A few dolphins in Australia’s Shark Bay have been observed using sponges plucked from the sea bottom to protect their noses while they search for food. In 1997 researchers proposed this as the first known use of tools by dolphins. The behaviour seems to be learned from their mothers:
Working with DNA from dolphins in Shark Bay–1 male sponger, 12 female spongers, and 172 nonspongers–the researchers found that all but 1 of the spongers shared markers in the DNA of their mitochondria, cellular organelles inherited exclusively from mothers. Despite examining 10 scenarios of inheritance, both for mitochondrial DNA and DNA from cell nuclei, the researchers were unable to explain genetically the observed female-biased pattern of sponge carrying.