Status, Distribution, and Conservation of Slender Lorises in India

Chapter 38

Status, Distribution, and Conservation of Slender Lorises in India Honnavalli N. Kumara, Mewa Singh, Mohammed Irfan-Ullah, and Shanthala Kumar

Abstract Two recognized subspecies of slender loris, Loris lydekkerianus lydekkerianus and L. l. malabaricus, are endemic to Peninsular India. L. l. lydekkerianus has been reported from the drier forests of the Eastern Ghats south of the Godavari River, while L. l. malabaricus has been found in the wet forests of the Western Ghats south of the river Tapti. On the basis on confirmed sightings of individuals, we present a review of current understanding of the distribution and conservation status of India’s endemic slender loris subspecies. A possible third subspecies occupies a patchy distribution along the eastern foothills of the southern Western Ghats. To facilitate conservation planning, we modeled potential distributions for each recognized subspecies.

H.N. Kumara (*) Sálim Ali Centre for Ornithology and Natural History, Anaikatty P. O., Coimbatore 641 108, Tamil Nadu, India National Institute of Advanced Studies, Bengaluru, Karnataka, India e-mail: [email protected] M. Singh Bio-Psychology Laboratory, Department of Psychology, University of Mysore, Mysore 570 005, Karnataka, India e-mail: [email protected]; [email protected] M. Irfan-Ullah Ecoinformatics Centre, Ashoka Trust for Research in Ecology and the Environment (ATREE), 659, 5th-A Main Road, Hebbal, Bengaluru, Karnataka 560 024, India RMSI Pvt. Ltd, A-7, Sector-16, Noida, UP 201301, India e-mail: [email protected] S. Kumar Riverstone Ruby, Flat No. 107, Vallalar Nagar, Vadavalli, Coimbatore 641041, Tamil Nadu, India e-mail: [email protected] J. Masters et al. (eds.), Leaping Ahead: Advances in Prosimian Biology, Developments in Primatology: Progress and Prospects, DOI 10.1007/978-1-4614-4511-1_38, © Springer Science+Business Media New York 2013

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Resume Deux sous-espèces reconnues de loris, Loris lydekkerianus lydekkerianus et L. l. malabaricus, sont endémiques de la Péninsule indienne. L. l. lydekkerianus a été signalé dans les forêts sèches des Ghâts orientaux, au sud du fleuve Godâvarî, alors que L. l. malabaricus a été trouvé dans les forêts humides des Ghâts occidentaux, au sud du fleuve Tapti. En nous fondant sur les observations directes, nous synthétisons l’information disponible concernant la distribution géographique et le statut de conservation des deux sous-espèces endémiques de loris indiens. Une possible troisième sous-espèce, à distribution discontinue, est rencontrée au pied des collines du sud des Ghâts occidentaux . Pour faciliter les plans de conservation, nous avons modélisé la distribution potentielle des sous-espèces reconnues.

Introduction In the taxonomic scheme commonly employed, slender lorises (Lorisidae) comprise two known species, Loris tardigradus Linnaeus 1758 and Loris lydekkerianus Cabrera 1908, and six subspecies endemic to southern Peninsular India and Sri Lanka. Four subspecies (L. lydekkerianus nordicus, L. l. grandis, L. tardigradus tardigradus, and L. t. nycticeboides) have been reported from Sri Lanka (Chaps. 9 and 10) and two (L. l. lydekkerianus and L. l. malabaricus) from India (Hill 1953; Groves 2001). L. l. lydekkerianus occurs in the drier forests of the Eastern Ghats south of the Godavari River, and L. l. malabaricus inhabits the wet forests of the Western Ghats south of the river Tapti (Groves 2001). Schulze and Meier (1995) undertook the first comprehensive attempt to map the distribution of slender loris subspecies based on records dating back almost 100 years. During the past century, however, habitat loss and hunting have had a major impact on the distribution and status of slender lorises. Although the specimens collected over this period were sourced from several different areas, the continued presence of slender lorises in all of these sites had not been confirmed through recent field work. New surveys, based on confirmed sightings of individuals, were started around Dindigul in Tamil Nadu by Singh et al. (1999), and later extended to Indira Gandhi Wildlife Sanctuary (IGWS) in Tamil Nadu (Kumar et al. 2002), southern Andhra Pradesh (Singh et al. 2000), and Karnataka (Kumara et al. 2006; Kumara 2007). On the basis of these studies, we present a comprehensive review of current understanding of the distribution and conservation status of India’s endemic slender loris subspecies. We also model potential distributions for each recognized subspecies to facilitate conservation planning.

Methods Geographic Area The Indian Peninsula has two major hill systems, the Western Ghats and the Eastern Ghats. The Western Ghats run parallel to the west coast of south-western India from 21°N to 8°N (Pascal 1988) (Fig. 38.1), passing through six states. Being close to the

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Fig. 38.1 Map of South India showing the Western and Eastern Ghats hill systems and ranges of recognized subspecies

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Arabian Sea, these ranges receive heavy south-westerly monsoons. The western slopes and ridges are covered with primary rainforests, while the eastern slopes, being in rain shadow, support dry forests. The Ghats, with a length of ~1,600 km from north to south and an east–west extent of 30–80 km, are a mosaic of habitat types. On the basis of biogeographic parameters, Ramesh (2001) classified the ecological zones of the Western Ghats as Wet Evergreen Forests, Dry Evergreen Climax Forests, and Deciduous Climax Forests. The rainfall varies between 3,000 and 6,000 mm on the western slopes of the hill system. The Eastern Ghats are a series of discontinuous hills running north-east to southwest, parallel to the coast of the Bay of Bengal. They cover an area of ~75,000 km2, from the Mahanadi River in the north to the Vaigai River 1,750 km to the south, passing through Tamil Nadu, Andhra Pradesh, and Orissa with small areas in the southern part of Karnataka. The region falls within the tropical monsoon climatic distribution, receiving rainfall from both the south-west monsoon and the north-east retreating monsoon. In the northern part the rainfall ranges from 1,200 to 1,600 mm, whereas it is lower in the central and southern parts (600 and 1,000 mm, respectively), and the climate is semiarid, except in the hilly peaks. The mean temperature in January ranges from 20 °C to 25 °C, reaching a maximum of 41 °C with an increasing trend from north to south. The vegetation in the Eastern Ghats includes moist forests in the high hills but mainly dry deciduous and scrub forests across the hill system. Slender lorises occur in both these hill systems and are distributed across six Indian states: Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu, and Andhra Pradesh (see Fig. 38.1). Previous surveys, however, were restricted to a few regions in south India that included the plateaus of Dindigul, Deccan, parts of the central and southern Western Ghats, and the Eastern Ghats. Our surveys since 1999, therefore, add significantly to our information on the distribution of India’s slender lorises.

Identification of Subspecies Morphological characteristics like body size, coat color, and shape of circumocular patches distinguish the Mysore slender loris from the Malabar slender loris (Groves 2001). The Malabar slender loris is reddish brown with large circumocular patches, while the Mysore slender loris is a relatively larger animal (about 260 g vs. 180 g for L. l. malabaricus) and grayish-brown with narrow circumocular patches (Kumara et al. 2006).

Abundance Surveys Surveys of slender lorises are available from Kalakkad-Mundanthurai Tiger Reserve (KMTR) in Tamil Nadu (Kar-Gupta, unpublished data), Dindigul in Tamil Nadu and southern Andhra Pradesh (Singh et al. 1999, 2000), IGWS in Tamil Nadu

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(Kumar et al. 2002), and Karnataka (Kumara et al. 2006; Kumara 2007) (Fig. 38.1). The goal of these surveys was to cover large spatial areas documenting slender loris abundance. Mapping entire distributions by ground surveys was beyond the capability of our research team, and we found the method to be biased toward easily accessible or well-sampled regions. Since systematic surveys had produced a good number of sight records for the loris subspecies, we used an alternative method to reconstruct their potential distributions, combining occurrence records with climatic and environmental parameters (see Kumara et al. 2009) to build ecological niche models (hereafter ENM; Peterson and Kluza 2003; Peterson et al. 2003; Peterson 2005).

Results Vegetation Types Occupied by the Slender Loris Subspecies and Population Status Recognized subspecies were observed in all study sites except KMTR and IGWS. L. l. malabaricus were sighted in the forests of western Karnataka, whereas L. l. lydekkerianus were observed in Dindigul, southern Andhra Pradesh, and south-east Karnataka (Table 38.1, Fig. 38.1). L. l. lydekkerianus occurred in various habitats except deciduous forests lacking undergrowth and degraded scrub forests, whereas L. l. malabaricus were found in all available forest types. Slender lorises found in the rain shadow areas of the Western Ghats, in mixed deciduous forests, riverine forests with thick vegetation, and plantations on the eastern slopes of the KMTR and IGWS, appear to represent a hitherto unrecognized subspecies. While they have pale coats like the Mysore subspecies, they are much smaller in body size and have circumocular patches that differ from those of both the Mysore and Malabar subspecies. In total, 785 lorises have been sighted during surveys to date, including 501 L. l. lydekkerianus, 119 L. l. malabaricus, and 165 individuals of the unidentified subspecies (Table 38.1). The L. l. lydekkerianus encounter rate varied substantially (0.13–1.10 animals/km) among different forest patches within the same region, with the highest encounter rate reported from Dindigul (Singh et al. 1999, 2000; Kumara et al. 2006). The L. l. malabaricus encounter rate was between 0.21 and 0.27 animals/km across all surveys.

Distribution Patterns of Recognized Slender Loris Subspecies The vegetation of western Karnataka is made up chiefly of the wet forests of the Western Ghats. The subspecies confirmed from this region, L. l. malabaricus (Fig. 38.1), is predominantly found in the wet forests of the western slopes, extending

Table 38.1 Details of areas surveyed to assess current ranges of slender loris populations in Peninsular India Subspecies Effort Vegetation types Vegetation type of slender loris (km walked/ No. loris Abundance State Region supporting lorisesa without lorisesa recorded motored) sighted (animals/km) MD, AS, SST, CVR – L. l. lydekkerianus 280.0 313 1.10 Tamil Nadu Dindigulb MD, RTU, PL, AS MOD, EG, MS, ? 818.0 37 0.04 Indira Gandhi DEG, CP Wildlife Sanctuaryc MD, RTU, PL EG ? 146.4 128 0.90 Kalakkad-Mundanthurai Tiger Reserved Andhra Pradesh Southern Andhra Pradeshe MD, DSU, AS, SST, RTU, CVR – L. l. lydekkerianus 734.0 98 0.13 Karnataka Western Karnatakaf MOD, EG, MS, DEG, CP – L. l. malabaricus 293.0 63 0.21 MOD, EG, MS, DEG, CP – L. l. malabaricus 203.0 56 0.27 Western Karnataka (three Protected Areas)g South-east Karnatakaf MD, AS, SST, RTU, CVR DSU, DOS L. l. lydekkerianus 255.0 90 0.35 a MD, Mixed deciduous; DSU, Deciduous forest with sparse undergrowth; AS, Acacia spp. dominated scrub forest; SST, Scrub forest with sparse trees; DOS, Degraded open scrub; PL, Plantation; RTU, Riverine forest with thick undergrowth; CVR, Cultivated land, villages and roadside trees; MOD, Moist deciduous; EG, Evergreen forest; MS, Montane scrub; DEG, Degraded evergreen forest; CP, Cardamom plantation b Singh et al. (1999) c Kumar et al. (2002) d Kar-Gupta (unpublished data) e Singh et al. (2000) f Kumara et al. (2006) g Kumara (2007)

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into moist deciduous forests on the eastern side of the Western Ghats. No evidence exists, however, of their presence in the Mangrove forests of the west coast. The forests of Dindigul, southern Andhra Pradesh, and south-east Karnataka support the dry forests of the Eastern Ghats, occupied primarily by L. l. lydekkerianus. The potential distributions of these taxa were modeled using ENM. Our results indicated that, in terms of environmental characteristics, the distribution of L. l. lydekkerianus may include large geographical tracts of drier forest patches and human-dominated landscapes spread across the rain shadow area of Peninsular India, while that of L. l. malabaricus is restricted to a relatively narrow geographic range and shows no overlap with L. l. lydekkerianus (Fig. 38.2). L. l. malabaricus is apparently confined to the western side of the Western Ghats—a region dominated by wetter climate, receiving summer (June–September) rainfall through south-west monsoons, while L. l. lydekkerianus prefers the drier habitats of the subcontinent’s rain shadow. The hitherto unrecognized subspecies appears to occupy a patchy distribution along the eastern foothills of the southern Western Ghats—a region characterized by intermediate climate and precipitation, receiving winter rains from the retreating north-east monsoons, and an average annual rainfall of ~1,500 mm.

Discussion According to our analysis, the two recognized slender loris subspecies in southern India occupy very different habitat types and show very different patterns of abundance. The hills of the Eastern Ghats include discontinuous and patchy forests surrounded by human-dominated landscapes with varying levels of disturbance (Jayakumar et al. 2002), and L. l. lydekkerianus abundance varied widely between forest patches within the region, possibly in response to the degree of disturbance. Slender lorises cannot leap between trees and find it hard to climb trunks of large girth; hence, they prefer scrubby forests with continuous, thin-branched pathways for easy movement (see Chaps. 9 and 10 for similar observations of slender lorises in Sri Lanka). L. l. lydekkerianus abundance also varied widely between regions (Kumara et al. 2006; Singh et al. 2000) and was particularly high in certain small forest patches in south-east Karnataka and southern Andhra Pradesh. By contrast, L. l. malabaricus consistently showed low abundance across its distribution, which could include continuous forests along the western side of the Western Ghats (Kumara 2007). The two subspecies are separated by large geographic areas in both the northern and middle regions of their distribution ranges; in mid-range, they are separated by approximately 200 km of the deciduous forests of the southern plateau from Kanakapura to the Coorg hills. In the south, the subspecies’ ranges approach each other more closely, separated by ~50 km. The extent of the L. l. malabaricus range on the eastern slopes of the Western Ghats, however, still remains to be confirmed taxonomically.

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Fig. 38.2 Map showing modeled potential distributions of slender loris subspecies in Peninsular India


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The potential subspecies distributions predicted by ENM accord well with their observed distributions. This allows us to develop a model-based framework for future sampling and for planning conservation strategies against the growing threat of landscape change and habitat loss linked to increasing urbanization. Our survey results suggest that the morphologically distinct subspecies are adapted to different environmental regimes, and this was supported by the potential niches derived by our ENM. We recommend a systematic molecular study of the subspecies be undertaken at the population level to establish the genetic status of the different morphotypes. During the course of the surveys, a previously unrecognized morphotype was identified from the eastern slopes of the KMTR and IGWS. This habitat is more similar to that of L. l. lydekkerianus, but the population’s status needs further investigation with respect to morphological, ecological, and genetic differentiation.

Conclusion Slender loris distribution has clearly undergone substantial changes in the past century, particularly in the case of L. l. lydekkerianus, which currently occupies a very large range and encounters varying degrees of anthropogenic disturbance. The rapidly changing, human-dominated landscape poses the major threat to loris survival through range reduction and fragmentation, as reported in south-east Karnataka (Kumara et al. 2006). Studies like ours can help to predict the most vulnerable parts of the species’ range and to identify previously unknown morphological variation and potential environmental adaptation among slender lorises. Ackowledgments We thank the forest departments of Karnataka, Tamil Nadu, and Andhra Pradesh for research permits and the organizers of the South Africa Prosimians 2007 meeting for sponsorship to attend the conference. We thank R. Sasi for helping in the preparation of map. We thank the editors for their support in improving the chapter.

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