The Training of the Shrew: Pitcher Plant Evolves Into Toilet

pitcher-plant toilet borneo evolution photo

Credit: Ch'ien Lee

Pitcher plants are carnivorous and usually eat insects for nutrients and nitrogen. But in the highlands of Borneo there are not enough for it to survive on insects alone, so the pitcher plant evolved into a toilet plant, complete with standing lid that serves an unusual purpose.

Dr. Jonathan Moran, Assistant Professor at the School of Environment and Sustainability at Royal Road University in Victoria, described it to Bob McDonald of Quirks and Quarks, a Canadian science radio show. It is really quite amazing.

The plant is big, almost the size of a football, The lid is covered in nectar, which attracts the tree shrew with a yummy snack; the bowl is shaped precisely to catch the shrew's poop. There is even some thought that the nectar might have laxative properties, because it certainly collects a lot of the stuff, which provides needed nitrogen for the plant.

McDonald calls it "an unusual example of mutualization." The shrew is common at all altitudes, but the adapted plant is found only at the high altitudes, so all of the adaptation has been by the plant. Listen to the interview here.

Last year in Live Science, Moran noted that this was a pretty sophisticated shift from the more common pitcher plant.

" Lowii[the pitcher plant] has modified their aerial pitcher to be a toilet," Moran said. For instance, the rim of the pitcher is not slippery like it is in the insect-trapping varieties such as the ground-lying, terrestrial N. lowii pitchers. That way, tree shrews stay safe from a spill while eating and pooping.

"It's very tough, there's lots of reinforcement, because [the pitcher is] hanging off the end of a leaf and it has to be able to support a tree shrew," Moran told LiveScience, adding the animals can weigh less than half a pound (150 grams).

And it even flushes:

"[The tree shrew] licks the lid, and if it needs to take a bathroom break then it's positioned perfectly for that," Moran said. "Plus it's a funnel so the next time it rains the feces will be washed into the pitcher."