First ever recording of leopard sharks mating in the wild reveals ‘threesome’

By Jack Guy, CNN

(CNN) — Endangered leopard sharks have been observed mating in the wild for the first time, with scientists witnessing a “threesome” involving two males and a female.

The encounter was filmed by Hugo Lassauce, a marine biologist at the University of the Sunshine Coast, Australia, and documented in a research paper published in the Journal of Ethology on Thursday.

Lassauce told CNN that mating events are rare to witness in any shark species, and researchers have only previously seen courtship interactions, where a male chases after a female, but not the act itself.

Leopard sharks, or Stegostoma tigrinum, are found in the Indian Ocean and the western Pacific Ocean, but populations are decreasing, according to the International Union for Conservation of Nature, which lists the species as endangered.

They have largely been studied in captivity, with little known about how they reproduce in the wild.

As part of his research, Lassauce monitors a site in New Caledonia, a French territory in the South Pacific, in collaboration with the Aquarium des Lagons, a local aquarium.

Leopard sharks are known to congregate at the site at certain times of the year, and “we suspected this aggregation to be for mating purposes,” Lassauce told CNN.

However, no one had seen a mating event — until now.

During a dive on July 12, 2024, Lassauce said, he “came across these two males grabbing the female’s pectoral fins with their mouth.”

Recognizing the potential significance of what he was seeing, Lassauce filmed the sharks for 90 minutes to make the first known recording of such an event.

According to the paper, the three sharks, all of which were around 2.3 meters (7.6 feet) in length, were spotted on the seafloor.

Both of the males held onto the female, who would occasionally struggle to free herself, for more than an hour.

One of the males then mated with the female for 63 seconds, before the second male did the same, lasting 47 seconds.

After copulating, the two males lay immobile on the seafloor as the female swam away.

Lassauce explained that the males are simply exhausted by the process.

“Holding a female while she is trying to free herself all the time, and mating with her while swimming is just taking all of the male’s energy,” he said.

After copulating, “the male is just out of it,” Lassauce added, needing to lie on the seafloor “for a couple of minutes to regain its energy.”

The observation is part of a wider study on the reproductive behavior and spatial ecology of leopard sharks, he said, and will inform ongoing conservation efforts targeting the species.

“This specific observation gives crucial information on the reproductive behaviour that would be used to improve artificial insemination protocols, for instance,” said Lassauce, who works with the ReShark international conservation initiative.

Next, Lassauce said, he will continue his research on egg-laying habitats and the movements of newly hatched wild leopard sharks.

Christine Dudgeon, a senior research fellow at the University of the Sunshine Coast, who has studied leopard sharks for two decades and co-authored the paper, said the sequential involvement of two males was “surprising and fascinating.”

“From a genetic diversity perspective, we want to find out how many fathers contribute to the batches of eggs laid each year by females,” she said in the statement.

Emily Humble, research fellow in conservation genomics at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies and the Roslin Institute, who was not involved in the study, told CNN that the “rare observation” highlights leopard sharks’ interesting reproductive processes.

“Not only can females reproduce without males through parthenogenesis, but they also appear to mate with multiple partners,” Humble told CNN.

“Genetic studies testing for multiple paternity will be key to understanding how these strategies shape genetic diversity in this endangered species.”

The-CNN-Wire
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