It’s breeding time for Horseshoe crabs, which prefer to mate at night during high tide. The male rides the back of the female as they head toward the beach, where the female deposits eggs into a nest she has dug, and male fertilizes them. These protected “living fossils” haven’t changed much in 445 million years.
The dune shacks in the Cape Cod National Seashore were originally built by the Coast Guard so that men looking for ships during storms would have a place to rest. They later became summer homes for artists and writers.