Hawaiian spinner dolphins need sheltered bays for rest

April 28, 2015

Hawaiin Spinner dolphin squareSpinner dolphins found off the Kona Coast, Hawai’i Island need sheltered bays for rest and protection from predators, researchers from Murdoch University and Duke University have found.

Spinner dolphins are small dolphins found in tropical waters around the world and are known for their acrobatic displays where they leap out of the water and spin along a longitudinal axis.

The researchers have been funded by the National Oceanic and Atmospheric Administration (NOAA), the Marine Mammal Commission, Dolphin Quest and Murdoch University to investigate the spinner dolphin population, habitat use and exposure to human activities.

Julian Tyne is a PhD candidate with the Murdoch University Cetacean Research Unit and has spent the last four years studying Hawaiian spinner dolphins to determine the importance of their resting bays and to assist the NOAA to implement a management strategy to reduce the intensity and number of human-dolphin interactions in Hawaii.

“During the day spinner dolphins use the sheltered bays to avoid predators and to recover from their night time foraging,” Mr Tyne said.

“Their predictable presence in the bays make it relatively easy for swimmers, kayakers and boats to actively seek them out for close-up encounters. This has raised concerns about the effect of their repeated exposure to humans.”

Mr Tyne’s research has shown that the sheltered bays are very important to the spinner dolphins and that they are unlikely to rest anywhere else.

“We used a combination of boat-based and land-based sampling regimes and novel statistical modeling to identify habitat features that contribute to the occurrence of resting Hawaiian spinner dolphins,” Mr Tyne said.

“Previous studies evaluating their resting habitats focused on areas inside resting bays only. In this research we combined data from inside and outside bays, revealing that they are unlikely to rest anywhere other than the sheltered bays.

“If the spinner dolphins are displaced from the resting bays because of human activities, it may have serious implications for the population.”

As part of the research Mr Tyne and his team have been collecting data about the number of dolphins using the bays.

“Our abundance estimates will now form the baseline for NOAA going forward and allow them to determine the success of their management strategies,” he said.

During his research Mr Tyne has been collecting data that reveals spinner dolphins preferred habitats and the cumulative effects of their exposure to swimmers, kayaks and boats.

His manuscript titled, The importance of spinner dolphin (Stenella longirostris) resting habitat: Implications for management’ has been published in the British Ecological Society’s Journal of Applied Ecology.

Looking forward, researchers intend to investigate the effects of human interactions on the spinner dolphins. The NOAA is mandated under the Marine Mammal Protection Act to monitor all marine mammal populations in US waters.

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Comments (2 responses)

Darragh McCurragh June 4, 2015

"… make it relatively easy for swimmers, kayakers and boats to actively seek them out for close-up encounters …" Hm – but didn't you mention these are their resting places? Isn't that a bit like invading someone's sleeping chambers to start a conversation, so to speak?

Hayley Mayne June 8, 2015

Hi Darragh, yes I would have to agree with you comment. Which is exactly why researchers are concerned for the dolphins.

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