A lamb sustained serious injuries during an attack by a dog at the Balancing Lakes in Wolverton on Monday.
The lamb suffered tear and puncture wounds to the throat, among other injuries.
The incident happened on land operated by The Parks Trust.
A spokesman said: “We urge all dog walkers and owners to ensure that dogs are kept on lead and under tight control around our sheep and lambs at all times.”
Anyone with information about Monday’s attack is urged to contact the police on 101 using the URN number 497 12031.
Last February, five sheep were attacked by a dog in Campbell Park, three fatally.