LIFE IN THE RAINFOREST
CANOPY LIFE: flying, gliding, prehensile tails
and other adaptations to life at the top

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The high life: In a rainforest, the canopy is where most of the food is. This is where the most leaves are, gathering sunlight. The canopy is home to a huge diversity of plants, many of which never grow on the ground (epiphytes). This huge salad bowl hosts an equally amazing array of small creature from aerial earthworms and termites, to bizarre insects that never see the ground. These in turn support larger predators.

Large tree-dwelling (arboreal) animals show high diversity as they have to develop special features in order to move efficiently in their 3-D environment: to find food, mates, and escape predators. Ground-dwelling animals, in contrast, do not need to develop such features.
 

How many bugs live in the penthouse?
In a renowned 1982 study, Terry L. Erwin studied one species of rainforest tree (Luehea seemannii) and found they contained 1,200 beetle species, of which 163 were found only on this tree species. From this he estimated that there were 8.15 million arboreal beetle species. Since beetles formed 40% of canopy arthropods, this would amount to about 40 million species!

That's just species and not individuals!
That's just bugs and not all other lifeforms!

 
FLYING is the best. It gets the creature from tree to tree without have to waste time and energy moving up and down, and negotiating the dangerously bare ground. This is probably why there is such a huge diversity of insects and birds, and why bats are the most diverse of all mammals. For more, see our page about why insects are so successful and how bats fly.
 
Gliding has developed in 3 mammals orders (marsupials, rodents and colugus), 9 reptiles (snakes, lizards) and 1 amphibian (frogs).
  GLIDING is the next best thing to flying. In fact, birds and bats may have evolved from gliding creatures! Gliding is used to move from tree to tree without wasting energy or risking danger by going to the ground. Their gliding membranes, however, make them less agile at climbing and moving. Gliding mammals eat mostly leaves, which are lower in nutrients than fruits, nectar or insects. Thus gliding may be a way for them to conserve energy. Canopy mammals that hunt moving prey must be agile, and those jump or fly must eat higher-calorie food.
 
Gliding mammals have thin skin between the limbs so the animal looks like a kite. Their gliding skin is covered with visible fur and is not skin-like as in bats. Limbs may be elongated to maximise "wing" area. Gliders also develop a good grip to hang on when landing (claws, opposable digits) and for climbing up to the next glide point.

Three marsupial families in Australia are gliders: Pseudocheiridae, e.g., the Greater Glider (Petauroides volans) which not only glides but also has a weakly prehensile tail! Acrobatidae which has the tiniest glider: the Feather-Tail Glider (Acrobates pygmaeus) (right) which is unique in having a tail with flattened stiff hairs arranged like a feather to help it steer. It is so manoeuvrable that it can weave between trees before landing! And Petauridae, e.g., the Sugar Glider (Petaurus breviceps) (left) is one of the four in the family that glides.

There are 35 species of gliding squirrels (Sciuridae) found in the Americas, Europe and Asia. Flying squirrels (Petaurista spp) use their tails to steer. Their side flaps make them less agile than other squirrels so these flying squirrels are nocturnal and secretive. The Spotted Giant Flying Squirrel (P. elegans) (left) can grow to 90cm from head to tail. 12 species of gliding rodents (Anomaluridae) are found in Africa; they have scaly-tails.

The Colugo (left) is often called the "flying lemur" but it doesn't fly and it's not a lemur; it's more closely related to bats. This cat-sized mammal is among the largest gliding mammals. It can glide more more than 100m and lose only about 10m in height by spreading it's kite-like membranes. Found in Southeast Asian forests, the colugo survives on a diet of low-nutrition leaves and flowers so it is usually inactive for long periods of time. It feeds upside down like a sloth. To avoid birds of prey, it is active at dawn or dusk. Cynocephalus variegatus from Malaysia and C. volans is from the Philippines.
 

Gliding reptiles and amphibians ...

Gliding lizards: Only the Flying Dragon (10 species of Draco spp) (right) can glide. They have skirts of skin on the side of the body which opens like a fan, stretched out by elongated ribs, and a projection under their throats (gular appendage) which they use to steer their flight (but they don't have webbed toes). They can glide up to 60m and control their descent. Upon landing, their skirts fold away against the body so they are camouflaged against the bark. They are active during the day.

The other lizards mainly parachute. The Gliding Geckos (Ptychozoon spp) (left) can't spread their side and tail flaps and webbed toes; these are raised as they parachute through the air. It eats mainly ants, beetles and moths. The Gliding Lacertid (Holaspis spp) has fringed toes and tail sides. They glide not only to flee predators but also to catch prey. Their colouration matches lichen and tree bark to camouflage them.

Gliding snakes form their bodies into U-shaped tubes to parachute up to 100m. The snake grips a branch, coils up, then straightens out quickly to launch itself. When airborne, it spreads out the ribs, sucks in its guts and the centre-hinged belly scales form a concave surface. It zigs and zags as it glides to maximise its lift. These snakes are nonvenomous, about 1m long and slender and colourful. The beautiful Paradise Tree Snake (Chrysopelea paradisi) (right) is a glider. Only the adults can glide.
Gliding frogs have webbed feet to form 4 parachutes and strong suckers on their feet to cling on when they land. Some can glide up to 45m. Wallace's Tree Frog of Sabah (Rhacophorus nigropalmatus) (left) also has flaps along the outer forearms. It glides from tree to tree and from tree to pond. It can manoeuvre in the air, even making turns!

 
Prehensile tails are a heavy investment in muscles. A howler monkey's tail is 6% of its weight, about as heavy as one of its legs. In contrast, a kangaroo's massive tail is only 4% of its body weight. This heavy tail make them less agile leapers, for example, the tailess gibbon can brachiate much further than a spider monkey with its prehensile tail.

But the investment appears worthwhile as this special adaptation has developed in 6 mammals (monkeys, some porcupines), 2 reptiles (chameleons, skinks) and 1 amphibian.
 
PREHENSILE TAILS are like hands, with a bare patch of skin for better grip and powerful muscles to cling and carry (right).

Life on the edge: Prehensile tails gets their owners to the ends of flimsier trees branches for fruits and newly sprouted leaves which other tail-challenged creatures can't reach.

An extra hand: With the prehensile tail providing a secure grip, the animal can use its hands to reach out for fruits and newly sprouted leaves at branch tips. Studies showed that monkeys with prehensile tails increased their feeding sphere by 150%. Tails also come in handy as an extra limb when climbing up and down trees, as well as for carrying things. The marmosa opossum collects large loads of fluffy cotton seed capsules in its prehensile tail, to line its nest.

An extra leg: The silky anteater (right) and the tamandua (left) use their prehensile tails as a third leg to form a sturdy tripod against which they can lean to force open termite nests with their claws.

Prehensile tails also make for easy escape from predators by moving onto flimsier parts of the forest which cannot support bigger predators. The silky anteater is photographed here in its typical defensive posture.

The only hand! Prehensile-tailed snakes use their tails to hang on to a branch or anchor themselves to a firm surface when they lunge put for prey. Some snakes catch flying prey this way (bats, humming birds).

 

There are even prehensile tailed porcupines (Coendu prehensilis). They are completely arboreal, have soft spines and are clumsy and slow when forced to move along the ground. They do this mainly to find another tree. Their spineless tails make up 9% of their body weight. For about this fascinating porcupine, see Utah's Hogle Zoo's page on it.
 
Tails versus Gliding: Most prehensile-tailed animals are found in South American rainforests and virtually none are found in Asian and African rainforest. Most gliders are found in Asian rainforests with few in Africa and none in South America. We don't really know why this is so.

One explanation is that this is because there are more lianas/climbers in South American forests. These lianas thickly fill the spaces between trees which makes gliding difficult, and a prehensile tail more handy for moving from tree to tree. There are fewer lianas in African and Asian jungles because unlike in South American rainforests, there are many forest-dwelling large herbivores like elephants and antelopes which pull these lianas down to eat. So gliding has replaced prehensile tails for moving quickly from tree to tree. Another reason could be because there are more tall emergents in Asian jungles, making gliding more efficient than prehensile tails.
 

Doin' the locomotion: Other special locomotion techniques to move quickly through the trees include:

Leapin' to the rhythm: many primates like leap with abandon from tree to tree, often making death-defying jumps many times longer than their body length. Most have powerful hind legs to make their enormous leaps; and long tails to help them balance. Some, like marmosets and tamarins, have sharp claws to help grip the bark as they land.

Swingin' along: Gibbons use their long arms to move smoothly along branches in a movement called brachiation.

Just hangin': The sloth (right) probably has the most energy-saving method of movement by hanging under a branch instead of attempting to stay upright. As a result, it has among the lowest muscle to body weight ratios of all mammals. Sloths, nevertheless can move quickly and smoothly (when they want to! but only for a short while) with their specially adapted limbs and claws. For more, see our page about sloths.

 

LINKS to more about the moving in the trees...

The Rainforest Database lots of detailed info about the complex interactions in a rainforest.
Animal Diversity Web has amazing details on the many ways mammals have gone airborne!
Vertebrate flight by the University of California Museum of Palaeontology: tons of info and links to gliding and flying vertebrates. Find out how dinosaur, bird and bat flight are the same and yet different, and how flight evolved.
 
General rainforest links and references    
       
   
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