All the animals you see are real, there is no CGI use.
Diane Ackerman's non-fiction book was greatly inspired by the unpublished diary of Antonina Zabinska and Jan Zabinski, the director of the Warsaw Zoo in Poland.
Director Niki Caro stated that her first film cut was nearly three and a half hours long, utilizing the entire screenplay. The final film was required to be two hours in length, and so an hour and a half was cut from the film in the editing room.
In between takes, Jessica Chastain claims she was taught "the nastiest German" swear words by co-star Daniel Brühl.
The current Warsaw Zoo opened on 11 March 1928. However, its roots can be traced to 17th century private menageries.