From Discworld & Terry Pratchett Wiki
The Beagles are a race of canine-derived beings whose path to sentience made them the dominant mammal on their homeworld, known to us as Earth West 1,617,524. On this planet they occupy the evolutionary niche taken by humans on Datum Earth and inhabit a planet ruled by warring Clans, who periodically indulge in destructive wars with each other. They are ruled by a matriarchy composed of the oldest and most cunning bitches in each pack, and males, such as Brian the Beagle are scorned. Humans have Stepped through this world. The Combers who have passed this way have a warped sense of humour and a knowledge of Datum Earth television and film trivia, seemingly, as not only did they bestow the name "Beagles" for a proud race (think of comic art's most famous beagle, Snoopy), individual dominant animals are proud to carry names like "Petra", "Brian" and "Snowy".