Western Ghats – Millennial Matriarchs

Poop. Not a subject of polite conversation. But with a six-year-old granddaughter, this is an integral part of my daily discussions—stories and jokes which feature poop, farts, and belches, and I thought nothing could get me.

But poop-eating plants did! This is one of those bizarrely strange tales from the natural world that makes me marvel at how much we don’t know.

The next time someone tells you that plants only need sunshine, nutrients from the soil and water, its time to pop out the word coprophagy. That’s the term for poop-eating. Most often it’s associated with animals—rabbits, dung beetles, and sometimes dogs. But it turns out that some plants may also be participants in this less-than-dainty buffet. Not many, mind you. It’s an exclusive club.

The pitcher plant (genus Nepenthes) is a frontrunner in this strange category. While most carnivorous plants are famous for trapping insects, some tropical species of Nepenthes have found an alternative nutrient source—bat poop. In places like Borneo, bats roost conveniently above the pitchers, and their droppings fall right in. Scientists call it a “nutritional mutualism.” The bats get shelter; the plant gets dinner. Apart from bat-poop, plants are known to eat the poop of tree shrews, lizards, and even of birds. These flowers even resemble toilets—all the better to catch the poop as it falls.

These plants don’t actually chomp up poop. Rather, they have evolved to extract nutrients from faeces, often via mechanisms like sticky leaves, enzymes, and old-fashioned decomposition. Some even form alliances with fungi or microbes to get the job done.

But why on earth would a plant choose poop? It’s a matter of efficiency. Poop, especially from animals like bats and tree shrews, is rich in nitrogen and phosphorus—two nutrients that are vital for plant growth but maybe in short supply in nutrient-poor soils where many of these carnivorous plants grow. Insects provide these too, but poop is like a ready-made fertilizer packet, no hunting required. Poop offers a shortcut—already digested, already broken down. Though the comparitive nutritive values have not been rigourously tested, it is believed that poop is more nutritious.The bats roost above the pitchers, do their business, and the plant simply absorbs the nutrients through specialized enzymes or microbes that help break things down. Also, insects are scarce on tropical peaks above 2,200 meters, so poop provides a good alternative source. In fact, scientists are finding that some carnivorous plants are evolving from eating bugs to eating poop! Some pitcher plants have even evolved shapes and scents to attract the animals specifically for their droppings!

Are there any Indian coprophagic plants?

Yes indeed! North East India is home to several species of pitcher plants or Nepenthes. Recent studies suggest that some species in the Nepenthes family (including those found in Southeast Asia) are more than happy to lap up the occasional faecal nutrient.

The Western Ghats, another biodiversity hotspot, also hosts a variety of unusual plants, including some that partner with fungi to decompose animal droppings in the soil. While not technically “eating” poop in the way a pitcher plant might, these interactions are still part of the larger cycle of nutrient recycling—with poop part of this circle of life.

So, the next time you see a lovely green pitcher in a botanical garden or on a damp forest trek in the North East, give it a respectful nod. It might be doing more than just sitting pretty. It might be part of a brilliant, bat-poop-powered system we’re only just beginning to understand.

Well, I know that after this story, Botany is definitely going to be my granddaughter’s favourite subject! Who knew botany could be this…entertainingly gross?

–Meena

Picture: http://www.kew.org/read-and-watch/poo-plants

That is surely the mantra of the Stick Insect! Known for one of the most effective camouflage strategies in Nature, the stick insect resembles the twigs among which it lives. It belongs to the order Phasmatodea, which includes the other master camouflaguer, the leaf insect. In fact, the name Phasmatodea derives from the Greek word phasma, meaning an apparition, phantom, or ghost.

The order Phasmatodea has over 3000 species in all—but how can one be sure, when many of them may be so well-hidden that they are impossible to detect! India has about 150 of these species. These creatures are related to grasshoppers, crickets, and mantises.

We were recently in the Western Ghats, where we encountered a beautiful Stick Insect. About 6 inches in length from the forward-legs to the tip of the body, it rode on a friend’s leg for a part of our walk through the wilderness. Going by stick insect standards, it was a only a moderately sized one, given that these insects range in length from the half-inch-long Timema cristinae of North America, to the 13-inch-long Phobaeticus kirbyi of Borneo. The latter measures over 21 inches with its legs outstretched, making it one of the world’s longest insects. Female stick insects are normally larger than their male counterparts. They are usually brown, green, or black, but some are brightly-coloured or striped. Some have wings. All continents except Antarctica have stick insects, though they are most abundant in the tropics.

The stick insect, also called the walking stick, spends most of its time up on trees, munching on leaves. When it senses a predator such as a bird approaching, it practically freezes, blending with the twigs and branches around it. In fact, studies suggest that some species have honed the ability to mimic the motion of twigs swaying in the wind to deceive even particularly observant predators. Stick insects are largely nocturnal and spend most of their days lying motionless on or under plants, and only coming out at night to feed. Unfortunately, the stick insects’ defences are not effective against bats which hunt by echo-location rather than sight, and these may be their most dangerous predators.

Even though their camouflage is extremely effective against most predators, they have several other tricks up their sleeves. Some species have evolved to release foul-smelling chemicals to deter predators, while others can secrete a liquid that temporarily blinds their enemies. Even if a predator spots a stick insect, it usually grabs a leg, which is the most prominent part of the insect. But that doesn’t bother our insect too much, because many of the species can detach the leg and scramble away—only to grow back the lost limb later.

And these master-tendencies start even at the egg stage! The females of some species lay eggs that look like plant seeds. This puts off carnivorous insects from eating the eggs!

Some of the stick insect species are today endangered, and the numbers of some are falling—thanks largely to habitat destruction and pesticide use. Another threat to these gentle insects is collection for the pet trade. Carausius morosus^,the ‘common’ or ‘Indian’ or ‘laboratory’ stick insect, which has its origins in India, is one of the species of Phasmatodea often kept as pets by schools and individuals.

Alas, however well a creature has evolved to protect itself against natural threats, there is little protection against humans!

–Meena

Tag: Western Ghats

The Curious Case of Poop-Eating Plants

Don’t Stick Out!