The dolphin which was found dead several days after it was led back to sea after following a Dutch sailing boat into Amsterdam harbour, probably died in a collision with another ship, an autopsy on the mammal has shown.

The animal’s tail was missing and it had a big bruise on its side, biologist at Utrecht University Lonneke IJsseldijk, who did the autopsy, told the NRC.

A man walking his dog found the bottlenosed dolphin, known as Zafar, on the beach at Wijk aan Zee. A CT scan has shown it had several fractured vertebrae but that it was eating and in good health before being struck. ‘

‘All the signs are the dolphin died on impact. It suffered a big blow and probably lost its tail in the propeller of the ship that hit him,’ IJsseldijk told the paper.

The dolphin was known to follow ships and latched on to the Les Tres Hombres on the French coast, swimming all the way past the IJmuiden locks to Amsterdam harbour on May 1. The same ship eventually enticed the animal to leave the harbour again a day later. On May 5 the dolphin was finally seen to swim away.

SOS Dolfijn, which had been involved in the rescue operation said the animal was fit and well when it entered the North Sea.

‘Zafar’s love of ships became his downfall,’ a spokesman of the organisation said.