Anup Shah / Crab eating / Long tailed macaque (Macaca fascicularis) feeding on Horseshoe crab, Sumatran Coast Indonesia

Cyril Ruoso / Horseshoe crabs (Tachypleus gigas) mating among pollution washed up in mangroves, Sungei Buloh Natural Park, Singapore.

Edwin Giesbers / Two Long-tailed / Crab-eating macaques (Macaca fascicularis) in mangrove habitat feeding on Coastal horseshoe crab (Tachypleus gigas) Bako National Park, Sarawak, Borneo, Malaysia

Anup Shah / Crab eating / Long tailed macaque (Macaca fascicularis) feeding on Horseshoe crab, Sumatran Coast Indonesia

Anup Shah / Crab eating / Long tailed macaque (Macaca fascicularis) feeding on Horseshoe crab, Sumatran Coast Indonesia

Juergen Freund / Naturalists examine underside of horseshoe crab {Limulus polyphemus} Florida USA

Juergen Freund / Naturalist examines underside of horseshoe crab {Limulus polyphemus) Florida USA

Joel Sartore / Photo Ark / Mangrove horseshoe crab (Carcinoscorpius rotundicauda) portrait, Singapore Zoo. Captive.

Joel Sartore / Photo Ark / Mangrove horseshoe crab (Carcinoscorpius rotundicauda) portrait, Singapore Zoo. Captive.

Joel Sartore / Photo Ark / Mangrove horseshoe crab (Carcinoscorpius rotundicauda) portrait, Singapore Zoo. Captive.

Ripan Biswas / Mangrove horseshoe crabs (Carcinoscorpius rotundicauda) pair mating in mud at dawn, Sunderban tiger reserve, West Bengal, India.