carnivory rarely pays, so even carnivorous plants avoid it when there is too little light or an easier source of nutrients, and they use as few carnivorous features as are required at a given time or for a given prey item. there are very few habitats stressful enough to make investing biomass and energy in trigger hairs and enzymes worthwhile. many plants occasionally benefit from animal protein rotting on their leaves, but carnivory that is obvious enough for the casual observer to notice is rare.