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Shifting a young orca from one side of Auckland to the other on a trailer was risking its life, an expert on marine mammals says.
Associate Professor Liz Slooten, an Otago University marine mammal biologist, said last night that although orca had a large home range - they had been known to move between Auckland and Kaikoura - the 4-year-old female rescued on Friday would be in danger if it remained on its own.
While she was unwilling to criticise the animal's relocation by trailer from Auckland's west coast to Takapuna Beach on the east, she questioned whether there were alternatives.
"It would have been a really tough call to know what to do. It might have been better to hold on to it in the Manukau Harbour [by keeping a boat with it] and see if the family came back or the weather improved so you could put it back out to sea on that side."
That would have been less disruptive to the animal than relocating it on a trailer, Professor Slooten said.
From reports that after its release it had repeatedly swum up the Waitemata despite boats trying to shepherd it in the opposite direction, it seemed the immature orca had been disoriented and was trying to find its way back to the west coast, without realising there was a landmass in the way.
The 3.4m-long whale - found beached on Friday at Whatipu, outside the Manukau Harbour - was last seen off Devonport on Sunday night, heading towards the Hauraki Gulf.
Orca Research Trust founder Dr Ingrid Visser, who spent yesterday unsuccessfully hunting for it among other orca, said it was relocated because of the danger trying to refloat it in the rough seas at Whatipu posed to it and its rescuers.
Another factor was that the orca was likely to join a new pod.
"We wouldn't have done it if it wasn't viable. The orca social structure in New Zealand is very fluid. The animals move quite frequently from one group to another and spend years with one group then maybe just a couple of weeks with another group."
Professor Slooten said a 4-year-old orca would not survive on its own as it had yet to fully develop its hunting, navigational and social skills. She was also less sure than Dr Visser about the fluidity of the social structure.
"I wouldn't want to jump to the conclusion that another group will adopt it. It might have been sensible to wait a little longer."
