Tool use by dolphins

Bottlenose dolphins spear sponges with their noses and then poke around in rocky crevasses to scare out the fish hiding inside or swab the sandy sea floor to expose hidden, burrowing prey. The sponges protect their noses, and the custom has persisted for generations, passed down from mother to offspring.

This is not a new discovery; it was first discovered several years ago. But now more information is available at the link above and at this research paper. (image credit here)