Scientists reveal secrets of sharks' sex lives by examining their bloody mating bite marks

An aquarium-housed sand tiger shark female with mating wounds from attempted copulation on June 22, 2020. (Image: Wyffels et al. 2024)

Scientists have uncovered intriguing details about the mating habits of sand tiger sharks along North Carolina's coast. By examining bite wounds, researchers gained clues about the secretive reproductive lives of these elusive predators.

Mating in sharks is no gentle affair. The act often involves males biting females to hold them in position, leaving visible injuries. This behaviour is particularly evident in larger shark species, where physical constraints make mating more challenging. The study, published in Environmental Biology of Fishes, reveals that some females retaliate, leaving scars on the males.

Using wounds to track mating and reproduction
The research team, led by Jennifer Wyffels of Ripley’s Aquariums and the University of Delaware, observed sand tiger sharks in aquariums and analysed 2,876 photographs of wild sharks. These images, submitted by citizen scientists to Spot A Shark U.S.A., spanned 15 years and highlighted North Carolina as a key mating area.

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A new four-stage scale was developed to categorise wounds, from fresh injuries to healed scars. Analysis showed an increase in fresh wounds in May, peaking by July. By late summer, wounds indicated that females remained in the region for gestation.

Sharks’ swift healing amazes researchers
Sharks demonstrate extraordinary healing abilities, with even deep wounds closing in weeks. In aquariums, injuries to a female healed completely within 85 days, confirming reports of sharks' rapid recovery. This resilience aids survival and reproduction in the wild.

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The study sheds light on sand tiger shark mating and gestation. It also highlights the importance of North Carolina as a habitat for this critically endangered species. Researchers hope these insights will inform conservation efforts.