This massive food supply attracts over a million shorebirds from mid May to early June, the largest spring concentration in the United States. Females can lay several times, and may lay up to 80,000 a season. With the receding tide, some are stranded. In thirty days the eggs hatch, the tiny larvae dig their way out of the sand, and begin to search the bottom of the bay for worms and other food. The young crabs molt frequently, and their dried shells can often be found along Jersey beaches.
Males reach sexual maturity when nine years old, but females require ten years.
Adult crabs were used as fertilizer by the early Native Americans, and today are used as bait for catching eels and conch, and in medicines. They are model animals for the study of eyes, and the chitin shell has been used to make chitin filament for suturing wounds, which enhances healing by 35 to 50 percent. Cape May. Only females can be used for this operation, but they are released unharmed within a few hours. Their populations, however, are threatened both by commercial fishing interests, toxic chemicals, and by oil spills in Delaware Bay. Video clip of a horseshoe crab walking .