Sperm whales stranded on a North Sea beach during the wave of strandings in early 2016.
Between January and February 2016, 29 sperm whales were found dead or dying on the coasts of the North Sea, according to the Common Wadden Sea Secretariat, which coordinates nature protection in the Wadden Sea shared by the Netherlands, Germany and Denmark. All of them were young males. Scientists who examined the carcasses concluded that the animals had lost their way into a sea that is far too shallow for them, and that they died from the effects of stranding itself. Plastic and fishing gear were found in several stomachs, but researchers said the litter did not kill them.
It was one of the largest sperm whale stranding events ever recorded in the region. Here is what happened, what the necropsies showed, and why a viral version of the story about "stomachs full of car parts" got the details wrong.
Where the 29 sperm whales were found
The strandings were spread across four countries. The Wadden Sea Secretariat counted 19 carcasses along the Wadden Sea coast and two near the German island of Helgoland. Six more came ashore around the Wash, a wide bay on the east coast of England, and one was found on the French coast near Calais. Those regional figures add up to 28 of the 29 whales the secretariat reported, so one animal is not placed in its summary.
Germany saw the largest share. The state of Schleswig-Holstein alone recorded 13 of the whales, while others came ashore in the Netherlands, the United Kingdom and France.
Sperm whales have been stranding on North Sea shores for centuries; records go back to the 16th century. In recent decades, though, it was usually one or two animals a year, most often in Denmark. A Danish museum expert quoted by the secretariat called the 2016 numbers highly unusual. The last comparable events were in 1996 and 1997, when groups of 16 and 13 sperm whales stranded on the Danish island of Rømø.
Map of the southern North Sea showing where the sperm whales stranded and how many were found at each site. © Klöpper / CWSS
Why sperm whales end up in the North Sea
Sperm whales are deep-ocean animals. They prefer water more than a kilometer deep, where they dive to hunt squid. Females and calves stay in warm, lower-latitude waters in stable family groups. Young males leave those groups and travel towards the poles, often in loose "bachelor" groups of similar age, before heading back south to breed.
That pattern fits the 2016 victims. All 29 were males of roughly the same age, size and weight, which led scientists to believe they were one travelling group, or several closely linked ones. Sascha Klöpper of the Wadden Sea Secretariat suggested they were migrating from feeding grounds off Norway towards the Azores. Instead of taking the usual deep-water route west of the British Isles, they turned into the North Sea.
The southern North Sea is a trap for a whale built for the deep ocean. Much of it is only tens of meters deep, with shifting sandbanks and very little of the squid sperm whales eat. Their echolocation, designed for open deep water, works poorly over gently sloping sandy shores.
Why they made the wrong turn is still not settled. Professor Ursula Siebert of the Institute for Terrestrial and Aquatic Wildlife Research (ITAW) at the University of Veterinary Medicine Hannover said the reasons remained unclear. She listed several possibilities: human activity, regional changes in the distribution of prey, and shifts in sea temperature that could draw squid, and the whales following them, into unusual areas. Other researchers have since suggested natural factors, such as solar storms disturbing the whales' magnetic sense of direction, but none of these explanations has been confirmed.
What the necropsies revealed
The whales were not starving. Abbo van Neer of ITAW reported that many stomachs held large numbers of squid beaks, the hard, indigestible parts that build up in a sperm whale's stomach over time, and that the animals were in good nutritional condition.
What killed them was the stranding itself. An adult male sperm whale typically measures around 15 to 16 meters and weighs roughly 45 metric tons. In water, that weight is supported. On a beach, it crushes the animal's own lungs and blood vessels. Van Neer explained that the probable cause of death was a collapse of the respiratory tract and an interruption of blood flow as the body's weight pressed on its organs. Many of the whales also came to rest on their sides, which can leave the blowhole under water.
The plastic found in their stomachs
Even though litter did not cause these deaths, what researchers pulled out of the stomachs was disturbing. A study published later in 2016 in the journal Marine Pollution Bulletin, led by Bianca Unger with colleagues from Germany, the Netherlands, the UK and France, examined the digestive tracts of 22 of the stranded whales. Nine of them contained marine debris.
The items included netting, ropes, plastic foils, packaging and a plastic part from a car. A press release from Germany's Schleswig-Holstein Wadden Sea National Park described four whales in that state with large amounts of plastic, including a fishing net about 13 meters long and a bucket. The authors concluded that none of the debris caused the deaths, but that the finds showed how heavily large ocean predators are exposed to plastic and lost fishing gear.
That matters because sperm whales feed by suction in the dark depths. They can mistake drifting nets and plastic for prey, and large items can block or injure the gut. Abandoned fishing gear, sometimes called ghost gear, makes up a significant share of the larger plastic items in the ocean.
The viral "car parts" story, fact-checked
In early 2019, almost three years after the strandings, a story spread on Facebook claiming that two whales had just been found dead in Germany with stomachs "full of plastic and car parts". Several sites recycled it, including an earlier post on this site, Sperm Whales Found Dead In Germany, Stomachs FULL Of Plastic And Car Parts.
The fact-checking site Lead Stories rated the claim inaccurate on 10 February 2019. Its main points:
- The event happened in 2016, not in 2019.
- It involved 29 sperm whales, not two.
- The strandings were in Germany, the Netherlands, the UK and France, not only Germany. The widely shared photo of two dead whales was taken in Skegness, England.
- Only one car part was identified: a plastic engine cover.
- Plastic was found in several whales but was not the cause of death.
The real story is serious enough without exaggeration. Getting the details right also keeps attention on what the science actually says: these whales died because they were stranded, and the litter inside them is a warning about the state of the sea.
Why a stranded whale carcass is dangerous
Removing a dead whale from a beach is difficult and can be hazardous. A sperm whale's thick layer of blubber traps heat, so as bacteria break down the body, the inside of the carcass can reach about 50°C. Gases from decomposition build up quickly. Van Neer warned that within days the bodies decay heavily and can even burst from the internal pressure.
That is why authorities close off stretches of beach, why heavy machinery is needed to move the carcasses, and why members of the public should never climb on, cut or poke a dead whale. Carcasses can also carry bacteria that are harmful to people and pets.
What the strandings teach us
Sperm whales are listed as Vulnerable by the IUCN. They recovered only slowly from centuries of commercial whaling, and today they face ship strikes, noise, entanglement and pollution. A single event like the 2016 strandings does not threaten the species, but it gave scientists a rare chance to study many animals at once, and what they found in the stomachs was a clear signal about ocean litter.
If you ever find a stranded whale, dolphin or porpoise, keep your distance, keep dogs away and call the local coastguard or marine stranding network. On a wider scale, supporting the recovery of lost fishing gear, cutting single-use plastic and joining beach clean-ups all reduce the amount of debris that ends up inside animals like these.
Sources: Common Wadden Sea Secretariat: Cause of sperm whale strandings is still unclear; Unger et al., "Large amounts of marine debris found in sperm whales stranded along the North Sea coast in early 2016", Marine Pollution Bulletin (2016); Lead Stories fact check (2019); Wikipedia: Sperm whale. Map: Sascha Klöpper, CWSS.
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