Five whales and whale sharks have died after stranding on Indonesian shores in just three weeks, from Bali to Aceh. The cluster, reported between Sept. 12 and Sept. 25, has prompted scientists to ask whether these deaths are rising and why, according to the South China Morning Post.

No single cause has been confirmed for any of the five animals — and for two of them, a full examination was not possible. Researchers point to a mix of possible explanations, including seasonal ocean conditions, human activity and the simple fact that more strandings are now photographed and shared.

The deaths matter beyond Indonesia. Whale sharks are the largest fish on Earth and an endangered species, and the ones that strand in Indonesia often belong to populations that travel across the Indian Ocean and Southeast Asia.

Five Animals, Five Locations

The series began in Bali. An eight-meter (26-foot) male whale shark was found on Pengeragoan Beach in Jembrana Regency on Sept. 12, then examined, necropsied and buried, The Bali Times reported, citing local police.

A second whale shark died on Sept. 19 in Sulawesi. The South China Morning Post placed it in South Sulawesi, while Indonesian outlets reported a stranding that day in Wakatobi Regency, Southeast Sulawesi, of an animal estimated at four to five tons that residents could not push back to sea.

On Sept. 21, a whale stranded at Agrabinta in Cianjur Regency, West Java. By the time the regency's livestock and fisheries agency learned of it two days later, residents had cut up and carried away most of the carcass, according to Antara. Agency head Iwan Setiawan urged people not to butcher stranded whales before officers arrive, since it is unclear whether the meat is safe to eat. The species was not confirmed.

On Sept. 23, fishermen found a decomposing whale about eight meters long and weighing roughly four tons in a mangrove forest along the Bahale River in Indragiri Hilir Regency, Riau, an area not known as whale habitat. Decay made identification difficult, and Indonesia's Ministry of Marine Affairs and Fisheries sent blood samples to the National Research and Innovation Agency, known as BRIN, to determine the species, Kompas reported.

The most recent case came on Sept. 25 at Lama Tuha Beach in Southwest Aceh, where a whale shark about five meters (16 feet) long died after stranding. Local authorities said it may have followed small shrimp into shallow water, The Jakarta Post reported. About 30 fishermen and residents tried to push it back to sea. "It was already very weak," said Teuku Indra Kusuma, the local traditional fishing community chief.

Competing Explanations, None Proven

The leading scientific framework comes from a peer-reviewed study in Scientific Reports by researchers with Konservasi Indonesia, the Elasmobranch Institute Indonesia, and other institutions. It documented 115 whale shark stranding events involving 127 animals across 23 provinces between 2011 and 2023. That Indonesian total exceeded the previously reported global combined count of 114.

The study linked many strandings to upwelling, when wind-driven currents bring cold, nutrient-rich water to the surface and draw feeding animals close to shore. On Java's southern coast, strong upwelling from July to October overlaps with frequent strandings. Juveniles dominate the records, which researchers view as a risk to population recovery.

But the rise in reported cases may partly reflect reporting itself — more phones, more posts, more records. Researchers have said greater smartphone use and social media sharing could explain much of the apparent increase. Human pressures such as fishing gear, vessel traffic and pollution are also under study.

Experts urge caution about the latest cluster. Iqbal Herwata of Konservasi Indonesia told the SCMP that the five incidents happened in areas with a history of strandings, but their timing differed from past patterns. Mark Meekan of the University of Western Australia noted that strandings have been recorded for centuries with many theories about why. Whale shark scientist Brad Norman of Murdoch University said, "We need to study this further."

The evidence so far is observational. The 2025 study found associations between strandings and ocean conditions, not proof that those conditions caused any single death. Two of the five carcasses were too decomposed or too damaged by butchering to examine fully, and lab results from Riau are still pending.

A Wider Ocean Signal Worth Watching

Whale sharks move between Australia, Christmas Island and Indonesia through areas with high stranding risk, and the lack of shared identification data across countries limits understanding of how these losses affect connected populations, according to Mongabay. Researchers have called for stronger regional cooperation.

Inside Indonesia, the response is improving but uneven. Konservasi Indonesia is working with the marine conservation group SeaLife to strengthen stranding response along Java's southern coast, a known hotspot. Local officials in Cianjur said they learned of the stranding only after the animal was gone, showing gaps in early reporting.

The incidents also carry a public health lesson. Eating meat from an animal that died of unknown causes can be risky, and Indonesian officials have asked residents to wait for trained responders.

For readers in the United States, the same rules apply on American coasts. Anyone who finds a stranded whale, dolphin, or sea turtle should keep a safe distance, avoid touching or pushing the animal, keep pets away, and report it to the regional marine mammal stranding network through NOAA Fisheries or local authorities. Untrained rescue attempts can injure both people and animals.

The next answers will come from BRIN's analysis of the Riau samples and from any necropsy findings released for the Bali whale shark. Until then, the cluster is a warning sign to investigate, not a confirmed trend.

What Readers Want to Know

What happened in Indonesia? Five whales and whale sharks died after stranding in Bali, Sulawesi, West Java, Riau, and Aceh between Sept. 12 and Sept. 25, 2026.

What caused the strandings? No cause has been confirmed. Scientists are considering seasonal upwelling that draws animals near shore, human activity such as fishing and vessel traffic, and improved reporting.

Are whale shark strandings increasing in Indonesia? Reported cases have risen, from fewer than 10 a year between 2011 and 2019 to more than 22 a year since 2020. Researchers say better reporting may account for much of that rise.

Why are whale sharks important? They are the world's largest fish and an endangered species. Many strandings involve juveniles, which threatens long-term population recovery.

Is it safe to eat meat from a stranded whale? Officials in West Java warned residents not to butcher stranded animals before responders arrive, because the cause of death and safety of the meat are unknown.

What should someone do if they find a stranded marine animal in the U.S.? Keep a safe distance, do not touch or push it, keep pets away, and report it to NOAA Fisheries' regional stranding network or local authorities.