This anime is about a world inhabited by apes and there are two kinds of them : the civilized apes living by the sacred sea/lake and uncivilized apes living in the mountain.
The apes cannot travel to the distant city at the other side of the lake/sea since their God will get angry if they get in the water. They'll find at the end that this is lie and they can go wherever they want to.
The civilized apes wear hats all the time, because they're not supposed to show their ears in public.
There are no humans in the anime, so the main character is an ape who fell by accident from the mountain, home of the uncivilized apes, to the city, home of civilized apes. This ape (I forgot his name) came out to be a very clever and intelligent. I don't remember what he did, but I think he started to learn and became a brilliant savant, but I am not sure.
I watched the movie 3 or 5 years ago on TV and I think it was new at the time, but again, I am not sure.
The "style" and the atmosphere of the movie resembles to that of Spirited Away of Miyazaki. Though, it's not a Miyazaki movie.
Anyone knows this great movie ?