Tree shrew uses pitcher plant as potty

Tasty deal... tree shrews pitch in
Evangeline Majawat, The Star 15 Mar 10;

KUALA LUMPUR: Potty training is a breeze for tree shrews (Tupaia montana) as they answer nature's calls perched delicately on the odd-looking pitcher plant.

The world's biggest carnivorous plant, the Nepenthes rajah, comes in handy as toilet for the small mammals, a new research has found.
The shrew's excrement is food for N. rajah and two other species of pitcher plants, the Nepenthes lowii and Nepenthes macrophylla, all found only in Borneo.

The nutrient-rich droppings supply important minerals to the plants. In return, the plants secrete a tasty nectar that the shrews love. So, those furry creatures can feed and defecate at the same time.

Ecologist Dr Charles Clarke and his student Chin Lijin, from Monash University Sunway campus, made the astonishing discovery last year at Mount Kinabalu.

"It's nature's toilet. It's a great discovery to make, which comes 150 years after N. rajah was first described.

"We've never understood why it has big pitchers, and so the finding is really good," Clarke told the New Straits Times.

Their finding, which was published in the journal New Phytologist earlier this year, busted the myth that larger pitcher plants depended on small animals for survival.

For a long time, N. rajah, believed to be the biggest meat-eating plant in the world, was reputed to trap small vertebrates.

"Actually, it was assumed it catches insects. Just occasionally, dead mice and rats have been found in the pitcher plants. It doesn't need big pitchers to catch large insects," said Clarke.
Last year, he suggested that Chin study the pitcher plants, known locally as periuk kera, because "nobody has looked at it in detail".

It wasn't long into their four-month research that they realised the three species of pitcher plants rarely caught small animals.

"When we studied the contents, we noticed tree shrew poo," said Clarke.

He knew from an earlier research that N. lowii was designed specifically to collect the shrews' faeces.

The duo confirmed their suspicion on the other two species when cameras caught the shrews in the act on their "thrones".

The result pleased them.

"At least half, and possibly 100 per cent of N. lowii's nutrients come from the tree shrews," Clarke said.

As for the other two species, they supplement their diets with insects.

For Chin, this turned out to be her lucky break in her first attempt at scientific discovery.

She said she hoped the findings would add conservation value to the rare pitcher plants.

"By understanding the species more, it'll provide more information to (afford) better protection of its habitats. N. lowii looks exactly like our toilet! It's amazing."

Huge meat-eater plant prefers poo
Matt Walker, BBC News 15 Mar 10;

The largest meat-eating plant in the world is designed not to eat small animals, but small animal poo.

Botanists have discovered that the giant montane pitcher plant of Borneo has a pitcher the exact same size as a tree shrew's body.

But it is not this big to swallow up mammals such as tree shrews or rats.

Instead, the pitcher uses tasty nectar to attract tree shrews, then ensures its pitcher is big enough to collect the feeding mammal's droppings.

Details of the discovery are published in the journal New Phytologist.

Big reputation

Pitcher plants have elaborate structures which entice creatures such as ants or spiders into a precarious position, from which they fall into a fluid-filled trap, where they drown and are ingested.

These arthropods are thought to provide the plant with vital nitrogen and phosphorus, which it cannot obtain any other way.

Pitchers are the largest carnivorous plants, and the largest pitchers grow in Borneo.

One, known as Nepenthes rajah , is believed to be the largest meat-eating plant in the world, growing pitchers that can hold two litres of water if filled to the brim.

This plant's pitcher is so big that they are reputed to catch vertebrates.

"This species has always been famous for its ability to trap rodents, but I've been looking at the pitchers of this species on and off since 1987, and I've never seen a trapped rat inside," says Dr Charles Clarke, an expert on carnivorous plants based at Monash University's Sunway Campus in Selangor, Malaysia.

"This made me wonder: if it is large enough to trap rats, but it only traps them very rarely, it is likely that the pitchers are large because of some other reason?"

To find out, Dr Clarke and colleagues Ms Lijin Chin of Monash University and Dr Jonathan Moran of Royal Roads University in Victoria, British Columbia, Canada turned their attention to tree shrews, which inhabit the same forest as N. rajah .

They did so after noticing that tree shrews, which are a similar size to rodents but most closely related to primates, sometimes left faeces in the traps of large pitchers.

"All of a sudden we realised that there may be some relationship between big pitchers and tree shrews," says Dr Clarke.

"So we decided to look at the pitcher geometry."

What they found "totally blew us away", says Dr Clarke.

Precise dimensions

N. rapah pitchers have huge orifices, but they also grow large concave lids held at an angle of about 90 degrees away from the orifice.

The inside of these lids are covered with glands that exude huge amounts of nectar.

Most importantly, the distance from the front of the pitcher's mouth to the glands corresponds exactly to the head to body length of mountain tree shrews.

The same is true for two other species of large meat-eating pitcher plant, N. lowii and N. macrophylla that are also visited by tree shrews.

However, the pattern does not hold for other pitcher species not associated with the small mammals.

"In order for the tree shrews to reach the exudates, they must climb onto the pitchers and orient themselves in such a way that their backsides are located over the pitcher mouths," explains Dr Clarke.

The tree shrews then appear to defecate as a way of marking their feeding territory.

That suggests these supposedly "meat-eating" plants have evolved a mutualistic relationship with tree shrews.

The tree shrews get nectar, a valuable food source, and in return, the plants get to catch and absorb the tree shrew's faeces which likely supplies the majority of nitrogen required by the plant.

These particular species of pitcher also live in the highlands where insects and other arthropods are more scarce.

Such creatures would normally provide the nitrogen needed by the pitcher, forcing it to evolve its huge size to attract tree shrews instead.

Radical rethink

"150 years after the discovery of N. rajah , we finally have an explanation for why the largest carnivorous plant in the world produces such big pitchers," says Dr Clarke.

Dr Clarke says it is the "neatest" discovery he has made in more than 20 years of studying Nepenthes meat-eating plants.

"The findings should radically alter how we look at these plants," he says.

He believes there is much we still have to learn about the true habits of carnivorous plants.

They suspect another highland species, N. ephippiata, likely feeds on faeces too, as may a huge meat-eating plant called N. attenboroughii which was only discovered last year.

In the lowlands of Borneo, bats roost in the pitchers of yet more Nepenthes species, suggesting these plants may too feed off the faeces of other small mammals.