Disclosed is a trailer for attachment to a vehicle. The trailer includes a frame having a first side and a second side that define a bottom area bordered by the first and second sides. Connected to the frame is an attachment arm configured to attach the trailer to the vehicle. At least one floor panel, supported by the frame, is included and is configured to selectively transition between a riding position and a running position. When the floor panel is in its riding position, the trailer is configured to carry and transport an animal. When the floor panel is in its running position, the trailer is configured to exercise the animal such that the animal is free to move under its own power in connection with the vehicle as the vehicle moves.