Malaysia has a rich biodiversity with forests that
covered more than two thirds of its land (Nasir, 2013). There are 298 species
of diurnal and nocturnal wild, non-marine mammals that occupied difference
niche in the forest, plantation and even in the rural area (Chua et al., 2007).
Some mammals have
evolved to species of nocturnality to occupy relative empty nocturnal niches
(Wu et al., 2017). These nocturnal
mammals are active at night and spending their days sleeping. According to the
“nocturnal bottleneck hypothesis”, nocturnal mammals evolved to avoid the
competition with diurnal reptiles during the Mesozoic era and early birds of the
Palaeocene, in order to decrease pressure and inter-species competition
(Gerkema et al., 2003)
(Charles-Dominique, 1975). On the other hand, arboreal mammals are animals that
spend most of their time on trees to eat, play and sleep. This arboreal ecospace
provides new food resources and protection from large ground dwelling predators
(Fröbisch and Reisz, 2009). Special
adaptations have evolved to enhance their arboreal and nocturnal lifestyle in
arboreal nocturnal mammals. This included different morphological, ecological
and behavioural adaptation (Barrett, 1985). Distribution and abundance of
arboreal nocturnal mammals can be study effectively by gaining the knowledge of
their morphological, ecological and behavioural adaptation for nocturnality and
arboreality in arboreal nocturnal mammals.
There are many studies about diurnal mammals but very
few about nocturnal mammals due to poor observation conditions at night and
increased potentially risks of dangers (Nasir, 2013). The cryptic nature of the
arboreal nocturnal mammals also increases the difficulties to study them. There
is very little information available about the abundance and distribution of arboreal
nocturnal mammals, such as colugos, red giant flying squirrels, slow lorises,
civets etc at Penang. Therefore, this study will be conducted to assess the
distribution and abundance of arboreal nocturnal mammals in selected sites of
Penang Island. I will use point count transect survey walks with a thermal imaging
camera to estimate the distribution and abundance of arboreal nocturnal mammals
and the data obtained will then be analyzed and for estimation of diversity and
abundance of arboreal nocturnal mammals.
1) To assess the nocturnal mammals’ distribution and
abundance in Penang Island.
2) To provide a baseline database of the nocturnal
animals in Penang Island.
3) To relate habitat features with nocturnal mammals’
This study will be conducted at six sites in Penang
Island: Penang Youth Park, Penang Botanical Gardens, Penang Hill, Tropical
Spice Garden, University Sains Malaysia and Penang National Park, Teluk Bahang.
Data collection will be conducted from September until
January 2017, at least twice per week. The sampling will be done from 9.00 p.m.
to 2.00 a.m. The distribution and abundance of nocturnal mammals will be
assessed using point count transect surveys. I will undertake transects surveys
in 10-15 different locations randomly at each field site. A transect of a
specified length of 500 m will randomly be deployed within each study site,
with counting stations to be located at regular intervals of 100 m along the
transect line. Each location will be surveyed using 20 line transects of 500 m x
20 m. For every 100 m per transect, we will stop and make observation for five
minutes with the help of thermal imaging camera. Thermal imaging camera
enhances the detection rates of the nocturnal mammals even when sleeping or out
of reach. The presence of animals will also be detected by the animal’s
eye-shine using regular head lamps (red light and white light). The presence of
every animals sighted, covariates such as weather, wind, moon phases, canopy
cover, tree diameter at breast height (DBH), temperature, altitude and clouds
will be recorded to determine any effect due to the environment in presence of
the animals. Another data included GPS location, species, sex and age (if
visible), number of individuals, distance to next tree, position on the tree,
height of the individual in the tree, behavior at first encounter will be
recorded when encounter an animal.
Additionally, I will use a local knowledge approach to
gather more information about local species by interviewing of different focus
groups, also named as Local Ecological Knowledge (LEK).
Adaptation for arboreality
traits are affected by the habitat use of the species especially the arboreal
nocturnal mammals (Guimarães et al.,
2014). The size of an arboreal nocturnal animal influences the places it can
access. Small body size enhances the locomotion in continuous substrates
(Lillywhite and Henderson, 1993). The overlapping tree crowns of the tropical
forest canopy and lianas provide continuous substrates for neither leaping nor
gliding slow lorries (Emmons and Gentry, 1983). N.coucang have small body size which facilitate them to move in
continuous substratum (Barrett, 1984). N.coucang
prefer trees with a high liana density for moving around the substratum and
they also found active in the understory with high density of small substrata
to forage fruits and insects (Barrett, 1984).
substrates such as in palm plantation, the distance between trees is not far
away from each other but there is a gap which acts as obstruction for arboreal
mammals. Thus, species such as P.petaurista
(order: Rodentia), and G.variegatus
(order: Dermoptera), overcome this gap by gliding to avoid predators on the
forest floor (Emmons & Gentry, 1983), to enhance locomotor efficiency
(Norberg, 1983) and wider foraging ranges (Byrnes et al, 2008). These types of
locomotion also facilitate by an open forest structure (Emmons and Gentry,
1983; Dial et al, 2004) and area with no or less lianas (Barrett, 1984). They
have flaps of extra skin, also known as patagium, for gliding (Lim and Ng,
2010) (Nasir, 2013). However, there are significantly differs of the extended
membrane between these two species. Dermoptera possess gliding membrane that
completely encloses its body from the limbs, to the toes, and to the tip of the
tail (Nasir, 2013) while P.petaurista’
gliding membrane extends to ankle, wrist and to the base of the tail (Harrison,
1966). Their knee and elbow joints almost fully extended during gliding
(Thorington and Heaney, 1981). According to Barrett (1984), Petaurista found
mainly in the upper levels of the forest with the greatest density of stable
substrate where most feeding occur here.
mammals require excellent balance in high places and narrow flexible supports
(Larson and Stern, 2006). According to the study by Larson and Stern (2006),
long tails are features among the arboreal adaptation that can use as
counterweights. Coordinated mechanism included sweeping tail rotation toward
the direction of imbalance in order to impart opposite angular momentum to the
body. Thus, restore the body balance by the use of the tail. As for arboreal
nocturnal mammals, P.petaurista have
long tail of the length 375 mm to 502 mm while the P.hermaphroditus have tail
length of 440-535 mm which equivalent to their body length that is around 480
mm to 590 mm (Medway, 1969). These long, prehensile tails act as balancing
organ (Barrett, 1984). The long tail of P.petaurista
provides its stability when gliding between trees (Muul and Lim, 1978). During
feeding, the tail usually folded over the back or hung below (Muul and Lim,
1978). On the other hand, N.coucang has
rudimentary tail as they do not leap or glide. Their small body size and
deliberate, slow locomotion provide them with good balance (Medway,1969).
The slow loris (Nyticebus coucang) possess the grasping
type of fore and hind feet with flattened-nail, opposed thumb and great toe
while the second digit of the hind foot are very short and bearing a sharp
curved claw that use for grooming. They move by holding on the branches with at
least one limb and climb slowly among vegetation (Medway, 1969). According to
Nowak and Paradiso (1983), colugos have broad feet with sharp, recurved claws
tipped on all digits which help them to grip well on the tree bark. They are
skillful climbers which they slowly ascending unbranched vertical trunks in a
series of lurches, with the head up and the limbs spread to grasp the tree.
Colugo mostly in upside down position during moving about on the branch or
feeding with their gliding membrane drawn down under their forelegs
(Nasir,2013) (Nowak and Paradiso, 1983).
are strictly arboreal foragers and the food become unavailable when it
fall from the tree (Kawamichi, 1997).
According to Lee, Progulske and Lin study, P.petaurista
consume mostly leaves (61%), flowers (11 %), seeds (9%), buds (5%), fruits (8%)
and barks (2%). Petaurista has long
abdominal cavity with long cecum and long intestine adapted for cellulose
digestion from their diet (Muul and Lim, 1978). From the study by Medway
(1969), there were no insects found in the stomachs of nine shot specimen while
fruit, leaves and shoots were found inside the stomachs. Because of their
gliding locomotion, they can explore wide variety of food while a single food
resource was unusual in giant flying squirrels (Kawamichi, 1997). They also
possess cheek teeth which are usually worn flat that aid them in grinding their
herbivorous diet (Muul and Lim, 1978). In the wild, Petaurista are often
observed to use one hand and long fingers to pull small branches toward them or
from overhead. (Muul and Lim, 1978). G.variegatus
are omnivorous animals that consume leaves, young shoots, flowers, buds and
tree saps, insects (Medway, 1969) (Nowak and Paradiso,1983) (Nasir, 2013). They
also obtain minerals, lichens and salts by licking on the surface of the tree
trunks (Nasir, 2013). N.coucang are omnivorous which consume a
mix of leaves, flower, trees sap, fruits and insects. Common palm civets, P.hermaphroditus, are also omnivorous
that feed on flesh and fruit (Barrett, 1984). They love the drinking the palm
sap in the vessels located in palm trees for making toddy or palm sugar
To adapt well in
the nocturnal niche, arboreal nocturnal mammals evolved highly developed senses
especially nocturnal vision. Three main adaptations regarding vision for
nocturnal mammals. Large eyes with a wider pupil and large cornea size relative
to eye size that can collect more ambient light and form a brighter retinal
image increase the nocturnal visual sensitivity which they able to detect weak
or dim stimuli (Young, 1975) (Kirk, 2006). The size of the cornea function to
constrain the total amount of light that can enter the eye at maximum pupil
dilation (Roos, 2000). Sensitivity-enhancing adaptations also include increase
the proportion of rods than cones (Duke-Elder,1958). The vision cells, rods,
which sense light and cones which sense colour. A nocturnal animal’s retinas
are composed almost entirely of rods that allow them to see much better in the
dark. A layer of cells beneath the retina, known as tapetum lucidum, acts like
a mirror reflecting light back into the rod cells and increase the sensitivity
of the eye allow intensities of light (Young, 1957). Nocturnal animal’s eyes seem
to glow in the dark also known as eyeshine reflected by tapetum lucidum. The arboreal nocturnal mammals; N.coucang, P.petaurista, G,variegatus
and P.hermaphroditus own big eyes
that give them better vision in the dark. According to Barrett, 1984, the
eye-shine from slow loris is a fiery orange-red colour while colugo and palm
civet reflect white or lemon-yellow colour of eye-shine.
Barrett (1984), social interactions for arboreal nocturnal mammals are largely
by indirect means of scent marks and calls. Most of the nocturnal mammals are
largely solitary. This type of social organization can be seen in P.petaurista and G.variegatus due to their wide-range foraging strategy to locate
food. N.coucang and P.hermaphroditus also found being
P.petaurista, G.variegatus and P.hermaphroditus easy to find suitable sleeping site than large
diurnal mammals due to their smaller size. They mostly sleep inside the tree
holes, cavities and hollows (Nasir, 2013). Sometime, G.variegatus can be found roosting on the tree bark during the day
time (Nasir, 2013). This is because Galeopterus
has shaded and mottled colour pattern on its fur are excellent
camouflage which make its well blend with the bark of trees (Nowak and
Paradiso, 1983) (Nasir, 2013) and harder their predator to spot them.
This study of the distribution and abundance of
nocturnal mammals has important implications for education related to
conservation of nocturnal animals as well as to develop plans of managing the
populations and provide a database for nocturnal mammals’ distribution on
Detailed data of the wild nocturnal mammals can be
extremely difficult to collect. It is often limited by weather, condition of
the technology devices and the decreasing population size of the nocturnal
mammals lessens the chance to find a certain species. Some species are
sensitive to light and will hide in denser vegetation when spotted. Therefore,
thermal imaging camera and red light will be used to detect these animals
because the use of thermal imaging camera is not hindered by dense foliage.
I expect that this study will provide a database for
nocturnal mammals on Penang Island especially the distribution of colugo in
Penang that does not mapped on the International Union for Conservation of
Nature (IUCN)’s geographic range that will be useful for future conservation
The study of nocturnal mammals is less due to
difficult to find and observe animals in dark. However, nowadays, nocturnal
mammals can be studied by using proper methods and tools. I expect this study
will built the interest on researchers to the study of nocturnal mammals. The
knowledge obtain through this study will be used for future education propose
and create awareness among the public about nocturnal mammals at their
Barrett, E. B. M. (1984). Ecology of some nocturnal
arboreal mammals in the rain forest of peninsular Malaysia (Doctoral
dissertation, University of Cambridge).
Byrnes, G., Lim, N. T. L., &
Spence, A. J. (2008). Take-off and landing kinetics of a free-ranging gliding
mammal, the Malayan colugo (Galeopterus variegatus). Proceedings of the
Royal Society of London B: Biological Sciences, 275(1638),
Charles-Dominique P (1975).
Nocturnality and diurnality: an ecological interpretation of these two modes of
life by an analysis of the higher vertebrate fauna in tropical forest
ecosystems. In Phylogeny
of the Primates: An Interdisciplinary
Approach (Luckett WP,
Szalay FS, eds.), 69–88. New York, Plenum Press.
Chua, L. S. L., Kirton, L. G., & Saw, L. G. (2007).
Status of Biological Diversity in Malaysia and Threat Assessment of Plant
Species in Malaysia. Proceedings of the Seminar and Workshop, 28-30 June 2005.
In Status of Biological Diversity in Malaysia and Threat Assessment of
Plant Species in Malaysia. Proceedings of the Seminar and Workshop, 28-30 June
2005.. Forest Research Institute Malaysia (FRIM).
Bloodworth, B., Lee, A., Boyne,P., Heys, J. (2004) . The distribution of free
space and its relation to canopy composition at six forest sites. Forest Science 50(3), 312-325.
S (1958). The Eye in Evolution. St.
Emmons, L. H., & Gentry, A. H. (1983). Tropical forest
structure and the distribution of gliding and prehensile-tailed
vertebrates. The American Naturalist, 121(4), 513-524.
Fröbisch, J., & Reisz, R. R. (2009). The Late Permian
herbivore Suminia and the early evolution of arboreality in terrestrial
vertebrate ecosystems. Proceedings of the Royal Society of London B:
Biological Sciences, 276(1673), 3611-3618.
Gerkema, M.P., Davies, W.I.L., Foster, R.G., Menaker,
M., & Hut, R.A. (2003) The nocturnal bottleneck and the evolution of
activity patterns in mammals. Proceedings
of the Royal Society B, 280 (1765).
Guimarães, M.; Gaiarsa, M. P.;
Cavalheri, H. B. (2014). Morphological
adaptations to arboreal habitats and heart position in species of the neo
tropical whipsnakes genus Chironius. Acta Zoologica:Morphology and Evolution, Oxford; 95 (3): 341-346.
Harrison, J. L. (1966). An
introduction to mammals of Singapore and Malaya. Singapore Branch, Malayan
Kawamichi, T. (1997). Seasonal
Changes in the Diet of Japanese Giant Flying Squirrels in Relation to
Reproduction. Journal of Mammalogy, 78(1), 204-212.
Kirk, E. C. (2006).
Eye morphology in cathemeral lemurids and other mammals. Folia
Primatologica, 77(1-2), 27-49.
Larson, S. G., & Stern, J. T.
(2006). Maintenance of above?branch balance during
primate arboreal quadrupedalism: Coordinated use of forearm rotators and tail
motion. American journal of physical anthropology, 129(1),
D.R.Progulske, and Y.S.Lin (1986) Ecological studies in two sympatric Petaurista species in Taiwan. Bulletin of the Institute of Zoology,
Academia Sinica, 25: 113-124.
Lillywhite, H. B. and Henderson, R. W. 1993.
Behavioral and functional ecology of arboreal snakes. In: Seigel, R. A. and
Collins, J. T. (Eds): Snakes: Ecology and Behavior, pp. 1–48. McGraw-Hill, New York
Lim, N.T-L., Ng,
P.K.L. (2010) Population assessment methods for the sunda cologu Galeopterus variegatus (mammalia:
Dermoptera) in tropical forests and their viability in Singapore. The Raffles Bulletin of Zoology, 58(1),
Medway, L. (1969). The wild mammals
of Malaya and offshore islands including Singapore. The wild mammals of
Malaya and offshore islands including Singapore.
Muul, I. and L.B.Lim
(1978) Comparative morphology, food habits, and ecology of some Malaysian
arboreal rodent. In The Ecology of Arboreal Folivores. (G.G. Montgomery ed.),
Smithsonian Inst., Washington, D.C.pp.361-368.
Nasir, D., (2013) Nature
history of the colugo. Penerbit
Universiti Kebangsaan Malaysia.
Norberg R.Å (1983). Optimal locomotion modes of foraging
birds in tree. Ibis. 125(2), 172-180.
Nowak, R. M., & Paradiso, J. L. (1983). Walker’s
Mammals of the World, 4th Edition. Johns
Hopkins University Press, Baltimore.
Ross, C. F. (2000).
Into the light: the origin of Anthropoidea. Annual Review of
Anthropology, 29(1), 147-194.
Thorington Jr, R. W., & Heaney, L. R. (1981). Body
proportions and gliding adaptations of flying squirrels (Petauristinae). Journal
of Mammalogy, 62(1), 101-114.
Tweedie, M. W. F. (1978). Mammals
of Malaysia. Longman Malaysia.
Wu, Y.H., Wang, H.F., & Hadly, E.A. (2017)
Invasion of ancestral mammals into dim-light environments inferred from
adaptive evolution of the phototransduction genes. Scientific Report, 7(46542).
Young, J. Z. (1975).
Life of mammals.