There are some dead areas in the brushwork leading me to believe that studio work was involved here, although that need not mean Jan was not involved as well! Gaskell reports that the picture is in rather poor condition with various abraded areas and retouching over areas that had flaked, which could also explain why some areas seem dead. Based on Infrareds that show pentimenti around some of the animals, Gaskell argues that this is an early version of the subject and entirely by Jan -- possibly a work prior to the Doria Pamphilj picture to which it is closely related.