Growing fears for rare Hector's dolphins as numbers in Banks Peninsula drop dramatically

The number of Hector's dolphin calves located around Banks Peninsula in Canterbury has dropped dramatically this summer, raising fears for a dolphin that is already under threat in New Zealand.

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The number of calves seen off the coast of Banks Peninsula has dropped dramatically this summer. Source: 1 NEWS

Otago University scientists say this year they've seen just a quarter of the number of newborn Hector’s calves that they usually see in summer.

Professor Liz Slooten of Otago University is an expert in dolphin behaviour. She and her team have been tracking the population for 35 years. She says the number of adult dolphins being spotted has also dwindled.

“So that's been the weirdest thing - even the dolphin numbers are low but the number of newborn calves are super, super low,” Ms Slooten told 1 NEWS.

A Hector's dolphin is supposed to live for around 20-25 years. The World Wildlife Federation has described the species as the "smallest and rarest marine dolphins in the world".

Ms Slooten said she is stumped as to why this summer newborn calves make up fewer than one per cent of the dolphins spotted.

“We're worried that something’s happening with the dolphins possibly - definitely with their breeding, with their reproductive rate,” she said.

One clue, Ms Slooten said, is that the water temperatures have been colder than normal.

Black Cat Cruises operates in the Akaroa Harbour, a spot usually brimming with the dolphins.

Paul Milligan, chief executive, wants the Government to reveal its threat management plan for the species.

“There’s only around 10,000-15,000 of these dolphins left and they're very slow to reproduce, so any decline in the number of calves being born is going to have a detrimental effect on their population,” said Mr Milligan.

Minister for the Environment David Park has said a draft plan is expected soon.