Fauna is all of the animal life of any particular region or time. The corresponding term for plants is flora.
In Grand Theft Auto: San Andreas, there is much fauna for the player to discover. However, most of it is lurking beneath the waters of San Andreas. If the player dives underwater while swimming, they can find jellyfish, dolphins, clownfish among other varied kinds of wildlife. If the player swims into wildlife (or a group of it), they will just swim away faster. Simple hawks and seagulls made out of particle textures can be seen flying in the skies. (However you cannot shot those birds out of the sky, no matter how good your aim is.) Flies can also be found next to garbage cans.