Strict liability, double damages after notice
Wisconsin's dog statute, Wis. Stat. 174.02, makes the owner liable for the full amount of damages a dog causes, and for twice the damages in the narrow circumstances of a repeat bite. A State Bar of Wisconsin article explains that no bite is required.
The Court of Appeals addressed double damages for a pack of dogs in Schroeder v. Kistner (2014), and the deadline is three years.