Humpback whales may not have hands, but that doesn’t mean they aren’t dexterous. A new study argues that the aquatic mammals should be counted as tool users because of their ability to catch krill with nets made of bubbles.
The whales in question were spotted by researchers off the coast of Alaska in July 2019. For five days, the scientists filmed the whales building their bubble nets, a widely observed behavior. Of particular interest was the actual composition of the nets, 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 nets. During this time, they ultimately documented hundreds of bubble nets built by dozens of individual whales. All of the documented nets contained multiple circular bubble rings, with each successive ring smaller than the previous one.
In an article published in the journal Royal Society Open ScienceThey analyzed this data and found that the whales did not create the nets randomly. Rather, the whales manipulated the size and composition of the nets in various ways, including changing their depth and the distance between the bubbles. The whales did this by changing the speed at which they created the bubbles while continuing to swim at a constant speed.
The nets formed barriers that served to herd krill, schools of fish and other food into a small area where the whales could then enjoy their feast.
Although it may seem that herding prey into a small area pays off because it means the whales have to expend less energy, the researchers concluded that this is not the case. The humpback whales breathed at a similar rate to whales that did not use nets and instead simply pounced on their prey. They also found that the energy used in building the nets was likely similar to that of a whale that does not build nets and is expended while feeding.
The advantage may be that they can catch more food in one bite. The scientists said that for every attack by a net-building whale, a whale without nets would make up to 15 attacks. Overall, they estimated that the prey density of the tool-building animals was seven times higher than that of their aggressive counterparts.
The researchers argue that this behavior fits the definition of tool use, that is, the purposeful use of an “unattached object from the environment” to modify, position, or otherwise control another object or organism.
“Many animals use tools to find food, but very few make or modify these tools themselves,” said Lars Bejder, director of the University of Hawaii’s Marine Mammal Research Program, in a press release. “These whales deftly blow bubbles in patterns that form webs with internal rings, actively controlling details such as the number of rings, the size and depth of the web, and the spacing between the bubbles.”
The ability to make tools has been found in many species, including mammals, birds, fish, and insects, but it’s relatively rare in animals. No wonder future aliens are so desperate to talk to humpback whales.
