Real Crappy Plant Research

If a plant is green, why be carnivorous? And if a plant if carnivorous, why be green? This was a central question surrounding the phenomenon of carnivorous plants. And science has known the answer for a long time.
Plants are awash in nitrogen (70% of the atmosphere), but plants can’t use gaseous nitrogen, and lack of this critical nutrient often limits plant growth. Some plants use bacterial symbionts to help them acquire nitrogen, e.g., legumes-Rhizobacter; mosquito fern-Anabaena. But carnivorous plants use their various trap devices to capture animals and acquire nitrogen from the digestion or decomposition of their bodies.

Since its discovery people have thought that the giant pitcher plant of SE Asia caught really large animals, things like mice, which for a plant is pretty large prey. Nice idea, but the "body" of evidence was always lacking. It turns out that this pitcher works in a different way. By positioning a nectar reward on its lid, small mammals like tree shrews are positioned such that when they defecate, the “results” end up in the pitcher. And when you think about it, this particular pitcher does sort of look like a toilet.
So this is one more way plants interact mutualistically with animals to acquire needed resources, but you can decide what to call this since it isn’t really an animal-eating plant anymore.

HT to Zooillogix.