North Sea sperm whales 'died in hunt for squid'
The deaths of 30 sperm whales in the North Sea were probably due to them straying into shallow waters while hunting squid, a marine expert said.
Six whales died after washing up on the east coast of England in Skegness and Hunstanton.
The others were found beached in France, Germany and the Netherlands.
Dr Peter Evans, director of the Sea Watch Foundation, dismissed suggestions man-made objects had affected the animals' ability to navigate.
He said: "We've now had 30 animals stranded around the southern part of the North Sea - making it the biggest we've ever had.
"The animals which were first stranded in Holland had quite a lot of a particular species of squid in their stomachs - which they can catch, up in the Norwegian Deep."
He said they "got into danger" after heading south, possibly following shoals of squid.
"What happens, particularly south of Dogger Bank, is that the depths are much shallower than anything they are accustomed to.
"They normally live out in very deep waters, about 3,000 metres deep - south of Dogger Bank it's mainly less than 50 metres - and can be less than 20."
Sperm whales, which normally live off the west coast of Norway, rely on sonar to navigate. They send out sound pulses, which bounce back off distant surfaces. In shallow waters their ability to navigate is affected.
Dr Evans said once the whales had swum south of Dogger Bank there was little chance of them surviving.
He also dismissed speculation man-made objects such as wind turbines interfered with how the mammals navigate.
"I can understand why people look for some human factor that may be causing these strandings, but there is certainly no evidence."
"Whale strandings occurred as far back as the 16th Century," he added.
Experts previously ruled out boat-strike or entanglement, which is a common cause of strandings.
All the whales were thought to have come from the same bachelor pod.