Whales can adapt to seasonal and environmental conditions. But they are not working alone… They, just like us, team up with a vast army of microscopic soldiers every day called the microbiome. Different microbes, including bacteria, fungi, and viruses, make up the whale’s microbiome. We can take a look at the composition of whales’ microbiomes to understand how changes in their conditions (like fasting) impact their health.
Humpback whales fast for a good part of the year
Humpback whales migrate from the poles in summer, where they feed, to warmer waters in winter, where they breed. They fast for a good part of the year during their migration to warmer waters and back. Food is scarce and not nutritious enough on their breeding grounds, forcing the whales to keep fasting.
Not looking for food allows the whales to invest all their energy in mating and taking care of their calves before returning to the poles. There, populations feed on huge amounts of krill – paper clip shrimp-like critters densely congregated in swarms. Humpback whales can swallow about 1,200 kg (2,600 pounds) of krill twice a day!
Dr. Catharina Vendl and her collaborators from the University of New South Wales, Australia, recently studied how starvation impacts the whales’ respiratory health by looking at their microbiome. To do so, they compared the microorganisms found in the blows of free-swimming humpback whales.
Microbes in the whale’s airways
The microbiome contains all microorganisms that live in or on a living being. Aside from age, diet is the next most influential factor in one’s microbiome composition. Specific groups of microbes communities (bacteria, viruses, fungi, and others) make up the microbiome of specific organs. For instance, gut microbial communities are super diverse in comparison to the respiratory microbiome.
Certain combinations of microbes are found mostly in healthy individuals. Scientists are trying to catalog microbiome compositions in whales and various other animals around the globe to understand their health. Humpback whales have microbes in their airways that regulate their respiratory health. The research team collected samples of exhaled breath spray, or ‘blow,’ from 20 whales at the beginning and end of their fasting period. The study site was Hervey Bay on the east coast of Australia.
How do you collect samples from a whale blow?
The short answer: small glass plates and a lot of patience!
Researchers put together useful instruments for sample collection and boarded a whale-watching vessel. They used glass plates fixed on a clear board attached at the end of a long pole. The glass plates allow bacteria, fungi, and other microbes to grow.
On a sunny day aboard, field biologists spend the day waiting for the whales to appear. Once they locate and cautiously approach a whale, catching a blow is a matter of chance. When a whale surfaces near the boat, scientists have to take the pole approximately 50 cm above the exhaling whale’s blowhole. The glass plates can then collect the droplets in the expelled water condensate.
To ensure the reliability of their data, scientists close and label each glass plate right after collection and then store them to preserve the samples’ integrity and avoid contaminants.
Starvation changes whales’ respiratory microbiomes
Vendl’s team found that whales had a more diverse and abundant microbiome at the beginning of their fasting period than those further along their fasting period. Moreover, they found some potentially pathogenic bacteria in both instances, some of which cause respiratory diseases in dolphins and pinnipeds.
During migration, whales exhaust their energy stores and lose around 40% of body weight mass. This might result in a weakened immune system. This may influence the proliferation of other types of bacteria in the whale’s airway. Scientists could not predict their pathogenicity or effect on the overall whale health yet.
Ultimately, the whales need to find enough food available when they resume eating to ensure a successful renewal of their energy stores and microbiome.
Is this the end?
The story continues! Researchers’ next steps are to do more experimentation to find out how other factors impact the whales’ microbiome, and how the microbiome, in turn, affects their health. Generating knowledge in microbiology and conservation will help us learn more about these magnificent giants.
You can find the study on whales’ respiratory microbiome published in Nature Scientific Reports here.
Come read our post about threats that affect baleen whales here.
What are the main threats affecting baleen whales?
Rox is an enthusiast biologist born and raised at the Andes Mountains' crossroads. Rox's deep admiration for the natural world and passion for science was sowed during her upbringing, surrounded by snowy volcanoes and biodiverse forests. With time, research has become a great companion and teacher of life for her. Rox's interests lie in the intersection of marine microbiology, climate, and One Health. She is also devoted to making research an eco-friendy practice wherever she goes. Outside the office, Rox contributes to initiatives in public health, inclusion in STEM, and science communication. But she is always interested in new collaborations.