A swan had to be put to sleep after a gang of youths deliberately set a pack of dogs on it at Cusworth Hall.
The RSPCA is appealing for information after the incident.
RSPCA inspector Sandra Dransfield said: “There was nothing we could do to save him, his injuries were just too severe.
“He had a large wound on his back, another on his chest and his neck had been torn open.
“We’ve been told he was attacked by several dogs the previous night, and that the dogs were deliberately set on him by a number of youths.
“We want to hear from anyone who saw anything or has any specific information about what happened on 0300 1234 999. They should ask to leave a message for me.”
The swan leaves behind a female swan and two cygnets.
The incident happened on July 23.
It is illegal to kill, injure or take a wild bird. The maximum sentence is six months in prison and/or £5,000 fine.