by Audrey MacLellan —

Cetaceans – you might know them as whales and dolphins, might have seen them on television or on a whale watching trip gracefully swimming through the ocean, feeding with their massive mouths on schools of tiny fish, or jumping playfully out of the water only to make huge splashes as they hit the ocean surface. They are massive animals, some species of cetaceans such as the blue whale reaching a whopping 100 feet in length! You might think that because of the size of cetaceans, scientists would know a lot about the diseases affecting these wonderful animals. Surprisingly, that is not the case, and time may be running out.

Cetacean populations are on the decline. Some species of cetaceans, such as the endangered North Atlantic right whale, have a population comprised of only about 300 individuals. Entanglement in fishing gear, ship strikes, and illegal hunting are only some of the problems cetaceans face that can lead to their death. There have been efforts to preserve cetacean populations, by creating special whale-friendly fishing gear, rerouting shipping lanes to avoid cetacean-dense areas, and by bringing awareness to the public through education outreach programs. Yet, despite the efforts of conservationists, there are other problems pertaining to cetacean health that cannot be observed as ship strikes or entanglement.

The health of cetaceans has been a big question mark to the scientific community for years. Cetaceans, just like humans and other animals, are prone to infections which, if not monitored or properly dealt with, can lead to their death. Cetaceans are especially prone to respiratory infections. It is extremely important to catch infections in animals before the infection has progressed to the point of no return. In order to do that, it is critical for scientists to understand what makes a healthy whale healthy, and a sick whale sick. But how do scientists tell the difference between a healthy whale and a sick whale? One approach to do that is by comparing their microbiomes. 

The role of microbiome in monitoring cetacean health

Bacteria are everywhere. You may think of it as a bad thing, but communities of both good and bad bacteria exist in the gut, on the skin, and in the mouth and lungs of animals. These communities of bacteria are called “microbiomes”, and they can help an animal fight off infection, digest nutrients, and much more. In a normal microbiome, bad bacteria do not necessarily hurt the animal, but if abundances of bad bacteria are too high, that is when problems begin to arise.

Each animal that has a microbiome, cetaceans included, have a “normal” microbiome consisting of various types of bacteria. But in order to find out what is considered “normal”, scientists need to study many individual animals within a species and compare data. Obtaining such data on normal microbiomes can be particularly difficult when studying cetaceans, as samples taken from their skin and feces can easily become contaminated with bacteria from the surrounding waters. Respiratory samples, on the other hand, have only previously been observed post-mortem. The problem with observing animals’ microbiomes post-mortem is that these samples may not provide data on “normal” respiratory microbiomes. So how could scientists easily collect samples of live cetaceans’ respiratory microbiomes?

The answer is drones. In a study conducted in 2015, scientists used drones to collect samples from live cetaceans’ respiratory microbiomes (Apprill et al. 2015). To achieve this, the scientists first sanitized the drones, then attached Petri dishes to the top of the drones. From a boat not too far away, the scientists flew the drones 2-4 meters above the target whale’s blow hole. When whale’s exhale through their blowhole, the bacteria and other germs in their lungs are expelled. In this study, the bacteria in the whale blow could be collected by having them stick to the petri-dish surface attached to the drone. The drone was then flown back to the scientists, who collected and analyzed the data. The study was performed on many whales, and when comparing the data, it showed that whales all have respiratory microbiomes with similar compositions of bacteria.

This study could be very important for furthering research into monitoring cetacean health. With advancements in technology and new methods for data collection, it is easier than ever to detect when whales have become sick before they have died. By using pre-existing data of healthy whales and comparing it to new samples taken from potentially sick cetaceans, any unusual bacteria detected in new samples taken from cetaceans’ respiratory microbiomes could mean that the cetacean is sick with a respiratory infection. This methodology could be very important for the conservation of many species of cetaceans, such as the endangered North Atlantic right whale.

Reference:

Apprill, A., Miller, C., Moore, M., Durban, J., Fearnbach, H., Barrett-Lennard, L., 2017. Extensive Core Microbiome in Drone-Captured Whale Blow Supports a Framework for Health Monitoring. MSYSTEMS 2. https://doi.org/10.1128/mSystems.00119-17