A mass stranding of over 50 pilot whales occurred last week in West Iceland’s Snæfellsnes peninsula. The event occurred on the sand island Gamlaeyri along Löngufjörur. The whales were spotted by David Schwarzhans, a pilot for Reykjavík Helicopters, and his guests during a tourist excursion.
This is Iceland’s second largest mass stranding of the past 40 years. The largest mass stranding occurred in 1986, when 148 pilot whales died at Þorlákshöfn. Over 30 pilot whales were similarly stranded at Rif on Snæfellsnes in 1983.
Pilot whale occurrence in shallow coastal waters has increased in West Iceland over the last few years. Edda Elísabet Magnúsdóttir is a marine biologist at the University of Iceland who specializes in whales. “Historically, we don’t have many strandings,” she says. “But this is the third year in a row at least where we’ve had pilot whales coming dangerously close to the shore. In this instance, they stranded.”
Whales have previously been spotted dangerously close to the shores of Rif, Arnarstapi, and Hellnar. Löngufjörur, however, is located in the southeast bend of the Snæfellsnes peninsula, which is farther from open ocean. “Where these whales stranded is a much worse situation,” says Edda Elísabet. “We didn’t know about it because it’s really remote—you can’t go to this beach unless you have a certain type of vehicle. It can be very dangerous because the tide comes in so quickly.”
Róbert Arnar Stefánsson is a biologist and director of West Iceland Nature Research Centre. “People can sometimes push them out [to sea] to prevent mortality,” he says. “It’s worrying that we’re seeing more and more of this in the last years.”
Stranded hypotheses
The beached whales extend in a line along Gamlaeyri’s coast, with most of the bodies grouped tightly together. Their distribution and numbers on the beach are linked to pilot whales’ behaviour of travelling as a herd. Each herd is combined of closely related smaller families; the herd can number 50-100 animals. Edda Elísabet explains, “If a pilot whale is stranded, it is very unlikely a single whale or 2 or 5. More like 20 or more.”
It is not well known why pilot whales strand, but there are several hypotheses. Pilot whales are named because they follow a lead animal, usually a matriarch. Edda Elísabet comments, “Pilot whales are very social animals. If the herd leader goes into an inconvenient area or is hurt somehow, the group won’t leave. We don’t know what happened [at Gamlaeyri], but that’s something that can happen.”
Anthropogenic factors
Róbert also indicates anthropogenic factors could contribute to mass strandings. “Sometimes, [mass stranding] is due to human impact, offshore drilling or military exercises,” he explains. “There are also hypotheses regarding Persistent Organic Pollutants (POPs), because they bioaccumulate and are in their highest concentration in the oldest animals. Those animals are sometimes the leaders and POPs can cause nerve damage. In some cases, that could be the reason.” POPs include cadmium, mercury, and the man-made chemicals DDT and PCBs used for pesticides that circulate through the food chain.
Róbert adds that these hypotheses are not very likely in the case of Gamlaeyri’s stranded herd. “It may have had to do with sickness in their leader, or that they were following prey. They’re used to catching prey in much deeper waters so they’re not as efficient in shallow waters.”
Edda Elísabet concurs that it is likely the herd followed prey, rather than other theories which have included sound pollution caused by military activity or avoidance of predators. “Pilot whales primarily feed off squid,” she says. “They also eat mackerel, which can go into shallow waters. One of the most obvious changes in Icelandic waters is the increased abundance of mackerel. The climate is changing and we are seeing lots of changes in prey distribution, which affects the whales.”
Tricky topography
Pilot whales have increased in abundance in the North Atlantic in recent years, and the waters west of Snæfellsnes are currently a feeding ground for pilot whales. Increased abundance is linked to a higher likelihood of mass stranding. In this instance, though, the whales were far into the fjord, which is not their natural habitat.
At the time of last week’s stranding, a spring tide brought strong currents with increased water during ebbs and floods. “They could have been swimming in when the tide was in,” theorises Edda Elísabet. “Pilot whales easily become disoriented in these environmental situations—strong currents, gradual bank, sandy bottoms. This is the worst scenario for this species and other deep-diving whales, since they use echolocation to navigate and locate prey. In Löngufjörur where you have gradual sand bottoms becoming shallower and softer, there is less reflection by echolocation. The whales can’t navigate as they would in deeper water.”
Edda Elísabet adds, “The topography of Snæfellsnes is less convenient for them than the topography of the coastal waters east of Iceland, where we have lots of pilot whales between Iceland and the Faroe Islands. They come close to the East Fjords as well, but there are not as dangerous sand bottoms and tidal currents as we have in Snæfellsnes.”
Pregnant whale
During The Reykjavík Grapevine’s visit to the site of the mass stranding, we noted that the whales were distributed with at least three males at the far ends of the group, with a larger grouping of females in the centre. Of note was a female pilot whale, who had been in the process of giving birth when she died. Her calf had partially emerged, with the amniotic sac torn but visible.
While neither Edda Elísabet nor Róbert have yet visited the site for direct observation, Edda Elísabet found the eye-witness account interesting. “I’m just hearing that for the first time now,” she says. “It’s hard to say if the way they strand is the way they were organised in the group. But if there was a female giving birth, then a large part of the group is involved in that. Other closely related females usually try to protect and look after the female giving birth. Males could have been guarding out at the side. If the one who was giving birth was the leading female, that could have caused what happened or had influence on what happened.”
Note: reaching Gamlaeyri is hazardous, as it’s on a tidal plane of treacherous wet sand. Don’t try to go there in a regular car, even a 4×4. Many thanks to Sigurjón at superjeep.is for getting us there in a modified Land Rover, and to Kristján at Stóra Hraun for guiding and accompanying us.
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