The RSPCA in Cornwall is appealing for information after the discovery of a swan's severed head.
They were called by a member of the public after the head of the adult swan was found in the car park at Par Sands Pond near St Austell on Saturday.
There was no sign of the body or any blood or feathers nearby.
RSPCA acting chief inspector Rob Skinner said he was in "no doubt" that it was a deliberate act and not the work of a wild animal.
'Brutal act'
It is not known whether the animal's head was removed while the creature was alive or dead.
Ch Insp Skinner said: "At best this bird died of natural or unrelated causes and somebody decided to cut off its head as some kind of tasteless prank.
"At worst we could be talking about a deliberate and brutal act where a person or persons killed this beautiful creature by cutting off its head.
"Either way we are desperate for information about who is responsible so we can find out exactly what happened and what action is needed."
The RSPCA has notified the police and anyone with any information is being urged to contact them.