A seal found dead in the Thames estuary may have been shot in the head, according to scientists from the Natural History Museum.
Researchers dissecting the female grey seal, thought to have been 20 years old and pregnant, found a piece of metal embedded in its skull.
"We believe what was found could be a bullet," a spokesman for the museum said. "The RSPCA have been informed and are investigating."
The large marine mammal was found in Walpole Bay in Margate on 21 May and was brought to the museum to be examined for signs it had consumed micro-plastics as part of a PhD student's research.
Scientists were then surprised to find the metal object buried in her skull, which was the only visible sign of trauma, the museum said.
Grey seals, which can be found in British coastal waters and come ashore in autumn and winter to give birth, are protected in the UK and there are only a handful of circumstances in which they can be controlled by fishermen to protect their equipment.
However, according to the museum, there have been "known cases" of illegal seal killings.
The case comes a week after the Times revealed that seal numbers in the Thames estuary have swelled to about 3,500 in recent years.
The animals are unpopular with some fishermen who complain that they pilfer fish from their nets.
