From Creatures Wikia
When a creature says that it's hungry it needs to eat. In Creatures 3 and Docking Station, this drive is most commonly stated by any creature as :"Eem x hungry for y" where x is a quantitative qualifier (quite, really, very, extremely, or intensely), y is starch, fat or protein, and Eem is the creature's name. There are agents that detect when creatures state a hunger drive, one example is the Electronic Butler (which also detects boredom statements). The Empathic Vendors in Docking Station also detect these statements, and create the appropriate type of food. Prior to Creatures 3, creatures do not have different types of hunger for different nutrients.