Malaysia has a rich biodiversity with forests thatcovered more than two thirds of its land (Nasir, 2013). There are 298 speciesof diurnal and nocturnal wild, non-marine mammals that occupied differenceniche in the forest, plantation and even in the rural area (Chua et al., 2007). Some mammals haveevolved to species of nocturnality to occupy relative empty nocturnal niches(Wu et al.
, 2017). These nocturnalmammals are active at night and spending their days sleeping. According to the”nocturnal bottleneck hypothesis”, nocturnal mammals evolved to avoid thecompetition with diurnal reptiles during the Mesozoic era and early birds of thePalaeocene, in order to decrease pressure and inter-species competition(Gerkema et al., 2003)(Charles-Dominique, 1975).
On the other hand, arboreal mammals are animals thatspend most of their time on trees to eat, play and sleep. This arboreal ecospaceprovides new food resources and protection from large ground dwelling predators(Fröbisch and Reisz, 2009). Specialadaptations have evolved to enhance their arboreal and nocturnal lifestyle inarboreal nocturnal mammals. This included different morphological, ecologicaland behavioural adaptation (Barrett, 1985).
Distribution and abundance ofarboreal nocturnal mammals can be study effectively by gaining the knowledge oftheir morphological, ecological and behavioural adaptation for nocturnality andarboreality in arboreal nocturnal mammals. There are many studies about diurnal mammals but veryfew about nocturnal mammals due to poor observation conditions at night andincreased potentially risks of dangers (Nasir, 2013). The cryptic nature of thearboreal nocturnal mammals also increases the difficulties to study them. Thereis very little information available about the abundance and distribution of arborealnocturnal mammals, such as colugos, red giant flying squirrels, slow lorises,civets etc at Penang. Therefore, this study will be conducted to assess thedistribution and abundance of arboreal nocturnal mammals in selected sites ofPenang Island. I will use point count transect survey walks with a thermal imagingcamera to estimate the distribution and abundance of arboreal nocturnal mammalsand the data obtained will then be analyzed and for estimation of diversity andabundance of arboreal nocturnal mammals.
2.0Objectives1) To assess the nocturnal mammals’ distribution andabundance in Penang Island.2) To provide a baseline database of the nocturnalanimals in Penang Island.3) To relate habitat features with nocturnal mammals’abundance. 3.0MethodologyThis study will be conducted at six sites in PenangIsland: Penang Youth Park, Penang Botanical Gardens, Penang Hill, TropicalSpice Garden, University Sains Malaysia and Penang National Park, Teluk Bahang. Data collection will be conducted from September untilJanuary 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 beassessed using point count transect surveys. I will undertake transects surveysin 10-15 different locations randomly at each field site.
A transect of aspecified 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 thetransect line. Each location will be surveyed using 20 line transects of 500 m x20 m. For every 100 m per transect, we will stop and make observation for fiveminutes with the help of thermal imaging camera. Thermal imaging cameraenhances the detection rates of the nocturnal mammals even when sleeping or outof reach.
The presence of animals will also be detected by the animal’seye-shine using regular head lamps (red light and white light). The presence ofevery animals sighted, covariates such as weather, wind, moon phases, canopycover, tree diameter at breast height (DBH), temperature, altitude and cloudswill be recorded to determine any effect due to the environment in presence ofthe animals. Another data included GPS location, species, sex and age (ifvisible), number of individuals, distance to next tree, position on the tree,height of the individual in the tree, behavior at first encounter will berecorded when encounter an animal. Additionally, I will use a local knowledge approach togather more information about local species by interviewing of different focusgroups, also named as Local Ecological Knowledge (LEK). 4.0Literature review4.1Adaptation for arborealityMorphologicaltraits are affected by the habitat use of the species especially the arborealnocturnal mammals (Guimarães et al.
,2014). The size of an arboreal nocturnal animal influences the places it canaccess. Small body size enhances the locomotion in continuous substrates(Lillywhite and Henderson, 1993). The overlapping tree crowns of the tropicalforest canopy and lianas provide continuous substrates for neither leaping norgliding slow lorries (Emmons and Gentry, 1983). N.coucang have small body size which facilitate them to move incontinuous substratum (Barrett, 1984). N.
coucangprefer trees with a high liana density for moving around the substratum andthey also found active in the understory with high density of small substratato forage fruits and insects (Barrett, 1984). For discontinuoussubstrates such as in palm plantation, the distance between trees is not faraway from each other but there is a gap which acts as obstruction for arborealmammals. Thus, species such as P.petaurista(order: Rodentia), and G.
variegatus(order: Dermoptera), overcome this gap by gliding to avoid predators on theforest floor (Emmons & Gentry, 1983), to enhance locomotor efficiency(Norberg, 1983) and wider foraging ranges (Byrnes et al, 2008). These types oflocomotion also facilitate by an open forest structure (Emmons and Gentry,1983; Dial et al, 2004) and area with no or less lianas (Barrett, 1984). Theyhave flaps of extra skin, also known as patagium, for gliding (Lim and Ng,2010) (Nasir, 2013).
However, there are significantly differs of the extendedmembrane between these two species. Dermoptera possess gliding membrane thatcompletely encloses its body from the limbs, to the toes, and to the tip of thetail (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 foundmainly in the upper levels of the forest with the greatest density of stablesubstrate where most feeding occur here. Arboreal nocturnalmammals 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 ascounterweights. Coordinated mechanism included sweeping tail rotation towardthe direction of imbalance in order to impart opposite angular momentum to thebody.
Thus, restore the body balance by the use of the tail. As for arborealnocturnal mammals, P.petaurista havelong tail of the length 375 mm to 502 mm while the P.hermaphroditus have taillength of 440-535 mm which equivalent to their body length that is around 480mm to 590 mm (Medway, 1969). These long, prehensile tails act as balancingorgan (Barrett, 1984). The long tail of P.petauristaprovides its stability when gliding between trees (Muul and Lim, 1978). Duringfeeding, the tail usually folded over the back or hung below (Muul and Lim,1978).
On the other hand, N.coucang hasrudimentary tail as they do not leap or glide. Their small body size anddeliberate, slow locomotion provide them with good balance (Medway,1969). The slow loris (Nyticebus coucang) possess the graspingtype of fore and hind feet with flattened-nail, opposed thumb and great toewhile the second digit of the hind foot are very short and bearing a sharpcurved claw that use for grooming. They move by holding on the branches with atleast one limb and climb slowly among vegetation (Medway, 1969). According toNowak and Paradiso (1983), colugos have broad feet with sharp, recurved clawstipped on all digits which help them to grip well on the tree bark. They areskillful climbers which they slowly ascending unbranched vertical trunks in aseries 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 orfeeding with their gliding membrane drawn down under their forelegs(Nasir,2013) (Nowak and Paradiso, 1983).
P.petauristaare strictly arboreal foragers and the food become unavailable when itfall from the tree (Kawamichi, 1997).According to Lee, Progulske and Lin study, P.petauristaconsume mostly leaves (61%), flowers (11 %), seeds (9%), buds (5%), fruits (8%)and barks (2%).
Petaurista has longabdominal cavity with long cecum and long intestine adapted for cellulosedigestion 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 whilefruit, leaves and shoots were found inside the stomachs. Because of theirgliding locomotion, they can explore wide variety of food while a single foodresource was unusual in giant flying squirrels (Kawamichi, 1997). They alsopossess cheek teeth which are usually worn flat that aid them in grinding theirherbivorous diet (Muul and Lim, 1978).
In the wild, Petaurista are oftenobserved to use one hand and long fingers to pull small branches toward them orfrom overhead. (Muul and Lim, 1978). G.variegatusare omnivorous animals that consume leaves, young shoots, flowers, buds andtree saps, insects (Medway, 1969) (Nowak and Paradiso,1983) (Nasir, 2013). Theyalso obtain minerals, lichens and salts by licking on the surface of the treetrunks (Nasir, 2013). N.coucang are omnivorous which consume amix of leaves, flower, trees sap, fruits and insects.
Common palm civets, P.hermaphroditus, are also omnivorousthat feed on flesh and fruit (Barrett, 1984). They love the drinking the palmsap in the vessels located in palm trees for making toddy or palm sugar(Tweedie, 1978).
4.2NocturnalityTo adapt well inthe nocturnal niche, arboreal nocturnal mammals evolved highly developed sensesespecially nocturnal vision. Three main adaptations regarding vision fornocturnal mammals.
Large eyes with a wider pupil and large cornea size relativeto eye size that can collect more ambient light and form a brighter retinalimage increase the nocturnal visual sensitivity which they able to detect weakor dim stimuli (Young, 1975) (Kirk, 2006). The size of the cornea function toconstrain the total amount of light that can enter the eye at maximum pupildilation (Roos, 2000). Sensitivity-enhancing adaptations also include increasethe proportion of rods than cones (Duke-Elder,1958). The vision cells, rods,which sense light and cones which sense colour.
A nocturnal animal’s retinasare composed almost entirely of rods that allow them to see much better in thedark. A layer of cells beneath the retina, known as tapetum lucidum, acts likea mirror reflecting light back into the rod cells and increase the sensitivityof the eye allow intensities of light (Young, 1957). Nocturnal animal’s eyes seemto glow in the dark also known as eyeshine reflected by tapetum lucidum. The arboreal nocturnal mammals; N.coucang, P.
petaurista, G,variegatusand P.hermaphroditus own big eyesthat give them better vision in the dark. According to Barrett, 1984, theeye-shine from slow loris is a fiery orange-red colour while colugo and palmcivet reflect white or lemon-yellow colour of eye-shine.
According toBarrett (1984), social interactions for arboreal nocturnal mammals are largelyby indirect means of scent marks and calls. Most of the nocturnal mammals arelargely solitary. This type of social organization can be seen in P.petaurista and G.variegatus due to their wide-range foraging strategy to locatefood. N.coucang and P.
hermaphroditus also found beingsolitary. 4.3Sleeping sitesN.coucang,P.petaurista, G.variegatus and P.hermaphroditus easy to find suitable sleeping site than largediurnal mammals due to their smaller size.
They mostly sleep inside the treeholes, cavities and hollows (Nasir, 2013). Sometime, G.variegatus can be found roosting on the tree bark during the daytime (Nasir, 2013). This is because Galeopterus has shaded and mottled colour pattern on its fur are excellentcamouflage which make its well blend with the bark of trees (Nowak andParadiso, 1983) (Nasir, 2013) and harder their predator to spot them. 5.0ConclusionThis study of the distribution and abundance ofnocturnal mammals has important implications for education related toconservation of nocturnal animals as well as to develop plans of managing thepopulations and provide a database for nocturnal mammals’ distribution onPenang Island.Detailed data of the wild nocturnal mammals can beextremely difficult to collect.
It is often limited by weather, condition ofthe technology devices and the decreasing population size of the nocturnalmammals lessens the chance to find a certain species. Some species aresensitive to light and will hide in denser vegetation when spotted. Therefore,thermal imaging camera and red light will be used to detect these animalsbecause the use of thermal imaging camera is not hindered by dense foliage.I expect that this study will provide a database fornocturnal mammals on Penang Island especially the distribution of colugo inPenang that does not mapped on the International Union for Conservation ofNature (IUCN)’s geographic range that will be useful for future conservationstep.
The study of nocturnal mammals is less due todifficult to find and observe animals in dark. However, nowadays, nocturnalmammals can be studied by using proper methods and tools. I expect this studywill built the interest on researchers to the study of nocturnal mammals. Theknowledge obtain through this study will be used for future education proposeand create awareness among the public about nocturnal mammals at theirsurroundings.
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