A 22-metre long blue whale washed up on a private Far North beach has excited a marine mammal expert but also sparked a health warning as the giant sea creature decomposes.

The whale was probably a blue whale, but whether it is a pygmy blue or a true blue whale would not be known until samples taken by the Department of Conservation had been analysed, Forest & Bird marine mammal specialist Anton van Helden said.

It washed up on a private beach about 40 minutes north of Kerikeri on Saturday.

Mr van Helden said even the best analysis may never uncover the cause of death.

At 22 metres long, the decomposing whale is starting to get
At 22 metres long, the decomposing whale is starting to get "very smelly" and potentially dangerous.

He said the whale had clear shark bites on it, including one large, almost circular wound, and while it appeared to have lost much of its colour, that did not mean it had been dead in the water for a long time.

"Whales have very thin skin - in terms of its colouring - and it can quickly get washed off as it turns over in the water when it's dead. We'd need to do further research to know for sure how long it had been dead."

Mr van Helden said the fact the whale's stomach had not exploded after becoming bloated also seemed to indicate it had not been in the water for weeks.

He said decaying marine mammals posed a serious risk to human health.

"Just like us, whales are mammals and like all mammals they carry bacteria and disease that can be passed on to other mammals including to humans," he said.

The whale washed up on a private beach, about 40 minutes north of Kerikeri, on Saturday.
The whale washed up on a private beach, about 40 minutes north of Kerikeri, on Saturday.

"So just like roadkill, you shouldn't pick up a dead possum from the side of the road without some sort of protection. Whales on beaches are just like roadkill, but a few thousand times bigger."

Land owner Andrea, who does not want her last name used, said the whale washed up on the family's private beach during Saturday's heavy storm about 5pm. She said the whale's tail was about 5m across.

DoC and local iwi were informed and both had been to investigate the whale.

"DoC said it had probably been in the water dead before the storm brought it ashore," said Andrea.

"It has a lot of bite marks on it from sharks.

"Also it's belly is getting a bit bloated so it might yet explode," she said.

"DoC said people can get quite sick from touching a whale and if it does explode that could cause problems."

Andrea said the whale was now getting very smelly as it decomposed, bodily fluids from the whale were also leaking into the sea, which was likely to attract sharks looking for an easy feed.

She said it was fortunate the whale was on a fairly isolated private beach with no public access from the land so that would deter people from going to have a look.

"It's a very cool thing to see, but also a bit sad ... I'd like to think it died from old age and was washed up here."

The family had owned the property since 1986 and it was the first time she had had a whale wash up.

"Although we also got some of those very large, ocean-going giant petrels on the beach on Saturday too. The storm may have driven them in too ... or they could have been following the whale in," she said.

"Now that it's really smelly I'm hoping nature takes its course and another big storm comes up to take it back out to sea."