Really, the genius of the game is that Trico acts like a real animal. Animals have minds of their own. They're going to do what they feel like, which is quite often contrary to what you might want. With training, though, they improve on that score, and it's what the game's all about. You have to treat Trico like a real critter, and if you do, you'll be rewarded. Treat him like a typical video game companion, and the reward is bottomless frustration.

(The bit where Trico actually swallows you is a major, major spoiler, however, and needs to be tagged as such. Suffice to say, all is not what it seems in that particular scene).