Stunned Cardassian vole
A Cardassian vole was an animal native to Cardassia Prime. Cardassian voles were about twenty-five centimeters long, had little hair on their bodies, and were generally regarded as pests. They had six legs and were attracted to energy fields. Voles featured spoon-shaped impression on their foreheads, similar to those of Cardassians, and lines at the base of the cheeks (under the ears).
Li Nalas likened Bajorans who were evacuating Deep Space 9 in 2370 to frightened Cardassian voles who were abandoning their homes. (DS9: "The Siege")
A pair of mating voles were said to "breed like tribbles", but that "they're not as cute." They had even been described as "disgusting hairy little creatures with ravenous appetites." They lived in nests, and were known to create secondary nests in addition to the main one. (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")
In 2370, 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 in 2373 and had to be temporarily closed down while they were exterminated. (DS9: "Playing God", "Ferengi Love Songs")
Although illegal in Bajoran space, it was possible to train Cardassian voles to fight. Quark was warned at least once by Odo that no live vole fights would be permitted on the station, and both he and Morn were once caught by Odo preparing a number of voles for a fight. (DS9: "Destiny", "Through the Looking Glass") There was apparently a market for their bellies. (DS9: "Body Parts")
Background
In Michael Westmore's Aliens: Season 2 from the DS9 Season 2 DVD special features, Michael Westmore explains that the voles were mounted on radio-controlled cars, that their teeth were made from acrylic, and their eyes from glass, and he notes that it was more complex to build a vole than a facial appliance. He also points out that because the voles are Cardassian, they too have the spoon design on their foreheads.
The script of "Playing God" described the vole as being "the Alpha Quadrant's nominee for ugliest creature in the galaxy".