Image credit: Dewald Kirsten / Shutterstock.com
Weighing whales in the past has been a difficult feat for researchers and scientists. In most cases weighing could only be achieved when either whales were beached or the carcasses of dead whales were washed up on shore.
This process lacked accuracy and was extremely laborious given the size and scale of the ocean-dwelling mammals. Now, scientists have developed an innovative technique using drone footage to calculate the weight of whales in the open ocean. The hope is this will go towards developing more accurate data models in research regarding individual whales and migrating pods.
Fredrik Christiansen from the Aarhus Institute of Advanced Studies in Denmark and lead author of the study stated, "It is very difficult to measure a whale on a scale - I mean you have to kill it to do it and that's exactly what we're avoiding here."
This is not really an option for researchers and scientists due to the ethical component, but also because it would be counterintuitive to any conservation efforts given the role whales play in entire ecosystems. Any misdirected intervention could prove to be catastrophic.
The drone method developed by Christiansen and his team produced precise results and statistics related to the body volume and mass of southern right whales in the wild. Taking the study to Argentina proved to be useful as here the whales converge en masse during their mating season.
This allowed the researchers to gather a sizable data set that would test and determine the accuracy of their study which was published in the British Ecological Society journal Methods in Ecology and Evolution (MEE).
The technique involved making a series of drone flights whilst whales were swimming close to the surface in clear water. The visibility of the mammal is a key factor in this study. The images were taken of both adults and calves in situ as well as when they came to the surface to breathe and made certain movements such as raising to the surface and rolling onto their backs. From a set of clear images the team could accurately gather the data of length, height and width of over 80 individual whales.
The ability to predict body mass from free-living whales opens up the opportunity for us to look at animals over time and look at how they change, how they grow.
Professor Christiansen
The role an individual plays in a pod can determine how that family group grows and evolves as a whole is reliant on a series of factors but size and mass is one of the more significant components to this.
Body mass plays an important role in the lives of all mammals and for most conservationists and researchers there are accessible ways to measure and record this for most species. For accurate research studies involving animal physiology and bioenergetics as well as conservation these are important factors to consider. However, for whales this has not been the case and the available data records may have lacked a certain accuracy regarding the metabolic rate and specific food requirements of this behemoth. In fact, some of the records derived from old whaling records and conservation and accurate data might not be high on the agenda there.
Therefore, by gathering accurate data models on the volume, or size and shape of the bodies of the whales, the team could then predict the weight of the animal. Additionally, from the data gathered during the study the researchers could create interactive and detailed 3D computer renders of the southern right whales. These 3D meshes will be a valuable component to both the study and research monitoring the development of the whales.
Weight measurements of live whales at sea inform how chronic stressors affect their survival and fecundity.
Dr. Michael Moore, Senior Scientist, The Woods Hole Oceanographic Institution
While, drone studies such as this can be applied to other whale populations beyond the southern right whale the exciting part is that the team believes they can extend this model to other marine animals. This creates further opportunity for the monitoring of sea-life that is not counter-productive to conservation efforts as invasive methods could be discarded.
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