Warmaisach
Here i see that the life of beings called specters heavily dependent on humans blood or corpses. In that case they have to take care about their food source (humans). Some of them are intelligent and extreamly powerful so they should understand if there will be no food they will die. Also intelligent being prefer the quality of food and it's taste over others. So the most powerful of them would kill other specters and protect their own food (humans) and make them prosper. Humans takes care about ships we are eating the same way. But i do not see it happen in the book so it's kind of illogical...