...a rare example of a large-scale animal study by the artist. Until recently the painting had been described as by a follower of Sir Anthony Van Dyck, however the authorship had been difficult to discern due to overpaint and background added later that dominated the original scene. With the removal of these later additions, the canvas has been revealed as a work of high quality, and a typical example of the spirited and rapidly painted oil sketches for which Rubens is celebrated. A similar composition and pose is evident in the foreground of Rubens’ Henry IV at the Siege of Amiens, at the Gothenburg Museum of Art.
[http://arthistorynewsreport.blogspot.nl/2017/01/sothebys-master-paintings-evening-sale.html]