Squirrel Cadogan Teapot

How do you fill this teapot?  The squirrel (or possibly rat?) lid does not come off, the entire teapot is one single piece.  Cadogan teapots are named after lady Cadogan who was reputed to have imported such teapots into Britain from China in the 19th century or encouraged them to be made by English potters.  This one is a miniature Cadogan teapot about 4 inches across.