In a new study from the University of Leeds, experts report that dolphins can learn foraging techniques outside of the mother-calf bond. The research has produced the first evidence of socially learned foraging behaviors in dolphins.
The findings suggest that dolphins share cultural similarities with great apes, including chimpanzees, gorillas, and humans.
The dolphins of Shark Bay in Western Australia have been observed by scientists for decades. In the 1990s, it was discovered that the dolphins were using a new foraging technique called “shelling.”
When prey hides inside of empty snail shells, the dolphins use their beaks to bring these shells to the surface and then shake the food into their mouths.
Foraging techniques are usually passed from dolphin mothers to their offspring, which is referred to as vertical social transmission. Up until now, this was thought to be the only way dolphins learned methods for finding food. However, the new study shows that some dolphins in Shark Bay learned shelling by observing individuals other than their mothers, or through horizontal social transmission.
For the current study, an international team of researchers surveyed the western gulf of Shark Bay between 2007 and 2018 to investigate how shelling behavior spread across the population.
Overall, 42 shelling events performed by 19 individual dolphins were documented. Even though shelling seems to be rare, the entire process of shelling happens in a matter of seconds, so it is difficult to observe.
The team analyzed behavioral, genetic, and environmental data to model the different transmission pathways of shelling, which revealed that the behavior had been learned through horizontal social transmission.
“These results were quite surprising, as dolphins tend to be conservative, with calves following a ‘do-as-mother-does’ strategy for learning foraging behaviors,” said study lead author Dr. Sonja Wild.
“However, our results show that dolphins are definitely capable, and in the case of shelling, also motivated to learn new foraging tactics outside the mother-calf bond. This opens the door to a new understanding of how dolphins may be able to behaviorally adapt to changing environments, as learning from one’s peers allows for a rapid spread of novel behavior across populations.”
“For example, an unprecedented marine heatwave in 2011 was responsible for wiping out Shark Bay’s critical seagrass habitat. There was a subsequent die off of fish and invertebrates, including the gastropods that live in those giant shells.”
“While we can only speculate as to whether this prey depletion gave the dolphins a boost to adopt new foraging behavior from their associates, it seems quite possible that an abundance of dead giant gastropod shells may have increased learning opportunities for shelling behavior.”
Study senior author Professor Michael Krützen has been studying social evolution of great apes and marine mammals for nearly 25 years.
“The fact that shelling is socially transmitted among dolphin peers rather than between mother and offspring sets an important milestone, and highlights similarities with certain primates, who also rely on both vertical and horizontal learning of foraging behavior,” said Professor Krützen.
“Despite their divergent evolutionary histories and the fact they occupy such different environments: both dolphins and great apes are long-lived, large-brained mammals with high capacities for innovation and the cultural transmission of behaviors.”
The study is published in the journal Current Biology.
By Chrissy Sexton, Earth.com Staff Writer