Hector’s dolphins link up with Māui
Scientists monitoring dolphin movement and behaviour in Aotearoa have found Hector’s dolphins within Māui’s dolphin populations.
Māui’s dolphins (Cephalorhynchus hectori maui) and Hector’s dolphins (Cephalorhynchus hectori) are closely related and are two subspecies of the same dolphin species, according to the Department of Conservation.
Māui’s dolphins are found only along the west coast of the North Island and it’s estimated there are only about 54 individuals remaining. The Hector’s dolphin population is estimated to be about 15,000, and they are classed as nationally vulnerable.
Classed as taonga by Māori, the Hector’s dolphin is one of the world’s rarest and smallest dolphins, and is found primarily in the coastal waters off the South Island.
DOC science adviser for marine species Anton van Helden said finding Hector’s dolphins within the Māui’s dolphin population was ‘‘a big insight’’.
‘‘So far, there’s no sign of interbreeding between Māui and Hector’s, even though they are a subspecies and in all likelihood, they should be able to.
‘‘But we do have animals and new animals that turn up in that Māui population from the Hector’s dolphin population at the moment. We don’t have enough information to say exactly where those animals are coming from — when we start to understand that, we can see what implications it has in terms of their management.
‘‘We’re always trying to find out more about the animals because they’re really important. They’re important to us, they’re iconic, they’re endemic to New Zealand, and they’re not found anywhere else in the world,’’ van Helden said.
Using the very latest research technologies, scientists have been hoping to find out if the Hector’s dolphin population in the Marlborough Sounds is genetically unique from other groups across the top of the South Island.
Although extensive studies have been carried out on other populations around Te Waipounamu, very little is known about those that reside in the Marlborough Sounds.
Van Helden said scientists were trying to get an understanding of the genetic relationships and the ‘‘connectivity’’ of adjacent Hector’s dolphin populations across the top of the south.
Epigenetic clocks had enabled the team to take biopsies of live dolphins and study them over the long term, rather than relying on samples collected from animals that had died.
Van Helden said new research tools also allowed scientists to see what the dolphins were feeding on, which in turn could give the team an insight into the animals’ movements.
It was hoped the data collected would allow the team to see if the populations across the top of the south remained separate, or whether animals interacted and moved between groups.
‘‘We have very little information about animals from Golden Bay and Tasman Bay, and whether they are related to either the animals on the top of the West Coast, Marlborough Sounds, or the animals in Cloudy Bay at the top of the East Coast.
‘‘Some of the questions to still ascertain are whether or not those Hector’s dolphins in the Marlborough Sounds are genetically different, or just an extension of the Cloudy Bay population and whether or not they’re in the Sounds all the time, or whether they move between those two populations.’’
Van Helden said the more information his team had about the animals and how they lived, the better equipped they would be in managing and protecting them from potential threats, including toxoplasmosis, an infectious parasite that was predominantly spread through cat urine and could be catastrophic to dolphin populations.
‘‘We know that dolphins all around the country are susceptible to catching this and dying from this disease, and that seems to be pretty significant,’’ van Helden said.