A dolphin carcass that washed ashore on the Zeeland coast last Friday and was initially assumed to be the beluga whale spotted off the Dutch and Belgian coasts is a Risso’s dolphin – the first of its kind recorded as stranded in the Netherlands in more than 50 years.

The body was recovered on the beach at Kamperland on the afternoon of April 10. It was so decomposed that it had turned white and the dorsal fin was no longer visible, which led observers and the rescue team to assume it was the beluga that has been drawing crowds along the North Sea coast.

“Given its colour and dimensions, we concluded it was a dead beluga,” sea mammal specialist Jaap van der Hiele told Dutch News. Even after a strip of skin in one of his own photos hinted at a dorsal fin, he said, “you are focused on the white colour, so being stubborn, you say no, it is not another animal.”

First stranding since 1970

Tests carried out this week at Utrecht University’s veterinary faculty confirmed the animal was a Risso’s dolphin, a deep-water species more commonly found around the Azores. Researcher Lonneke IJsseldijk told NOS that the last recorded stranding of the species in Dutch waters was in 1970.

She and her colleagues identified the dolphin from its skull: Risso’s dolphins have teeth only in the lower jaw, while belugas have them in both. “That gave it a bit away,” she said.

Almost no organs remained intact, making it impossible to determine the cause of death or even the dolphin’s sex. The skeleton will be transferred to the natural history museum Naturalis in Leiden.

Van der Hiele had spent days searching for the body before it washed up, working with drift models commissioned from the transport ministry’s water experts and from the Belgian Institute of Natural Sciences. A coastguard flight had failed to locate the carcass.

“On Monday we were informed it was not a beluga, but a Risso’s. I was very surprised to hear that; I was convinced it was a beluga,” he said. He suspects the dolphin “died somewhere in the Channel and was pushed into the North Sea by the current” – a pattern he has also observed in stranded sea turtles.

Sperm whale dragged back to Renesse

Meanwhile, a 16-metre sperm whale that beached on a sandbank near Renesse on Monday, only to be carried back out by the tide, was hauled back to land on Tuesday afternoon by lifeboat charity KNRM.

A post-mortem led by IJsseldijk’s team is taking place on Wednesday. She said that the examination is likely to establish only where 45 tonne whale came from and what killed it – not why it ended up in the North Sea from the Atlantic in the first place.