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Chatty dolphins

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Dolphin acoustics

Dolphins communicate with whistles, clicks and buzzes. In a world where visibility is rarely more than a few meters, sound is the way to go to find each other… or other species!

Similarly to bats, dolphins use echolocation to precisely detect their prey. That is the reason behind their bulbous head: a sac of oil called the melon helps produce their whistles and clicks.

Little is known about the significance of each sound… however, we do know dolphins use something similar to a name: the “signature whistle”. Each individual dolphin has its own signature whistle, and calves will often imitate their mothers’, with their own unique tempo of course!

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Behavioural assessment: Marine mammal behaviour budget and transitions – Markov Chains

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Markov chains are used to assess how the behaviour of marine mammals changes across a range of variables (depth, group size, presence of calves or vessels…). Results indicate bottlenose dolphins spend less time feeding and resting, but more time milling and socialising in the presence of vessels. This work follows from a Massey unviersity study conducted in 2016 – https://www.doc.govt.nz/globalassets/documents/conservation/marine-and-coastal/bottlenose-responses-dolphin-vessel-activity-northland.pdf  

Oceanic bottlenose dolphin (tursiops truncatus), false killer whales (pseudorca crassidens) and pilot whales (globicephalia melas)

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Did you know not all bottlenose dolphins are the same?

Two ecotypes can be found here: a coastal and a pelagic (or offshore) bottlenose dolphin. While not different enough to be classified as separate species, those two “groups” do not mix, and the TriOceans team even assisted in a study identifying they use slightly different whistles. So how can you tell the difference? Look for circular scarring along their flanks: these scars come from the cookie cutter shark (Isistius brasiliensis) and are only seen on the pelagic individuals. The pelagic ecotype remains widely unknown, however it does seem to be of a friendly nature: they are often seen in association with pilot whales or false killer whales. In fact, false killer whales in New Zealand have never been seen without pelagic bottlenose dolphins around! The video above was recorded during scientific research in Northland and shows the close association between 2 different species. Don’t forget to turn your sound on! Can you hear the difference between the 2 species?

Large orca tangled in crayfish line in Northland - Stuff article

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An expert crew has spent Christmas eve trying to free a large male orca that has become tangled in a crayfish line in Northland.

Department of Conservation said it received a report of the incident in the water off Tutukaka on Monday night.

An expert crew headed to the scene at first light on Tuesday and located the orca, a spokeswoman said.

The crew tried to disentangle it from the crayfish line.

The spokeswoman said an orange buoy was attached to the line, but there was no crayfish pot.

She said boats were asked to stay at least 50 metres away from both the whale and the DOC crew as they needed room to help the orca.

People were also asked to stay out of the water.

Three other orcas were with the tangled whale, she said.

Shortly before 7pm, the decision was made for the crew to leave the water for the day the spokeswoman said.

“We managed to get the orca hooked twice, but it rolled away from us, we were unable to free it.”

“It was an amazing team effort from DOC, coastguard and trioceans. We will continue to be on call and hope to be successful another day.”

Earlier this year, a humpback whale also managed to get itself stuck in a craypot line.

The whale, first spotted at Knife and Steel Harbour, between Big River and Waitutu River in Southland, by a fishing vessel, was believed to be tangled in craypot line trailing up to 30 metres behind it.

“People seeing the whale can assist our rescue response by staying with the whale, monitoring it and advising of its exact location for our disentanglement team to get to it,” DOC ranger Mike Morrissey said in a statement.

The department warned against boaties trying to cut off lines and floats attached to the whale, as it is “very dangerous” and could make it more difficult for the whale and the rescue team.

Large orca tangled in crayfish line in Northland – Stuff article