IN THE RAINFOREST
gliding, prehensile tails
and other adaptations to life at the top
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.
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!
just species and not individuals!
That's just bugs and not all other lifeforms!
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.
has developed in 3 mammals orders (marsupials, rodents and colugus),
9 reptiles (snakes, lizards) and 1 amphibian (frogs).
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.
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.
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.
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.
reptiles and amphibians ...
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.
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.
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
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
But the investment appears worthwhile as this special adaptation has
developed in 6 mammals (monkeys, some porcupines), 2 reptiles (chameleons,
skinks) and 1 amphibian.
TAILS are like hands, with a bare patch of skin for better
grip and powerful muscles to cling and carry (right).
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
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.
the locomotion: Other special locomotion techniques to
move quickly through the trees include:
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.
their long arms to move smoothly along branches in a movement called
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
to more about the moving in the trees...
Rainforest Database lots of detailed info about the complex interactions
in a rainforest.|
Diversity Web has amazing details on the many ways mammals have
gone airborne! |
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