Bottlenose dolphins in Shark Bay, Western Australia, are intentionally using sea sponges as tools to protect their snouts while foraging on the seafloor, a behavior researchers have been documenting for decades. The practice, observed in a subset of the local dolphin population, shields the animals from abrasions caused by rocks and the stings of hidden marine life.
The behavior was first noted by researchers with the Shark Bay Dolphin Research Project in 1984, and has been the subject of ongoing study. Currently, Dr. Ellen Rose Jacobs of Aarhus University is leading research focused on understanding the mechanics and implications of “sponging,” as the practice is known. Jacobs and her team are investigating how the sponges alter the dolphins’ sensory perception during hunts.
According to recent findings, the sponges act as a buffer against physical harm, but also subtly distort the dolphins’ echolocation abilities. Dolphins rely on clicks emitted through an organ called the melon, and interpret the returning echoes via their lower jaw to locate prey. When a sponge is held over the snout, the sound waves are altered as they pass through the sponge tissue twice, scattering energy and affecting timing. “Everything looks a little bit weird, but you can still learn how to compensate,” Jacobs explained during fieldwork in Shark Bay.
The utilize of sponges is not widespread among the Shark Bay dolphin population. Data indicates that only approximately 11% of adult female bottlenose dolphins engage in the behavior. Researchers are working to understand why this tool use is limited to a specific segment of the population and how the knowledge is transmitted across generations. The transmission of this learned behavior is considered a rare occurrence in the animal kingdom.
The research team’s operate involves tracking both the dolphins and the sponges themselves, analyzing how the dolphins select specific sponge types and the impact of the tool on their foraging success. The altered sensory input created by the sponge requires the dolphins to adapt and refine their hunting techniques, demonstrating a level of cognitive flexibility.
