Rodent tool use

It's not just any rodents, but the "highly social, intelligent" degus. And they don't use tools in their natural habitats, but were taught specially by researchers. But it's still pretty interesting:

After two months of practice, researchers say, the degus can move the rake as smoothly and efficiently as croupiers in any Las Vegas casino.
This is first time rodents have been trained to wield tools, said Atshushi Iriki, a neuroscientist, who led the experiments at the Laboratory for Symbolic Cognitive Development at the Riken Institute in Tokyo. But other species may soon join them.
While it has long been thought that tool use is a hallmark of higher intelligence, Dr. Iriki said, the brain structures that underlie such abilities may lie dormant in many animals with good hand-and-eye or paw-and-eye coordination. Training them to use tools in captivity provides insights into the plasticity of their brains, he said, and may shed light on how early humans evolved tool use in the first place.

A high degree of sociality also probably makes a difference to the ability to learn these behaviors.

In separate studies, they are examining gene expression in the brains of macaques and marmosets trained to use tools.