Stalking and biting might not the obvious key to a female's heart but it seems to be the mating ritual of choice among whale sharks, new findings suggest.
Rare footage filmed by a multi-institutional research team from Australia captured a sexually mature male whale shark following and biting a smaller female in the wild, revealing new insights into the mating rituals of these elusive creatures.
Following and biting are known to be common events during courtship and copulation of other species of elasmobranchs (cartilaginous fish including rays, sawfish, sharks, and skates). However, very little is known about the reproductive behaviours of whale sharks (Rhincodon typus).
Why is so little known about the mating behaviour of whale sharks?
Though whale sharks are usually found in the coastal waters of warm and tropical areas throughout the world, juvenile males often comprise the majority of these populations, and observations of their behaviour inform much of the existing research.
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Adults are more elusive, according to the research team. "Our knowledge of adult whale sharks, particularly their reproductive and behavioral ecology, is largely derived from chance observations of sharks caught by fisheries or from animals held in aquaria," they write.
The research team's study involved an annual two-week field expedition in early May (the peak of the seasonal aggregation of whale sharks) at Ningaloo Reef, Western Australia from 2009 to 2024. The footage of the mating behaviour was recorded in May 2024.
The researchers described what they saw after observing the male following the female: "The male was observed to open its mouth and lunge forward towards the caudal fin of the female. The male shark increased its swimming speed and lunged again at the caudal fin of the female, this time making contact and briefly biting the tail. The female responded by rapidly pivoting with pectoral fins pointing downwards to face the male.
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"After a brief pause in forward movement, the female again turned rapidly, with contact occurring between the snout of the male and the caudal fin of the female. The female then rapidly descended to depth followed by the male. At this point, the researchers lost sight of the sharks from the surface.”
Was the whale shark successful?
Interestingly, the researchers reported that the behaviors did not appear to result in successful mating.
"Although it was possible that mating could have occurred after the sharks that we followed descended to deep water, the female appeared to actively resist the attention of the male," they added. They speculate that this may be due to the male having pursued a sexually immature female.
The scientists say their recent observations are consistent with earlier anecdotal reports of courting behaviours in whale sharks provided by fishers at St Helena Islands and the pilot of a light plane over Ningaloo Reef in 2019.
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