In a fascinating discovery, scientists have observed that humpback whales in Alaskan waters use bubbles as sophisticated tools to trap and capture their prey, challenging our understanding of tool use in the animal kingdom. The whales’ bubble-blowing behavior is not random; rather, it is a deliberate and complex strategy designed to maximize their food intake with minimal energy expenditure.
New Classification of Tool Use
Marine biologist Lars Bejder from the University of Hawaiʻi at Mānoa explains that these whales create intricate “bubble nets” to capture krill, their primary prey. The whales skillfully blow bubbles in patterns that form nets with internal rings, controlling variables such as the number of rings, the size and depth of the net, and the spacing between bubbles. This method allows them to catch up to seven times more prey in a single dive.
This behavior, according to the researchers, meets the criteria for tool manufacture and use, placing humpback whales among the rare group of animals known to create and use tools, such as crows, orangutans, and chimpanzees.
A Masterful Hunting Strategy
During the summer and fall, when humpback whales feed in Alaskan waters, they prepare for the long migration to Hawaii, where they give birth and raise their young during the winter months. During this time, the adults do not eat, making the feeding season crucial for their survival.
The whales’ bubble-netting technique is remarkably ingenious. A whale will dive deep, swimming in a circle around a shoal of krill, blowing bubbles as it goes. The rising bubbles form a cylindrical barrier, trapping the prey. The whale then swims up from below with its mouth open, consuming the trapped krill.
Learned and Cooperative Behavior
Not all humpback whales use this technique, indicating that it may be a learned behavior. Some whales also collaborate in these hunts, working together to create larger, more effective bubble nets.
To better understand this behavior, researchers used drones to film the whales from above and attached cameras and sensors to the whales using non-invasive suction cups. They documented 83 bubble nets produced by solitary whales, allowing them to analyze the shape, size, and spacing of the bubbles, as well as the energy cost of creating these nets. The results showed that bubble nets significantly increase prey capture without adding extra energy costs.
Implications for Conservation
Understanding how humpback whales hunt and forage is vital for their conservation. Although humpback whale populations recovered after commercial hunting was banned in 1985, recent studies have shown a worrying decline in their numbers between 2012 and 2021. By studying their foraging strategies, scientists hope to better protect their feeding grounds.
Marine biologist Andy Szabo of the Alaska Whale Foundation highlights the importance of these findings: “Humpbacks have developed complex tools that allow them to exploit prey aggregations that would otherwise be unavailable to them. This behavioral flexibility and ingenuity may be key to their survival as our oceans continue to change.”
The research has been published in Royal Society Open Science.
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