JAMESTOWN, St. Helena — Whale sharks, the largest fish in the ocean and perhaps the largest fish ever known, are surprisingly elusive when it comes to their mating habits. Despite their massive size, making them conspicuous in warm oceans worldwide, scientists have yet to observe whale sharks mating.
This intriguing aspect of their behavior has led researchers to the remote volcanic island of St. Helena in the South Atlantic Ocean — historic for Napoleon Bonaparte’s exile — as a potential mating ground for these gentle giants. It’s the only noted location where adult male and female whale sharks congregate in nearly equal numbers, and intriguing courtship behaviors have been noted, although actual mating remains unobserved.
Kenickie Andrews, the marine conservation project manager at the St. Helena Trust, has witnessed male whale sharks pursuing females, nibbling on their pectoral fins, and engaging in displays reminiscent of mating rituals seen in other shark species, such as great whites. Andrews reports, “What we’ve seen here is classic shark courtship behavior. To this day, we haven’t seen successful copulation, but it is proof that whale sharks are in our waters trying out these behaviors.”
These enormous creatures, averaging 12 to 18 meters in length and weighing up to 14 tons, feed mainly on plankton. Despite the lack of direct proof of mating, scientists emphasize the importance of locating these mating and birthing grounds for conservation purposes. Whale sharks are categorized as endangered by the International Union for Conservation of Nature, with populations significantly reduced and needing protection from threats like fishing.
Globally renowned whale shark researcher Simon Pierce has documented presumed mating scars on female whale sharks around St. Helena. These marks likely result from male sharks biting onto the females’ pectoral fins to maintain their position during mating attempts. Other regions like Australia, Mexico, the Arabian Sea, and the Maldives have also reported gatherings of whale sharks, but these tend to involve mature males and younger females, unlike the adult gatherings in St. Helena.
Eyewitness reports from fisheries experts in St. Helena describe considerable activity at the water’s surface between two massive sharks in proximity, possibly mating. However, without video evidence, such reports remain scientifically unverified.
In an effort to uncover the secrets of their underwater interactions, Cameron Perry, a research scientist from the Georgia Aquarium in Atlanta, collaborates with local researchers to attach camera equipment to the sharks. However, the devices often fall off when the sharks dive deeper than 2,000 meters, a challenge due to the incredible underwater pressure. Perry states, “We have some very tantalizing and teasing video. We have two sharks about to make contact, and then our camera falls off.” Yet, there is hope that emerging technology will provide the much-needed insights into their behavior at these depths.
Alistair Dove, previous researcher on the island and current CEO of the Museum of Science & History in Jacksonville, Florida, has observed male whale sharks exhibiting sexual behaviors towards adult females, including the rotation of their claspers, a behavior akin to an erection. Dove explains, “These sexual behaviors are very, very rare in whale sharks. This is one of the huge, unanswered questions about the biggest fish in the world.”
Andrews, representing the St. Helena Trust, remains optimistic that definitive video proof of whale shark mating behavior will eventually surface. However, he also acknowledges the possibility that research efforts and the presence of technology could potentially interfere with natural behaviors. “Maybe they don’t want to be seen,” he reflects. “Maybe, like everyone else, they need privacy.”