Growing up you believe the world is meant to be the way it is. The older I get the more I realise that this is not the case. The world is full of injustices and atrocities that governments and the voice of faith expect us to accept, though with each passing year they grow fewer and fewer, at least one would hope. I have created this blog as a space for me to rant about all things science, politics, philosophy and religion, before it’s too late and the vessel of new atheism propelled by a growing surge in secularism solves all of the world’s problems for good.

Monday, 8 August 2011

Malaysian rainforest gliders

Uhh, wait! Not this kind!
I was watching TV recently and chanced upon an epic doco about the Malaysian rainforest and its numerous inhabitants, which have evolved to glide from tree to tree. It's believed so many species have co-evolved this ability as the rainforest in south-east asia is so complex with a multilayered canopy of some of the world's tallest trees. This has resulted in a wide range of taxa, amphibians, reptiles and mammals, that have all conquered the age old problem of getting to food sources at the tops of trees by gliding. It's a great deal more efficient and safer than descending down a tree, walking to its neighbour and climbing many metres up it to reach one's food. Jumping would have presumably been the first attribute mastered by these animals. However, those species who had the winning numbers in the evolutionary lottery gained the primary traits such as slightly larger membranes between toes or under arms, or who could compress their bodies to provide great air resistance. They would have been able to leap further and fall more slowly and reach more distant trees and thus had an advantage over their counterparts.

Sunda Flying Lemur or Colugo
First I'll start with the mammals who commonly known as flying lemurs or Colugos. The name flying lemur is a little misleading as they're not lemurs nor primate, however they are believed to be on the closet living relatives of primates. This group of gliding mammals are freaking cool, despite looking like the love-child of a sloth and a bat. And they are probably the most evolutionarily advanced of all the gliders mammal or not. That may be a big call, but wait until you have a look at the extent to which they have adapted their body for gliding through the rainforest canopy. The membrane they use is called a patagium and has evolved to be as large as is physically possible for the animal. It spreads from the neck and shoulder blades to the fore-paw, from the tip of the last finger to the tips of the toes, and from the back legs to the tip of the tail, which is unlike any other gliding mammals in the world. You may think the Australian sugar glider could hold a flame to these guys, but alas their membrane spans only from their hands to their feet... Clearly they are gliding noobs in anyone evolutionist's books!
Australia Sugar Glider

Unlike Sugar Gliders, which are marsupials and thus have a pouch for their young to comfortably enjoy their flights in, the Colugo is a Eutherian and has no such useful baby pocket. Instead its young have to cling tightly around their mother's waist during her nocturnal tree gliding. Perhaps this is a secondary evolutionary trait that has made the young into a make-shift airbag for mum's tummy when she lands on a tree?
A Colugo in full spread with its young holding on

Amazingly enough it's thought that the majority of Colugos never touch foot on solid ground. Instead they are able to live their entire lives arboreally, up in the trees, gliding from tree to tree when they are avoiding predators or looking for food or shelter.

What I found most astonishing about these guys was their ability to maneuver whilst moving through the air. A PhD student in the doco had caught a wild Colugo and put a camera on its back and released it. He could track the camera and waited for a few days until it had fallen off the animal, then watched the footage. It was insane seeing the first footage from a Colugo's perspective as it glided from one tree to another, while being able to move left and right and dodge obstacles in its path... truly epic considering it is unable to fly!

Flying Dragon skeleton
Next here are the reptiles, which include a snake and a lizard that have both acquired the skill of gliding by using their ribs. The lizard, Draco Volans or Flying Dragon, lives high up in the trees and is insectivorous feeding mainly off termites and arboreal ants. Evolution has given these lizards a number of very long ribs that can be flexed outwards and turn them from a normally shaped lizard into one that appears to have swallowed a frisbee. It is also able to flatten out the sides of its neck to give additional gliding surface area.

Flying Dragon in full spread
For these guys the ability to glide is important for getting from one tree to another to find food, but possibly even more so for avoiding predators, one of which is also a gliding reptile. To aid in subterfuge they have brilliant camouflage making them almost invisible when sitting still on a branch.

Their would-be assassins are a group of snakes in the Chrysopelea family known more commonly as Flying Snakes (wow, back in the day people had such imagination when it came to naming animals, bet you can't guess the common name of the amphibian coming up!). These snakes are mildly venomous to humans and only grow to about 1m in length. The guy in the doco studying them just grabbed one from a tree and got bitten but ignored it, so pretty piss weak I'd imagine, not that I'm signing up for a test-drive of their toxin.

These guys feed off small animals, which obviously includes the Flying Lizard. They're believed to be in an evolutionary 'arms race', which effectively means one's evolving attributes that allow it to better catch its prey, whilst the other is evolving attributes that allow it to better evade its predator. As one gains an advantage over the other, it forces the other to catch up, leading to a very slow evolutionary game of cat and mouse.

Flying Snake gliding
So these Flying Snakes would have learned over a great deal of time that they could throw themselves (don't think you can call it jumping when it has no legs) from one tree to another when in hot pursuit of a meal. This would have eventually lead to those who could move further through the air because they were able to better compress their ribs, just like the Flying Dragons, to flatten themselves out and slow their descent and further their leap. This has lead to a snake that now turns itself into an S shape after each jump, and compresses its body into the shape of an airplane wing. This makes these guys almost more amazing than the other gliders as by turning themselves into a wing shape with the top being curbed and the underside being flat, they are able to generate lift much like a plane does. Whereas the other gliders don't appear to be able to do this. All the more awesome is that the snakes can judge what they'll land on and can change their body's orientation/shape in order to deal with it. When they want to land on a branch they shape themselves in mid-flight like a hook to catch onto the branch, whereas when they know they'll land on the ground, they stay more in the S shape and lift their head while throwing their tail down first. This allows their body to do the "worm" break dancing move when they impact, and thus their head is the last thing to hit the ground and no single part of the body absorbs all of the impact and avoids damage.

Another interesting thing to note about these guys is that you can see their heart while they're flattened out in gliding mode. In the above picture you can just see it about a foot back from the head of the snake.

Wallace's Flying Frog
Last of all we have the Flying Frogs. Again, these guys are pretty unique animals, as they rely solely upon the webbing between the toes of both their front and hind feet for gliding, though what they do is referred to as gliding, it's more like controlled parachuting. They also have lateral skin flaps that run down the sides of the legs and arms, but no where near to the same extent as the Colugo. Similar to the lizard, it has most probably evolved its gliding traits in order to reach trees while look for food or avoiding those pesky Flying Snakes!

There are numerous Flying Frogs, however the best glider is Wallace's Flying Frog, which is able to glide as far outwards as it falls. In other words it can fall at a 45 degree angle to the ground.

A future flyer?
Interestingly enough they weigh comparatively less than do other frogs of the same snout-vent length (perhaps following those dinosaur like birds who first became light in weight and gained feathers/wings to become airborne fully fledged flyers! Perhaps keep your eyes pealed for this guy to the left in a few short million years.

When compared to the other gliders, they're probably bringing up the rear with regards to mastering this ability of gliding, though nonetheless it is impressive to see an amphibian joining the mile-high club! And when it comes down to it, they've mastered the ability of surviving so what else can you say!

Wallace's Flying Frog, base juuuuump!
I'll throw up some videos below of these magnificent gliding critters for all you doco junkies out there! For those with a keen eye, watch for the wagging tail of the Colugo while gliding, and also check out how the snake positions itself into a J-shape before throwing itself into the air.



 The Colugo

The Flying Dragon and Flying Snake

The Flying Frog

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