Once thought to be a uniquely human characteristic, the use of tools is considered a sign of intelligence. Only a handful of animals have been credited with employing tools.
A tool is defined as any physical item that can be used to achieve a goal, especially one that is not consumed in the process. For example, sea otters use stones as tools to crack open mollusc shells so as to eat the abalone inside.
Interestingly, dippers face a problem similar to that of sea otters, but with caddisfly larvae. The larvae are encased in found materials (sand, wood) that prevent easy access to the grub inside. A solution sometimes employed by a dipper is to shake off the casing. That, of course, does not represent using a tool, which would necessitate using of an external physical object for the task.
However on this occasion, a dipper does seem to make use of a tool.
A dipper surfaces from a dive with a caddisfly larva encased in found material. Dot is standing in shallow water atop anchor ice.
To remove the casing, Dot swishes it through the water. The water has become the tool that is used to remove the casing, much as a rock is used to remove a shell by a sea otter.
The casing having been removed, the grub is exposed.
Five seconds after the first picture, the larva has been consumed.
Can we really credit this dipper with having employed a tool to gain access to the grub?