A young human, the player, takes the train to move to a town populated by animals. On the train, a cat named Rover greets the player and asks them about their move; upon finding out the player has no place to stay, he calls Tom Nook. Nook greets the player upon arriving in town and lets them pick out a house; he then has them work part-time at his shop to help pay off their home loan and get acquainted in the town.
Doubutsu no Mori has no required objectives; after the player completes their part-time job for Tom Nook, they are free to do as they wish. One objective given to the player by Nook is to pay off their home loan, though this is entirely optional. The main mechanic of the game is its real-time clock; the town goes through day-night cycles and adjusts with the seasons, affecting what the player can do. The clock continues to advance when the game is turned off.[nb 2]
Up to four players can live in a town, and each has their own house. Players can interact with each other by sending letters, but only one player can play at a time.
The town, named by the player, consists of 30 acres (6 rows, 5 columns) and has establishments and villager houses spread throughout it. It is bordered to the north by train tracks, on the sides by cliffsides, and to the south by the sea. The town’s foliage includes trees, flowers, and bushes. The town is bisected by a river and split into two or three layers separated by inclines.
Buildings in the town include the four player houses, which can be decorated with furniture; Tom Nook’s store, which sells various items; the post office, where the player can send letters; and the police station, where random items appear in the lost and found. Aside from the buildings in town, there are other structures and landmarks, including the train station, where the player can travel to other towns; the dump, where items can be discarded; and the shrine, where certain events take place and the player can check the town’s Field Rank.
The town is populated by animal villagers with whom the player can interact. Each villager has one of six personality types (lazy, jock, and cranky for males; normal, peppy, and snooty for females) that determines their dialog. The player can speak to villagers either to have a conversation, or to request that the villager give them a favor to do. The player can write letters to villagers using stationery and mail them at the post office.
The town starts with six villagers, with more moving in over time until a maximum of 15 is reached. Once this maximum is reached, villagers occasionally move out and are replaced with new ones. There are a total of 216 villagers in the game.