Scientists monitoring the movements and behavior of dolphins in Aotearoa have found Hector’s dolphins in 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 (DOC).
The Māui dolphins are only found along the west coast of the North Island, and it is estimated that only about 54 individuals remain. The Hector’s dolphin population is estimated to be around 15,000, and they are classified as Nationally Vulnerable.
Classified as a taonga by Māori, the Hector’s dolphin is one of the world’s rarest and smallest dolphins and is mainly found in the coastal waters of the South Island.
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DOC scientific advisor for marine species Anton van Helden said finding Hector’s dolphins in Māui’s dolphin population was “a great insight.”
‘So far there is no sign of crossbreeding between Māui and Hector’s, although they are a subspecies and in all probability they should be able to.
“But right now we have animals and new animals popping up in that Māui population of the Hector dolphin population. We don’t have enough information to say exactly where those animals come from, and if we start to understand that, we can see the implications it has for their management.
“We are always trying to learn more about the animals, because they are very important. They are important to us, they are iconic, they are endemic to New Zealand and they are not found anywhere else in the world,” says Van Helden.
Using cutting-edge research technologies, scientists hope to find out if the Hector’s dolphin population in the Marlborough Sounds is genetically unique from other groups at the top of the South Island.
Although extensive studies have been conducted on other populations around Te Waipounamu, very little is known about those living in the Marlborough Sounds.
Van Helden said scientists were trying to understand the genetic relationships and “connectivity” of adjacent Hector’s dolphin populations in the crest of the south.
Epigenetic clocks allowed the team to take biopsies from live dolphins and study them over the long term, rather than relying on samples collected from animals that had died.
“The typical way we have assessed and understood the ages, and how long an animal can live, at what point in their life cycle they can become reproductively active – we did that from dead animals that washed ashore and looked at the age of teeth” , said Van Helden.
This means that “teeth are cut in much the same way you would look at rings in a tree,” he said.
“But now we’ve developed new techniques, and it’s very exciting because we’re just getting started, and it allows us to look at the age of animals by simply using small biopsy samples.”
Van Helden said new research tools also allowed scientists to see what the dolphins were feeding on, which in turn could give the team insight into the animals’ movements.
“The research on their diet is quite new. To be [about] understand their isotopic range, which will essentially tell us where they feed and what kind of species they feed on.
“This will help us through time as we try to understand the implications of things like climate change for the distribution of animals and their diets,” Van Helden said.
It was hoped that the data collected would allow the team to see whether populations at the top south remained segregated, 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 the animals at the top of the west coast, Marlborough Sounds, or the animals at Cloudy Bay at the top of the east coast.
“Some of the questions that remain to be determined are whether those Hector dolphins in the Marlborough Sounds are genetically different, or just an extension of the Cloudy Bay population and whether or not they are 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 they would be at dealing with and protecting against potential threats, including toxoplasmosis, a contagious parasite spread primarily through the urine of cats and catastrophically. could be. for dolphin populations.
“We know that dolphins all over the country are predisposed to get this and die from this disease, and that seems to be quite important,” Van Helden said.
He said an earlier attempt to conduct an aerial survey to determine the population size of Hector’s dolphins in the Marlborough Sounds was thwarted by problems with the aircraft.
“Because of limitations on the aircraft they were using at the time to do that research, while the rest of the South Island was using that particular approach, they weren’t able to do that over the Sounds.
Scientists hope to use a large fixed-wing drone with artificial intelligence to count Hector’s dolphins and better protect the species.
“So one of the new techniques we hope to use to get a sense of the population size in the Marlborough Sounds is to partner with Maui63, who have developed a large fixed-wing drone that uses artificial intelligence to can spot dolphins.
“It will be able to run transects – lines going back and forth with the drone and counting the number of animals in an area and then repeating it.
“By doing that, we can capture and recapture the assessment and get a population size,” said Van Helden.