From the back cover:
Once players start venturing out from the safety of civilisation and into the wilderness, they will be confronted with all manner of exotic and strange fauna. From deadly predators that will stalk a heavily armed party for weeks before making their lethal ambush, to harmless furballs that make for good pets, Animal Encounters will allow a referee to create new creatures to populate his worlds, each tuned specifically to its environment.
As well as providing many examples of animals already discovered on distant worlds, Animal Encounters not only provides a complete system for referees to create their own, but also a chapter on very strange animals, such as those that live in super-dense gravity environments, or those that can be found floating in the higher reaches of the atmosphere in a gas giant.