Larger animals are highly undesirable prey because they tend to be able to free themselves from a carnivorous plant (low value), with a high probability of seve

Larger animals are highly undesirable prey because they tend to be able to free themselves from a carnivorous plant (low value), with a high probability of severe damage to the plant in the attempt (high cost): they can just walk or climb away, but also involuntarily break a stalk with their weight, tear open a sac with talons, rip away slowly regenerated adhesive parts, eat something that should be dangerous, and so on.