A post mortem has ruled out human involvement in the macabre death of six New Zealand fur seal pups found on the Banks Peninsula last month.
The headless pups were discovered by a tourism operator, floating in the tidal wash at Scenery Nook on the south side of the peninsula on December 19.
Initially, and due to the fact there were no other visible bite marks or damage and the pups being found together, the Department of Conservation [DOC] suspected people were involved in their deaths.
To determine the exact cause of death, DOC sent three of the dead seals to Massey University for a necropsy [post mortem].
DOC Mahaanui Operations Manager Andy Thompson said the necropsy ruled out human-inflicted injuries.
"We're really pleased to have been proven wrong and that people aren't to blame, but the mystery continues. We still don't know for certain what has removed the heads and flippers of the six seals.
The report found the pups' injuries weren't consistent with any land-based predator or scavenger, but the nature of the injuries indicated the pups could have potentially been killed by another seal.
Fur seals/kekeno are protected under the Marine Mammals Protection Act and it is a criminal offence to harass, disturb or harm them. Unfortunately, there are a number of known cases of people injuring or killing seals.
"Its possible other fur seals killed the pups, which would be the first record of this in New Zealand. However, attacks among the same seal species have been recorded in other countries.
"Another theory is a leopard seal or even a sea lion could be to blame for the pups' deaths, but sea lions are rarely seen around Banks Peninsula.
"It's still unusual only the heads were removed and there were no additional bite marks to the bodies - although there was evidence of soft tissue bruising, indicating at least some of the damage was inflicted before the pups were killed."
As the necropsy has indicated no foul play, DOC's approach to fur seal management is to let nature run its course and the department is no longer appealing for sightings of boats in the area or investigating the incident.
"The reality is we might never solve this mystery - we're just relieved this macabre incident is not at the hands of humans," Thompson said.