Animal Encounters is a fine bestiary for Mongoose Traveller. Not only are the advertised encounters present for all sorts of worlds and habitats, but a very workable animal creation system. The creatures rolled will be unique and memorable thanks to the quirks system.
One complaint is that the animal NPCs in the encounter section do not have a size given. One is supposed to infer size from physical characteristics. The book is skimpy in the art department, but what's there isn't bad. Overall, this is a book that I definitely recommend. It takes the animal creation process from the core book and adds many options.
[4 of 5 Stars!]