New research on Hector's dolphins in Lyttelton Harbour
LPC funded research is providing new data about Hector’s dolphins, with researchers using acoustics to understand more about them and how they move around Lyttelton Harbour.
Using four acoustic monitoring buoys, LPC, with the help of Styles Group and Vision Environment, has been able to collect more than a year’s worth of data on Hector’s dolphin movements around the Harbour – day and night, in fair weather and storms.
“The acoustic monitors are like a microphone under the sea,” says Researcher Dr Deanna Clement. “They listen to the frequencies that Hector’s dolphins tend to echolocate at, which are really high. Boats tend to be low range frequencies and other dolphins are mid range. Hector’s dolphins’ high-frequency sounds are perfect for the naturally cloudy waters of Lyttelton Harbour.
“Those sounds bounce around really well in that kind of water – and that’s probably why they live there,” Dr Clement says. “The cloudy water suits them and it’s harder for their competitors or their predators. So it’s perfect, in terms of their little niche.”
Hector’s dolphins are masters of echo-location or understanding their world by bouncing sound.
“In a dolphin’s mind, images are more formed from what they hear rather than what they see,” says Dr Clement.
They are incredibly good at it. They learn fast and can differentiate between even subtle objects.
The research shows that peak times for Hector’s dolphins being in the Harbour might be feeding times – dawn and dusk. The research also shows there are fewer animals in the Harbour in winter.
Hector’s dolphins are an endangered species found only in New Zealand. They are distinctive because of their size. They measure about 1.5m when they are fully grown and have a distinctive round dorsal fin, which is often compared to the shape of a Mickey Mouse ear.
Dr Clement says Hector’s dolphins are slow breeders. They don’t start until they are around seven years old and they only produce one calf every two to three years. The subspecies, Maui dolphin, has dwindled to just 54 animals in the North Island, but South Island Hector’s dolphins are estimated to be around 15,000.
Banks Peninsula has the highest concentration of South Island Hector’s dolphins, with an estimated population of between 3,000 to 6,000.
“Hector’s dolphins eat just about anything, so long as it’s the right size,” Dr Clement says. “Dolphins don’t rip their food up. They have to swallow
it whole. So they often choose juvenile species or bait species like sprats. They’ll eat squid, too. They’re not picky.”
The next step of the project will be to deploy hydrophones to record noise in the Harbour from recreational boats, ships and port activities. Overlapping this with the baseline data from the past 18 months will build a better picture of how Hector’s dolphins respond to underwater noise.
Lyttelton hasn’t been studied in as much detail as the rest of the Peninsula and Dr Clement hopes the research data will eventually assist in developing national guidelines for marine activities like pile driving that are specific to Hector’s dolphins, but potentially applicable to other dolphin species as well.
Overseas standards exist, and are used here, but they may not be relevant to New Zealand marine mammal species.
“This is a way that all ports could line up and come together with a standard. That would be the ultimate,” Dr Clement says.