C 2006) International Journal of Primatology, Vol. 27, No. 4, August 2006 ( DOI: 10.1007/s10764-006-9057-9
Distribution and Conservation of Nycticebus bengalensis in Northeastern India Sindhu Radhakrishna,1,2,5 Arup Ballav Goswami,3 and Anindya Sinha1,4 Received January 10, 2005; revision May 31, 2005; 2nd revision March 24, 2005; accepted June 14, 2005; Published Online August 1, 2006
We assessed the distribution and conservation status of Bengal slow lorises (Nycticebus bengalensis) in Assam and Meghalaya in northeastern India. We surveyed forest reserves, plantations, tea estates, and areas bordering forests in 10 districts of the 2 states and sighted slow lorises in only 4 districts in Assam. Disturbances caused by tree felling, road kills by speeding vehicles, and trapping and hunting are the chief survival threats to the species. We emphasize immediate implementation of conservation measures to ensure the future of the species and recommend additional population surveys to define the distributional extent of Bengal slow lorises. KEY WORDS: conservation; distribution; forest fragmentation; India; Nycticebus bengalensis; relative abundance; threats.
INTRODUCTION Two genera of lorises (Primates: Loridae) inhabit Asia—the slender lorises (Loris lydekkerianus and Loris tardigradus) in southern India and Sri Lanka, and the slow and pygmy lorises (slow loris: Nycticebus bengalensis and Nycticebus coucang; pygmy loris: Nycticebus pygmaeus) 1 National
Institute of Advanced Studies, Bangalore, India. Conservation Society, Bangalore, India. 3 Honorary Wildlife Warden, Assam, India. 4 Nature Conservation Foundation, Mysore, India. 5 To whom correspondence should be addressed; e-mail:
[email protected]. 2 Wildlife
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in northeastern India, Burma, Indonesia, Brunei, peninsular Malaysia, Thailand, Cambodia, southern China, Laos, and Vietnam (Brandon-Jones et al., 2004). Bengal slow lorises (Nycticebus bengalensis) live in the forests of northeastern India, Burma, Cambodia, southern China, Laos, Thailand (north of the Isthmus of Kra), and Vietnam (Brandon-Jones et al., 2004). The Bengal slow lorises are a nocturnal and arboreal species, and primatologists know very little about their population status or behavioral ecology, primarily because of the lack of a quantitative field study on the species. We know relatively more about the natural behavior of Sunda slow lorises (Nycticebus coucang) (Groves, 2001); 3 field studies, based on populations in Malaysia (Barrett, 1984; Wiens, 1995, 2002; Wiens and Zitzmann 2003), present comprehensive information on their socioecology. Preliminary field surveys indicated the presence of Bengal slow lorises in Assam, Arunachal Pradesh, Mizoram, Nagaland, Meghalaya, Manipur, and Tripura in northeastern India (Choudhury, 1992, 2001; Srivastava, 1999). The studies (Choudhury, 1992; Srivastava, 1999) caution that hunting and deforestation pose serious dangers to the continued existence of the species but provide no further details on specific survival threats or conservation strategies. The IUCN Red List (2004) classifies Nycticebus bengalensis as Data Deficient. The status has not changed since 1996 (IUCN, 1996), underlining the almost complete lack of information on the status and distribution of the species, even in unpublished literature. We aimed to assess the conservation status and distribution of Bengal slow lorises in Assam and Meghalaya in northeastern India. More specifically, we aimed to ascertain population densities of the species, evaluate the survival threats facing the populations, and achieve an understanding of the ground realities involved in implementing conservation strategies for slow lorises in the region.
STUDY AREA We surveyed 29 sites in northeastern India for the presence of slow lorises, 25 of them in Assam and 4 in Meghalaya (Table I; Fig. 1). In addition to forest reserves, we also surveyed plantations, tea estates, and areas bordering forests and villages. The forest types in the surveyed areas included primarily semi-evergreen forests along the upper Brahmaputra River plains in Assam and subtropical forests in the Khasi and Garo hills in Meghalaya (Rawat et al., 2001; Rawat and Wikramanayake, 2001).
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Table I. Surveyed sites in Assam and Meghalaya, India Site no.
Sites surveyed
District
1
Bashishta RF
Kamrup, Assam
2
Lakhara RF
Kamrup, Assam
3
Rani RF
Kamrup, Assam
4
Barnodi WLS
Darrang, Assam
5
Bihali RF
Sonitpur, Assam
6
Sanglithan RF
Sonitpur, Assam
7
Dhulli TE
Sonitpur, Assam
8
Nameri NP
Sonitpur, Assam
9
Haldibari Range
Golaghat, Assam
10
Hathikuli TE
Golaghat, Assam
11
Panbari Range
Golaghat, Assam
12
Nambor-Garampani WLS
KarbiAnglong, Assam
13
Nambor-Doigrong WLS
Golaghat, Assam
14
Nambor RF
KarbiAnglong, Assam
15
Gibbon WLS
Jorhat, Assam
16
Borajan fragmenta
Tinsukia, Assam
17
Bherjan
fragmenta
Tinsukia, Assam
18
Podumoni fragmenta
Tinsukia, Assam
19
Joypur RF
Dibrugarh, Assam
20
Oguri Range
KarbiAnglong, Assam
21
Kotalguri RF
Nagaon, Assam
22
Dharamtull Range
Marigaon, Assam
23
Komaraketta RF
Nagaon, Assam
24
Hojai RF
Nagaon, Assam
25
Lumding RF
Nagaon, Assam
26
Nongkhyllem WLS
Khasi Hills, Meghalaya
Representative location 26◦ 05 N 91◦ 47 E 26◦ 06 N 91◦ 44 E 25◦ 58 N 91◦ 32 E 26◦ 46 N 91◦ 45 E 26◦ 52 N 93◦ 22 E 26◦ 55 N 93◦ 24 E 26◦ 51 N 93◦ 07 E 26◦ 55 N 92◦ 49 E 26◦ 35 N 93◦ 19 E 26◦ 35 N 93◦ 24 E 26◦ 37 N 93◦ 31 E 26◦ 23 N 93◦ 52 E 26◦ 23 N 93◦ 52 E 26◦ 13 N 93◦ 49 E 26◦ 40 N 94◦ 21 E 27◦ 25 N 95◦ 21 E 27◦ 31 N 95◦ 21 E 27◦ 32 N 95◦ 18 E 27◦ 14 N 95◦ 24 E 26◦ 03 N 92◦ 17 E 26◦ 04 N 92◦ 16 E 26◦ 06 N 92◦ 21 E 26◦ 00 N 92◦ 47 E 25◦ 55 N 92◦ 52 E 25◦ 51 N 93◦ 04 E 25◦ 49 N 91◦ 45 E
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Radhakrishna, Goswami, and Sinha Table I. Continued
Site no.
Sites surveyed
District
27
Balpakram NP
Garo Hills, Meghalaya
28
Bagmara RF
Garo Hills, Meghalaya
29
Siju WLS
Garo Hills, Meghalaya
Representative location 25◦ 11 N 90◦ 51 E 25◦ 12 N 90◦ 39 E 25◦ 20 N 90◦ 40 E
Note. RF = reserve forest; WLS = wildlife sanctuary; TE = tea estate; NP = national park. a In the Bherjan-Borajan-Podumoni Wildlife Sanctuary.
Fig. 1. Sites surveyed for slow loris in Assam and Meghalaya, northeastern India (sites numbered in accordance with Table I).
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METHODS We surveyed the sites from January 2004 to April 2004. Most of the study areas were unsafe to work in at night because of the presence of armed insurgents or poachers and elephants. Hence, 2–8 armed forest guards accompanied us on all our surveys. They were usually reluctant to walk after 2300 h and hence we could conduct only partial night surveys (1730 h–2300 h). The limited time available for field work and the number of areas to be covered also constrained the use of formal line transect sampling methods (Burnham et al., 1980). Instead we employed an encounter rate survey using recce sampling (Walsh and White, 1999) and based on direct sightings of slow lorises. We considered individuals/km as an index of the relative abundance of slow lorises in the surveyed areas. We walked existing trails, beat paths, and roads and representatively sampled the area, and used a hand-held GPS unit (Garmin, Hampshire, UK) to note geographic locations of the sites and calculate the distances covered during walks. We conducted a vehicle survey (Singh et al., 1999, 2000) in only 1 instance, on the National Highway 39 through the NamborGarampani Wildlife Sanctuary and the Nambor-Doigrong Wildlife Sanctuary in Assam. Slow lorises emit a distinctive brilliant orange-red eyeshine in response to flashed light, and we used the feature to detect the presence of individuals in foliage. We walked at an average speed of 1–1.5 km/h searching the undergrowth, lower, middle, and upper canopy levels of the forests with the aid of Petzl headlamps (Petzl, Crolles, France). When we spotted an eyeshine, we approached the individual closely, to confirm identification of the species and note details such as height of individual, tree species on which found, and interindividual distance between conspecifics, if any. We collected secondary information on parameters such as food items slow lorises consumed, tree species used, and the size of subject groups. Sources of secondary information were informal interviews with forest officials, local villagers, wildlife conservationists, wildlife veterinarians, and the records maintained at the Forest Range Office in Guijan, Assam. We also recorded information on other habitat features such as logging pressure, evidence of hunting, traffic of vehicles or people on roads within forest reserves, proximity of human settlements to forest reserves, and presence or absence of insurgents within forest reserves. We looked at cut tree stumps, felled branches, wood chip litter, and the sounds of woodcutting within the forest reserves as evidence of the presence or absence of logging. Foliage peepholes that poachers use to shoot animals in the forest and the sound of firearms during the night indicated hunting activities within the surveyed site.
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Radhakrishna, Goswami, and Sinha Table II. Relative abundance of slow lorises and flying squirrel in the study sites Slow loris sightings
Flying squirrel sightings
Total distance Total number Relative Total number Relative surveyed (km) sighted abundance sighted abundance
Sites surveyed Lakhara RF Barnodi WLS Nambor forests Gibbon WLS Borajan fragmenta Bherjan fragmenta Joypur RF Oguri Range Dharamtull Range Lumding RF Nongkhyllem WLS
3.92 3.90 63.79b 35.23 12.71 7.87 26.37 2.28 7.85 12.05 59.21
None None 3 1 None 2 None None None 4 None
— — 0.05 0.03 — 0.25 — — — 0.33 —
3 1 None None 3 None 4 1 5 None 6
0.77 0.26 — — 0.24 — 0.15 0.44 0.64 — 0.10
Note. RF = reserve forest; WLS = wildlife sanctuary. a In the Bherjan-Borajan-Podumoni Wildlife Sanctuary. b 39.79 km walked, 24 km motored.
RESULTS Slow Loris Abundance and Body Measurements We covered 376.6 km during the survey, of which we motored 24 km and walked 352.6 km. About 24% of the distance was along forest edges, in tea estates, plantations, and areas bordering forests and villages; 76% of the distance covered was in the interior areas of the forests. We sighted 10 slow lorises in 4 sites in Assam; we did not spot them in any of the other surveyed areas in either Assam or in Meghalaya (Table II). Local villagers and forest staff concurred that sightings of slow lorises had become very rare in recent years or that the species was no longer in areas that they had previously inhabited. The relative abundance of the species did not vary across the sites (Table II). All sightings occurred on the edge of beat paths or clearings in the forest or in the outer edges, ca. 500 m–1 km from the boundary of the forest; we observed individuals at an average height of ca. 9 m (n = 10, range = 0–11 m, mean ± SD = 8.5 ± 3.4 m). The sighted individuals included 4 infants, 1 juvenile, and 4 adults. We could not clearly identify the age class of 1 individual. The height at which we spotted the individuals, however, made it difficult to identify their sexes. We observed slow lorises on thickly leaved trees as well as on open trees overgrown with vines and climbers. Secondary sources of information reported that slow lorises inhabit predominantly bamboo vegetation and that they feed on tender
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bamboo shoots and leaves. Individuals also fed on the fruit bodies of some fungi such as Foames and Ganoderma (Padmeswar Gogoi, pers. comm.). We also sighted 23 flying squirrels (Hylopetes spp., Petaurista spp.) in 7 study sites in Assam and Meghalaya (Table II). We did not sight flying squirrels in any of the slow loris sites, and did not sight slow lorises in any of the flying squirrel sites. Based on the body masses of wild slow lorises rescued from tea estates or villages in 3 districts in Assam (from records Goswami maintained), we calculate the mean body mass of a male slow loris to be 1587.5 g (n = 4, range = 950–2700 g) and that of a female, 890 g (n = 2, range = 880–900 g). We took morphometric measurements of a wild-caught female slow loris living in the Guijan Forest Range Office in Tinsukia, Assam. The measurements, taken with the aid of a wildlife veterinarian, are Dorsal body length (snout to anus) = 33.5 cm Ventral body length (snout to clitoris) = 29 cm Right forelimb length (shoulder joint to tip of longest digit) = 19 cm Right hindlimb length (hip joint to tip of longest digit) = 24 cm Girth (in mid-torso) = 23 cm
Habitat Disturbance Illegal tree felling, hunting, the presence of insurgents, and the proximity of human settlements and roads added to high disturbance levels within many of the surveyed forest areas (Table III). Logging pressure in the surveyed areas varied with the status of legal protection—in Assam, more cut tree stumps and felled branches were present in unclassed forests and reserve forests than in national parks and wildlife sanctuaries; in Meghalaya, private forests and community-owned forests appeared seriously degraded in comparison to forest land protected by the Forest Department. It was not easy to determine the exact magnitude of poaching pressure, and the actual extent of hunting pressure in the surveyed forest reserves may be underestimated in Table III. Secondary sources unanimously agreed that hunting for meat was widely prevalent among indigenous populations that lived beside forest reserves; we thus propose that hunting pressure may be relatively more intense in reserves that are adjacent to human settlements (and thus score higher in the Others category of Table III). The presence of armed insurgents within forest reserves poses a serious threat to the species not only because they hunt wildlife and fell trees
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Table III. Levels of disturbance in the surveyed forests of Assam and Meghalaya, India Disturbance levelsb Surveyed forest reserves Bashishta RF Lakhara RF Rani RF Barnodi WLS Bihali RF Sanglithan RF Nameri NP Haldibari Range Panbari Range Nambor-Garampani WLS Nambor-Doigrong WLS Nambor RF Gibbon WLS Borajan fragmenta Bherjan fragmenta Podumoni fragmenta Joypur RF Oguri Range Kotalguri RF Dharamtull Range Komaraketta RF Hojai RF Lumding RF Nongkhyllem WLS Balpakram NP Bagmara RF Siju WLS
Logging pressure
Poaching pressure
Presence of insurgents
Othersc
+ + + + ++ + + + + + + ++ + ++ + ++ + + ++ ++ ++ ++ + 0 0 + 0
0 0 0 0 + 0 0 0 0 ++ ++ 0 0 0 0 0 0 0 ++ 0 0 0 0 0 0 0 0
+ ++ + ++ 0 0 0 0 0 ++ ++ 0 0 0 0 0 ++ + + 0 0 ++ ++ 0 ++ ++ ++
++ + + 0 + + + ++ ++ ++ ++ ++ ++ ++ ++ ++ + 0 ++ + ++ ++ + + ++ + +
Note. RF = reserve forest; WLS = wildlife sanctuary; NP = national park. a In the Bherjan-Borajan-Podumoni Wildlife Sanctuary. b Evaluated on an arbitrary scale; 0: absence/low level; + : medium level; + + : high level. c Disturbance caused by vehicular traffic/movement of people on roads/paths within forest reserves, proximity of human settlements, or the presence of railway tracks.
but also because forest guards consequently fear to patrol the forests. Most of the forest range and beat offices in the protected areas lack sufficient manpower to patrol the reserves efficiently, and fear of armed poachers and insurgents contributes to laxness in protection during the night, particularly in the interior areas of the forest reserves. Certain indigenous agricultural practices are also responsible for largescale degradation of the land—jhum (a form of shifting cultivation in which forests, usually on slopes, are first burnt down and the land then used for agriculture), in particular, has resulted in clearing of vegetation on entire hillsides.
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Threats to the Slow Loris Animal rescue records maintained at the Guijan Range Forest Office in Assam and long-term observations of Goswami reveal that conservationists have rescued significant numbers of slow lorises (14 individuals in 6 yr from 3 districts of Tinsukia, Golaghat, and Karbi Anglong in Assam alone) from villages and tea estates bordering the forest reserves. Hunting of wildlife for meat is pervasive here; and though people do not systematically hunt and kill slow lorises, unlike some of the bigger mammals such as elephant and gaur, hunters bludgeon or trap and kill individuals for food in the peripheral areas of the forest. Speeding vehicles also kill slow lorises when they attempt to cross roads through most forest reserves in Assam and Meghalaya. Goswami recorded 10 slow loris road kills in 5 yr (September 1998–November 2003) on National Highway 39 through the Nambor-Garampani and the NamborDoigrong Wildlife Sanctuaries. We made observations on the road kills during occasional journeys along this highway; hence, the actual number of individuals killed may be significantly higher. DISCUSSION We sighted Bengal slow lorises in
