WOODS HOLE – Researchers from Aarhus Institute of Advanced Studies in Denmark and the Woods Hole Oceanographic Institution have devised a way to accurately estimate the weight of free-living whales using only aerial images taken by drones.
The innovative method, published in the British Ecological Journal “Methods in Ecology and Evolution,” can be used to learn more about the physiology and ecology of whales.
By measuring the body length, width, and height of free-living southern right whales photographed by drones, researchers were able to develop a model that accurately calculated the body volume and mass of the whales.
Because of their large size and aquatic life, previously the only way to obtain data on the body mass of whales was to weigh dead or stranded individuals.
“Knowing the body mass of free-living whales open up new avenues of research,” says Fredrik Christiansen, an assistant professor at AIAS and lead author of the study, which was funded by a research grant from the National Geographic Society.
“We will now be able to look at the growth of known aged individuals to calculate their body mass increase over time and the energy requirements for growth. We will also be able to look at the daily energy requirements of whales and calculate how much prey they need to consume.”
Michael Moore, a biologist at WHOI and co-author of the paper added, “Weight measurements of live whales at sea can inform how chronic stressors affect their survival and ability to produce offspring.”
To calculate body volume and mass of southern right whales the researchers first took aerial phots of 86 individuals off the coast of Peninsula Valdes, Argentina.
The clear waters and the large number of whales that gather there every winter for breeding made it an ideal place for researchers to collect high quality images of both the dorsal and lateral sides of the whales.
From these the team was able to obtain length, width, and height measurements.
The model also allowed the researchers to collaborate with the Digital Life Project at the University of Massachusetts at Amherst to first recreate a 3D mesh of the whale, and then to work with the CG artist Robert Gutierrez to recreate the full-color 3D model of the right whale.
These models can be used for both scientific purposes, such as studying movement, as well for educational uses.
By adjusting the parameters of the model, the approach could be used to estimate the size of other marine mammals where the alternative, more invasive, methods are no longer feasible or desirable.
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