A new paper by Michael Krützen and colleagues (2005) presents evidence for extractive foraging in bottlenose dolphins. Evidently some individuals break marine sponges off the sea floor, wear them on their noses, and use them to probe the sea floor for fish.
The paper is a long consideration of whether this behavior might be a product of genetic inheritance, or fundamentally ecologically determined. They conclude that it is neither, and likely a good example of a behavior transmitted by social learning.
Krützen M, Mann J, Heithaus MR, Connor RC, Bejder L, Sherwin WB. 2005. Cultural transmission of tool use in bottlenose dolphins. Proc Nat Acad Sci USA 102:8939-8943. Full text online