The fluid that spews out the top of a dolphin or whale's head when it exhales can provide scientists with valuable genetic information, giving them an alternative to shooting the animals with a retractable dart to collect a small tissue sample, new research suggests.
"The advantage of this method is that it capitalizes on the natural breathing behavior of dolphins and can be applied to even very young dolphins," Céline H. Frère, of the University of Queensland in Australia, and colleagues wrote in August in the journal PLoS ONE. "Both biopsy and blow-sampling require close proximity of the boat, but blow-sampling can be achieved when dolphins voluntarily bow-ride and involves no harmful contact."
Tissue samples for genetic studies are often collected from wild marine mammals using remote techniques, which include a crossbow or a long pole. Although some researchers have reported problems — including the death of one dolphin, an extreme example — most studies conducted by experienced scientists are issue-free, according to The Society of Marine Mammalogy's guidelines for the treatment of animals in field research.
The researchers tested the effectiveness of blow sampling using six bottlenose dolphins living at the National Aquarium in Baltimore. The dolphins were trained to exhale on command, and the researchers captured four to six exhales' worth of breath in an inverted tube for testing. These samples were used to generate DNA profiles, which matched profiles generated from blood drawn from the dolphins during their routine physical examinations.
While this work was limited to dolphins living in an aquarium, it shows promise for use on wild animals, the researchers wrote. This blow-sampling has previously been used for other types of studies.
Although the dolphin's exhalation evidently contains DNA, its make-up isn't entirely clear, although lung surfactant, which keeps these organs open and expanded, is likely to be the primary biological fluid. Lung cells are also likely to be present in the samples, they wrote.
"It is likely that blow is a mix of several types of biological fluids and may hold the answers to numerous biological questions," the researchers wrote.
Other, less invasive techniques — skin swabbing and fecal sampling — have been either inadequate or have not been fully tested, according to the research.