The Mystery of the Norfolk Strandings

Since January this year, six sperm whales have been stranded on beaches along the Norfolk and Lincolnshire coastline. This number makes this the worst sperm whale stranding in the UK since 1913 when records began and brings the total number of sperm whale strandings in the southern North Sea up to 30 this year. All the animals are thought to be from the same bachelor pod that was traveling south from the deeper waters around Norway.

In all likelihood the whales in the UK died after they became stuck on the beaches whilst looking for food in the North Sea. It is still unknown as to why the whales became stranded on the east coast beaches, though several explanations have been put forward.  Disease could be one reason for the deaths and sea changes related to climate change is another. Recently concerns have been raised over the now banned chemicals PCBs. PCBs are lipophilic molecules, which means they can dissolve in fats, oils and lipids. As a result they can be found in high concentrations in the blubber of marine mammals, including whales.

Another concern is over heavy metals which are now so concentrated in fish stocks that pregnant women and children are warned not to eat more than two portions of fish per week.  The sperm whale lives on a fish diet, particularly squid. Ingesting large amounts of fish affected by heavy metals would lead to the biomagnification of these substances, such as lead, mercury and cadmium, in the whale’s system to highly toxic levels. A sample from the animal’s livers would be able to tell scientists whether a concentration of heavy metals is responsible for the deaths of the whales. However, the rapid decomposition of the whale carcasses makes getting samples difficult and consequently, scientists simply do not have enough data at present to speculate on the cause of the whale’s deaths.

However, currently the most likely solution is that the whales became disoriented and lost when they entered the shallow waters of the North Sea. Sperm whales are usually deep sea living creatures, entering shallower water affects their ability to use echo-location to navigate and unless they can get back to their feeding grounds they quickly become starved and dehydrated. Once in shallower water they also become less buoyant which can lead them to become crushed under their own weight.

There is still no clear evidence as to why this number of whales beached on the coasts around the southern North Sea. However, experts say that these strandings may be good news for sperm whale populations, it is hard to estimate marine populations accurately but it is generally thought that the bigger the population, the more likely strandings are to occur. It is therefore hoped that sperm whale populations are recovering after whaling has ceased.

Sources: The Guardian; BBC News