The male attracts the females with some pincer clicking and posturing. After fertilization, the eggs develop on the underside of the female and must be kept moist and clean. She will let waves wash over her to accomplish both cleaning and wetting. When the eggs are developed near the point of hatching, she will go into the surf and do a bouncing dance as the eggs are released.
The eggs and subsequent hatchlings stay in the upper columns of water and go through three developing stages while feeding on plankton. At the last stage they start to look like crabs and sink to the bottom. The few that survive, crawl up a sandy shore to begin their land life.
Living on the beach is not too easy for them. Night herons, raccoons, foxes, and other animals want to eat them. Humans crush them with their beach trucks and, of course, step on them. The denser the population of beach-goers, the fewer crabs.
When you go to beach try to avoid stepping on the crabs or their holes. They will try to pinch if you pick one up but otherwise they will keep their distance on their four fast feet.