T.The 45-foot cadaver lay in the surf on Fort Funston Beach, south of San Francisco, and attracted a small crowd of hikers and kites. The stench lingered in the evening breeze as sea birds circled the animal, a young fin whale.

The whale was the fifth to wash ashore in the area this month. The other four were gray whales – giant whales that migrate a staggering 18,000 kilometers from Alaska to Baja and back each year – all of which were found on beaches near the city in just eight days.

Each was a startling scene that immediately worried many observers. Whales are an important part of the ecosystem and are often viewed as markers of ocean health. Your death can serve as an indicator that something is wrong.

However, scientists say the picture is more complicated. The investigation into the whale deaths continues and experts say there is no smoking weapon as of yet. Some marine researchers believe the deaths could be more cyclical than a sign of disaster.

“It sounds awful at first,” says Joshua Stewart, a research fellow with the National Oceanic and Atmospheric Administration (Noaa). “But this is not an isolated incident and to a certain extent it calms me down personally.”

After gray whales were nearly extinct in the 1950s, they made a remarkable recovery, recovering to levels that enabled them to be removed from the list of endangered species in 1994. Now they are among the most commonly spotted along the California coast as they migrate south in winter, north in early spring.

They are also one of the best-studied marine mammals, with data going back to the 1960s. Every time a whale lands on land, scientists have a new opportunity to learn about the state of the oceans.

However, the gray whale population on the west coast has declined in recent years and has declined by around 24% since 2016. According to Noaa, there are an estimated 20,580 whales left today. And the high number of deaths that month wasn’t the first – in 2019, Noaa declared an ongoing “unusual mortality event” when 122 whales washed across the west coast of California to Alaska, more than four times the previous 18-year average of 29 .

Stewart, who tracks gray whale numbers, notes that despite the decline, the population is still close to an all-time high. “Despite these downturns, which were very stressful at the time, they have come back several times,” he says, adding that they are an extremely adaptable and resilient species. “We want to know whether this decline will continue or is it just temporary.”

Gray whales are among the most widely studied marine mammals.Gray whales are among the most widely studied marine mammals. Photo: Guillermo Arias / AFP / Getty Images

On April 8, two whales were examined in the bay at the same time. A carcass had swum for days before landing in the Berkeley Marina. The other was washed ashore on Muir Beach, north of San Francisco. Teams from the Marine Mammal Center and California Academy of Sciences performed autopsies, which involved taking tissue samples, examining the internal organs and reproductive tract, and examining the ribs and vertebrae for signs of trauma or impact.

Moe Flannery, senior bird and mammal collections manager at the California Academy of Sciences, was on hand to perform the autopsies and says the teams have not yet completed their investigations – although culprits could be a lack of food or illness.

“There aren’t any real answers yet,” she says, adding that despite the deaths, the scientists are confident that the gray whale population will bounce back. “They are a resilient species and I think it’s worrying, but we hope this is just a small leap in time and that the species will recover as it has in the past.”

Ship attacks have already been identified as the cause of death, including the fin whale found on Friday. In contrast to the gray whales, fin whales are still considered endangered. The west coast of California, Oregon and Washington is only estimated to be 3,200, and ship attacks are the greatest threat to their survival.

“It shows how many threats these whales are exposed to,” says Callie Steffen, project scientist at the Benioff Ocean Initiative. Steffen works on a team that developed the Whale Safe project, which uses data to help seafarers determine where whales are when planning trips to Southern California. The system, which she says is “like a fire warning from Smokey the Bear, only for whales,” has had a positive impact.

According to a 2019 study by the University of California’s San Diego’s Scripps Institution of Oceanography, whales may be closer to the coast, putting them at greater risk of damage from ship attacks, loud noises from harbors, chemical pollution and tangles to take . The study’s authors believe the change has something to do with the whales’ biological clocks.

Ari Friedlaender, a marine ecologist who teaches and directs a laboratory at the University of California at Santa Cruz, says whales, whether killed by malnutrition or ship attacks, should be considered red flags. While we can’t point the finger at a single cause of the decline, human activity – from shipping to the climate crisis – is driving changes that negatively affect whales.

“It means that humans are likely to influence and change the ecosystems from which these whales need food,” says Friedlaender. “There are so many downstream effects and repercussions from the things we do in our daily lives. The measures we take on site can have consequences and effects very far away and over long periods of time. We have to keep our eyes open. “