How can a shark the size of a bus stay out of human sight? The birthplace of whale sharks is still unknown, but a precious observation of a newborn sheds light on the secrets of where these giant fish begin their lives.
Salih Bay, located on the Indonesian island of Sumbawa, is almost perfectly enclosed, fed by a narrow channel that brings in cold, rich water from the depths of the ocean. For the island's local community, this nutrient-rich influx means a bay full of mackerel and squid, caught from floating structures known as pagans.
Locals fished at night, shining spotlights on the water to attract fish to baited nets under the pagan platforms, but on September 6, 2024, they informed local scientists that they were not alone on the water's surface.
Shortly after 04:30, they captured a video of a whale shark resting in the net, mouth open, with a charcoal gray body adorned with shimmering white spots resembling the night sky.
The whale shark is the largest species of fish in the world. But this little shark, about 5 feet (1.5 meters) long, wasn't breaking any records.
It was estimated to be only about four months old, and was about one-tenth the length of a full-grown adult whale shark.
For marine biologist Mushamad Iqbal Hirwata Putra, it was its small size that made the discovery even more exciting, as it was the first whale shark newborn discovered in Indonesia, and one of only a few dozen ever documented by science.
Despite these creatures' enormous size and their spread in warm waters around the world, no one has ever seen a whale shark mate or give birth. But the appearance of this little one represents one of the best evidence yet that the elusive birthplace may be close.
Weighing as much as six elephants, an adult whale shark is the largest cold-blooded, or endothermic, animal on the planet.
Because they are solitary creatures that spend a large part of their lives moving across the open ocean, whale sharks did not receive extensive scientific study until the late twentieth century.
But by the 1990s, they were found to congregate in seasonal groups - sometimes a few hundred individuals - in specific coastal locations, such as off the coast of the Yucatan Peninsula in Mexico.
These regular gatherings allowed scientists to install tracking devices that revealed their epic journeys, explaining how some of their individuals could undertake migrations that span the globe. One female swam a whopping 7,000 kilometers (5,000 miles). Since then, these fish have become one of the most widely studied marine megafauna, according to Shark Research Foundation researcher Ben Di Antonio.
De Antonio says the huge, mysterious whale sharks evoke a "sense of wonder." These giant creatures have roamed the Earth's oceans for tens of millions of years.
The baby that appeared in Saleh Bay may still roam the seas until 2150, if a way is found to deal with the increasing threats it faces, including climate change, fishing and maritime traffic.
Hirwata Putra, a marine wildlife expert with the Jakarta-based non-profit Conservatory Indonesia, says the discovery of a newborn gives us a "rare glimpse" into an early stage of life that we rarely see.
Whale sharks are attracted to Saleh Bay because of the same abundance of food that Pagan fishermen depend on.
“There are a lot of krill (small marine creatures) because there is a system of mangroves surrounding the bay,” says Hirwata Putra.
For juvenile whale sharks, this place is ideal for growth and weight gain with minimal effort, and it also provides protection from predators such as the blue shark, which can easily prey on a young whale shark.
Hirwata Putra suspects that this protected bay may have been a birthing area and incubator used during the first weeks of life. But we don't yet know whether the whale shark began its life here or, which is the most likely possibility, according to Di Antonio, "it came from somewhere else and chose a favorable bay."
Finding a nursery is a “fundamental discovery,” Di Antonio says, praising the community collaboration that “amazing” Indonesian scientists like Hirwata Putra have built with local fishermen, many of whom feared or previously pursued whale sharks.
He adds that these relationships and efforts to map important natural habitats may be vital to reversing the decline in their numbers.
The number of whale sharks in the world has decreased by more than half since the 1980s, and they are now classified as an endangered species. Today, marine biologists across the planet are racing against time to find and protect these critical sites in the life cycle of the threatened whale shark.
Our best clue to the whale shark's birthplace was found in 1995 in Taiwan, where marine biologists examined a 10-meter (33-foot) specimen caught by harpoons by local fishermen. This female, which was called Mega Mama, revealed much of what we know today about whale shark reproduction.
Her womb contained 304 fertilized eggs and embryos, which showed that whale sharks reproduce viviparously, meaning that they hatch the eggs inside their bodies and give birth to live young ones that are able to swim freely.
This was the largest number of hatchlings ever recorded for any shark species.
A genetic analysis conducted in 2010 confirmed that all of these cubs, which were in different stages of development, belonged to a single father, which constitutes strong evidence that the mother stored sperm and fertilized the eggs over a period of time.
Some remained inside the egg casings, while 15 were large enough to survive, including two hatchlings kept alive in aquariums in Japan and Taiwan.
Science has documented only 33 newborn whale sharks, and all of them appeared in tropical regions, from the Atlantic Ocean to the Arabian Sea, and from Pakistan to the Galapagos Islands.
In a recent paper, Freya Womersley, a research scientist at the Marine Biological Society, tried to find a pattern by comparing these locations to areas of low oxygen known as permanent minimum oxygen zones.
Womersley says newborn whale shark babies are being spotted in these areas more frequently than would be expected by chance.
She adds: "In fact, sightings of these babies are very rare, but when they are seen they tend to share similar environmental conditions, which prompts the question: Is this just a coincidence or is there some kind of strategy?"
The study explores the exciting possibility that female whale sharks may choose these areas to provide a kind of ocean curtain, hiding their young in places where predators do not go.
Although the open ocean may appear to us as one undivided body of water, creatures that live in the depths, such as whale sharks, move between various oceanic layers, from active surface waters to areas in the depths that are almost completely devoid of oxygen, as Womersley explains.
Many open-ocean predators, such as blue sharks and marlin, avoid these oxygen-poor areas, making them a potential haven for juvenile whale sharks, with the added advantage that plankton often congregates at the boundaries of low-oxygen layers, providing an early forage for the young.
Although many mysteries still surround the reproductive life of whale sharks, we are getting closer to answers, according to Womersley, who is preparing to travel to Mexico to install tracking devices equipped with cameras that will shed more light on this issue.
“I think it's only a matter of time before someone finds the right shark, attaches the right equipment to it, the conditions align, and we get these amazing shots,” she says. “When I say it's 'a matter of time,' I don't know how long it will take.”
During the 1980s and 1990s, hundreds of whale sharks were killed annually for their meat and fins, including “Mega Mama,” which was harpooned in a “legal” fishery in Taiwan.
Conservancy Indonesia aims to establish a marine protected area in the northern Gulf, which will be the first reserve established in the Asian country specifically to protect whale sharks.
Hirwata Putra says recognizing and protecting these essential sanctuaries can make a big difference.
Of the 25 whale sharks that were equipped with tracking devices in Saleh Bay, most spend the majority of their time inside and around the bay, and these creatures only leave from time to time before returning to take advantage of the food supply available throughout the year.
