Although it's important for biologists to know the weight of the whales they're studying, currently the only way of finding out involves hoisting a dead or stranded animal up on an industrial scale. That could be about to change, though, as scientists have now used a drone to calculate the weight of live whales as they're swimming.
The researchers – from the Woods Hole Oceanographic Institution and Denmark's Aarhus Institute of Advanced Studies – started with aerial photos taken of 86 southern right whales in the clear waters off the coast of Península Valdés, Argentina. Those pictures were shot by a DJI Inspire 1 Pro quadcopter drone, which was also equipped with a laser rangefinder in order to gauge its distance from those whales.
The scientists then developed a formula for determining the body volume of each animal, based on its length, width and height as captured at various key body points within the photos.
"We used this model to estimate the body volume of whales caught in scientific whaling operations, for which body girth and mass was known," says Aarhus' Asst. Prof. Fredrik Christiansen, lead author of a paper on the study. "We could then calculate the density of the whales, which we in turn could use to estimate the mass of free-living whales photographed by our drones."
The technology also allows for the creation of full-color 3D computer models of the photographed whales, which could subsequently be used for both scientific and educational purposes.
"Knowing the body mass of free-living whales opens up new avenues of research," says Christiansen. "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."
The paper, which was co-authored by Woods Hole's Dr. Michael Moore, was recently published in the journal Methods in Ecology and Evolution.
Sources: Woods Hole Oceanographic Institution, British Ecological Society
