Horseshoe Crabs Mating

Horseshoe crab mating on YouTube

Horseshoe crabs often referred to as a living fossil, is one of the most interesting creatures on earth because it’s origins dates back to millions of years ago. The video shows an interesting shot of the mating behaviour of the horseshoe crabs.

Background information of Atlantic Horseshoe Crabs

The horseshoe crab or Atlantic horseshoe crab, Limulus polyphemus is found along the eastern coast of North and Central America. It belongs to the Limulidae family which consists of three other species. It is a misconception that horseshoe crabs are crabs. In fact, they belong to the phylum of Arthropods, which consists of animals having an articulated body and limbs (The Horseshoe Crabs). Horseshoe crabs are now considered endangered animals due to the loss of habitats.

Mating behaviour

The female Limulus give off chemical attractants called pheromones, which the males can detect (The Horseshoe Crab). Once the male Limulus detects a female offshore, he grasps her with his specially modified claws, and the attached couple crawls toward the high tide line. Once copulation is over, the female, with the male still attached, digs into the sand and lays thousands of eggs which the male fertilizes externally (Rudloe, 1980). It was found that some male Limulus remain attached to the females for as long as 2 weeks!

Horseshoe Crabs mating

Horseshoe Crabs mating

However, there is strong competition between males for females because it was found that females tend to reach sexual maturity later and they return to the nest less frequently than males (Rudloe, 1980). Because of this, there is a difference in ratio between the males and females therefore leading to an intense competition for females as seen in the video. Even if a male is attached to a female, other satellite males will still “join in” to mate with the female by pushing away the current attached male.


H. Jane Brockmann. Mating Behavior of Horseshoe Crabs, Limulus polyphemus. Behaviour, Vol. 114, No. 1/4 :pp. 206-220.

“Horseshoe crab mating,” by solatia. YouTube Channel, 3 April 2007. URL: (assessed on 4 March 2010)

Natural History:Spawning Behaviour. URL: (assessed on 4 March 2010)

Rudloe, A.E. 1980. The breeding behavior and patterns of movement of horseshoe crabs, Limulus polyphemus, in the vicinity of breeding beaches in Apalachee Bay, Florida. Estuaries 3, p. 177-183.

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