In April of 2004, the Town of Slaughter Beach and its residents declared the town a Horseshoe Crab Sanctuary and banned harvesting horseshoe crabs from its beaches because of concern over dwindling numbers during spawning season. Knowing that Slaughter Beach is prime spawning ground for the species, they sought to reduce pressure caused by harvesting and human development and to preserve the annual spawning spectacle for future generations. On June 12, 2004, the Town Council approved Resolution Number 35 adopting the Atlantic horseshoe crab as the town's official symbol. Horseshoe crabs, which do not sting or bite, can become stranded upside down along the shoreline during spawning season in May and June and can be helped by being gently turned over from the side of the shell rather than by the tail. An ancient species whose closest ancestor is probably the trilobite, they existed in recognizable form for 450 million years and predate birds and dinosaurs. The Atlantic horseshoe crab, Limulus polyphemus, is the most numerous of the world's horseshoe crab species and is found along the eastern coast of North and Central America, with the epicenter of spawning and population in Delaware Bay, whose sandy protected beaches and tidal flats provide ideal conditions for spawning and juvenile growth. Each spring, as many as a million migratory shorebirds gather at Delaware Bay, and at least 11 species rely on horseshoe crab eggs as their primary food during a 2 to 3 week stopover before continuing northward; these birds mainly eat eggs brought to the surface by wave action, so their feeding has limited effect on the horseshoe crab population. The horseshoe crab also contributes to human health because its copper-based blood contains a clotting factor that detects gram-negative bacteria, and the biomedical product derived from it, called LAL, is used to screen all injectable medicines and implanted medical devices for bacterial contamination. During May and June, adult horseshoe crabs return from deeper waters to spawn on protected beaches in bays and coves, with peak spawning on evening high tides during new and full moons. They form clusters at the water's edge, often with as many as 12 satellite males around one female; females burrow into the sand and lay masses of green eggs that males fertilize, returning on successive tides to lay 4-7 egg clusters per tide, each incubating 5-8 inches below the surface and containing about 4,000 eggs, for about 25 egg clusters in a year. Horseshoe crabs seen during spawning are fully adult, reaching sexual maturity about halfway through a twenty-year lifespan, so disruptions during spawning can affect the population for years. Fertilized eggs hatch in about 14 days under optimal conditions, juveniles spend their first and second summers on intertidal flats, and as they grow they molt repeatedly, remaining only about 1/2 inch wide at the end of the first year and later molting once a year by age 3 or 4, often in July and August. As they age, they move to deeper waters with greater food supply, continue annual molting until sexual maturity, and then begin the yearly spring migration back to spawning beaches.