Well, here’s another putative example of “tool use” that people can debate, but this seems to qualify as the real thing—even given the various and conflicting definitions of animal tools (the one I like best involves carrying an object for future use).
Physorg.com reports that, in Shark Bay in western Australia, bottlenose dolphins (Tursiops aduncus) have been seen surfacing with a conch shell in their mouths, which they shake. This dislodges any small fish inside the shells, which are promptly nommed by the dolphins. Further, the behavior may be spreading—an example of cultural evolution:
A dolphin “conching” (photo from Phys.org)
It’s not clear whether the dolphins actually herd the fish into the shells to trap them, simply carry empty shells to the surface to capture any fish that may be inside (but how do they know that the shells don’t have the conch inside, which can’t be eaten?), or, as some researchers suggest, set out the shells, open side down, as fish traps to be harvested later.
“Shark Bay” may ring a bell with some of you. It’s not only a World Heritage Site, a marine reserve harboring large numbers of dugongs and dolphins, but also one of the few places on earth where we can see groups of living organisms, cyanobacteria (formerly called “blue-green algae”), that form structures nearly identical to some of the earliest traces of life on earth. These living bacteria form layers of biofilms that trap sediments which, over time, build up into dome-like structures called stromatolites.
You can see living stromatolites at only a few places on Earth, for they require special conditions, especially extremely salty water that precludes grazing animals who would quickly destroy the domes. Here are some stromatolites in Shark Bay:
Some fossil stromatolites, of undoubted biological origin, are 3.5 billion years old: the layers that they form are unmistakable, and absolutely similar to the layers of the modern, life-containing domes. Here’s an ancient stromatolite.