"Sponging" Dolphins May Reveal Animal Culture
Culture, "the act of developing the intellectual and moral faculties especially by education," was once thought of as only a human trait. Today, we know it is present in some animal societies. However, only primates have demonstrated methods of tool use that are learned through culture—until now. Off the coast of Western Australia at Shark Bay, 15 bottlenose dolphins and seven of their offspring seem to pass on the behavior of using sea sponges as tools for protection.
Biologists first witnessed dolphins with sea sponges over their beaks two decades ago and have studied the clever "spongers" ever since. "Sponging" occurs when a bottlenose dolphin picks up a sea sponge from the ocean floor and wears it over her beak as protection from sharp coral and unknown hazards, possibly while foraging for fish and other prey. Unfortunately, it is difficult to observe these animals on the ocean floor.
In June, a group of researchers from around the world published an online study of the Shark Bay dolphins. Findings from the study ruled out any ecological explanations, and since none of the other approximately 119 dolphins in the area are spongers, biologists have concluded habitat is not forcing the behavior. The research also determined any genetic link or common "sponging gene" among the dolphins is highly unlikely.
"When we looked at all these possible transmission mechanisms on a family and population level and compared it with our actual genetic data, we found it did not agree," research leader Michael Krutzen told The Washington Post. This means sponging is the first case of material culture documented in a marine mammal species.
The dolphins do share a maternal gene, indicating they are all descended from an original sponging female. And unlike tool use in apes, sponging is almost exclusively socially transmitted within a matriline that is part of a larger population. Young dolphins, both male and female, spend their first years with their mothers, gaining the essential development of foraging skills—but only one of the 15 adult spongers is male.
Many studies have found dolphins to have complex cognitive ability, and they are known for their imitative skills. Therefore, it is not surprising that they are capable of social learning. While social learning is not always indicative of culture, researchers studying the Shark Bay dolphins believe their unique behavior should fit the definition. These scientists are interested in the parallels between primates and dolphins, and they will continue to challenge our primate-centric views of tool use and culture.