Biologists often announce that a certain kind of animal has been found capable of using tools; this usually refers to something like using a stick to hunt for ants in a log, or a stone to crack nuts  But such announcements are completely unsurprising, since all animals use tools  Birds build nests, fish hide in the mud to escape predators, and squirrels use buildings as shortcuts between trees
If an animal executes its purpose by means of an external physical object, then that object can reasonably be regarded as a tool
It calls into question the basis of the biologists' conception of a tool.