An orca which washed up on an Auckland beach on Tuesday did not die from blunt force trauma after being hit by a boat, further investigation has found.
The adult male was found on Whatipu Beach and initially was thought to have suffered blunt force trauma to the head.
While a post-mortem by a team at Massey University was able to rule out some theories, the Department of Conservation (DoC) wasn't notified about the orca for several hours, meaning it was too decomposed for the team to find a definite cause of death.
"We were able to identify that live-stranding wasn't involved, and to identify that blunt-force trauma wasn't able to be caused by a boat," Dr Karen Stockin, Massey's coastal-marine research group director, told Newshub.
"Unfortunately if the animal had been in a fresher condition when we were notified to be able to post-mortem it, there could have been evidence in the tissue that it indicated had some underlying health issue.
"Because it was highly decomposed, we couldn't get that level of information from it."
But they were able to identify it from its dorsal fin. The orca is believed to be Nibbles, known to the Orca Research Trust and with a stranding history of stranding itself while chasing prey.
Dr Stockin doesn't think that's what caused its death.
"These animals have to feed quite regularly… You would usually expect usually, even if not very freshly ingested prey in the stomach, you would expect some element of prey digested remains in some of the other secondary changes," she said.
"The key thing with this animal is that we weren't able to find evidence of feeding at all - there was nothing in any of the chambers."
She said that could be possible if Nibbles had live-stranded, but because they already ruled that out it hinted to an underlying issue.
It's likely Nibbles died at sea and its body washed ashore - but we will probably never find out why.
DoC marine ranger Krista Hupman told Newshub the case shows how important it is DoC is alerted to a washed-up marine mammal.
"If we don't hear from members of the public we don't know about it and therefore we're not able to make the best use of this animal," she said.
"Use might be a strange word to use, but we find out most of our information about animals that are apex predators, like killer whales, from strandings, because it's really hard to find that information at sea.
"If we don't get there as soon as possible we could miss that important information."
It's believed Nibbles initially washed up around 9am Monday morning, but DoC wasn't alerted until around 3:30pm that day.
By the time a ranger got out there, the Massey team was assembled and permission was obtained by iwi to perform an autopsy, it was night time, too dark to work with and tides adding another complication.
They could only get out to take samples in the morning. By then the corpse had decomposed to the point they couldn't identify a cause of death.
"The equivalent of a six or seven hour difference in the post-mortem could have been the difference in us being able to determine an underlying health issue versus not being able to do that," Dr Stockin said.
Dr Rankin says if anyone sees a stranded animal, or sees an animal about to strand, they should tell the Department of Conservation as soon as possible.
Killer whales are considered nationally critical in New Zealand and their known threats include fisheries interaction and boat strike, and anyone who accidentally kills or injuries a marine mammal has to report the incident to DoC or a fishery officer within 48 hours.
A vessel travelling over five knots could cause severe damage to a whale or a dolphin, but travelling above 15 knots would result in a likely death.
Newshub.
