From the publishers website:
Some people like to talk about the peace and tranquility of nature. Their eyes glaze over, and they rave about cool breezes, fresh air, and flittering butterflies.
They're not paying attention, and that makes them easy pickings for any of the predators, including me. The Sixth World's a place of eating or being eaten. Sometimes the critters are waiting deep in the jungle; other times they're hiding in your bedroom closet.
Proving you're the fittest only ends when you aren't anymore. Know your prey—it's the only way to catch them. But remember, you just might be something's prey too.
Running Wild is a sourcebook for Shadowrun, Fourth Edition. It presents a detailed overview of the animals, spirits, and other non-metahuman entities that dwell in the Sixth World: from mundane animals that have survived the incursions of mankind, to paranormals that have Awakened, to emergent animals that have found their own ways to embrace the Matrix, to the spirits and feral AIs that may not even acknowledge metahumanity. Game rules and mechanics are provided for these beings and their unusual abilities, but so are rules for characters to interact with, to augment, and to train the critters presented. Every living being is constantly in search of its ecological niche, Running Wild can make a campaign home to hundreds of them.