Fact sheet

NATURE Crash: A Tale of Two Species

In breathtaking images from the tip of South America to the Arctic, NATURE explores the fascinating intersection of the small Red Knot shorebird and the horseshoe crab - and our role in their continued survival. Below are facts about these two unassuming yet awe-inspiring creatures.

• The horseshoe crab has existed for around 350 million years.
  
  
• The Red Knot's annual migration is 18,600 miles round-trip - from Tierra del Fuego to the Arctic.
  
  
• Most of the world's horseshoe crabs are found in the middle of the U.S. eastern seaboard.
  
  
• Red Knots stop in the Delaware Bay each year to feast on horseshoe crab eggs, refueling for the rest of their migration.
  
  
• Some experts estimate horseshoe crab numbers have crashed by as much as 75 percent in the Delaware Bay in the past decade; the crabs are used as bait by the eel and conch fisheries on the Atlantic coast.
  
  
• The population of Red Knots that winters in Tierra del Fuego has plummeted 70 percent in the last five years.
  
  
• In 2006, a two-year moratorium was placed on harvesting horseshoe crabs in the Delaware Bay, though it was amended in 2007 to allow a harvest of 100,000 male crabs.
  
  
• Horseshoe crabs spawn in sync with full and new moons in the spring, when the tides are highest.
  
  
• Female crabs lay more than 80,000 eggs in a season; 10 or fewer might survive to adulthood.
  
  
• Male horseshoe crabs shed their shells 16 times in their life; females, 17 times.
  
  
• Studies on the horseshoe crab's vision led to a Nobel Prize in 1967.
  
  
• Horseshoe crabs have been used by the biomedical community for their blood since the 1970s.
  
  
• Horseshoe crab blood is blue, containing copper rather than iron. It has a unique clotting agent, Limulus Amoebocyte Lysate, or LAL, that is used to test intravenous drugs for bacteria; no drug reaches the market without this FDA-mandated testing.
  
  
• Scientists at the University of Delaware are developing an artificial bait that they hope can replace horseshoe crabs.