The dog is not seen in game, but the many uses of the word dog implies it's existence in some form. Dogs bear similar characteristics to Burricks (sans the gastronomic based weaponry), such as grunting, panting and whining. Dogs have been known to be kept as pets.
Most of the time, the term is used as an insult, such as when a guard charges, and when a thief is searching. Other times it is used in metaphor, such as 'working like a dog'. The pirates that first invaded Markham's Isle called the light house owner a 'cripuld dog', Fey Weavers calls Grundholm a dog in a letter regarding poor quality helmets. The cook at the Rutherford Castle calls Lord Ember and Lord Julian dogs; one a scared poodle, and the other a whipped cur. City Watch Officers are known as 'bulls' or 'bulldogs'.
Alerted Thief Sword Guards occasionally threaten Garrett to unleash dogs against him when searching for him, however as there are no dogs ingame they simply continue their search until they find Garrett or give it up.
In the Stonemarket area, in Thief: Deadly Shadows, the background music has the barking of a dog, along with some turkey, rooster and calf call.
The dog's natural enemy is the Cat.