The sperm whales that stranded on Texel last week had not eaten for several days, but were otherwise healthy. This was found in research by Imares Wageningen UR, who studied their digestive tract content.
Photo: Salko de Jong/Ecomare
The last meal of the animals was a couple of days ago, before they swam up the North Sea. All the soft food scraps were thus already digested in the stomach and small intestine and no North Sea fish was found. The period before that, the animals ate squid and anglerfish, this was deducted by the presence of - hard and thus indigestible - squid beaks and otoliths in their stomach and intestines.
All the sperm whales were healthy and had a normal amount of fat and muscle. Furthermore, they found fishhooks , a bunch of rope and plastic residues in the digestive tracts.
The five sperm whales that stranded on 13 January died a day later. During their journey to the south the animals probably ‘took a wrong turn’ past the British Isles. The cause is unknown.
A team of Imares researchers obtained their stomach and intestines, with a length of 140 to 170 meter. During the next six days the intestines were cut open, flushed and the content was sieved. ‘A tough job’, says Mardik Leopold, researcher for Imares Wageningen UR, ‘it is physically demanding work. With a team of four to six people we could do one and a half whale a day.’
Further research should provide a more detailed picture of the menu of the sperm whales. Leopold and colleagues will wash all the found hard parts in the coming days, and will look at which animals the residues belong to. Furthermore, in the laboratory of the NIOZ (Dutch Institute for Sea Research) they will look at which marine life DNA is present in the intestines. Leopold is not only interested in the species found, but also if the methods yield different results. ‘That really is a litmus test .’
Leopold usually studies the stomach content of porpoises. Occasionally they have also looked at the menu of pilot whales and rorquals.