World's first shark threesome observed off New Caledonia

Scientists observing sharks off the coast of New Caledonia documented what researchers believe is the first recorded threesome involving a leopard shark. In a 110-second sequence, two male leopard sharks mated with a female in rapid succession, according to researchers who documented the encounter.

Dr. Hugo Lassauce, a marine biologist at the University of the Sunshine Coast, was snorkeling about nine miles off the coast when he observed the scene. "I'd seen males swimming fast after females before and I'd arrived on the scene just after a male and female separated, but I'd never seen the whole sequence," he said. The first male's mating lasted 63 seconds, followed by a 47-second copulation by the second male. After the sequence ended, the two males appeared exhausted and lay immobile on the sea floor, while the female swam away actively.

Researchers noted that this is the first documented observation of two males copulating with a female in this species. In their study, published in the Journal of Ethology, the researchers describe a structured sequence: prolonged pre-copulation positioning, the males grasping the female's fins and tail, a conspicuous siphon sac, copulatory thrusting, and the use of claspers consistent with prior observations from captive settings.

Leopard sharks (Stegostoma tigrinum) are listed as endangered by the International Union for Conservation of Nature (IUCN) and have historically been studied primarily in captivity. Also known as zebra sharks because of the striped pattern seen on the skin as pups, the species occupies coastal waters across the Indo-West Pacific region, from eastern Africa to the Pacific Islands and Australia.

Researchers hope the sighting will inform artificial insemination research aimed at aiding rewilding efforts for the endangered species. Dr Christine Dudgeon, senior author of the study, said: "It's surprising and fascinating that two males were involved sequentially on this occasion. From a genetic diversity perspective, we want to find out how many fathers contribute to the batches of eggs laid each year by females."

The discovery arrives as scientists continue to study the behavior and reproduction of leopard sharks, a species whose unusual mating ecology has long intrigued researchers and conservationists alike. While triadic mating has been documented in other animals—including bonobos, bottlenose dolphins, grey whales, spotted hyenas, and some primates—this observation marks a first for the leopard shark and raises new questions about mating strategies in wild shark populations.