The Department of Conservation is "disappointed" the carcass of a common dolphin has been mutilated.
It received reports last week the dolphin had washed ashore at West Auckland's Huia Beach.
Further reports and a photograph sent to DOC showed the carcass appeared to have been mutilated, with its head cut off.
DOC's Dylan Swain described the incident as a "disturbing act" which is "completely unacceptable".
"Dead marine mammals washing ashore is not uncommon and we ask people to let them be and decompose naturally. As Auckland is at Alert Level 4 we are only responding to wildlife emergencies in this region until the time comes where we can safely dispose of the animals if need be," he said.
"We are disappointed people are disrespecting and mutilating marine mammals. Dolphins are a taonga species and it is our duty to respect them in life and in death.
"This act is an offence under the Marine Mammals Protection Act. An investigation is underway to find out who did this."
Swain said the public’s information is vital to the investigation and he urged anyone in the community to come forward if they had details of the mutilation.
Short-beaked common dolphins are found in waters throughout New Zealand and Australia. In New Zealand, the species tends to remain a few kilometres from the coast and are particularly common in the Hauraki Gulf and off Northland.
Separating any part of the carcass of a marine mammal is an offence under the Marine Mammals Protection Act and anyone caught will face up to two years in prison, or a fine of up to $250,000.
Any information relating to this, or any other allegations of New Zealand native wildlife crime should be directed to 0800 DOC HOT (0800 362 468) or email@example.com.