Dolphins on opposite sides of Australia, thousands of kilometres apart, have independently learned to use a remarkable invention: chasing fish into empty seashells and tipping the trapped meal into their mouths. This behavior, known as 'shelling', has been observed in both Shark Bay on Australia's west coast and Hervey Bay on its east coast. The study, published in Marine Mammal Science, presents the first published records of this behavior from Queensland's Great Sandy Marine Park, adding to the growing body of evidence that dolphins on opposite sides of the continent have independently invented the same tactic.
The behavior is fascinating because it showcases the ingenuity of dolphins in adapting to their environment. By using empty seashells as traps, dolphins can effectively catch fish that would otherwise be difficult to capture. This invention is not just a simple tool use; it requires a combination of skills, including the ability to locate suitable shells, exploit the fish's tendency to hide inside them, and manipulate the shell to bring the prey within reach.
What makes this discovery even more intriguing is the geographic separation between the two populations. The authors of the study emphasize that there is no plausible chain of ordinary dolphin associations connecting the two study sites, suggesting that the invention of shelling is an independent development. This raises questions about the mechanisms of innovation and cultural transmission in dolphins.
The study also highlights the importance of social learning in the spread of this behavior. While the dolphins in Shark Bay have been observed using shelling, the authors found that the strongest support for transmission through social associations. Dolphins were estimated to be 10 to more than 300 times more likely to acquire shelling through their social network than through genetic inheritance or learning alone. This suggests that the invention of shelling can spread horizontally between peers or obliquely from older non-parents to younger animals.
The Hervey Bay mother-calf sequence adds a possible transmission route, as the calf picked up the same shell three minutes after watching its mother use it. However, the researchers caution that this is not conclusive evidence of deliberate teaching, and further observations are needed to understand the mechanisms of social learning in dolphins.
In conclusion, the discovery of dolphins using shelling on opposite sides of Australia highlights the ingenuity and adaptability of these marine mammals. It also raises questions about the mechanisms of innovation and cultural transmission, and the role of social learning in the spread of this behavior. Further research is needed to fully understand the extent and mechanisms of this remarkable invention.
