A young whale found beached in a West Auckland river yesterday is thought to be the calf of a whale that died on Waiheke Island last week.
The female juvenile beaked whale, which is similar in appearance to a dolphin, was found on a mud-bank, about 4km up the Whau River, in Avondale at 8am.
Department of Conservation marine ranger Karl McLeod said there was a possibility the 2m whale was the calf of the 4m female found on Waiheke Island.
The calf may have become disoriented after losing its mother.
Mr McLeod said dolphins had been beached up the river before, but he had never heard of it happening to a whale.
When DoC staff arrived, the calf was thrashing around in a pool of mud. It had some cuts and was stressed.
They manoeuvred a stretcher under the half-tonne calf and dragged it to the water.
Once it was on an inflatable pontoon, the calf was dragged slowly out into the harbour and lifted aboard a larger boat.
Mr McLeod said lifting the calf was a delicate operation, because placing too much stress on parts of its body could damage organs.
Once the whale was on board a pump was used to continuously pour seawater over it.
Last night, the whale was taken out near between Rakino Island and Waiheke Island, where it was released.
Mr McLeod said the calf "swam away comfortably" after being released in 30m deep water. He was confident it would survive its ordeal.
The whale found on Waiheke Island was a Gray's beaked whale. Little is known about the species and scientists are not even sure if it is rare.
The calf found yesterday was also a beaked whale, but DoC staff were not entirely sure which species it is.
Last week marine mammal biologist Dr Rochelle Constantine, of the University of Auckland, told the Herald about 15 of 21 species of Southern Hemisphere beaked whales were found in New Zealand waters.
"Until we know more about these whales we can only assume there aren't many of them," Dr Constantine said.
She described them as dwelling in deep water and living individually or in small groups.
"Given the number of people about in boats around coastal New Zealand all the time, there are not many people who can say they have seen a beaked whale.
"That includes those of us who work out on the water spending a lot of time looking at marine mammals.
"They really are an unknown quantity