Some bottlenose dolphins in Shark Bay, Western Australia, display an extraordinary and rare example of animal tool use: they wear marine sponges on their beaks to hunt fish hiding in the seafloor.
Known as “sponge foraging” or “sponging,” this behavior involves dolphins placing a marine sponge over their snout—much like a clown nose—to protect it while they dig into the sandy seabed to flush out hidden prey such as barred sandperch.
Sponge-Tool Hunting: A Complex Learned Skill
According to a new study published in the journal Royal Society Open Science, this technique is not as simple as it may appear. While it offers significant advantages in finding prey, it also comes with trade-offs. The sponge muffles the dolphin’s echolocation, a key sensory ability used for underwater navigation and hunting.
“It has a muffling effect, much like wearing a mask,” explained marine biologist Ellen Rose Jacobs from Aarhus University in Denmark, co-author of the study. “Everything sounds a little different, but experienced dolphins adapt and compensate for it.”
Using underwater microphones, Jacobs confirmed that dolphins continue using echolocation clicks even while wearing the sponge. However, modeling revealed that the sponge distorts these sound waves, making precise hunting more difficult.
Only a Few Dolphins Master the Technique
Despite its advantages, sponge foraging is a rare behavior. Fewer than 5% of the bottlenose dolphin population in Shark Bay—around 30 individuals—practice this technique. The reason? It’s incredibly hard to learn.
“It’s like hunting while blindfolded—you have to be very skilled and well-trained to succeed,” said Mauricio Cantor, a marine biologist at Oregon State University, who was not involved in the research.
Marine ecologist Boris Worm from Dalhousie University adds that sponge hunting takes many years to master. Not all young dolphins stick with it, and only the most persistent develop the skill.
A Cultural Tradition Passed from Mother to Calf
What makes this even more fascinating is how the skill is transmitted. Sponge tool use is not instinctive—it’s cultural. Dolphin calves learn it by observing their mothers during the early years of life, typically between ages 3 to 4. The behavior is exclusively passed down from mother to offspring.
“This is one of the few known examples of cultural tool-use in wild marine mammals,” said co-author Janet Mann, a marine biologist at Georgetown University.
Evolutionary Trade-Offs in Animal Behavior
The study, titled “Cultural transmission of animal tool-use driven by trade-offs: Insights from sponge-using dolphins” (DOI: 10.1098/rsos.241900), highlights how animal traditions and learned behaviors evolve under ecological pressures. While sponge foraging protects dolphins’ beaks and improves hunting in certain habitats, it also requires them to overcome sensory limitations—demonstrating a fascinating trade-off between efficiency and complexity in nature.