An animal’s weight is more than just a random characteristic: It’s a window into understanding fundamental truths about how animals survive. By weighing animals, experts glean insights into how much those animals eat, how quickly they and their population are growing and — perhaps most crucially — how outside stressors like the byproducts of human life can impact their health.
That information is a crucial launching pad for conservationists to determine how best to protect these species.
But weighing especially large mammals isn’t easy. When it comes to whales, which can grow over 100 feet long and weigh upward of 200 tons, scientists have had to rely on the limited information provided by dead specimens that were caught in fishing nets, washed up on shore or were intentionally killed for the purpose of research. Though obviously better than no specimens at all, this narrow scope pales in comparison to what scientists could learn from live specimens, especially as whales come under increased threat.
That’s where drones come in.
Scientists have figured out a way to pair drone photographs with historical data, using the combined information to develop a model used that accurately calculates a whale’s body volume and mass. The new model can be used to track both individual whales and various species over time.
This breakthrough, which was published in Methods in Ecology and Evolution in October, is an important step in both researching and protecting whales.
“Knowing the body mass of free-living whales opens up new avenues of research,” Fredrick Christiansen, the lead researcher of the study from Aarhus Institute of Advanced Studies, told Cosmos.
Standing on the deck of sailboats, researchers controlled drones and took photos of 86 southern right whales. Though these photos helped create a model endemic to this species of whale, scientists believe the approach can be adjusted for use with other large marine animals.
“Weighing live whales with a drone at sea, we can get growth rates and changes in body conditions,” Michael Moore, a senior scientist at Woods Hole Oceanographic Institution and a co-author of the study told Cape Cod Times. “We learn a lot more about stressors like food, what lack of food does to animals.”
Moore also noted that the model can help when trying to detangle whales from fishing gear. The model will allow veterinarians and conservationists to give an accurate dose of sedatives when freeing the whale.
Two co-authors of the study are already using the model to look at the links between survival rates of southern right whale calves and kelp gull harassment, which is when birds land on the backs of the calves and attack, which can negatively impact the calves’ health and survival rates.
Co-authors Mariano Sironi and Marcela Uhart, from the Southern Right Whale Health Monitoring Program, told Cosmos that “the use of drones to estimate whale weight and condition, as well as to individually track calves while they grow beside their mothers, has been a real breakthrough in our investigation.”