Humpback whales may not have hands, but that doesn’t mean they’re inconvenient. A new study suggests that aquatic mammals should be classified as tool users because of their ability to catch krill using bubble nets.
Researchers discovered the whales in July 2019 off the coast of Alaska. Of particular interest is the actual composition of the webs, including their size and the distance between the bubbles. Over the next two years, the researchers returned for more expeditions and continued to measure the bubble network. They ended up documenting hundreds of bubble nets created by dozens of whales during that time. All documented webs contain multiple rings of bubbles, with each successive ring smaller than the last.
In a paper published in the journal Royal Society Open Sciencethey analyzed the data and found that the whales did not build their nets randomly. Instead, whales manipulate the size and composition of their webs in a variety of ways, including changing the depth of the web and the space between bubbles. Whales are able to do this by changing the speed at which they create bubbles, while still swimming at a constant speed.
These nets create barriers that trap krill, fish, and other food in a small area for the whales to feast on.
While concentrating prey into a small area might seem to pay off by requiring the whales to expend less energy, the researchers concluded that this is not the case. Humpback whales breathe at a similar rate to whales that do not use nets and instead pounce directly on their prey. They also found that the energy used to build the webs may be similar to the energy expended by whales that do not build webs while feeding.
Instead, the benefit may be that more food can fit into one bite. Scientists say whales that don’t build webs can perform up to 15 sprints for each sprint.
The researchers believe this behavior fits the definition of tool use, which they say is the purposeful use of “independent environmental objects” to alter, locate or otherwise control another object or organism.
“Many animals use tools to help them find food, but few animals actually create or modify these tools themselves,” Lars Bjed, director of the Marine Mammal Research Program at the University of Hawaii, said in a press release. “These whales expertly blow bubbles to form webs with inner rings, actively controlling details such as the number of rings, the size and depth of the web, and the spacing between bubbles.”
Tool-making abilities are found in a variety of species, including mammals, birds, fish, and insects, but are relatively rare among animals. No wonder aliens from the future are so eager to talk to humpback whales.
