New technique to collect DNA from dolphin breath

Researchers demonstrate collecting the DNA sample

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Biologists have developed a new way of harmlessly collecting DNA from dolphins from their exhalations or "blow".

Understanding dolphin genetics is critical to the conservation of wild populations.

Current methods to collect dolphin DNA use a procedure which can be harmful.

Scientists hope the new technique, successfully used to extract DNA from aquarium dolphins, can also be used in the wild.

The most commonly used way of collecting DNA from dolphins and whales is by "Dart biopsying". This involves firing a dart with a small barb into the flank of the animal, which then extracts a small plug of tissue.

For whales this procedure is less invasive than it is for smaller dolphins and there has been one documented case of death of a dolphin from a dart biopsy.

Finding a new technique has become a priority particularly for internationally protected species of dolphins.

Dolphins are mammals, so get their oxygen from breathing air. They breathe out through their blowholes, located on tops of their heads.

The "blow" is exhaled at great force at speeds of 70 litres per second. Because of this cells from the surface of their lungs can be found in their blow and so DNA can be extracted from it.

The researchers worked with six bottlenose dolphins at the National Aquarium in Baltimore, US, which were already trained to blow on command with a touch on the forehead.

Janet Mann, professor of biology and psychology at Georgetown University in Washington DC, is one of the authors of the study.

Blow up

"The blow goes way up high in the air as if it's a geyser and we know what it's like because they blow in our faces and that's also partly what gave us the idea. You could think of it as analogous to when a human is coughing hard."

The scientists held a test tube above the dolphin's blowhole to collect the sample. By taking DNA from blood samples and comparing it to the DNA taken from their blow, they were able to prove that DNA can successfully be extracted using this technique.

Being able to get a good picture of the genetics of dolphin and whale populations is critical to their conservation.

"You can tell by looking at the DNA, their genetic diversity... It's really important in understanding what's happening to wild dolphins and whales." she told BBC News

Now the idea has been successfully demonstrated with aquarium dolphins, the researchers are confident it can be used in wild populations. They often like to bow ride at the front of research vessels and so are used to being close to their boats.

"They breathe near our boats anyway so we hope we can get the fluid without stressing them. If you can get this kind of information without stressing them at all then it's golden."

Professor Mann also hopes the technique could, in the future, be used to measure dolphin hormones.

"With hormones you can look at stress hormones or reproductive hormones. Being able to pregnancy test a dolphin would be fantastic. That would be the Holy Grail for us.

"Also, fatty acids can tell you what type of fish they're eating, because each fish species has a fatty acid signature. So you could assess diet," she told BBC News.

The research was published in the journal Plos (Public Library of Science) One.

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