Elevational diversity patterns of small mammals on Mount Kinabalu, Sabah, Malaysia

© 2001 Blackwell Science Ltd. http://www.blackwell-science.com/geb

41

ELEVATIONAL GRADIENTS IN MAMMALS: SPECIAL ISSUE

Global Ecology & Biogeography

(2001)

10

, 41–62

Blackwell Science, Ltd

Elevational diversity patterns of small mammals on Mount Kinabalu, Sabah, Malaysia

SHUKOR MD. NOR

Field Museum of Natural History, 1400 South Lake Shore Drive,

Chicago, IL 60605, U.S.A.

ABSTRACT

1

Diversity patterns of small mammals werestudied along an elevational transect on MountKinabalu, the highest mountain in South-eastAsia, utilizing data from previously existingsources and a new field study. A mark-and-releasestudy (conducted during wet and dry seasonsbetween November 1994 and April 1995) resultedin captures of 12 small mammal species, includingtwo species of squirrels, two tree shrews, sevenmurid rodents and one gymnure.

2

Based on data compiled from this survey,museum specimens, and published and unpub-lished literature (analysed by locally weighted sumsof squares and quadratic polynomial regressions),species richness of small mammals formed amiddle elevation bulge, highest at about 1200–1400 m and declining at lower and higher eleva-tions. Trapping during two seasons did notchange the assessment of the pattern.

3

A cluster analysis of these data indicated thatthere are two elevationally associated faunas, onein the highlands and another in the lowlands.The transition between these two assemblages isat 1700–1800 m elevation. The lowland faunalassemblage has the highest number of species,

with maximum species richness at about 1300 mfor total small mammal species, about 1200 m forarboreal species and about 1400 m for terrestrialspecies.

4

The areas where much overlapping of speciesoccurs are the elevations where climate and vegeta-tion change rapidly from lowland to montane types.Tree species, gymnosperms, orchids and fernsshowed a similar curvilinear pattern along thesame elevational gradient, with maximum spe-cies richness at about 1400–1500 m. Temperaturedeclined progressively with increasing elevation,but rainfall and humidity reached their highestlevels at about 1700 m.

5

Maximum diversity of small mammals thusoccurred at the elevation where a highland anda lowland assemblage overlapped, where severaltypes of plants reached their maximum divers-ity, and where rainfall and humidity reachedtheir maxima. Similar patterns have been docu-mented for small mammals, plants, and climate atsites scattered in Indo-Australia from Taiwan toNew Guinea.

Key words

Biodiversity, climate, elevational gra-dients, Malaysia, mid-elevation bulge, mountains,plants, Sabah, small mammals, species richness.

INTRODUCTION

As the highest point in South-east Asia, MountKinabalu has been the focus of research ontropical ecology and biological diversity, including

mammals, for more than a century and a half,probably because it is generally believed thatthe mountain supports the most diverse biota ofany single mountain between the Himalayas andNew Guinea (e.g. Kitayama, 1991, 1992a, 1992b).However, because most past studies of mammalsemphasized systematics and taxonomy, littleecological information is available, especiallyon community structure, habitat utilization and

Current address: Faculty of Science and Technology, Uni-versiti Kabangsaan Malaysia, 43600 Bangi, Selangor,Malaysia.

E-mail: [email protected]

GEB231.fm Page 41 Tuesday, February 20, 2001 6:31 PM

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© 2001 Blackwell Science Ltd,


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diversity patterns of the diverse small mammals(Medway, 1977; Payne

et al.

, 1985). The need togather these ecological data has become increas-ingly urgent as rain forest destruction has increased,exacerbating the need for appropriate conserva-tion measures to maintain faunal diversity. Thepurpose of this study was threefold: (1) to docu-ment patterns of elevational distribution anddiversity among small mammal species along the4101 m elevational gradient on Mount Kinabalu,using both existing and newly collected data;(2) to investigate the composition and organiza-tion of small mammal assemblages during thewet and dry seasons at six elevational sites,as a means of evaluating the data concerningthe elevational gradient pattern; and (3) toinvestigate climatic variation and plant diversitypatterns along the same transect as a meansof interpreting variation in mammalian speciesrichness.

STUDY AREA AND SPECIES

Geology

Borneo is the third largest island in the world,covering an area of 743 244 km

2

. About 85%of Borneo, especially the southern and easternregion, consists of lowlands and swampy plains.In the central and north-western region arehigh hills and mountains reaching 1000–2000 mabove sea level. Most of the highest peaks arein Sabah, one of the two states of Malaysia inBorneo, with an area of approximately 76 115 km

2

(Fig. 1). The mountains are interconnected andform a long high strip from north to south-west in Sabah. Among these mountains isMount Kinabalu, which rises up to 4101 m.This mountain lies at 6

°

5

′

N and 160

°

33

′

E,and stands within the Kinabalu National Park,which was established in 1964 and encompassesan area of approximately 754 km

2

(291 miles

2

;Fig. 1).

Mount Kinabalu is one of the world’s youngermajor non-volcanic mountains. It was formedby an intrusion of a granite pluton through theoverlying Crocker Range during the Pleistocene,beginning about 1.5 million years ago (Jacobson,1970, 1978). The massif is still growing, pushingup the summit and the Crocker range at a rateof about 0.3 cm/year (Jenkins, 1971). The present

summit above 3500 m is a bare and unvegetatedsurface of fresh granodiorite. During the latePleistocene this zone was covered by an ice fieldof about 5 km

2

. The ice, which melted about9200 years ago, pushed boulders of granite andsandstone to the surrounding areas and leftbehind several features of glacial erosion such asstriations and grooves, and polished and pluckedsurfaces (Flenley & Morley, 1978; Jacobson, 1978).One of the major deposits is the boulder andsandstone bed, about 140 m in thickness, knownas the Pinosok Plateau, which sprawls irregularlybetween 1200 and 2400 m, and covers an areaof about 50–60 km

2

(Jenkins, 1971).On Kinabalu, soils are considered zonal; they

depend on topography and may vary with eleva-tion. The lowland soils are Oxisols, the montaneare Histic or Pedozolic (Spodosols) with well-developed eluviated horizons, and above 2800 mthey are categorized as Incorptisols, where anappreciable amount of organic matter is incorpor-ated with mineral particles from the granite rock(Kitayama, 1991; 1992a,b). The denuded rocknear the summit zone (>3000–3200 m) has littlesoil, suggesting the effects of continuing erosionby rain water and a slow rate of soil formation(Kitayama, 1991). In addition, there is soilderived from ultrabasic rock. The extent of thisserpentine soil around the main massif is verylimited and forms mosaics. These soils may below in available calcium, potassium and phos-phorous but high in iron, chromium, cobalt,magnesium and nickel. Thus, they are oligo-trophic and may be growth-inhibiting or toxicfor some plants (Brunotte & Kitayama, 1987;Kitayama, 1991).

Climate

Like most tropical mountains, Mount Kinabaluhas a humid tropical climate. In general, Marchand April are the driest months and November–December are the wettest months (Table 1 inKitayama, 1992b). Mean air temperature at10 m elevation is 28

°

C, decreasing to 8

°

C at3780 m elevation (Fig. 3 in Kitayama, 1992b).Saturation deficit and actual vapour pressuremaximum at noon are typically highest at thelowest elevation and decrease with increasingelevation (

loc. cit.

). The cloud zone develops inthe mid-slope region: clouds start to develop


Small mammal elevation patterns in Malaysia

43



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above about 1200 m elevation and more fre-quently at about 2000 m. The upper limit ofclouding, however, varies only from about 3000 min the early morning to about 3200 m after lateevening and throughout the night.

The mean monthly air temperature at 1680 melevation is about 20

°

C with a daily fluctuation

of 7–9

°

C. The annual rainfall at the same ele-vation fluctuates greatly, ranging from 2000 to3800 mm. A prolonged dry season (usually duringMarch and April) may result in severe droughts.Within the last 10 years, drought has occurredat least three times: in 1979, 1981 and 1983(Beaman

et al.

, 1985; Table 1 in Kitayama, 1992b).

Fig. 1 Location and topography of Kinabalu National Park, showing the locations of study sites (1–6).


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The droughts recur periodically in relation tothe El Niño-Southern Oscillation (Beaman

et al.

,1985).

Vegetation

Kitayama (1991) estimated that 93.5% of the parkis covered by natural vegetation, while disturbedvegetation accounts for 6.5% and shifting cul-tivation (hill-rice) for 0.6%. Mount Kinabalupossesses one of the world’s richest assemblagesof plants, over 4000 species of vascular plantshaving been collected from the area around themountain (Beaman & Beaman, 1990). Further,more than half of the families of flowering plantsin the world are represented on Kinabalu. Thereare at least 21 types of vegetation (Kitayama,1991), the distribution of which is influenced byelevation in association with climate and soil(Cockburn, 1978; Kitayama, 1992a,b). The major-ity of the natural vegetation is either tropicallowland forest (35%) or tropical montane rainforest (37%). The vegetation of Kinabalu hasbeen classified by many workers (Cockburn, 1978;Kitayama, 1987), but there is little consist-ency among studies in assigning the vegetationzones on this mountain. Here the vegetationzones described by Kitayama (1992a,b) are fol-lowed, because this is the most recent classifi-cation, based on the most robust vegetationanalysis. He identified four discrete elevationalvegetation zones on Mount Kinabalu: lowland(<1200 m), lower montane (1200 to 2000–2350 m),upper montane (2000 to 2350–2800 m) and sub-alpine (2800 to the forest line, 3400 m).

Existing data on mammals

Previous publications on the mammals of MountKinabalu span more than a century (Thomas,1889; Lyon, 1911; Banks, 1931, 1949; Davis,1962; Harrison, 1964; Medway, 1967, 1977; Lim &Muul, 1978; Payne

et al.

, 1985; Junaini, 1986).No previous study has described the elevationaldiversity pattern of mammals on this moun-tain in detail. Lim & Muul (1978) suggested thatthe number of small mammal (volant and non-volant) species declines with increasing eleva-tion. Junaini (1986) described the ecology anddistribution of small mammals at four elevationalsites on this mountain: Poring Hot Spring (700 m),

Park Headquarters (1700 m), Carson Camp(2700 m) and Panar Laban (3200 m). Her totaltrapping effort at each site was low, between240 and 480 trap-nights.

Trapping sites

The field portion of this study was conductedalong a transect on Mount Kinabalu fromOctober 1994 to April 1995 at six elevationalsites (Md. Nor, 1997). The six elevational sitesare: lowland forest at 700 m and lower montaneforest at 1200 along the East Ridge trail, andlower montane forest at 1700 m, upper mont-ane forest at 2200 and 2700 m, and subalpineat 3200 m along the Summit Trail (Fig. 1).These sites were chosen for their accessibility byfoot.

Lowland forest at 700 m (Poring Hot Spring; 26 January–1 February, 19–23 March 1995)

The 700 m site was located at the lowest end ofthe East Ridge trail, near Poring Hot Spring(Fig. 1). This site was covered by canopy trees,mainly dipterocarps up to 35 m in height withdiameter at breast height (d.b.h.) of 1.8–2.6 m.The understorey of saplings, primarily diptero-carps, and the ground cover of ferns and herb-aceous dicots were each very sparse. Some openareas due to fallen logs were extensively coveredby figs (

Ficus

), saplings (primarily dipterocarps)and ferns. Soils were clay mixed with sand, witha thin layer of leaf litter. All the trapping lineswere located in primary forest, except about 20%of one line that was in secondary forest.

Lower montane forest at 1200 m (Poring Miabau; 7–13 February, 13–17 March 1995)

The transition between lowland and lowermontane forest occurs at about 1200 m eleva-tion (Kitayama, 1992a). The site at PoringMiabau was covered with canopy trees of 15–30 m height and 0.4–1.3 m d.b.h. The under-storey consisted mainly of tree saplings and treeferns. Rattan palms and climbing pandans wereuncommon, and woody vines and moss werecommon. About 15

Rafflesia

buds of 10–20 cmdiameter were also uncovered under a moderateleaf litter cover near Kepungit river. The groundcover also was moderate, mostly pandans, ferns,and sedges.



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Lower montane forest at 1700 m (Park Headquarters; 7–15 November 1994, 3–7 April 1995)

The lower montane forest at this site is alsoknown as ‘oak–chestnut forest’ (Sato, 1991). Inthis primary forest the canopy trees reachedheights of 10–25 m and most trunks were coveredwith epiphytes, ferns and mosses. The understoreyconsisted of small shrubs, saplings and tree ferns.The ground cover consisted of ferns, rattans,climbing bamboo, orchids and mosses.

Upper montane forest at 2200 m (Kambarangoh; 7–13 December 1994, 6–10 March 1995)

The upper montane forest at this site is alsoknown as ‘mossy forest’ (Sato, 1991; Kitayama,1992a). The tree canopy was at a height of 7–15 m.Tree trunks were covered with thick mosses andepiphytes. Mosses, climbing bamboo, orchids,and pitcher plants were very abundant on theground. In some areas mosses reached up to20 cm depth.

Upper montane forest at 2700 m (Carson Camp; 23–29 November 1994, 25 February–2 March 1995)

The upper montane forest at this site is alsoknown as ‘ultrabasic rock forest’ (Sato, 1991). Here,the canopy was dominated by 2–5 m tall treesof the genera

Leptospermum

and

Dacrydium

.Ground surfaces were mostly covered by ferns,pandans and shrubs, but pitcher plants andorchids were also abundant. Moss was uncom-mon and found only on tree trunks.

Subalpine at 3200 m (Panar Laban; 18–24 February, 27–31 March 1995)

This uppermost site was located in forest domin-ated by

Leptospermum

and

Rhododendron

. Theground was largely derived from a deposit ofgranitic boulders (Sato, 1991) mostly covered byshrubs and a very thin layer of litter.

MATERIALS AND METHODS

Only non-flying small mammals whose adult liveweight ranges from approximately 2 g to 5 kgwere considered in this study (Bourliere, 1975;Hayward & Phillipson, 1979). This group includesmost indigenous Sabahan species from the mam-malian orders Insectivora, Scandentia, Rodentia,Lagomorpha, and small-sized Carnivora andPrimates, but excludes middle-sized mammals

such as badger and wild canids (Bourliere, 1975;Hayward & Philipson, 1979).

Field survey

Two trapping sessions were conducted at eachsite. Three trapping lines more than 200 m apartfrom one another were established at each of thetrapping sites. Each line consisted of 15 stationsset at about 10-m intervals. At each station,traps were placed on the ground and left for3 consecutive days and nights. Since the object-ive of this study was to document as manyspecies of terrestrial small mammals as possible,after the first 3 nights trapping was continuedfor another 3 consecutive nights for the firstsession, but for only 1 night for the secondsession. During the extended trapping periods,only one trap-line was operated at each site.This line consisted of 90 stations set at 10-mintervals. The number of trap-nights in the firstand second session were 405 (135 in the first3 consecutive trapping nights and 270 in the sec-ond 3 consecutive trapping nights) and 225 (135in the first 3 trapping nights and 90 in the next1 night), respectively, for a total of 675 trap-nightsper site. To avoid human disturbance, especiallyfrom climbers and visitors regularly using thetrail, the trap-lines were established at least15 m from the main trails.

The capture–release method was employed inthis study. Local live traps (270 mm

×

110 mm

×

90 mm) made of chicken wire with 1–2 cm meshwere used. This type of trap is inexpensive, locallyavailable, and performs better than other kindsof live traps (e.g. Sherman live-trap) in catchingsmall mammals in Borneo (Md. Nor, 1996).

Trapping for the first three consecutive trap-ping nights started at 0600 h with fresh baitplaced in each trap. Three types of bait, live earth-worms (each about 7–9 cm long, taken fromonly one site at 1700 m), fried coconut smearedwith peanut butter, and ripe banana, were usedalternately at each station following a Latin squaredesign (Sokal & Rohlf, 1981). Traps were revisitedat 0800 h and at 1000 h. The captured smallmammals were released after identification, mark-ing by clipping the toes of the hind limbs andexamining for sex, age and reproductive condi-tion. After the 1000 h visit, the traps were leftopen until dusk, with the night session starting


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at 1800 h. The same procedure was followed atnight. For the second consecutive trapping nights(3 nights in the first session and 1 night for thesecond session), traps were serviced twice, between0600 and 0900 h and between 1500 and 1800 h.

Two to four individuals of each species weretaken as voucher specimens. Removal of voucherswas carried out only towards the end of thetrapping session, except in a few instances. Thespecimens collected are now housed at the FieldMuseum of Natural History, Chicago, U.S.A. andat Sabah National Park Headquarters, Ranau,Sabah, Malaysia. Identification of the species ofsmall mammals was based on Medway (1977) andPayne

et al

. (1985) and comparison with specimensin the Field Museum.

Mammal data compilation and analysis

The elevational diversity pattern of small mam-mals on this mountain was analysed using twosets of data: first, the trapping data describedabove; and secondly, data compiled from myfield survey together with published (Allen &Coolidge, 1940; Davis, 1962; Medway, 1977;Payne

et al.

, 1985) and unpublished (Junaini, 1986)literature, and museum specimens housed atthe Field Museum of Natural History, AmericanMuseum of Natural History, Zoology Museumof the Universiti Kebangsaan Malaysia in Sabah,Sabah State Museum, Sabah National ParkMuseum, and the Zoological Reference Collec-tion of the National University of Singapore. Thesedata were compiled for 33 elevational sites from500 m (the lowest boundary of the KinabaluNational Park) at 100 m intervals, up to 3700 mnear the forest line, including more than 800small mammal specimens, some of which werecollected as early as 1887 (Medway, 1977; Payne

et al.

, 1985). It is assumed that each species occursat all elevations between the lowest and highestdocumented elevations. Most species are well-documented, and the estimate is based on manyelevational records; some are poorly known,and the estimate is more tenuous. For this reason,drawing overly detailed conclusions about precisedetails of the patterns was avoided.

To determine whether the diversity pattern ofsmall mammals is linear or curvilinear alongthe elevational gradient of this mountain, theoverall trend in the data was first sought with

(locally weighted sums of squares), a regres-sion technique designed to identify the underlyingtrend in a dataset without prior specificationof a model (Cleveland, 1979; Systat, 1992). Next,a simple linear regression model was used to testfor a linear pattern and quadratic polynomialregression model for a curvilinear pattern (Sokal& Rohlf, 1981; Systat, 1992). Note that the

x

-axis (elevation) for each of these analyses waslog-transformed to obtain a better fit on the model(Abramsky & Rosenzweig, 1984).

Cluster analysis was used to define mammalcommunity relationships among sites. This ana-lysis is based on Jaccard’s similarity coeffici-ents using the unweighted pair-groups method(

) (Jongman

et al.

, 1995). Jaccard’s similar-ity coefficients were calculated based on thepresence and absence of small mammal species,and dendrograms were constructed using theMultivariate Statistics Package (1999).

Vegetation analyses

Data on trees

≥

10 cm d.b.h. were taken fromKitayama (1992a, 1992b). He surveyed these treesat 14 sites at 200 m intervals, using the point-centred method (Mueller-Dombois & Ellenberg,1974; see Kitayama, 1991), along the same transectwhere my trapping stations were located on thesouth-eastern slope of Mount Kinabalu (Kitayama,1992a). Cumulative diversity of trees from samplingareas of at least 0.1 ha were used in this analysis.

The number of species of ferns, orchids andgymnosperms for each elevation on MountKinabalu were tallied by the following authorsfrom herbarium specimens. For ferns, Parris

et al

. (1992) examined more than 4400 specimensrepresenting 621 species, some collected as earlyas 1858 by at least 44 collectors. Information onorchids was based on more than 5000 specimenscollected by at least 93 collectors (Wood

et al.

,1993). Gymnosperm data were based on about700 specimens (representing 28 species), collectedby at least 74 collectors, commencing as early as1851 (Beaman & Beaman, 1990).

Climate data and analysis

Rainfall data from 1992 to 1994 were obtainedfrom the Malaysian Meteorological Department(unpublished data), Mammut Copper Mine



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(unpublished data) and Kitayama (submitted).Daily air temperature and relative humiditywere collected for 5–9 days at each of my studysites. Temperature and humidity readings weretaken every 4 consecutive hours at 0600, 1200,1800 and 2400 h, using an electronic digitalthermohygrometer.

RESULTS

Field survey

A total of 824 captures of small mammals in3780 trap-nights was recorded, for a total trap-success of about 21.8%. Average trap-success ateach elevation varied from 5.4% (or 35 individuals)at 700 m to 33.7% (or 212 individuals) at 2200 m(Table 1). Species accumulation curves reachedasymptotes at all elevations (Fig. 2). The numberof species appeared to approach an asymptoteby the end of the first session (405 trap-nights)at all of the trapping-sites, except for adding onespecies at 3200 m elevation during the secondsession. From the entire trapping session, no newspecies were added after 2025 cumulative trap-nights, or 53.6% of the total trapping effort.

Twelve species of small mammals were cap-tured in this study, including two squirrels(

Callosciurus orestes

and

Dremomys everetii

),two tree shrews (

Tupaia montana

and

Tupaiatana

), one gymnure (

Hylomys suillus

) and sevenmurid rodents (

Leopoldamys sabanus

,

Maxomysochraceiventer

,

M. surifer

,

M. whiteheadi

,

Nivi-venter cremoriventer

,

Rattus baluensis

and

Sun-damys infraluteus

(Table 2). Among these species,

T. montana

was the most numerous, with 375individuals trapped, or 46% of the total catch.

R. baluensis

was the next most abundant, witha total of 253 individuals or approximately 30%of the total animals caught.

The small mammal species were not evenlydistributed at the six elevational sites (Table 2).Only

L. sabanus

was distributed widely androughly in equal abundance across the elevations.There were three species restricted to a singleelevation:

C. orestes

and

T. tana

were the rarestspecies, caught only twice at 1700 m and threetimes at 700 m, respectively. Both of these arescansorial, and may not have been effectivelysampled by my terrestrial traps.

M. ochraceiventer

was moderately abundant, but occurred onlyat 1200 m elevation. There were three species

Table 1 Captures, trap success (percentage per trap-night) and number of species of the first/second 3consecutive trapping-nights (only 1 night in the second session)

Site elevation (m) Total captures1

700 1200 1700 2200 2700 3200

Session 1 8/9 21/18 48/53 84/53 6/51 40/60 247***/244***Session 2 13/4 15/8 46/15 68/7 53/13 65/19 260***/66***Total 21/14 36/26 94/68 152/60 99/64 105/79 507***/310***

% Trap success2,3,4

Session 1 5.9/3.7 15.6/6.7 35.6/19.6 62.2/19. 6 34.1/18.9 29.6/22.2Session 2 9.6/4.4 11.1/8.9 34.1/16.7 50.4/7.8 39.3/14.4 48.1/21.1Total 7.8/3.9 13.3/7.2 34.1/18.9 56.3/16.7 36.7/17.8 39.3/21.9

Number of species5

Session 1 4/5 6/4 6/6 5/5 4/5 4/4 12/12Session 2 4/2 4/4 3/2 5/3 5/3 3/3 11/8Total 5/5 7/5 8/6 7/5 5/5 4/4 12/12

1 Comparison of sessions 1 and 2, first 3 consecutive trapping-nights (paired t-test, d.f. = 5, P = 0.787). 2 Comparison of sessions 1 and 2, first 3 consecutive trapping-nights (paired t-test, d.f. = 5, P = 0.787). 3 Comparison of sessions 1 and 2, second 3 consecutive trapping-nights (paired t-test, d.f. = 5, P = 0.213). 4 Comparison of sessions 1 and 2, all trapping-night (paired t-test, d.f. = 5, P = 0.130). 5 Comparison of sessions 1and 2, first 3 consecutive trapping-nights (paired t-test, d.f. = 5, P = 0.224), **P < 0.01, ***P < 0.001.


48 S. Md. Nor

© 2001 Blackwell Science Ltd, Global Ecology & Biogeography, 10, 41–62

of murid rodent that occurred only at the lowerelevations: M. surifer at 1200 m and below,N. cremoriventer at 1700 m and below, andM. whiteheadi at 2200 m and below. Four smallmammal species occurred only at upper elevations:D. everetii and T. montana at 1200 m and above,H. suillus at 1700 m and above, and R. baluensisat 2200 m and above. One species, S. infraluteus,was found only between 1700 and 2200 m a.s.l.Finally, two congeneric species, T. montana and

T. tana, exhibited parapatric elevational distri-butions. T. tana was found only at the lowestelevation (700 m) and T. montana from 1200 mto 3200 m (Table 2).

In both sessions, there was significant vari-ation in the number of captures and percentageof trap success (the total number of capturesdivided by the total number of trap-nights) ofsmall mammals among the sites (Table 1, Fig. 3).The total number of captures (in the first 3

Fig. 2 Cumulative number of species (triangles) and percentage of trap success (squares) over time (cumulativenumber of trap-nights) at six elevational sites on Mount Kinabalu. First trapping session at each elevationalsite ended after 405 trap-nights.


Small mammal elevation patterns in Malaysia 49


consecutive trapping-nights) and percentage oftrap-success (in the first and second consecutivetrapping-nights) at each site across elevationswere similar between trapping sessions (Table 1,Fig. 3). The total number of captures at eachelevation in the first session was not signific-antly different from the second session (paired

t-test of the elevational trapping sites, Table 1) andthe total number of individuals of each speciesat each elevation in first session was similar tothe second session (Table 2). Also, percentageof trap success across elevations from the firstsession was not significantly different from thesecond session. Thus, these data indicate that,although the density and diversity of small mam-mals varies with elevation, relatively little variationwas found between sessions at any elevation onthis mountain.

Regardless of the session, the pattern of thetotal number of individuals captured and per-centage of trap success at each elevation alongthe transect on this mountain was the same:depauperate at low elevation (dipterocarp for-est, 700–1200 m), highest at middle elevation(montane forest, 1700–2200 m) and moderatelyhigh at high elevation (subalpine, 2700–3200 m)(Table 2, Fig. 3a, b). At 700 m elevation, amongfive species recorded here, M. surifer andN. cremoriventer were equally abundant, with10 individuals of each species (or 29.4% of thecaptures at this site), and T. tana was the leastcommon with three individuals (or less than 9%)(Table 2). T. montana dominated the communityof small mammals at 1200, 1700 and 2200 m eleva-tion, with 48.3%, 77.8% and 62.6%, respectively, ofthe total captures. At these elevations there were,respectively, 7, 8 and 7 recorded species. R. baluensiswas the most abundant species, with 49.7% ofthe captures among five species at 2700 m, and69.7% among five species at 3200 m elevation.

At each elevation, the number of species cap-tured in the first 3 consecutive trapping nightsdid not differ significantly between the first andsecond sessions (Table 1; paired t-test). Bothsessions had the same total number of speciescaptured (12) across all elevations (Table 1). Whenthe data from the two sessions were pooled,species richness showed a peak of eight speciesat 1700 m, with fewer species at both higherand lower elevations (Table 2, Fig. 4).

Analysis of distribution and diversity pattern

Based on all available data (published andunpublished), 80 species of volant and non-volantsmall mammals have now been documentedfrom this mountain. They represent six ordersand 13 families. Among these species, 19 are

Fig. 3 (a) Numbers of individual captures of smallmammals in the first three consecutive trappingnights at six elevational sites on Mount Kinabalu.(b) Relative abundance (measured as percentage trapsuccess) of small mammals at six elevations onMount Kinabalu. (CF3TN = combination of the first3 consecutive trapping-nights, SESS1 = session 1,SESS2 = session 2).


50 S. Md. Nor


Table 2 Captures of small mammals on Mount Kinabalu, by species and by elevation of the first/secondconsecutive trapping sessions. Probabilities are for χ2-test of even capture frequencies (total captures of bothsessions) across elevations. Sites with frequencies greater than expected are underlined

Species Session1 Site elevation (m) Total

700 1200 1700 2200 2700 3200

Callosciurus orestesa 1 0/0 0/0 1/1 0/0 0/0 0/0 1/1nc 2 0/0 0/0 0/0 0/0 0/0 0/0 0/0nc

Total 0 0 2 0 0 0 2nc

Dremomys everetii 1 0/0 1/0 6/51 1/5 2/5 6/14 26/292 0/0 0/0 3/0 10/1 1/0 7/3 21/4Total 0 1 14 27 8 30 80***

Hylomys suillus 1 0/0 0/0 1/1 2/0 1/6 0/1 4/82 0/0 0/0 0/0 0/0 1/0 0/0 1/0Total 0 0 2 2 8 1 13***

Leopoldamys sabanus 1 2/3 4/1 2/0 0/1 0/2 2/0 10/72 0/0 0/0 0/0 2/0 3/1 0/0 5/1Total 5 5 2 3 6 2 23

Maxomys ochraceiventer 1 0/0 4/3 0/0 0/0 0/0 0/0 4/32 0/0 7/2 0/0 0/0 0/0 0/0 7/2Total 0 16 0 0 0 0 16***

Maxomys surifer 1 0/1 3/2 0/0 0/0 0/0 0/0 3/32 7/2 1/1 0/0 0/0 0/0 0/0 8/3Total 10 7 0 0 0 0 17***

Maxomys whiteheadi 1 2/3 1/0 5/3 1/5 0/0 0/0 9/112 1/0 0/0 0/2 0/0 0/0 0/0 1/2Total 6 1 10 6 0 0 23***

Niviventer cremoriventer 1 3/1 0/0 1/0 0/0 0/0 0/0 4/12 4/2 1/1 0/0 0/0 0/0 0/0 5/3Total 10 2 1 0 0 0 13***

Rattus baluensis 1 0/0 0/0 0/0 20/9 20/21 24/40 64/702 0/0 0/0 0/01 1/1 30/10 50/17 91/28Total 0 0 0 41 81 131 253***

Sundamys infraluteus 1 0/0 0/0 2/1 0/0 0/0 0/0 2/12 0/0 0/0 2/0 1/0 0/0 0/0 3/0Total 0 0 5 1 0 0 6***

Tupaia montana 1 0/0 8/12 30/42 50/36 23/17 8/5 120/1122 0/0 6/4 41/13 44/4 18/2 8/31 17/26Total 0 30 126 134 60 24 375***

Tupaia tana 1 1/1 0/0 0/0 0/0 0/0 0/0 1/12 1/0 0/0 0/0 0/0 0/0 0/0 1/0Total 3 0 0 0 0 0 3nc

Number of species 5 7 8 7 5 5 1 2

1 Sessions 1 and 2 of the first 3 consecutive trapping-nights (paired t-test, d.f. = 5, P = 0.590). nc Not calculatedbecause of small sample size. **P < 0.01, ***P < 0.001.




volant (15 insectivorous bats and four fruit bats)and 61 are non-volant (31 arboreal and 30terrestrial; Table 3). The numbers of arborealand terrestrial non-volant small mammal speciescompiled for 33 elevational bands on this moun-tain are given in Table 4. (See Md. Nor (1997)for data on bats and large mammals.) When thecompiled data were analysed with , thediversity of arboreal and terrestrial non-volantspecies in 33 elevational bands on this mountain

was again found to be highest at middle eleva-tions. From the lowest elevation, terrestrial smallmammal diversity gently ascends and peaks atabout 1400 m. Diversity then drops abruptlyfrom about 25 species at 1400 m to about 11species at 2200 m elevation (Fig. 4a, Table 4). Thedrastic drop in number of species was alsoobserved for arboreal and all non-volant smallmammals combined after about 1300 m elevation(Fig. 4a, Table 4). Each of the curvilinear patternswas fitted significantly with a quadratic poly-nomial regression model (Table 5).

Cluster analysis (Figs 5 and 6) depict twogroups of small mammals, easily defined as high-and low-elevation assemblages. The similaritybetween these two groups is below 3%, whereaswithin-group similarity values are relatively high.The dendrograms suggest that the boundarybetween low and high-elevation assemblages fallsbetween 1200 m and 1700 m above sea level(a.s.l.) using the new trapping data (Fig. 5), orbetween 1700 and 1800 m a.s.l. using the com-bined data (Fig. 6). Given that the combined dataare based on more extensive data and smallerelevational intervals, it is appropriate to rely moreheavily on it in this context, suggesting that theboundary between these two faunal assemblagesis centred near 1700 m. In comparison with thevegetational zones recognized by Kitayama (1992b),it is apparent that the first group is composedof the small mammals distributed in the low-lands (dipterocarp and lower limit of lowermontane forest), and the other group is made upof species distributed in the highlands (uppermontane forest and subalpine).

Fig. 4 Elevational diversity pattern of small mammalsacross elevations on Mount Kinabalu. (a) Basedon combined data; lower curve is arboreal, middlecurve is terrestrial and upper curve is the sum ofarboreal plus terrestrial. (b) Based on field trappingat the six elevational sites. All curves were calculatedby regression.

Fig. 5 Dendrogram from a cluster analysis basedon presence and absence of each small mammalspecies recorded during the field survey, utilizingJaccard’s coefficient and the unweighted-pair groupsmethod ().


52 S. Md. Nor


Table 3 Distribution of small mammals on Mount Kinabalu based on museum specimens, field survey (bold),and published and unpublished literature (, lowest elevation; H, highest elevation; Or, Order; Fa, family).Terr/Arb = terrestrial or arboreal

Species L(m) H(m) Or/Fa Terr/Arb

Chimarrogale himalayica 460 1700 Ins/Sor terrCrocidura fuliginosa 0 3700 Ins/Sor terrCrocidura monticola 1400 1600 Ins/Sor terrSuncus ater 1700 1700 Ins/Sor terrSuncus etruscus 0 650 Ins/Sor terrHylomys suillus 1000 3400 Ins/Ern terrDendrogale melanura 900 3350 Scn/Tup arbTupaia minor 0 1070 Scn/Tup terrTupaia montana 900 3170 Scn/Tup terrTupaia tana 0 1500 Scn/Tup terrNycticebus coucang 0 1650 Pri/Lor arbAeromys tephromelas 0 500 Rod/Sci arbAeromys thomasi 0 1600 Rod/Sci arbCallosciurus adamsi 0 900 Rod/Sci arbCallosciurus baluensis 300 1980 Rod/Sci arbCallosciurus notatus 0 1600 Rod/Sci arbCallosciurus orestes 600 1700 Rod/Sci arbCallosciurus prevostii 0 1000 Rod/Sci arbDremomys everetii 980 3400 Rod/Sci terrExilisciurus whiteheadi 900 3000 Rod/Sci arbGlyphotes simus 1300 1700 Rod/Sci arbHylopetes lepidus 1370 1370 Rod/Sci arbHylopetes spadiceus 1280 1280 Rod/Sci arbIomys horsfieldi 0 1800 Rod/Sci arbLariscus hosei 1279 1530 Rod/Sci arbPetaurista elegans 1070 1680 Rod/Sci arbPetaurista petaurista 0 900 Rod/Sci arbPetinomys setosus 0 500 Rod/Sci arbPteromyscus pulverulentus 550 550 Rod/Sci arbSundasciurus brookei 600 1070 Rod/Sci arbSundasciurus jentinki 900 3140 Rod/Sci arbSundasciurus lowii 0 1070 Rod/Sci arbChiropodomys gliroides 300 1220 Rod/Mur arbChiropodomys major 900 1500 Rod/Mur arbChiropodomys muroides 1100 1200 Rod/Mur arbHaeromys margarettae 0 900 Rod/Mur arbLenothrix canus 550 550 Rod/Mur terrLeopoldamys sabanus 0 3100 Rod/Mur terrMaxomys alticola 1070 3360 Rod/Mur terrMaxomys baeodon 900 1400 Rod/Mur terrMaxomys ochraceiventer 0 1700 Rod/Mur terrMaxomys surifer 0 1680 Rod/Mur terrMaxomys whiteheadi 0 2100 Rod/Mur terrNiviventer cremoriventer 0 1530 Rod/Mur terrNiviventer rapit 940 3360 Rod/Mur terrRattus alticola 900 3360 Rod/Mur terrRattus argentiventer 0 1646 Rod/Mur terrRattus baluensis 1524 3360 Rod/Mur terrRattus exulans 0 1650 Rod/Mur terr




Elevational climate changes

Mean air temperature recorded during thisfield study decreased linearly and strongly withelevation at the six trapping sites (Table 6;y = 28.10 − 0.005x, R2 = 0.967). My measures oftemperature differed slightly from those ofKitayama (1992a), whose data were based onfour months of hygrothermograph measurementsat 10 m, 500 m, 1680 m, 3200 m and 3780 m(y = 27.45 − 0.0055x, R2 = 0.999). My short-termmeasurement at 1680 m (Park Headquarters)was similar to long-term (1987–89) measurements(19.7 °C vs. 20.48 °C, Md. Nor 1997).

Mean relative humidity at the six studysites varied from 87.5% at 700 m up to 99.0%at 1700 m, then fell progressively to 66.9% at3200 m (Table 6). analysis showed aclear mid-elevation peak, and a quadratic poly-nomial regression of humidity on elevation wassignificant (y = 68.34857 + 0.03615x − 0.00001149x2,R2 = 0.981, P = 0.0066).

Monthly rainfall data were available fromsix weather stations near the transect: Poring(549 m), Kundasang (1280 m), Mammut CopperMine (1500 m), Park Headquarters (1680 m), theTelecommunications Station as Kamborongh(2200 m) and Sayat-Sayat (3780 m). Mean annualrainfall at these sites from 1992 to 1994 was2032 mm, 1926 mm, 2582 mm, 2490 mm, 3184 mmand 2418 mm, respectively (Md. Nor, 1997).Monthly rainfall from these sites indicated aperiod of low precipitation from January toApril, and high precipitation from May to

Table 3 continued.

Species L(m) H(m) Or/Fa Terr/Arb

Rattus rattus 0 1700 Rod/Mur terrRattus tiomanicus 0 1700 Rod/Mur terrSundamys infraluteus 920 2930 Rod/Mur terrSundamys muelleri 0 1650 Rod/Mur terrTrichys fasciculata 0 900 Rod/Hys terrArctogalidia trivigata 0 1500 Car/Viv arbHemigalus hosei 1200 1300 Car/Viv terrPrionodon linsang 0 1800 Car/Viv arbPaguma larvata 0 2150 Car/Viv arbMartes flavigula 0 1700 Car/Mus arbMelogale personata 1000 3000 Car/Mus terrMustela nudipes 0 1700 Car/Mus terr

Table 4 Species richness of nonvolant small mammalsin 33 elevational bands on Mount Kinabalu, basedon data in Table 3

Elevation (m) Total Terrestrial Arboreal

500 35 17 18600 38 18 20700 35 16 19800 36 17 19900 42 20 22

1000 42 22 201100 42 22 201200 45 23 221300 46 24 221400 44 25 191500 42 23 191600 39 23 161700 36 20 161800 20 12 81900 18 12 62000 17 12 52100 17 12 52200 16 11 52300 14 11 32400 14 11 32500 14 11 32600 14 11 32700 14 11 32800 14 11 32900 14 11 33000 14 11 33100 13 10 33200 11 8 33300 8 6 23400 8 6 23500 2 2 —3600 2 2 —3700 2 2 —


54 S. Md. Nor


December, with a slight depression in August(Md. Nor, 1997). The steep increase in annualrainfall evident between 1280 m and 2200 mwas also observed by Kitayama (1992a) in 1989,but at a slightly higher elevation than apparent

in the larger dataset. A steep increase in totalrainfall at 1600 m to 2200 m correlates favourablywith the frequent presence of clouds and fog atthese elevations (Kitayama, 1992a). analysisshowed a mid-elevation peak at c. 2200 m, but

Table 5 Simple linear and curvilinear (quadratic polynomial) regressions of small mammal diversity onMount Kinabalu as functions of elevation (x). Elevation was log transformed for the regression analysis.Each term in the each of the regression models is significant at P < 0.05 or higher. Probability indicatedfor the general model

Group (y) N Regression model R2

T-S-M (t) 6 Curvilinear y = −250.014 + 162.708x − 25.693x2 0.863*T-S-M (c) 33 Curvilinear y = −514.491 + 356.167x − 59.218x2 0.828***A-S-M (c) 33 Curvilinear y = −245.914 + 194.174x − 35.317x2 0.856***All-S-M (c) 33 Curvilinear y = −760.405 + 550.341x − 94.535x2 0.857***

*P < 0.05,**P < 0.01, ***P < 0.00. T = terrestrial, S-M = small mammals (t) = trapping (c) = compiled, A = arboreal,N = number of elevational sites (determined based on the available of data), = general trend based onlocally weighted sums of squares.

Fig. 6 Dendrogram from a cluster analysis based on presence and absence of all small mammal speciescompiled from field survey, museum specimens and published and unpublished literature. Analysis wasbased on Jaccard’s coefficient using the unweighted-pair groups method ().




a quadratic polynomial regression of rainfall onelevation was not significant (R2 = 0.54, P = 0.31).

Elevational vegetation changes

About 4000 species of native vascular plantshave been documented on Mt Kinabalu (Beaman& Beaman, 1990, 1993). At my sites, a curvilinearpattern was found in species richness of trees>10 cm d.b.h., increasing from 27 species at 600 mto 39 species at 1400 m, then declining to 11 spe-cies at 3400 m (Table 7; Fig. 7). analysisshowed a clear curvilinear pattern, and a quadraticpolynomial regression of tree species richnessagainst elevation was significant (y = −7.51.485 +513.84x − 84.375x2, R2 = 0.751, P < 0.001).

The species richness pattern of ferns, orchidsand gymnosperms documented in other studieswas similar to that of trees >10 cm d.b.h.; theyhad moderate to low diversity at low elevation,increased substantially to a peak near 1400 m,then declined rapidly at higher elevations (Fig. 7). analysis showed a curvilinear patternfor all three groups, and quadratic polynomialregressions for all three were statistically significant;for ferns (y = −7827.098 + 5045.185x − 798.552x2,R2 = 0.889, P < 0.001); for orchids (y = −7747.367+ 5003.664x − 795.030x2, R2 = 0.759, P < 0.001),and for gymnosperms (y = −588.528 + 377.361x− 59.898x2, R2 = 0.579, P < 0.001).

The number of trees with diameter ≥10 cm andthe number of small mammals in 14 elevationalbands (Table 7) is significantly correlated for ter-restrial species of small mammals (y = −2.567 +0.731x; R2 = 0.780, P < 0.01), for arboreal mammals(y = −9.088 + 0.822x; R2 = 0.637, P < 0.001), and

for all species (y = −11.655 + 1.553x; R2 = 0.730,P < 0.001). A similar test of the associationbetween small mammal species richness and com-bined counts for orchids, ferns, gymnosperms andtree species yielded the same results (Md. Nor,1997). In other words, both mammal and plantspecies richness are significantly curvilinear withrespect to elevation, and mammal and plantspecies richness follow a significantly correlatedpattern along the elevation gradient.

Table 6 Species richness of terrestrial small mammals based on trapping data, daily mean air temperature,and relative humidity, for a transect sampled on Mount Kinabalu between October 1994 and April 1995

Elevation (m) Terrestrialsmall mammals

Daily mean

Air temperature (°C) Relative humidity (%)

700 5 25.9 87.51200 7 21.7 95.31700 8 19.7 99.02200 7 17.4 89.82700 5 15.8 82.33200 5 13.7 66.9

Table 7 Species richness of canopy trees (greaterthan or equal to 10 cm d.b.h.), terrestrial and arborealsmall mammals, and the sum of terrestrial plusarboreal small mammals at 14 elevational sitesalong a transect on Mount Kinabalu. *Sites wherenumbers were extrapolated based on plots thatwere smaller than 0.1 ha

Elevation(m)

Canopy trees(per 0.1 ha)

Small mammals

Total Terrestrial Arboreal

600 27 36 17 19800 27 36 17 19

1000 24 42 22 201200 33 44 23 211400 39 43 25 181600 29 37 21 161800 24 19 12 72000 24 17 12 52350 25 14 11 32600 13 14 11 32800 17 14 11 33000 17 13 10 33200 14* 8 6 23400 11* 3 3 0


56 S. Md. Nor


DISCUSSION

Small mammal density and diversity and elevation on Mount Kinabalu

The number of mammal species (80) documentedon Mount Kinabalu in this study is lower thanthe 101 species estimated by Lim & Muul (1978),who included potentially occurring as well asdocumented species. Many of the potentiallyoccurring species are bats, which are gener-

ally poorly sampled, but bats are not includedin this study in any case. Only a few of thepotential species are non-volant small mam-mals, and these seem increasingly unlikely tobe present.

Since the cumulative number of species docu-mented at each elevational site reached an asymp-tote, the trapping effort used in this study seemsto be sufficient to record the common terrestrialor scansorial small mammal species on this

Fig. 7 The diversity patterns of trees ≥10 cm d.b.h., ferns, orchids and gymnosperms, across elevations ofMount Kinabalu. See text for sources. All curves based on regressions, and all quadratic regressions aresignificant (see text).




mountain that normally forage actively on theforest floor. For most murids rodents that areeither terrestrial or scansorial species, they caneasily be caught in wire live-traps on the forestfloor baited with banana or coconut. Squirrels,especially the larger species such as Ratufaaffinis and smaller species such as Exilisciuruswhiteheadi, flying squirrels such as Petauristapetaurista, and shrews, however, are almostimpossible to capture in this kind of trap. Theother sampling bias concerns the ability to recordthe presence of rare species. For species thatare very low in density, the chance of beingcaptured in traps is slim. During this surveyonly two rare species were captured, C. orestesfrom Park Headquarters (1700 m) and T. tanafrom Poring Hot Spring (700 m).

In lowland forest at 700 m elevation (the low-est site), total trap success was less than halfthat documented in lowland forest on BanggiIsland, Sabah (24.6 per 100 trap-nights; Md.Nor, 1996). It was similar to that in lowlandforest near Kuala Lumpur, Peninsular Malaysia(5.0 per 100 trap-nights; Medway, 1966) andlowland forest on Catanduanes Island in thePhilippines (5.2 per 100 trap-nights; Heaneyet al., 1991), but higher than in lowland forestat Pasoh, Peninsular Malaysia (1.2 per 100trap-nights; Kemper & Bell, 1985) and AmpangForest Reserve, Peninsular Malaysia (2.9 per100 trap-nights; Lim, 1973). It was within therange of primary habitat between 150 and 1000 mon Kedah Peak, Peninsular Malaysia (3.4–6.6 per100 trap-nights; Langham, 1983), lowland forest ofDanum Valley Reserve, Sabah (1.9–5.6 per 100trap-nights; Jum, 1987) and primary forest onLeyte Island, the Philippines (1.8–4.4 per 100trap-nights; Heaney et al., 1989). Compared tothe five higher elevational sites, the low trapsuccess at this elevation is typical for most tropicallowland forest, where most trapping has norm-ally been performed at or near ground level(Harrison, 1969; Kemper & Bell, 1985; Heaneyet al., 1989; Rickart et al., 1991; Heaney, 2001).At Kamborangah (2200 m), trap success washigher than at the five other trapping sites onthis mountain. At Park Headquarters (1700 m),trap success was higher than in primary forestof comparable elevation (1600 m) on MountIsarog in the Philippines (15.3 per 100 trap-nights; Balete & Heaney, 1997).

Mammal elevational distribution and diversity on Mount Kinabalu

Cluster analyses based on Jaccard’s similaritycoefficients on presence and absence of smallmammal species (Figs 5 and 6) enabled identifica-tion of two groupings within the fauna, high-land and lowland. The boundary between thesetwo groups is between 1700 and 1800 m elevation.From 1700 to 1800 m, small mammal richnessdrops drastically, with richness of terrestrial andarboreal small mammals dropping from 20 to 12and 16 to 8 species, respectively (Fig. 4a, Table 4).The drop in number of species above 1700 m isassociated with the disappearance of all low-land small mammal species (Tables 2 and 3).

Although the elevation of the lowland/uplandboundary for both the terrestrial and arborealportions of the small mammal fauna occurredat about 1700 and 1800 m, the pattern of changediffered in number of species (Fig. 4a). At the lowerelevations, the number of arboreal species washigh compared to terrestrial species. Both groupsincreased in diversity to about 1500 m and bothdeclined thereafter, but the arboreal speciesdeclined quite abruptly above 1700 m, the eleva-tion above which upper montane (mossy) forestpredominated. There were no arboreal speciesabove 3400 m elevation, the level above whichtrees are virtually absent.

A mid-elevation diversity peak was evident inall mammal datasets, including my field trappingdata and the compiled data, for both terrest-rial and arboreal small mammals (Fig. 4b). Forboth datasets, although the peak was some-what below the faunal boundary where muchoverlapping of species actually occurs, it is clearthat species overlap contributes substantially tothe peak in species richness at middle eleva-tions. It should be noted that many highlandspecies penetrated at least a short distancebelow the overall faunal boundary, whereas mostlowland species disappeared abruptly above thisboundary (Tables 3 and 4).

Elevational pattern of climate and plant species richness

As anticipated, the effects of adiabatic coolingresulted in declining air temperatures with increas-ing elevation on Mount Kinabalu. However, both


58 S. Md. Nor


rainfall and humidity showed a pronouncedmiddle-elevation peak, at about 1700 m. Whiledetailed data on climatic variation along eleva-tional transects in South-east Asia, and in thetropics in general, are scarce, it appears that thesepatterns are common (Whitmore, 1984: 254;Heaney, 2001).

Nearly 4000 species of vascular plants havebeen collected within the ≈700 km2 area ofMount Kinabalu, representing over 180 familiesand 950 genera (Beaman & Beaman, 1990, 1993).Compilations based on extensive enumerationsby botanists during the last 150 years, plus morerecent studies by plant ecologists, have foundthat most plant taxa have their highest divers-ity at middle elevations, usually between 1400and 1500 m. Orchids, represented by over 300species (Parris et al., 1992), show a significantcurvilinear pattern that reaches its maximum atabout 1500 m, and the same is true for fernsand gymnosperms (Beaman & Beaman, 1993;Wood et al., 1993).

The species richness of trees ≥10 cm d.b.h.surveyed by Kitayama (1992a) was also highestat the middle elevation (1400 m), with a slightdepression in the overall pattern at 2600–2800 m.The same general pattern was reported by Sato(1991), who also found the same slight depres-sion at 2700–3000 m. Low species richness from2600 to 3000 m was stated by both authors tobe associated with soils that are derived fromultrabasic rock, with presumed oligotrophy andsoil toxins (Kitayama, 1991; Sato, 1991). Vegeta-tion on serpentine soils derived from ultrabasicrock covers about 16% of the park, and isfound as a mosaic of small patches along thetrail to the summit where their studies and myfield study were conducted.

Additional groups of plants that have beenless intensively studied on Mount Kinabalu showthe same general pattern of a middle-elevationbulge in diversity. Pitcher-plants (Nepenthes)peaked in diversity at about 1000 m (Kurata,1976), and mosses and liverworts peaked some-what higher (Frahm et al., 1990). On othertropical mountains, similar patterns have alsobeen found. Bryophyte diversity on a mountainin Colombia (Sierra Nevada de Santa Maria)peaked at middle elevations, between 2000 and2300 m (Gradstein & Pocs, 1989). Ferns reportedfrom several mountain ranges in New Guinea,

the Andes and Mexico also showed a similardiversity pattern, although the elevation of max-imum species richness varied from 2300 m inNew Guinea to 1800 m in the Andes, and to1300 m in Mexico (Tryon, 1989).

Alternatively, several groups of plants showedmaximum diversity at low elevation. Diptero-carp trees decreased linearly from low eleva-tion to about 1700 m in montane forest, atwhich point they disappeared (Choke & Poore,1978; Cockburn, 1978); the same finding wasreported by Ashton (1964). For all dipterocarpsin Brunei, the number of species declines withincreasing elevation up to 1500 m, above whichthey disappear (Fig. 7.9 in Jacobs, 1988). Thesame pattern of declining species richnesswith increasing elevation may characterize theplant families Bombacaceae, Ebenaceae, Euphor-biaceae, Leguminosae, Sapindaceae and Sapotaceae(Cockburn, 1978).

Small mammals, climate, plants and elevation in South-east Asia

It is obvious that the peak of species richnessof small mammals on Mount Kinabalu coin-cides with the area of habitat transition betweenlowland and montane forest. Kitayama (1992b)recognized that the transition between lowlandand lower montane forest on Mount Kinabaluwas between 1200 and 1400 m. Medway (1972)observed a similar pattern of maximum diversityin an area of habitat transition among small mam-mals on Gunong Benom in Peninsular Malaysia.

It would, however, be an oversimplificationto describe the pattern solely as one in whichthere is a bulge in species richness where twoassemblages happen to interdigitate. On MountKinabalu, remarkably similar middle-elevationbulges have been documented in several groupsof plants: ferns, gymnosperms, orchids and trees≥10 cm d.b.h. (Kitayama, 1992b). The diversitypatterns of these vegetation groups are signific-antly correlated with the diversity of smallmammals on this mountain (Md. Nor, 1997). Themaximum diversity of these plant groups all occurat about the same elevation, and all are correl-ated with the small mammal diversity pattern.Moreover, rainfall and humidity also reach theirmaxima at about the same elevational level.Clearly, there is a general phenomenon at work.




The pattern of a mid-elevation bulge in spe-cies richness is one of the two most commonlydocumented animal diversity patterns along ele-vational gradients (Brown, 1988; Gradstein &Pocs, 1989; Rosenzweig, 1992; Rosenzweig &Abramsky, 1993). A decrease of diversity withincreasing elevation is probably the most com-monly observed pattern across elevational gradi-ents, now documented in such organisms as birdson the mountains of New Guinea (Kikkawa& Williams, 1971; Beehler, 1981), fruit bats onthe mountains of the Philippines (Heaney et al.,1989, 1999), birds on the Amazonian slope ofthe Andes in Peru (Terborgh, 1977; Brown,1988: Fig. 3.1), bats in Peru (Graham, 1983;Patterson et al., 1996, 1998) and amphibiansand reptiles in southern Peru (Cadle & Patton,1988), and dipterocarp trees on Mount Kinabalu(Choke & Poore, 1978; Cockburn, 1978). Thistrend duplicates in many respects the latitudinalgradient (Kikkawa & Williams, 1971; Terborgh,1977; Brown, 1988), but unlike latitudinal gradi-ents these factors change very rapidly over veryshort horizontal distances (Kitayama, 1992a, 1992b),often only a few hundred metres.

The second common elevational pattern is amiddle-elevation peak in diversity. This has beenreported for non-volant mammals on MountKitanglad, a 3000-m peak in northern Mindanaoin the Philippines: there was a middle-elevationpeak in diversity, with highest diversity near thetransition from lower montane to upper montane(mossy) forest at about 2200 m elevation (Rickart,1993; Heaney, 2001). On Mount Isarog, a 2000-mmountain on Luzon Island in the Philippines,maximum diversity occurred near 1500 m, atthe transition from lower montane to uppermontane (mossy forest), with a slight declineat the peak. A significant correlation was alsofound between diversity and density of non-volant small mammals (Heaney et al., 1989,1999; Rickart et al., 1991; Heaney, 2001). On NewGuinea, Kikkawa & Dwyer (1992) observed thatnon-flying mammals were most diverse in mid-montane forest between 700 and 1500 m, with56 species of non-flying mammals in mid-montane forest, compared to lowland forest(100 m) with 17 species and high montane for-est between 1900 and 2600 m with 37 species.On a mountain in Taiwan, from a survey acrossthree elevational transects in two seasons (wet

and dry), Yu (1993, 1994, 1995) found a similarhump-shaped diversity pattern, with the highestdiversity in the area between 2000 and 2700 m.Taken together, these data, especially in the absenceof data to the contrary, imply that the pattern ofmaximum species richness among non-volantsmall mammals at middle elevations, particularlyin the area of transition from lower montane toupper montane forest, is common in communitiesof tropical small mammals in Indo-Australia.

The primary question remaining at this pointis why this pattern of a middle-elevation bulgein species richness should be so widespreadamong small mammals in Indo-Australia (aswell as in many other taxa). As a first step, thedata presented here permit the testing of someof the hypotheses presented by Heaney (2001).The following hypotheses can be rejected: thenull hypothesis of no pattern; the hypothesisthat diversity decreases progressively with eleva-tion; that diversity increases in areas of infre-quent perturbations (for the reasons cited byHeaney, 2001); and that diversity increases withincreasing area. Alternatively, there is supportfor the hypotheses that diversity peaks in areas ofcommunity interdigitation, that diversity increaseswith increasing rainfall (and humidity) and thatdiversity increases with increasing abundanceand/or biomass of the group under study. Perhapsmost importantly, hypotheses that associate divers-ity with productivity, with resource diversity,with habitat complexity, with habitat diversity,with decreased competition, and with high ratesof speciation, all remain to be addressed forthis fauna. In other words, the data presentedhere address only the most proximate associ-ations, e.g. elevation, temperature, rainfall,etc. The ultimate causal factors — associationswith productivity, and with patterns of resourceavailability, habitat diversity and complexity,competition and predation, all remain to beaddressed. Addressing the impact of those factorswill be crucial for developing a complete under-standing of variation in diversity patterns.

CONCLUSION

The non-volant small mammal fauna on MountKinabalu constitutes one of the most diverse andthoroughly sampled mammal faunas in Asia,with relevant data collected over a 150-year period.


60 S. Md. Nor


Both recent live-trapping and a compilation ofhistorical data yield a clear picture of speciesrichness peaking at middle elevations (1200–1400 m), dropping by about 30% in the low-lands and at least 80% at the mountain’s upper-most levels. Trapping in two different seasonsproduced information about reproductive biologyand population changes but did not change theassessment of diversity patterns. Relative densitycovaried with species richness, which implies thatthe two are influenced similarly by causal forces.

Cluster analysis indicated that the smallmammal fauna can be broadly grouped intospecies associated with two habitats, lowlandforest and highland forest. Species richness ofsmall mammals is highest at the elevations wherethese two broadly defined groups overlap, butthis is also the area where habitat changesrapidly from warmer, drier and more seasonalconditions to cooler, wetter and less seasonalconditions, and is the area of highest rainfalland humidity. It is also the elevation at whichseveral diverse groups of plants (orchids, ferns,gymnosperms and tree species) reach their peakdiversity, demonstrating that the mid-elevationbulge is a general feature of at least a largeportion of the biota on Mount Kinabalu. Thereasons for the placement of the diversity peakand the shape of the curve of small mammaldiversity remains uncertain, but several intricatelyinterwoven biotic and abiotic causal factors maybe involved. The patterns detected on MountKinabalu seem to be widespread among non-volant small mammal faunas in Indo-Australia,implying the persistent presence of broad-scalecausality.

ACKNOWLEDGMENTS

I wish to thank Drs Lawrence Heaney, JoelBrown, Hank Howe, Mary Ashley, ChristopherWhelan, and two anonymous reviewers for theirconstructive ideas and helpful comments on themanuscript. I much appreciate Dato’ Lamri Ali,the Director of Sabah National Parks for permis-sion to conduct this survey on Mount Kinabalu(Kinabalu National Park) and Ms Yang ChangMan, the Collection Manager at the ResearchCollection, Zoology Department, National Uni-versity of Singapore for permission to study thespecimens previously collected on Mount Kinabalu.

I am also grateful to the staff at KinabaluNational Park, Ranau, especially Mr MarklarinLakim, Mr Jamili Nais and Mr Alim Biun forthe generous hospitality and logistical sup-port. For help in the field, I wish to thankMr Jhonny Sani, Mr Jeffrin Ginsos, Mr JimmyGinsos, Mr Johan Radani, Mr Yamun Tuak,Mr Jailis Radani, Mr Lourince Gumbih andMr Jhonesius Kundong. This publication rep-resents a portion of my PhD dissertation at theUniversity of Illinois at Chicago, which was fundedby Universiti Kebangsaan Malaysia, and in partby the Ellen Thorne Smith Fund through theField Museum of Natural History, Chicago.

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Elevational diversity patterns of small mammals on Mount Kinabalu, Sabah, Malaysia