The premise of Doubutsu Banchou is quite simple: To hunt and be hunted as a creature of the wild, subject to the law of the jungle (or desert, plains or swamp) and striving to climb to the top of the food chain. You arrive in the world as a pig, comprised only of a head and one body piece.

In order to grow stronger, you must hunt and kill other animals and take from them their power by devouring their flesh. The mechanics of attacking and killing are to first target and tackle your prey and then devour them, finally killing them and getting piece(s) of flesh. Different animals have different colors each with distinctive characteristics and strength levels. The color of animal you kill corresponds with the color of flesh you receive.

The first area, a desert, is basically a transparent tutorial where you can familiarize yourself with the controls and basic hunting techniques while eating simple bugs and collecting attraction hearts. The main goal is to eat other animals and transform, growing strong enough to defeat the Animal Leader. If you eat another animal and swallow their flesh, a part of your body will assume the color of the animal you ate. If all of your body parts, which can vary in number from one to six depending on strength, become the same color, you transform into a new animal. What you transform into depends on how many body parts you have, the color of your body parts, and the shade of color (dark, normal, or light) of animal you’ve eaten.

When you eat a defeated animal’s flesh, their color properties are absorbed into your body and various changes take place. Piecemeal body color change is the fundamental effect of color absorption. When all parts of your body have become the same color, your overall shape will change, allowing you to grow stronger and take on different characteristics. Even if the shade of color of your body parts differ, but are of the same color, transformation is possible.

Eat flesh and transform! For example, if you eat a single piece of flesh, that particular color is assumed into your body. If you eat more (the necessary amount depending on the number of parts that make up your body) you will transform into an entirely different type of animal.

As the diagram indicates, if a two-part animal (in this case purple) eats one piece of blue flesh, one 'leg' part becomes blue.

Thus, if two blue parts are eaten, you transform into a blue animal with a new form.

In order to advance in the animal world, you have to kill and eat as many animals as possible and transform many times. Each time you transform into a brand new animal (one that you haven’t been before), you gain a ‘rank level.’ While the ultimate goal of DB is to defeat the animal leader, you must climb to the 100 rank (or ‘Lord of 100 Beasts’) before you are given the chance to do so. Thus, it is vital to transform as many times as possible to try an discover brand new forms, but at the same try to avoid de-evolving into a weaker animal by eating the wrong type of animal.