Their ecology is based on a free for all, where the bigger eats the smaller

Then we go nighttime dumpster diving in the alley behind a bargain seafood restaurant. I mean, no we don't, this is all scary and serious and stuff. But there is sort of a running gag later where Dave and maybe some other people keep referring to these things humorously in terms of seafood analogies. But of course you don't eat these things, they eat YOU. Okay, that probably isn't true either. Although they do have huge, nasty mouths, as you can see. Which makes you wonder, what do they eat? What's even out there in the void? Smaller horrorterrors? That's probably it. There's likely just an entire diverse ecology of horrorterrors, with smaller ones very plentiful and larger ones more scarce, to keep the food chain balanced. Other than that, it's a complete free for all. I'm just literally making all this shit up right now, if it wasn't clear

-Book 5 page 300