The fishermen who pulled the animal from the water in May took photos of the remains before tossing them back into the water, thinking that it was illegal to keep the carcass, according to the Online Journal of the Natural History Museum, Rotterdam.
By looking at the photos, experts said that the animal died just after birth. They made the determination saying that its tail had not stiffened and it had a flat dorsal fin. It also had hairs on the upper lip that normally fall out just after birth, New Scientist reported.
Harbour porpoises are the smallest cetaceans in North West Europe, according to the journal.