A member of the public discovered the swan, badly injured and distressed at Pen Ponds in Richmond Park, close to midday.
The five-year old swan is currently on antibiotics and recovering at the Swan Sanctuary, but will not be strong enough to be released for some weeks yet.
Adam Curtis, Assistant Park Manager at Richmond Park, said: “Apart from the obvious physical damage, dog bites can be incredibly serious due to the risk of blood poisoning.
“Unfortunately, dog attacks on swans are not uncommon in Richmond Park, and it’s for this reason we have made it mandatory to have your dog on a lead around Pen Ponds. We are deeply saddened that the owner may have witnessed this attack and did not call anyone. Thankfully a member of the public alerted the park office but it’s unclear how long the swan might have been lying there suffering.”
PC Paul Barber, from the Royal Parks Operational Command Unit of the Metropolitan Police said: “Since we updated the signage around Pen Ponds, we have noticed a decrease in the amount of people walking their dogs off leads around Pen Ponds, which is encouraging. However, as this situation demonstrates, when people ignore the rules the consequences can be severe.”
“We are appealing for anyone who might have seen anything to come forward. If you have any information, please call or text 07920586546.”