A dolphin’s breath can say a lot about its health. A sulfurous whiff suggests digestive trouble; a sweet scent means pneumonia. Veterinarians often rely on their own noses to detect these differences, but they may soon get some help from modern science. Researchers have developed a technique for detecting hundreds of chemical compounds in the animals’ exhalations. The advance could eventually lead to a Breathalyzer of sorts for dolphins and other animals that could measure a suite of health parameters far more easily and less stressfully than current diagnostic methods do.
“It’s going to be a game changer for whale and dolphin research,” provided that researchers can figure out how to interpret all the compounds, says Kathleen Hunt, a research scientist at the New England Aquarium in Boston, who was not involved in the present study.
Blood is the material of choice for learning about an animal’s health, because it contains every substance circulating in the body. But obtaining it is difficult for researchers and hard on animals. A sample of an animal’s breath is much easier to obtain, and researchers believe it contains as many diagnostic molecules as blood, just at lower concentrations that are much harder to detect and analyze. More than 1800 compounds have been identified in human breath, and tests are being developed for diabetes, cancer, and other afflictions.
In the animal world, researchers have been especially keen to study the breath of cetaceans, a group that includes dolphins and whales. Pollution, overfishing, and climate change are thought to be harming many whale and dolphin species, but scientists are struggling to understand how, because assessing the animals’ health is difficult. Try convincing an enormous whale to hold still for a blood draw in choppy seas—it just isn’t going to happen. Whale breath, or “blow,” on the other hand, bursts regularly and conveniently into the air, and you can catch some without even touching the whale. In recent years, scientists have been methodically working out how to interpret useful compounds they’ve found in cetacean blow, which include DNA, microbes, metabolites, and hormones.
To catalog all the compounds in breath, rather than just a targeted few, Cristina Davis, a chemical sensing expert at the University of California, Davis, and her colleagues teamed up with researchers at the National Marine Mammal Foundation in San Diego, California, who study a group of trained bottlenose dolphins owned by the U.S. Navy. They developed a device that sits on or over a dolphin’s blowhole and collects and condenses exhalations in a chilled chamber. With it, they sampled blow from the Navy dolphins, which obligingly presented their blowholes, and from wild bottlenose dolphins they temporarily captured in Florida.
The researchers figured out analytical methods to identify about 500 different compounds in the samples—a “first library” of dolphin-breath chemicals—they reported online before print in Analytical Chemistry. These included the chemicals responsible for dolphin’s fishy-smelling breath, along with amino acids, lipids, pharmaceuticals, and water contaminants also found in the dolphins’ habitats. There were intriguing differences in the breath profiles of healthy versus sick, wild versus captive, and fasting versus fed dolphins. “It’s very rich,” Davis says of dolphin blow. “There’s a lot of information in there.”
The researchers are now analyzing breath samples collected over time from the Navy dolphins to begin pinpointing which compounds indicate particular health conditions. Davis says that once these associations are fully worked out, the approach could tell researchers a great deal about a dolphin, such as its diet, activity level, environmental exposures, or illnesses. This could help scientists learn how wild dolphins are responding to environmental changes and stressors and lead to better veterinary care for captive animals.
Davis says she thinks the techniques will translate nicely to other animals. She and colleagues identified 70 chemicals in blow collected from a dying gray whale, they reported last month in Metabolites. Other researchers are looking into trying out her methods on dogs and Weddell seals.
“This really opens the door to do a broad-scale assessment of an animal’s health without having to get a blood sample,” says Hunt, who pioneered the analysis of whale blow and poop for hormones that indicate sex, maturity, reproductive state, and stress level. She hopes to be able to use some of Davis’s analytical methods to identify a wider array of compounds in whale blow. Still, she says it’s unclear how well the new approach can transfer to large, free-swimming whales. The present study required capturing several complete breaths—no problem if you have a small, stationary animal. But with large whales, Hunt usually has just a split second to snag a portion of one breath. “The whale’s rolling, there’s waves, the boat’s tipping, everything in motion,” Hunt says. “We’re going to have to do something much cruder than what she’s doing.”