A sperm whale washed ashore near Nelson could have died after becoming disoriented by seismic research north of Tasman Bay, a zoologist says.
Otago University zoologist and researcher Liz Slooten said other possibilities were a fishing vessel hit it, or it got tangled while eating off a longline.
Without an autopsy it was hard to say, she said.
The whale, which beached on Rabbit Island near Nelson yesterday, was one of several seen in the bay in recent days, and which was initially thought to have been a humpback or right whale.
Dr Slooten said it looked too well to have died of natural causes.
She said the fully grown male, which was still young, could have died after becoming disoriented by seismic research being done north of Tasman Bay.
An online ship-tracking system showed two seismic research vessels had been operating seismic detectors each side of Cook Strait — one in the Taranaki Basin, north of d’Urville Island across to Farewell Spit and up to New Plymouth, the other east of Wellington.
The technology pinpointed areas for oil drilling, or studied the geology of the sea floor by towing equipment which shot loud blasts of compressed air through the water and deep into the seabed.
The waves reflected back information about buried oil and gas deposits.
Dr Slooten said Cook Strait was an occasional transit zone for sperm whales, which normally lived in ocean depths of up to 1000 metres — and never in shallow depths such as those in Tasman Bay.
