Prioritizing Remnant Forests for the Conservationof Mysore Slender Lorises (Loris lyddekerianuslyddekerianus) in Karnataka, IndiaThrough Estimation of Population Density

Sayantan Das & Saurav Dutta & Madhur Mangalam &

Rakesh Kumar Verma & Subhani Rath &

Honnavalli N. Kumara & Mewa Singh

Received: 6 February 2011 /Accepted: 26 April 2011 /Published online: 12 July 2011# Springer Science+Business Media, LLC 2011

Abstract Information on a species’ distribution, abundance, and habitat require-ments is important for formalizing a comprehensive management and conservationstrategy. This becomes an even higher priority when the distribution of a species lieslargely outside demarcated protected areas for wildlife. We used line transectdistance sampling to estimate the density of an arboreal, nocturnal, and threatenedprimate, the slender loris (Loris lyddekerianus lyddekerianus) across diversehabitat types including both reserve forests and production landscapes in thesouthern part of the state of Karnataka, India. Abundance estimates varied from0.16 individuals/ha in Devrayandurga State Forest to 2.57 individulas/ha in IppadiState Forest, with the mean density estimate being highest in the Forest Division ofTumkur, at 165 individuals/km2. Based on density estimates for the survey regions,

Int J Primatol (2011) 32:1153–1160DOI 10.1007/s10764-011-9531-x

S. Das : S. DuttaIndian Institute of Science Education and Research, Mohanpur, Nadia, India

M. MangalamIndian Institute of Science Education and Research, Pashan, Pune, India

R. K. VermaJaipur National University, Jagatpaura, Jaipur, India

S. RathPondicherry University, Kalapet, Puducherry, India

H. N. KumaraSalim Ali Centre for Ornithology and Natural History, Coimbatore, India

M. Singh (*)Biopsychology Laboratory, University of Mysore, Manasagangotry, Mysore 570006, Indiae-mail: mewasingh@bsnl.in

their current habitat status, and perceived threats, we identify Ippadi, Ujjani,Devrayandurga, and Savanadurga state forests as priority areas for conservation ofthe slender loris. We propose that these areas be declared protected. The requiredmanagement intervention is preventing further degradation of the habitat andenhancing canopy contiguity to facilitate loris movement.

Keywords Conservation . Density estimation . Distance sampling . Karnataka .

Line transect . Lorisidae . Loris lyddekerianus lyddekerianus . Remnant forests

Introduction

Mysore slender lorises (Loris lyddekerianus lyddekerianus) are cryptic, solitary, andnocturnal (Radhakrishna 2004), generally found in scrub forests with tree speciessuch as Acacia sp., Lantana camara, Azadirachta indica, etc. (Singh et al. 1999,2000) in relatively open forests along the Eastern Ghats mountain ranges inpeninsular India (Molur et al. 2003). It is currently classified as Highly Endangeredby the Indian Wildlife Act (1972) and Near Threatened by the IUCN (IUCN 2010).Forest fragmentation, habitat loss, hunting, and trapping for traditional medicinal useand biomedical/anatomical research are recognized as major threats to its survival(Kumara et al. 2006). The current occurrence of this species is restricted to remnantforest fragments and plantations, and the population is thought to be decliningsteadily (IUCN Red List). However, a statewide survey of the species based onarchival information, local interviews, and field surveys suggested a relatively highabundance of the species in the forest divisions of Tumkur, Bangalore (Rural) andKolar (Kumara et al. 2006). These forest divisions are thus extremely important forthe conservation of slender lorises. Populations appear to have become isolatedleading to spatial patchiness in loris distribution (Kumara et al. 2006). Retention,protection, and management of these fragments and plantations are necessary toconserve this species. All forest fragments that hold a high abundance of lorises inthese forest divisions have a status of reserve forests but are not included under theProtected Area network for wildlife. Further, forestry activities such as extraction oftimber and manipulation of vegetation are legal in these forest fragments, makingthem vulnerable to local extinction of animal species.

The population status of Mysore slender lorises has been presented as anencounter rate (individuals seen/km) in various studies (Kumara et al. 2006; Singhet al. 1999, 2000). However, encounter rate is not a true measure of the density andlacks comparability across space and time (Buckland et al. 2000). Having interactedwith wildlife managers for >3 decades (M. Singh), it is our experience that encounterrate data fail to convince managers to initiate conservation steps and establish long-term population monitoring if rates are not converted into density estimates.

The method applied to determine density should be robust and quick in bothapplication and in furnishing results. Distance sampling is a widely used techniquefor estimating the density of biological populations (Buckland et al. 1993, 2001;Burnham et al. 1980). The primary methods are line transects and point transects,and these techniques have been used successfully and replicated in a diverse array oftaxa, including trees, insects, amphibians, reptiles, birds, fish, and marine and land

1154 S. Das et al.

mammals (Karanth and Nichols 2002), including lorises (Kumara 2008; Nekariset al. 2008; Pliosungnoen et al. 2010). We selected the remnant forest patches insouthern Karnataka to estimate the density of slender lorises employing a distancesampling technique. Our goal was to prioritize some fragments for the conservationof slender lorises using density as an index of population size of slender lorises.

Methods

Study Area

The study areas included the forest divisions of Tumkur (Huliyurdurga and Tumkurforest ranges), Bangalore Rural (Magadi and Nelamangala forest ranges), and Kolar(Malur and Bangarpet forest ranges) (Table I; Fig. 1). The study area lies between11°31′–18°45′N and 74°12′–78°40′E. The mean annual precipitation in these areasranges from 450 to 900 mm depending on topography. Although most of thevegetation in the regions is xerophytic, with a mean tree height of 3 m characteristicof the Eastern Ghats, a variety of forest types including open scrub, closed canopyscrub, deciduous forests, and monoculture plantations of Acacia sp. and Eucalyptussp. occurs in different parts of the study area (Table I). The temperature remains hotand humid throughout the year, at 22–42°C.

Surveys

We undertook surveys in two phases. During the first phase, we surveyed forestfragments of Tumkur Forest Division between June 20 and July 20, 2009. During thesecond phase, we surveyed the remaining forest fragments of Tumkur, BangaloreRural, and Kolar forest divisions between May 14 and June 31, 2010. Because thefocal species is nocturnal, we relaxed 1 assumption of Distance sampling, i.e., “all

Table I Administrative division and range of the forests with vegetation type and area

Division Range Forest Vegetation type Area (ha)

Tumkur Huliyurdurga Ujjani SF DDF 2385

Tumkur Ippadi SF SF/PL 1574

Nagavalli FL 500

Tumkur Devrayandurga SF DDF 4224

Bangalore Rural Magadi Savanadurga SF DDF 280

Kudurbetta PL/FL —

Nelamangala Nijakal SF SF/PL 507

Kolar Malur Sorkayanahalli SF SF/PL 399

Laxmisagar SF SF/PL 229

Kamasandra SF DDF 3775

Bangarpet Kamasandra SF DDF 3706

SF state forest, DDF dry deciduous forest, PL plantation, FL farmland, SF scrub forest

Population Density of Mysore Slender Lorises 1155

animals on a transect are likely to be sighted.” We verified the applicability of theestimation procedure a priori for the regions of Ujjani, Ippadi, Nagavalli,Devrayandurga, and Savanadurga state forests, which were large enough to lay aminimum of 8 transects. We did not attempt density estimates in the remaining forestfragments owing to the low number of detections. We estimated the abundance ofslender loris in these regions as encounter rate.

We followed the protocol set by Kumara (2008), Nekaris et al. (2008), andPliosungnoen et al. (2010) to estimate loris density. Following this protocol, weestablished transect lines by spatially representing the entire selected fragment andcovering all possible vegetation types following Burnham et al. (1980) andBuckland et al. (1993, 2001). We maintained an intertransect distance of 400 m inall fragments. Two researchers walked at a mean pace of 1.76 km/h on each side ofthe transect between 19:20 h and 02:00 h. We used a PETZL head lamp with a redfilter to detect lorises using the tapetum lucidum, a layer present in the loris’s eye,which emits an orange-red reflection that is distinctly different from the eyereflections of other nocturnal species (Singh et al. 1999, 2000). We used a morepowerful MAGLITE 3-battery torch to measure distance using a range finder. Welaid a minimum of 8 and a maximum of 11 transects per fragment depending on thesize of the fragment. We walked each transect 6–8 times (mean 6.87). We did notconsider calls as loris presence unless we also sighted the individual. At eachdetection, we recorded time of sighting, bearing with respect to transect orientation

N

Fig. 1 Map showing the 3 districts of Karnataka with black diamonds (♦) marking the location of thesurvey sites (inset). For location numbers, see Table II. SF = state forest.

1156 S. Das et al.

using a liquid-filled compass, observer-to-subject distance using an analog rangefinder, and the number of individuals.

Data Analysis

We calculated the encounter rate per kilometer by dividing the number of sightingsby the length of transect walked and determined the significance of difference inencounter rates among fragments via the G test (Gibbons 1971). We estimateddensities only for regions wherein we had >40 detections. We used Distance 5(Buckland et al. 2001; Thomas et al. 2010) to estimate densities. We truncated thedata at different distances of farthest sightings to achieve a reliable density estimateby improving the shape of detection function (Buckland et al. 1993). We selected thebest model among those with the same truncation distances using the AkaikeInformation Criterion values generated by fitting parametric key functions inDistance 5 (Buckland et al. 2001). We generated estimates of cluster density, meancluster size, density of individuals, coefficient of variation of the density ofindividuals, and 95% confidence interval from the selected best model.

Results

The number of lorises detected and the resulting encounter rates differedsignificantly between areas (G=384.99; df=9; p<0.001, Table II). Encounter rateranged from 0.18 to 7.89 individuals/km. We observed high encounter rates inKudurbetta (7.89/km) and Ujjani (5.20/km); medium encounter rates in Ippadi,Nagavalli, Savandugra, and Nijakal; and low rates in Devrayandurga, Sorkayanahalli,Laxmisagar, and Kamasandra.

Loris density varied among fragments, being highest in Ippadi followed byNagavalli, Ujjani, Savandurga, and Devrayandurga (Table III). The distrcit of

Table II Number of transects placed in a forest, their total length, effort, individuals detected, andencounter rate

Number (asin Fig. 1)

Forest No. oftransects

Total length oftransects (m)

Effort(m)

Detections Encounter rate(ind./km)

1 Ujjani SF 8 2831 12,065 63 5.20

2 Ippadi SF 10 3659 14,636 70 4.78

3 Nagavalli 10 3960 15,840 62 3.90

4 Devrayandurga SF 8 7230 36,150 42 1.16

5 Savanadurga SF 8 3827 19,135 62 3.24

6 Nijakal SF 8 2750 3600 15 4.16

7 Kudurbetta 4 650 1900 15 7.89

8 Sorkayanahalli SF 6 4200 10,000 3 0.30

9 Laxmisagar SF 10 6167 18,500 7 0.38

10, 11 Kamasandra SF 53 37,500 61,300 11 0.18

Population Density of Mysore Slender Lorises 1157

Tumkur that included the first 4 fragments had a mean density of 1.65 individuals/havs. only 0.96 individuals/ha in Bangalore district that included the fragment atSavanadurga.

Discussion

Our results revealed that the forest fragments of Ujjani, Ippadi, Nagavalli, andSavanadurga had the highest densities of slender lorises, at 1.85 individuals/ha. Forcomparison, Ayyalur, in the state of Tamilnadu, is considered to be a high lorisdensity area and is recommended for protection and conservation (Singh et al.1999). Long-term studies of the Ayyalur population give home ranges, home rangeoverlaps, and a number of individuals (Nekaris 2003; Radhakrishna and Singh 2002)that suggest a mean loris density of 1.80 individuals/ha. This indicates theimportance of Ujjani, Ippadi, Nagavalli, and Savandurga fragments for lorisconservation.

Loris populations in human dominated landscapes are a significant conservationconcern for several reasons: 1) populations are remnant (Kumara et al. 2006), 2)these forest fragments are unprotected, and 3) the habitat is highly susceptible tovarious anthropogenic activities. On the other hand, slender loris conservation insuch regions has a relatively good prospect because 1) unlike other primates, slenderlorises do not compete with humans for resources, and hence there is no human–lorisconflict, and 2) cultivated areas with fences and interspersed with trees, along withtrees along roads, can serve as significant corridors between unconnected forestpatches (Singh et al. 1999). We propose that the forest fragments of Ippadi, Ujjani,Nagavalli, and Savanadurga that harbor a high density of lorises be declaredProtected to conserve the slender loris. The only interventions required in theseforests are preventing further degradation of the habitat and enhancing canopycontiguity for loris movement. Because these forest fragments lie almost in a lineand the distance among them is ≤10 km, and because lorises have been observedinhabiting roadside trees and trees and fences in cultivated lands (Singh et al. 1999),a long-term management goal could be to establish a metapopulation of loriseswith fragments serving as source populations and the interspersed lands asdispersal habitats.

Table III Total number of detections (N) considered, effective strip width (ESW), density estimate(D̂) ,percentage coefficient of variation (CV), 95% confidence interval, and detection probability acquired onrunning the model in Distance

Forest N ESW (m) D̂(ha–1) CV (D̂)% 95% CI (ha–1)

Ujjani 63 17.86 1.52 18.53 1.02–2.27

Ippadi 65 9.52 2.57 21.27 1.65–3.98

Nagavalli 62 8.86 2.36 16.58 1.66–3.35

Devrayandurga 41 33.88 0.16 31.61 0.08–0.34

Savanadurga 62 16.81 0.96 24.68 0.56–1.67

1158 S. Das et al.

Although the relative encounter rate was high in Nagavalli and Kudurbetta, theforests in these 2 regions are totally degraded and fragmented and the prospect forlorises in these 2 areas is bleak. However, restoration of these forests with theplantation of tree species such as Acacia, Tamarindus, and Mangifera indica couldhelp enhance habitat quality. Because there is no conflict between people and lorisesfor resources, such plantations both serve as corridors for loris and fulfill theeconomic needs of the farmers. Similarly, the Eucalyptus plantations in LaxmisagarState Forest should be eventually replaced with native vegetation including Acaciasp., Caesalpinia sp., Azadirachta indica, etc., which had high subject detections.The villagers in the vicinity use these fragments for grazing by the domesticlivestock, which can be permitted on a restricted basis to earn the goodwill of thelocal community because lorises seldom use the undergrowth and trunk for feeding(Nekaris 2006).

Acknowledgments We thank Karnataka Forest Department for permission to work in the forest areas. S.Das, S. Dutta, M. Mangalam, R. K. Verma, and S. Rath thank Science Academies of India for the award ofSummer Fellowships. M. Singh thanks the Department of Science and Technology, Government of Indiafor the award of a Ramanna Fellowship during which this work was conducted. We thank 2 anonymousreviewers and the editor-in-chief for their helpful comments.

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