Tool use among animals is a research topic that has captured the attention of many scientists and researchers for decades. Traditionally associated with primates and some birds, this behavior is a sign of intelligence and adaptability. However, a recent study has revealed that humpback whales not only use tools, they make them with surprising sophistication.
Bubble webs can be understood as complex structures created by these whales to improve their feeding efficiency. By controlled release of air from their blowhole while swimming in group circles, humpback whales create curtains of bubbles that act as barriers to concentrate their prey, mainly krill.
This discovery not only expands our understanding of tool use within the animal world, but also sheds light on the remarkable intelligence and adaptability of these cetaceans. The ability of humpback whales to use these movements for their own benefit demonstrates their cognitive and behavioral flexibility, which could be crucial for their survival in increasingly changing marine environments given the environmental problems facing our planet and all its inhabitants.
In this article, Let’s explore in detail how humpback whales have learned to use toolsexamining the structure of bubble nets, their manufacturing process, and the benefits they bring to these fascinating giants of the ocean.
Tool use is generally defined as the use of existing objects in our environment to more efficiently alter the shape, position or condition of another object, organism or the user themselves. Some researchers have emphasized the intentional nature of tool use and its role in problem solving.
Although several species of mammals, birds, fish, and insects have been studied for their tool use, this behavior is considered relatively rare. Even rarer are the species that make or modify their own tools, such as chimpanzees, orangutans and New Caledonian crows.
Conscious tool making often involves complex sequences of behaviors, such as selecting and modifying natural materials.. This sophisticated behavior, along with the finding of greater brain size and complexity among tool-making species, has led researchers to suggest that the rarity of tool use and making is cognitively limited in its taxonomic distribution.
Humpback whales have been seen and studied producing complex bubble webs to promote their feeding. Therefore, they are among these rare species that make tools and make profits by modifying their environment.
Bubble nets: a unique tool
Bubble nets are considered complex structures created by humpback whales and observed in their process of foraging and subsequent feeding. These aquatic tools are formed when whales (consciously?) release air from their blowhole as they swim in a circular pattern beneath the water surface. The rising bubbles create vertical curtains that, when viewed from above, appear as one or more concentric rings.
Research has revealed that bubble webs produced by solitary whales consist of 1 to 6 tangential internal rings, generating an average of 3.1 rings per web. The area of the average inner ring was 37 square meters, being significantly smaller than the outer ring. Interestingly, the size of the inner ring does not correlate with the body length of the creator whales, but does decrease as the number of rings in the web increases.
A crucial aspect to understanding these bubble networks is the distance between neighboring bubbles, delimited by researchers as the “mesh size.” In the inner ring, this distance was shown to be significantly smaller (1.2 meters on average) than in the outer ring, generating a more effective barrier to contain prey.
The whales were seen initiating bubble production at an average depth of 22.1 meters, continuing their descent while deploying their net. The complete creation of these bubble networks was temporally measured at an average of 80 seconds. This sophisticated technique for manufacturing tools to obtain food demonstrates the intelligence of whales to increase their feeding efficiencyallowing them to exploit resources that might otherwise be energetically unprofitable.
Tool use in whales
The research was conducted in Southeast Alaska, using novel, cutting-edge technology to observe, study and analyze the behavior of solitary humpback whales during bubble net feeding.
The researchers used unmanned aerial systems (UAS or drones) equipped with high-resolution cameras and laser rangefinders to capture detailed aerial images of the whales and their bubble nets. This allowed us to precisely measure the length of the whales and the structural characteristics of the webs, such as the number of rings, the area of each ring, and the distance between neighboring bubbles.
Additionally, CATS (Customized Animal Tracking Solutions) data recording tags attached to the whales were used. These devices included motion sensors, video cameras and pressure sensors, providing detailed information on the speed, orientation and depth of the whales during netting and feeding.
To complement these observations, standard photo-identification techniques and dual-frequency echo sounders were used to estimate the depth of prey layers in the vicinity of the whales. This combination of technologies allowed researchers to gain unprecedented insight into the process of making and using bubble nets by humpback whales.
Key findings of the study
The study revealed fascinating details about the structure of bubble nets and the behavior of humpback whales during their creation and use.
In terms of structure, bubble networks were found to be more complex than previously thought. They consist of multiple concentric rings, with an average of 3.1 rings per network. The inner ring, crucial for prey concentration, has an average area of 37 square meters, significantly smaller than the outer ring. Interestingly, the size of the inner ring is not related to the size of the whale, but decreases as the number of rings in the network increases.
An important finding was the difference in the “mesh size” (distance between neighboring bubbles) between the inner and outer rings. In the inner ring, this distance has an average measurement of 1.2 meters, while in the outer ring it is significantly greater. This denser structure in the center thus creates a more effective barrier to contain prey.
In terms of behavior, whales begin producing bubbles at a depth of approximately 22.1 meters. They maintain a constant speed of 1.5 meters per second during the creation of the network, which takes around 80 seconds. They then accelerate at 2.1 meters per second as they ascend through the center of the web to feed quickly.
One of the most significant findings was that Bubble nets concentrate prey (mainly krill) up to 7 times their natural density. This allows whales to efficiently exploit low-density prey patches that would otherwise not be energetically profitable.
Surprisingly, the production of bubble nets does not appear to significantly increase energy expenditure compared to feeding without networking. However, it was observed to reduce the rate of diving lunging compared to other feeding methods.
Implications and discussion
The use of bubble nets by humpback whales demonstrates remarkable intelligence and adaptability in their foraging behavior. This technique allows them to exploit food resources that might otherwise be energetically unprofitable, thus expanding their ecological niche.
The manufacturing of these tools appears to be a specific response to particularly challenging feeding conditions.such as shallow, low-density prey patches. In these situations, bubble nets offer an advantage by significantly increasing prey concentration without an apparent increase in energy expenditure as attacks occur.
However, the relatively infrequent use of this technique (according to the study, these correspond to only 2.8% of whales observed in systematic studies) suggests that there are associated costs that limit its widespread application. The reduction in lunge rate by immersion compared to other feeding methods could be one of these costs.
Thus, humpback whales have demonstrated a remarkable ability to make and use tools by creating bubble webs to improve their feeding efficiency. This behavior allows them to concentrate low-density prey, increasing their intake without significantly increasing energy expenditure. This finding highlights the intelligence and adaptability of whales, suggesting that they can exploit broader ecological niches in a changing marine environment.
