Posts on Places

On the Wings of Dragons

14 January 2015

If you’ve ever been on a walk in the rainforests of Borneo you may have experienced this not-uncommon occurrence: out of the corner of your eye you glimpse a leaf falling down from the canopy, only instead of it continuing down to the forest floor it abruptly vanishes onto the side of a tree. It might take a few moments to register, but suddenly you realize that there was just something not quite right about the trajectory of that leaf. A keen eye (and often a pair of binoculars) and a scan of the tree trunk will reveal the real culprit of the fraud: a gliding lizard. And, as it turns out, you were meant to be deceived.

With over 40 species distributed across Asia (and 10 in Borneo), Draco lizards are perhaps the most effective gliders in the animal kingdom. Although typically measuring less than 20 cm from nose to tail tip, they have been recorded gliding over 50 meters in a single leap. This is achieved by extending a flap of skin (patagium) on their sides which is supported by movable ribs, effectively turning the reptile into a miniature frisbee. Steering in mid-flight is controlled by the tail and perhaps also by the front legs which are pressed over the top of the wings while airborne.

Within a forest habitat the ability to glide is an enormous advantage and this may account for why these lizards are so successful and species diverse. Traveling from tree to tree with ease, Draco are able to forage over a greater area (they feed predominantly on ants) as well as escape certain predators without ever having to descend to the ground. Flight, however, brings with it certain dangers, and although the lizards are highly camouflaged when perched against tree bark with their wings concealed, their movements through the air put them at risk from detection by keen-eyed predatory birds.

A newly published paper in Biology Letters (see link below), with research supported by the National Geographic Society, finds evidence that the patagia of several Draco species mimic the color of dead leaves, providing the lizards with effective camouflage even while in flight. Researchers measured the color of Draco wing membranes and compared it with the color of fallen leaves occurring in the vicinity. Amazingly, a color correlation was found not only between each species’ patagia and the color of the most abundant falling leaves in their preferred habitat, but two separate populations of a single species (D. cornutus) matched the predominant leaf color at the different locations they were found in: reddish-brown mangrove leaves vs. dark-brown lowland forest leaves. More work remains to be done to substantiate this trend in other populations and species of Draco.

Studies like this continue to decipher the amazing minutiae of adaptations that rainforest organisms possess and show that, in a habitat teeming with predators and prey, deception plays no small part in the struggle for survival. Next time you see a leaf falling down through the forest, have a second look – in the jungles of Borneo things aren’t always what they seem.

Draco cornutus

References:

Klomp DA, Stuart-Fox D, Das I, Ord TJ. 2014 Marked colour divergence in the gliding membranes of a tropical lizard mirrors population differences in the colour of falling leaves. Biol. Lett. 10: 20140776. http://dx.doi.org/10.1098/rsbl.2014.0776

A Tale of Two Kitties

30 May 2014

Several days ago whilst hiking up a hill in Danum Valley to check on one of my camera traps, I had a chance encounter with one of Borneo’s most beautiful creatures: a Marbled Cat (Pardofelis marmorata), the first I have ever seen. I was about to ford a creek at the bottom of a small gulley and noticed something moving in the undergrowth on the opposite bank. The cat was so perfectly camouflaged that I didn’t realize I was staring directly at it until it moved again. About half a metre in length with a tail at least as long again, it was beautifully patterned with dark and tan blotches. It had seen me already (of course) and was slowly slinking away up the stream bank.

As luck would have it I had just left my camera in a hide a few hundred meters down the trail so taking a photo was out of the question. Without thinking I raised my hand to my lips and squeaked out a simple rodent alarm call. The cat stopped in its tracks and turned around, staring at me. Unbelievably it then began stalking back down the stream bank towards me until it reached a point on the opposite bank less than 4 meters from where I stood. We locked eyes for a few seconds, the cat trying to decide exactly what was going on, and me just trying to savor as much of the experience as I could while keeping my heart rate at a reasonable level. A moment later it turned and sulked away, uttering a low growl as it went, and disappeared quickly among the underbrush.

I glanced at my watch: 10:30 AM sharp. Bright sunny day and blue sky. While we normally think of the shy wild rainforest cats as strictly nocturnal, or even crepuscular creatures, it seems that the Marbled Cat is often active during the middle of the day. My good friend Dr. Jedediah Brodie, who has done a enormous amount of camera trapping in Borneo for his research on mammal ecology, thinks that this cat may use daylight hours as a means of avoiding confrontations with the apex carnivore of Borneo rainforests, the Sunda Clouded Leopard (Neofelis diardi diardi), which is more active at night and early morning. Although confusingly similar in coloration, the Clouded Leopard is several times larger than the Marbled Cat and wherever present would occupy the role of top predator without dispute.

As if just to prove a point, twenty minutes later and another 500 meters ahead on the trail I crouched down to examine the catch on my camera trap which had been running for the past two weeks, and a possible reason for the Marbled Cat’s diurnal habits became clear – a Clouded Leopard had been on the prowl just the night before:

Sunda Clouded Leopard (Neofelis diardi)

With five species of wild cats, Borneo is exceptionally rich in felid species even were it not an island. In addition to the Marbled Cat and Clouded Leopard, Borneo is also home to the Leopard Cat (Prionailurus bengalensis), Flat-headed Cat (Prionailurus planiceps), and arguably the least known of all the world’s cat species, the rare endemic Bay Cat (Catopuma badia). All except for the Leopard Cat, which survives well in disturbed habitats, are under threat due to habitat loss and poaching, making them the focus of long-term studies and conservation efforts.

New Pitcher Plant Species from New Guinea

29 November 2013

It wouldn’t be far-fetched to say that we are presently experiencing a Golden Age of pitcher plant discovery. Scarcely 16 years ago there were 84 officially recognized species in the genus Nepenthes; now that total is fast approaching 150, with nearly 30 new taxa described in the past 5 years alone. Whilst most of these new taxa are only slight variations of previously described species or are ‘splits’ where a single taxon has been divided based on what are deemed significant differences, a few are unique and represent striking new forms (e.g. N. attenboroughii and N. undulatifolia).

Last month, whilst trekking through the mountains of Papua (Indonesian New Guinea) with longtime friend and colleague Dr. Charles Clarke, we were excited to encounter yet another undescribed species of Nepenthes on a remote forested ridge. Our 2-week expedition had been fraught with numerous setbacks, including illness and inter-tribal warfare which nearly thwarted our entire climb and ultimately prevented us from reaching the summit we had originally targeted. Nevertheless, we were able to explore some incredibly beautiful and pristine montane habitats and in a fortunate turn of luck, stumble across this new and distinctive species.

Because of this plant’s unique features, it’s taxonomic affinities with other Nepenthes, both within and outside of New Guinea, are not yet evident. The globose lower pitchers (below left) with their broad and strongly-toothed peristome, and the funnel-shaped upper pitchers (below right) bear little resemblance to other Papuan taxa. Additional unusual traits include the leaves, which are broad and sub-petiolate, and the dense coating of brownish hairs which cover all parts of the plant, giving it a “wooly” appearance. Unfortunately, as our expedition was purely a photographic one we did not collect herbarium specimens, and a formal description of this species will have to wait for a future survey equipped with collecting permits.

Nepenthes sp. New GuineaNepenthes sp. New Guinea

This discovery is further remarkable considering the relative paucity of Nepenthes in New Guinea. Despite the island’s vast size, the presently recognized diversity of the genus on the New Guinea mainland is quite small (only 11 species). Unlike other islands of the Indonesian archipelago such as Borneo (39 species) and Sumatra (37 species), where pitcher plants occur in abundance on most mountains exceeding 2000 m, Nepenthes are patchily distributed in New Guinea and are seemingly absent from large regions of highland areas. In 2004 and 2006 I climbed two separate mountains each exceeding 3000 m in elevation and, whilst the habitats were very rich in a variety of typically associated plants, I did not observe a single Nepenthes.

Notwithstanding the large number of new Nepenthes which have been distinguished in recent years, the addition of this interesting species shows that we still have a long way to go towards our complete understanding of the genus, with perhaps other great discoveries to be made in the mountains of Papua.

References:

Jebb, M. & M. Cheek (1997) A Skeletal Revision of Nepenthes (Nepenthaceae). Blumea 42: 1-106.

Jebb, M.H.P. 1991. An account of Nepenthes in New Guinea. Science in New Guinea 17(1): 7–54.


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