Become a Creature Cowboy and round up those critters. Use your Gravity Gun to pick up the creatures and get them back to their pens. Make sure you don't mix up the ones that dislike each other or they may end up fighting and knocking each other out of the pen.

Build a high score by getting as many creatures in the pens before the time runs out. A multiplier is added for getting a variety of creatures in the pens which will make your score go up faster.