Bermuda’s offshore bottlenose dolphins dive deeper and longer than previously thought, marine mammal scientists have discovered.

Researchers have been assessing and tagging four deep water dolphins as part of the Bermuda Wild Dolphin Project, which is offering scientists a glimpse into the daily lives of these animals, including travel patterns, dive depths and durations, and bioacoustic information.

“The data we are getting from these animals are amazing,” said Randall Wells, of the Chicago Zoological Society’s Sarasota Dolphin Research Program.

“Within just the first week of tracking they have established new records for how deep the offshore ecotype of bottlenose dolphins has been documented to dive, and how long their dives last.”

He added: “After over four decades of studying bottlenose dolphins in Sarasota, Florida and in collaboration with zoological institutions like Dolphin Quest (in Bermuda), we have learnt quite a bit about the coastal ecotype of bottlenose dolphins which thrive in shallow waters. The offshore ecotype found in the deep waters surrounding Bermuda are much more of a mystery, and that is why this ongoing project is so exciting.”

Dr Wells will be tracking the four sub-adult dolphins, named Devonshire, Hamilton, Paget and Pembroke after Bermuda’s parishes, for the next several months via small satellite-linked tags fitted on each animal’s dorsal fin.

“We are very excited to see where they go over the next few months, and to learn what they have to tell us about their diving capabilities,” he added.

The research is being carried out by an international team of marine mammal scientists, Dolphin Quest veterinarians and animal care professionals under a special permit from the Department of the Environment and Natural Resources.

According to Andreas Fahlman, lead investigator of the Wild Dolphin Project and Director of Research at Oceanografic Foundation in Valencia, Spain, the dolphins provide a unique opportunity to better understand the health and status of the ocean because they “inhabit a pristine environment that appears to be minimally affected by pollution, urbanisation and shipping traffic”.

“To restore the marine ecosystem following man-made damage, such as overfishing or an oil spill, we need to better understand the health and status of our oceans,” he explained.

“Consequently, understanding the overall health of this population will provide important insights about dolphins that likely have not been significantly impacted by humans.”

He added that the Bermuda Wild Dolphin Project aimed to enhance their understanding of the health, size, and behaviour of the dolphins using Bermuda’s waters.

“Bottlenose dolphins may be particularly sensitive to climate change. They may be the canary in the coal mine that signals severe changes at lower trophic levels.”

According to Dr Fahlman, the lung function data are vital to understanding how Bermuda’s deep-diving dolphins differ from their shallow-diving cousins in Sarasota Bay, Florida and how they can regularly dive to more than 900 metres for more than 13 minutes without being affected by the extreme pressure or decompression sickness.

“This information will assist veterinarians caring for stranded dolphins and may provide important clues of clinical significance for humans.”

And Frants Jensen, of the Aarhus Institute of Advanced Studies in Denmark, attached small sound and movement recording tags to the backs of three of the dolphins via suction cups.

The tags released after collecting detailed information on the sounds the animals make and hear as they perform their deep dives.

Dr Jensen said this would help scientists understand how the dolphins catch their prey, communicate, and how much noise they encounter in their daily life.

“This is the first time such tags have been deployed on offshore bottlenose dolphins that are normally extremely difficult to study.”

“The data collected will help us understand not only the behaviour of the animals here, but also how echolocating animals in general adapt their sonar to find food in different habitats.”

The data collected from these animals will build on previous results from Dolphin Quest’s 2003, 2004 and 2005 studies. It will compared with other wild dolphin populations as well as healthy dolphins in professional human care.

Summaries of the dolphins’ movement patterns and other information will be made public on Dolphin Quest’s website.