What happens when you give a breathalyzer test to a dolphin?

Breathalyzer tests bring to mind erratic drivers and those who can't walk in a straight line. But researchers are exploring new ways of using breathalyzers in marine biology – and dolphins are swimming to the forefront of this research.

According to a report published last week in the journal Analytical Chemistry, scientists have created a device that can monitor bottlenose dolphins' health by measuring chemicals in their breath. It's a less invasive technique than gathering skin or blood samples to assess the well-being of these marine mammals, which last year washed up on shores along the US Atlantic Coast in alarming numbers. Scientists discovered that a disease, cetacean morbillivirus, likely killed those dolphins. 

The breathalyzers serve two purposes: keeping dolphins alive and gaining a better understanding of marine mammals' biology.

To reach these goals, the researchers designed a long, cylindrical tube that traps and then freezes breath exhaled from a dolphin's blowhole. They analyzed the breath samples of 21 managed bottlenose dolphins at the National Marine Mammal Foundation in San Diego and 21 wild dolphins in Sarasota Bay, Fla., to establish a baseline profile for healthy animals. That makes it easier to detect variations in metabolites – compounds that can hint at an animal's environmental exposure or disease states.

"We were able to basically answer a lot of fundamental questions," said Cristina Davis, professor at UC Davis's Department of Mechanical and Aerospace Engineering, which participated in the study. "What does dolphin breath look like? What types of chemicals are in it?"

As it turns out, dolphins are ideal breathalyzer test subjects. Because dolphins eat through their mouths but breathe through their blowholes, it's actually easier to capture a pure breath sample from the marine mammals than it is from humans, whose nasal cavity and mouth meet at the pharynx. Also, dolphins' tracheas are short, allowing them to be explosive breathers.

In the dolphins' breath samples, the scientists found thousands of compounds, including biogenic ones such as amino acids and peptides, along with a variety of environmental contaminants. The report notes that the researchers even discovered compounds that are presumably responsible for the "fishy" smell of dolphin breath.

"Thanks to Cristina's team the technology is now there where compounds can be detected in the beautifully compound rich dolphins' breath to detect what's in their blood, therefore their health," said Stephanie Venn-Watson, director of the National Marine Mammal Foundation's Translational Medicine and Research Program.

Davis said that more data is needed to understand which metabolites are associated with certain health conditions. Her lab has already begun a new study – funded by the Office of Naval Research – that analyzes changes in dolphin breath over time and in response to varying environmental conditions.

"If you have baseline knowledge about a person and you look at different health changes, you might be able to provide earlier indicators for a specific person's health changing in the future," she said. "We'd like to be able to do that for dolphins."