Calorie tracking
Interestingly, the whales did not always use bubble nets. In Alaska, only about five to ten percent of whales eat bubble nets. “This is certainly due to the rarity, not the everyday occurrence,” says Bejder. “This also applies to all populations.”
During the three-day observation period, the team observed 70 to 80 whales feeding with bubble nets. But just a week later, the same whales stopped using this tactic. Why was that?
When and where humpback whales use bubble nets may be related to prey density. “It takes a long time to set these nets, and if the food is so dense that you don’t need a net, it might even be better not to,” Szabo says. But when prey is not very dense, bubble nets allow the whales to take advantage of an otherwise unavailable resource. “You can actually use these nets to turn something that wasn’t profitable before into a profitable food source,” he says.
Researchers now know that humpback whales (pictured here at Cape Evensen in Antarctica) can control the size and shape of the bubble rings they use to catch their prey. Photo by Yva Momatiuk and John Eastcott / Minden Pictures
While impressive, it’s not particularly surprising, says Jan Straley, a biologist and professor emeritus at the University of Alaska Southeast who has studied humpback whales since 1979. Humpback whales are known to use their bubble nets differently depending on prey location, environmental conditions and population density. She has observed young whales learning from their mothers and apparently copying new techniques from conspecifics.
“I think these whales really know their environment and the physics of their environment very well. They know the physical properties of the water column and how sound travels,” she says. “They’re really smart about their world.”
