Tasmanian wildlife authorities believe a dog was responsible for the deaths of nearly 30 penguins near Bicheno.
The carcasses were found at Waubs Bay Beach on Friday and rangers have been investigating.
Autopsies carried out at the Mt Pleasant laboratory have revealed injuries consistent with a dog attack.
The same cause of death was found in the slaughter of 58 penguins at Low Head in the North in October.
Dog owners who allow their animals onto rookeries can be fined more than $3000.
Anyone with information can leave anonymous tip-offs with DPIPWE's Wildlife Enforcement Section.