Whale behaviour mystifies experts
A rare visit by a species of beaked whale to Nelson’s harbour has left whale experts questioning whether warmer oceans are changing the animals’ behaviour patterns.
Project Jonah general manager Daren Grover said four Arnoux’s beaked whales, first seen in Nelson Haven last Thursday, made their way out into the wider Tasman Bay on Saturday. On Sunday afternoon, they were spotted near Adele Island in Abel Tasman National National Park.
‘‘The behaviours that we were seeing were behaviours that we didn’t have concerns with. There was some nice breaching – they were travelling. When they were in the harbour, they were very slow,’’ Grover said.
Arnoux’s beaked whales are one of 22 species of beaked whales found in New Zealand waters. They had a distinctive bulbous forehead, and could also be identified by the shape of their rostrum or beak, Grover said.
It was only third time in 12 years that the species had been reported so close to shore, he said. The other sightings were in Auckland and the United States.
Why the whales came close to Nelson’s shoreline was unknown, Grover said. ‘‘That’s like asking, ‘Why do they strand?’.’’
Usually when whales came so close to shore, it was because there was an underlying illness or problem, he said.
‘‘We’re all scratching our heads, and we’re all quite delighted that they haven’t stranded.
‘‘The statistics the last couple of years, what we’re seeing and when, has become a lot less predictable.’’
Pygmy killer whales, a species only recorded as being seen once before in New Zealand, had stranded on Ninety Mile Beach in Northland at the end of 2018, Grover said.
‘‘Only one individual has ever been seen in New Zealand in 100 years. We saw 12 of them at once.
‘‘What’s happening out there, it’s hard to say.’’
Also for the last two years, there had been no mass strandings of pilot whales in the three or four hotspot areas where they were seen ‘‘quite regularly’’, he said.
‘‘Traditionally, December, January and February is a time where we’re likely to see a mass stranding in the Golden Bay area, as those whales migrate annually through Cook Strait.
‘‘So we’re wondering whether increased ocean temperatures is causing them maybe to track either not so far north, or not so far south.
‘‘We’re just sitting and watching and being prepared for whatever might occur,’’ he said.