Stunned Cardassian vole
A Cardassian vole is an animal native to Cardassia Prime. Cardassian voles are about 25 cm long, have little hair on their bodies, and are generally regarded as pests. They have six legs and are attracted to energy fields. Voles feature spoon-shaped impression on their foreheads, similar to those of Cardassians, and lines at the base of the cheeks (under the ears).
A pair of mating voles are said to "breed like tribbles", but that "they're not as cute." They have even been described as "disgusting hairy little creatures with ravenous appetites." (DS9: "Ferengi Love Songs")
In the mirror universe, Dr. Phlox was operating on a vole in 2155, when he heard Commander Jonathan Archer's announcement that he had taken command of Enterprise. (ENT: "In a Mirror, Darkly")
Deep Space 9 suffered an infestation of formerly uninhabited sections of the station. After the supposed eradication of the infestation, Quark's suffered from a further infestation and had to be temporarily closed down while they were exterminated. (DS9: "Playing God", "Ferengi Love Songs")
Although illegal, it is possible to train Cardassian voles to fight. Quark had been warned at least once by Odo about "vole fights" he had supposedly been preparing for. (DS9: "Destiny", "Through the Looking Glass") There was apparently a market for their bellies. (DS9: "Body Parts")
Background
Michael Westmore discusses the creation of the Cardassian vole in the DS9 Season 2 DVD's Special Features.
The script of "Playing God" described the vole as being "the Alpha Quadrant's nominee for ugliest creature in the galaxy".