I have recently gotten a email asking if horseshoe crabs are poisonous. While horseshoe crabs can look intimidating they are totally harmless. They cannot bite and their tail is not used for defense, but instead they use it to navigate and to turn themselves upright should they get turned over.
The only defense that a horseshoe crab has against predators is it’s hard shell. What they do is bury themselves in the mud or sand which makes it difficult for predators to turn them over or to get a good hold of them.
Sterling Silver Horseshoe Crab Wire Earrings
Horseshoe crabs really don’t have many predators when they are mature, but when they are young they are eaten by many other animals and their eggs are particularly vulnerable. Many shore birds depend on horseshoe crab eggs for nourishment and to put on weight for their migratory journeys.