Trick or Treat? Both for These “Carnivorous” Plants!

You’re back, dear audience, for the apotheosis of our Great Plant Circus of the Laidback Gardener! It’s a pleasure to see you here, week after week, for this strange show. For our very last show, I’ve found the ultimate plant! The one that, in the plant world, is a curiosity tinged with a large dose of… irony!

This specimen is not a dangerous or peculiar-looking plant, no! It’s a plant that pushes the limits of derision, and I invite you today, not to shudder in horror, but to savor the diversity of the world… and no doubt to laugh a little at evolution’s antics at the same time!

For your amazed eyes, our star of the day is… triple! Even quadruple! Oh, and let’s dream big, five species will be featured in our Halloween issue. Five nepenthe species that have partially or totally left carnivory behind to become champions of nitrogen absorption!

Meet the coprophagous nepenthe!

The what?

Carnivorous plants that don’t feed on prey, but on excrement! Today, folks, it’s Halloween, and we’re going to talk about… poo!

(Note that our artificial intelligence FINALLY knows the plant requested! But here’s a picture of one of our stars).

Fecal Matter for All!

Of course, when it comes to feeding on fecal matter, we get all kinds of reactions, from laughter to disgust. But in the plant world, eating excrement is, if I may say so, a must. Gardeners know: nothing beats a few good shovelfuls of manure for well-stocked flowerbeds, or a productive garden.

The interesting thing is that manure is a great source of nitrogen… but plants can’t usually consume it “fresh”. It has to be quite “mature”, which means that a whole bunch of other organisms have to have gone through it first: bacteria, microorganisms, fungi and the like, are needed to transform the nitrogen in excrement into a simpler, more soluble form that will be accessible to plants.

But that’s the traditional and, let’s face it, rather lengthy route taken by the average plant to feed itself. The plants featured in this issue are far from ordinary, and they don’t need an intermediary to absorb their nutrients!

Ironic Fate or Supreme Evolution?

Nepenthes are carnivorous plants that feed mainly on insects. But what can you do when prey is scarce? On the island of Borneo, in Southeast Asia, the high-altitude rainforests are sorely lacking in prey for carnivorous plants, and some species have had to find a solution.

What to replace insects with? Insects are rich in nitrogen, but not as rich as a good dose of fresh fecal matter! Some species have hyper-specialized over millions of years of evolution to become champions of nitrogen uptake.

Champions how? Digesting faecal matter is twice as effective at obtaining the precious molecule as digesting insects!

Dear audience, let me remind you that we’re talking about plants here. We humans get all our nitrogen from our normal food. Even if it’s Halloween, please don’t eat droppings! I prefer to warn you, because humans… do funny things sometimes! Since we’ve had to put a “Caution, hot coffee” sign on our paper cups, you’ll understand that your ringmaster no longer takes chances and prefers to warn you!

Let’s get back to our nepenthe… These carnivorous plants aren’t so carnivorous after all: they’re back to the more “traditional” plant food… But rather than going through decomposition, water and roots, they absorb faeces directly through their traps. In short, we’ve gone back to basics, but in the most efficient way possible!

But there are two questions: whose excrement? And how do they get into the traps?

From Mouth to Toilet Bowl

The droppings come from small mammals. They are very happy to deposit their own little gifts, almost free of charge. The secret lies in the shape of the trap. Many call these traps “mouths”, since this is, after all, where the plant “eats”. Certainly, looking at a dionea (the famous Venus flytrap), it’s easy to imagine a mouth, with two lips and teeth…

But what about N. lowii, N. rajah and N. macrophylla?

No, dear audience, it’s not a porcelain toilet bowl, but the traps of more-than-carnivorous plants! Under the “lid” of these bowls, a sweet nectar beckons its “prey”.

Can we really call this lucky little animal a prey? It’s more like a patron! A donor! A kind neighbor who gives out candy when a child in costume rings his doorbell on October 31! And here he is, this door-to-door milkman who leaves good fresh nutrients: the tupai (Tupaia montana).

This cute little mammal feeds on insects and fruit, but sweet nectar is an excellent complement. It sits on the pitfall trap and licks the nectar, while happily defecating into the nepenthe urn. The shape and size of the urn is exactly the same as that of the tupai, ensuring that the plant doesn’t lose any of its host’s gifts.

Fascinating Fact

The color of the trap is perfect for the vision of the tupai, which sees colors in much the same way as primates or humans.

This is an absolutely fascinating example of co-evolution found in a dozen species of nepenthe. Some are hybrids of the three main species that have developed this mode of nutrition, but as researchers are constantly making new discoveries, there may be more!

From Mouth to Sleeping Bag

I promised you five stars for today’s show, and here’s the fourth: Nepenthes hemsleyana.

Still on the island of Borneo, another nepenthe specializes in coprophagy. This time, it’s a well-known flying mammal, especially on this Dracula holiday.

The parabolic shape of the trap is such that the bats’ echolocation cries bounce off it, signalling their presence like a beacon in the night. The upper part of the urn is much less viscous or sticky than other nepenthe traps, allowing bats to slip in and out safely.

Folks, another surprise specimen just for your amazed eyes: the woolly bat (Kerivoula hardwickii).

Why does this little beauty slip into a trap? Quite simply to rest during the day! The plant offers a safe haven in which to hide, the digestive fluid of the bell being in the bottom part too narrow for its guest to accidentally find its way in. As a thank-you for this forest shelter, the bat defecates during its resting hours, dropping its droppings directly into the bottom of the calyx.

Around a third of the nitrogen consumed by Nepenthes hemsleyana comes from the defecation of its little flying guests. Obviously, dear audience, nature does its work: you’ll have understood that the bat doesn’t consciously pay for its passage! This is a fine example of mutualism, with both species benefiting from each other, no doubt even unconsciously. The plant feeds and the animal is sheltered, with fewer parasites and a generally better physical condition than those not using Nepenthes hemsleyana.

I hesitated to introduce it to you, because it’s not exactly a coprophagous species. It’s a detritivore. But why limit ourselves? It’s now or never! There’s a fine line between manure and compost, isn’t there, gardeners? For this specimen, we’re staying in the high-altitude rainforests of Borneo, but it can also be found in Malaysia, New Guinea and Sumatra.

A Detritivorous Species

N. ampullaria , then, is a plant that harvests its nitrogen from plant debris that falls from trees. Curious, considering that other nepenthes often use their opercula to protect themselves from debris that might fall into their urns!

Here, the operculum is very small and produces little or no nectar: no need to attract insects or tupais. For individuals living under the forest canopy, dead leaves falling from trees account for around half of their diet. Incidentally, you may have noticed that the layout of the traps on the ground is quite tight, ensuring that debris is caught efficiently.

What’s particularly interesting about these compost traps is that over sixty species use them to live, lay eggs or feed. Tiny frogs, spiders, ants, bacteria and more. All these organisms also feed the plant in their own way, either with their excrement, by dragging their own food along with them, or by dying. Some even clean the traps by removing excess plant matter, preventing rot!

Since digesting plant matter takes time, these traps have a much longer lifespan than other nepenthe traps. Insect and frog eggs therefore have time to hatch and complete their larval stage without worry. Kalophrynus pleurostigma, a small frog, can lay up to a hundred eggs in a single bell. The result is tadpoles that defecate, much to the delight of their greedy host, of course!

The End… or Not!

Plant curiosities are literally infinite. We don’t know everything, and there’s no reason why an undiscovered species shouldn’t bloom one day every ten years on the summit of Mount Everest, when it’s a leap year. If that’s the end of our ephemeral circus, know that mystery and the strange are everywhere! All you have to do is be curious and attentive…

Come on, dry your tears! I know this great journey has been full of emotions, but your stage master must retire…

I insist! I’ve got to go!

… What? You want an encore? But… today’s October 31st, and after that, Halloween’s over. I can’t possibly go on with my stories of poison and vampires, can I?

… Unless…

No, that would be going too far…

… But there is a possibility… A small one… That the Day of the Dead might be favourable for an extra?

What do you think? Do you want an encore? Oh, come on, louder! You know I like to be applauded and wanted!

Well, I must leave you now, but if you keep asking for me, who knows, maybe the big boss of the circus (Mathieu) will have no choice but to give up a place for me on Saturday, November 2, to properly celebrate the Feast of the Dead… I just happen to have a returnee somewhere in the dressing rooms…!