The basic rules for generating animal/wilderness encounters and animals are pretty well defined in most versions of TRAVELLER . I am not looking for those today.
- The Gamelords Environment Series were the best at describing the particulars of a terrain, but unfortunately each only addressed a single terrain.
- T5 Core Rules is best overall IMHO as it provides the most varied terrains with descriptions and the terrains roll up into more generic terrains types at larger map scales.
- Cepheus Engine has Dirtside from Zozer Games.
- MgT 1e Supplement 11: Animal Encounters provided terrain definitions at least.
- GURPS 3e First In used "biomes" but they looked like "Terrain" from other Traveller versions.