Ferret 16 Month 2012 Calendar. The ferret is a domesticated animal kept primarily as a pet. It belongs to the Mustelidae family which contain a number of other small, elongated carnivorous mammals. Contrary to popular belief, ferrets are not rodents; this is a common mistake as they are often linked with Rats, Mice and such like. Ferrets are more directly related to other mammals such as weasels, stoats, and martens. This colourful square wall calendar features 16 months and 13 full colour photographs of this inquisitive creatures.