Drones: Weighing Whales and Assessing Associations

Candice Gaukel Andrews November 9, 2021 0
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Drone technology is now helping to reveal secrets from the natural world, including weights of whales and the workings of cetacean social connections.

Baleen whales, which include species such as blue and gray whales, are the largest animals on Earth. Their hefty body masses, in fact, are central to their success as an animal group. Because of their large sizes and aquatic life, however, whales are hard to weigh. But researchers have now devised a way to accurately estimate the weight of free-living whales using only aerial images taken by drones. And by adding these small, uncrewed aircraft to their tool kits, scientists have been able to dive into the social lives of cetaceans as never before.

Aerial shots by drones offer unique points of view, showing behavior, movements and patterns that otherwise would go unseen. For example, drones have taken breathtaking shots of bobcats relaxing in the woods, migrating herds of wildebeests flowing across African plains and ice shapes forming around boats in the Great Lakes.

Now, drones are revealing the secrets of whales, both behaviorally and physically.

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Aerial shots by drones offer unique points of view and reveal patterns that are hard to see by any other means.

Whale weight

In the past, the only way to obtain data on the body masses of whales was to weigh dead ones, with most samples coming from accidental fisheries bycatches, beach-stranded individuals or whaling operations. However, basing data on dead whales has limitations, such as being unable to collect longitudinal data over a whale’s life span and inaccuracies from physical distortion of carcasses caused by bloating and deflation.

But now, researchers have created a method of accurately estimating the weight of free-living whales solely by using drone photography.

Working off the coast of Patagonia’s Peninsula Valdes in Argentina, scientists first took aerial photos of 86 southern right whales. The clear waters and the large number of whales that gather here every winter for breeding made it an ideal place to collect high-quality images of both the dorsal and lateral sides of the whales. From these drone shots, they were able to obtain height, length and width measurements.

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Natural threats to southern right whales include diseases and predation from orcas and large sharks. Kelp gulls have also been observed attacking these whales.

Tested against the body volume of whales caught in scientific whaling operations—for which body girth and mass were known—the researchers were then able to take these drone-obtained measurements and use them to accurately model the body shape and volume of the Patagonia southern right whales.

The model yielded body mass estimates to a high level of accuracy, although there were some limitations due to the relative proportion of different tissues in baleen whales. The researchers had to assume a constant body density in each whale, which is not realistic as the ratio of different body tissues (such as fat and muscle) changes seasonally as whales deposit or lose body condition.

Still, this groundbreaking method opens new avenues for research. It can be used to learn more about the ecology and physiology of whales. Scientists will now be able to look at the growth of known-aged individuals to calculate the increases in their body masses over time and the energy requirements for growth. They’ll also be able to look at the daily energy requirements of whales and calculate how much prey they need to consume. And weight measurements of live whales at sea inform how chronic stressors affect the mammals’ survival and fecundity, as well as enabling accurate sedative dosing of animals entangled in fishing gear that are averse to attempts to free them.

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From early June to the beginning of November, hundreds of right whales come close to the shore of Patagonia’s Peninsula Valdes to mate and breed, making it an ideal place to film the animals by drone.

The researchers say that their model is already being used to assess the impacts of kelp gull harassment on the health and survival of southern right whale calves. The use of drones to estimate whale weight and condition, as well as to individually track calves while they grow beside their mothers, has provided breakthroughs in cetacean investigations.

The model also allowed the researchers to collaborate with the Digital Life project at the University of Massachusetts Amherst to re-create a 3D mesh of a whale and to work with a computer graphics artist to make a full-color, 3D model of a right whale. Such models can be used for scientific purposes, such as studying movement, as well as for educational activities.

In addition, by adjusting the parameters of the model, the method could be used to estimate the size of other marine mammals where alternative, more invasive approaches aren’t feasible or desirable.

Southern right whales were hunted extensively by the whaling industry until the 1960s. Current threats include fishing gear entanglement, industrialization of coastal habitats, ocean noise, vessel strikes and climate change. ©Nestor Galina, flickr

Cetacean connections

Not only are drones being used to collect physical data on whales, they are also being employed in studies regarding whale cultures.

Orcas, sometimes known as “killer whales,” have complex social structures—including close friendships—according to a new study that used drones to film the animals over a 10-day period. The 651 minutes of drone footage that resulted showed that southern resident orcas, a critically endangered population found only in the waters off the West Coast of the United States and Canada, ranging from Northern California to Southeast Alaska, spend more time interacting with certain individuals in their pod and tend to favor those of the same sex and of similar age. Results of the study also demonstrated that the whales become less socially connected as they get older.

Until now, research on orca social networks had relied on seeing the whales when they surface and recording which whales were together. However, because resident orcas stay in the social groups into which they’re born, how close the related whales were seemed to be the only thing that explained their social structure. But looking down into the water from a drone allowed scientists to see details, such as contact between individual whales. And even within their tight-knit groups, they found that the orcas preferred to interact with specific individuals. Patterns of physical contact—one of the social interactions the study measured—suggested that younger whales and females play a central social role in the groups. The older the whale, the less socially influential it became.

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Images of orcas captured by drones allowed scientists to see how much physical contact occurred between whales. Even within tight-knit groups, each whale preferred to be with specific individuals.

In many species, including humans, physical contact tends to be a soothing, stress-relieving activity that reinforces social connections. But the researchers say that they were amazed to see how much contact there is between whales; how tactile they are. They also examined occasions when whales surfaced together, as acting in unison is a sign of social ties in many species. They concluded their remarks by stating that they found fascinating parallels between the behavior of whales and other mammals and are excited about the next stages of this research.

Drone denigration

Drones have gotten a bum rap in many outdoor spaces. They have been crashed in once-pristine places and used to invade people’s privacy. But drones are just tools. And as with any other implements, drones can be bad or good depending on the actions and purposes of the people flying them.

Weighing whales and assessing cetacean connections seems, to me, to fall into the latter category.

Here’s to finding your true places and natural habitats,

Candy

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