Beavers have historically been kept in captivity for entertainment, fur farming and conservation breeding. Zoos have displayed them since at least the 19th century, though not commonly. Captive beavers require access to water, substrate for digging, and artificial shelters. Archibald Stansfeld "Grey Owl" Belaney pioneered beaver conservation in the early 20th century. Belaney wrote several books and made the first professional film about beavers in their natural habitat. In 1931 he moved to a log cabin in Riding Mountain National Park, after he had been given the job of "caretaker of park animals", and raised four rescued beaver kits which were later released.