A cluster of whale and whale shark strandings across Indonesia – five in the past three weeks alone – has raised questions over whether such incidents are becoming more frequent, with experts pointing to a mix of environmental shifts, human activity and improved reporting as possible explanations. On September 25, a whale shark became stranded and died on a beach in Aceh province, just days after a decomposed whale carcass was discovered in a mangrove in Riau province.

Another whale was found dead in West Java on September 21, just two days after a whale shark stranded and died in South Sulawesi. The latest incidents began on September 12, when a dead whale shark washed ashore in Bali. The recent deaths reflect a longer-term rise in reported whale shark strandings across the archipelago.

A 2025 study by the Elasmobranch Institute Indonesia and Konservasi Indonesia recorded fewer than 10 whale shark strandings per year from 2011 to 2019. From 2020 onwards, however, that average jumped to more than 22 cases a year. Published in Scientific Reports, the study linked strandings to seasonal and oceanographic conditions – including sea-surface temperatures, wave height and marine productivity – particularly in areas affected by seasonal upwelling, an oceanic process where wind-driven currents pull cold, nutrient-rich deep water to the surface, drawing feeding marine life closer to coastlines.

But researchers have said that increased smartphone use and social media reporting could account for much of the apparent rise. While whales are marine mammals and whale sharks are the world’s largest fish, both species are endangered, making the circumstances behind their deaths a pressing conservation concern. Still, scientists say it is too early to determine whether the five recent incidents are directly linked.

Speaking about the Aceh incident, Miftach Tjut Ade, a traditional fishing community chief who oversees maritime issues across the province, said it was rare to come across a stranded whale shark. “It seemed to be accidental and local residents tried everything they could to push it back to sea,” he said.

“But it was too heavy.”

Mark Meekan, an adjunct senior research fellow at the University of Western Australia’s Oceans Institute, said strandings had been recorded for centuries and there were many theories about why they occurred. “In the past, a stranding on a remote Indonesian island would not have made the press. But these days, everyone has a smartphone connected to the internet and social media, so [they] can alert a much wider audience.”

The causes of individual strandings can be difficult to establish, particularly when carcasses are found in advanced stages of decomposition. Regarding the whale found in Riau’s mangroves, Ahlul Fadli, an advocacy and campaign manager at the Indonesian Forum for the Environment in Riau, described it as “a rare discovery”, but said the decomposition had hindered efforts to identify it.

Official test results from the National Research and Innovation Agency in Jakarta were still pending. Ahlul warned against speculation without solid data, but highlighted key threats from human activity. He said disturbances to ocean activity, including seismic operations, military sonar and high-intensity noise from shipping, could disorient whales, while marine pollution was another possible factor.

“It is possible the animal ingested solid waste, such as plastic, which obstructed its digestive system, triggering health complications or death,” Ahlul said.

Meekan said navigational errors involving echolocation, geomagnetic anomalies and social behaviour could also cause individual whales or entire pods to beach themselves.

For whale sharks – which are solitary, slow-moving filter feeders that spend much of their time near the surface – colliding with ships and pollution are the primary human-driven hazards. Brad Norman, a research fellow at Perth’s Murdoch University and whale shark scientist, warned against drawing conclusions without a full review of the cases.

He also said it was “very hard to be sure” whether strandings globally were on the rise and that it was “too early to say” whether seasonal and oceanic patterns might be factors.

“It is important that we collate strandings from across the globe and analyse these for trends and potential threats,” he said.

“We need to study this further, then maybe we will have a better understanding.”Iqbal Herwata, a focal species conservation senior manager at Konservasi Indonesia, said that while the five recent incidents occurred in areas with a history of strandings, the timing differed from historical patterns.

“The influence of climate variability, including El Nino, requires further study – specifically by analysing data on sea temperatures, currents and marine productivity,” Iqbal said.

With the causes of many strandings still uncertain, preventing them is difficult.

Meekan said understanding the cause of each incident was important, but some factors were easier to address than others.

“For individual strandings where the cause is man-made, such as entanglement in fishing gear or pollution, the solution to the problem is in our hands,” Meekan said.

donesia, Konservasi Indonesia is working with marine conservation organisation SeaLife to strengthen the response to strandings along Java’s southern coast – a known hotspot for whale shark incidents.

“These efforts aim to ensure local teams and stakeholders possess the capacity to respond to incidents, handle live whale sharks and conduct necropsies on deceased animals,” Iqbal said. “This is expected to improve rescue success rates while providing the scientific evidence needed to determine appropriate preventive measures.”