Researchers in Japan’s Institute of Physical and Chemical Research have taught degus how to use rakes to obtain food. Degus are small rodents closely related to chinchillas. This is apparently the first instance in which rodents have been taught to use tools.
(Degus learn to use rakes video)
The degu is placed on one side of a fence and sunflower seeds are placed on the other side. When provided with a small rake, the small rodents pull the seeds through. Degus are also referred to as the Brush-Tailed rat, even though they are closer to guinea pigs and chincillas. They are social animals who are able to coordinate their digging activities in constructing large burrows.
Science fiction fans are irresistibly reminded of the wonderful 1962 novel Little Fuzzy by H. Beam Piper. Although written as a juvenile, this novel has a grown-up preoccupation with the basic question "What makes us human?"
In the story, a distant planet is colonized under a charter to a large corporation. However, one of the conditions of the charter is that the planet does not have any sapient, human-like intelligent life.
The corporate lawyers are not very happy when a sol stone miner named Jack Holloway finds an odd little creature in his house, and then sees him using tools.
(Little Fuzzy cover art)
Here's a good example of their tool-using abilities.
A land-prawn, which must have gotten in while the door was open, was crossing the living room. Little Fuzzy ran after and past it, pivoted and brought the corner of the chisel edge down on the prawn's neck, neatly beheading it... then slid the chisel under it and flopped it over on its back, slapping it twice with the flat and cracking the undershell.
In their extraordinary 1974 novel The Mote in God's Eye, Larry Niven and Jerry Pournelle write about a race of beings trapped in an isolated solar system. One subspecies, the Watchmakers (nicknamed the Brownies), are small, rodent-like animals with remarkable tool-using abilities. Without realizing the danger, human visitors to the Mote allow Brownies into their ship. Eventually, the brass are concerned.
"Gunner, have you ever heard of 'Brownies' aboard this ship?"
"Well, not officially, Captain. I will say some of the spacers lately seem lately to believe in the Little People..."
"Some of the men in my watch sections, Captain - they say that if ye leave some food - grain, cereals, mess left-overs, anything at all - in the corridors or under your bunk along with something that needs fixing, it gets fixed."
...Microscopes with smoother focusing operations than the best things ever made by Leica Optical. A handmade lamp in the biology section. Boots and shoes customized to individual feet... sidearms individualized...