Animal Treasure Island [どうぶつ宝島 Doubutsu Takarajima] (1971)
AKA Jolly Joker
Starring Minori Matsushima, Asao Koike, Eiko Masuyama, Fusako Amachi, Jouji Yanami
Directed by Hiroshi Ikeda
This film is pretty much what it says: an adaptation of Robert Louis Stevenson’s famous novel Treasure Island with lots of animals in it. The only human characters are the main character Jim, his baby brother Baboo, and a girl named Kathy who shows up about halfway through the movie. The rest of the cast are anthropomorphic animals of all kinds, and the film is full of all the swashbuckling seafaring adventure that you would expect of a pirate story.
I’ve never read the novel it was based upon, but I did look over a summary of the plot for comparison. It seems that Animal Treasure Island is a very loose adaptation. The basic premise is pretty much the only thing the two stories have in common. A boy named Jim with large dreams of exploring the ocean lucks upon a pirate treasure map and the money to finish his own homemade boat. So he sets off with his mouse pal Glan and his baby brother in tow, running afoul of pirates lead by a pig named Captain Silver.