We studied the population status of Phayre's langur (Trachypithecus phayrei) in the Sepahijala Wildlife Sanctuary (23°37′N to 23°42′N and 91°17′E to 91°21′E), West Tripura district, Northeast India, from December 2009 to February 2010. Using line transect and recce sampling, we recorded seven groups comprising 95 individuals. The average group size was estimated at 13.14 individuals per group (range 8–19, SD = 3.77). The population comprises 7.4% adult males, 34.7% adult females, 23.2% of sub adults, 26.3% juveniles, and 8.4% infants.
Phayre's langur, Trachypithecus phayrei (Blyth, 1847), is found in Bangladesh, Myanmar, China, India, Thailand, and Vietnam (Roonwal and Mohnot 1977; Stanford 1988; Gupta and Kumar 1994; Srivastava 1999; Bose 2003; Min et al. 2005). In India, the nominate subspecies is found only in the lower northeastern states bordering Bangladesh (Menon 2003); Tripura, Mizoram, and Assam, from sea level to 800 m (Mukherjee 1982; Choudhury 1987, 1994a, 1994b; Srivastava 1999; Bose 2003; Aziz and Feeroz 2009). It inhabits subtropical evergreen, broadleaf, deciduous, and bamboo forests and semi-evergreen forests (Srivastava and Mohnot 2001; Molur et al. 2003; Walker and Molur 2007). Phayre's langur is found in higher densities in mixed-species plantations than in monoculture plantations (Gupta 1997). In Tripura, Phayre's langurs are reported from all over the state, but more in the southern districts than in the western and northern districts (Mukherjee 1982; Gupta 1997). The healthiest population is found in the Trishna Wildlife sanctuary (Gupta 2001). The species has been studied by Mukherjee (1982), Gupta and Kumar (1994) and Gupta (1997, 2001). Gupta (2001) recorded 81 plant species in the diet of a Phayre's langur group in the Sepahijala Wildlife Sanctuary. He listed the major food plants and described the group composition and the breeding season. There have been no studies carried out on Phayre's langur in the Sepahijala Wildlife Sanctuary since 1993. In this paper, we report on the population status and threats to Phayre's langur in the Sepahijala Wildlife Sanctuary.
The Sepahijala Wildlife Sanctuary (1,853 ha) is situated in the western part of Tripura, in the Bishalgarh Civil Subdivision of West Tripura district, about 20 km from the capital Agartala (Fig. 1). It lies between 23°37′N and 23°42′N and 91°17′E and 91°21′E, altitude 50 m above sea level. It was created in 1987 with an area of 18.53 km2 but, in 2008, 5.08 km2 of the Sepahijala Wildlife Sanctuary was declared a Clouded Leopard Sanctuary to protect the endangered clouded leopard (Neofelis nebulosa) (Chakraborty 2004–2005). Sepahijala Zoological Park was established in the buffer zone of the Sepahijala Wildlife Sanctuary with the approval of Central Zoo Authority (CZA). The terrain is undulating, with small hillocks. Summer temperatures vary from 20.5°C to 36.2°C, and winter temperatures from 7°C to 27.1°C. Annual rainfall is about 234 cm.
The forest is classified as Moist Mixed Deciduous, with Secondary Moist Bamboo Brakes. There are also man-made forests of sal (Shorea robusta), teak (Tectona grandis), patches of acacia or wattle (Acacia auriculiformis) and rubber (Hevea). The five primates found in Sepahijala Wildlife Sanctuary are Phayre's langur (Trachypithecus phayrei), capped langur (Trachypithecus pileatus), pig-tailed macaque (Macaca nemestrina), Rhesus macaque (Macaca mulatta) and the Bengal slow loris (Nycticebus bengalensis).
Habitat degradation caused by eco-tourism and the communities living in and around the sanctuary are the main threats to the sanctuary's integrity. Tourism is associated with rubbish (plastics). Teasing the monkeys and playing loud music inside the sanctuary is also an issue. There is a road inside the sanctuary used for tourism, resulting in occasional road kill.
A preliminary survey was carried out to record the habitat types and habitat quality, and to become familiar with the trails that would be used for the survey. Previous census data of the Phayre's langur was obtained from the forest department, and local people were questioned about how many Phayre's langur groups they believed occurred in the sanctuary.
From December 2009 to February 2010, we carried out surveys using line transect and recce sampling on all trails in the sanctuary (Swapna et al. 2008). Transects were walked from 05:30 to 12:00 and from 14:00 to 18:00 or sunset. On each survey we stopped every 200 m to look and listen for monkeys. When a group was seen, we recorded its size and age-sex composition. Only total group counts were used to estimate the group size (Srivastava, et al. 2001a, 2001b; Fashing 2002; Pruetz and Leasor 2002; Srivastava 2006; Medhi et al. 2007). We recorded the time they were seen, GPS location, duration of observation, and the tree species they were in or feeding on. Each trail was surveyed three times.
Individuals were classified as adult male (AM), adult female (AF), subadult (SA), juvenile (J) or infant (I) based on the morphological characters and differences described by Bhattacharya and Chakraborthy (1990), Choudhury (1987), Srivastava (1999) and Gupta (2001). Some subadults could not be sexed due to the dense vegetation and poor visibility. In adults, sex was determined by the sex organs and by the pale yellow patch that surrounds the eyes. It is circular or elliptical in the males, and triangular or cone shaped in the females (Choudhury 1987; Gupta 2001). The pale patch is not prominent in juveniles and infants. The juveniles were identified based on their closer contact with their mothers when they rest and roost. The infants were identified by their orange color that begins to change to adult coloration at about three months of age (Srivastava 1999). Groups were monitored to record changes in size. Births typically occur from November to February (Gupta 2001).
Survey trails and their vegetation types in the Sepahijala Wildlife Sanctuary, West Tripura.
We recorded evidence of human activities in a 10-m radius at points every 200 m along the trails. Disturbance included wood cutting, grazing, logging, cultivation, houses, bamboo collection (illegal), firewood collection, forest fires, and trampling. The presence of dung indicated grazing pressure. The various forest types along each transect were also recorded (Table 1).
The habitat types found in the sanctuary include moist mixed deciduous forest, sal (Shorea robusta) forest, sal (Shorea robusta) mixed forest, teak (Tectona grandis) mixed forest, secondary bamboo brakes, and bamboo plantations. The previous census data of Phayre's langur recorded four groups, comprising 46 individuals (Tripura Forest Department). Reports from local people indicated that the population was made up of just three troops.
An estimated seven groups, comprising 95 individuals, were recorded during the study period (Table 2). They were identifiable by their size and composition. Groups four and seven were the same size (12 individuals), but differentiated by the broken tail of the adult male in group 7. The smallest group had eight individuals and the largest group 19. The average group size was 13.14 individuals (range 8–19, SD = 3.77). Percentage group composition was 7.4% adult males, 34.7% adult females, 23.2% of subadults, 26.3% juveniles and 8.4% of infants. The groups were found to have one male and from three to seven females; a uni-male, multi-female social system. Eight births were recorded during the months of January and February. A single infant was present in each group except for one, which had two infants.
Size and composition of the Phayre's langur (Trachypithecus phayrei phayrei) groups recorded in the Sepahijala Wildlife Sanctuary.
Human disturbance in the forest included logging, grazing, cultivation, firewood collection, fires, illegal bamboo collection, trash (plastics), and tourists agitating and teasing the monkeys and other wild animals. The percentage recorded occurrence was as follows: grazing 20%, cutting of trees for timber 20%, cultivation 16%, human habitation 7%, illegal bamboo collection 2%, forest fires 2% and other illegal activities such as firewood collection 24% (Fig. 2). Grazing and firewood collection are the most frequent disturbances in the sanctuary. Timber collection was prominent on three of the trails. Transect number three that traversed the rubber plantation and passed through the mixed deciduous forest was the least disturbed, and five of the seven groups of the Phayre's langur groups were seen there. Since the Sepahijala Zoological Park is located by the wildlife sanctuary, a road connecting the zoological park with the highway that is used by tourists is also a threat to the Sepahijal Wildlife Sanctuary. During the study period we reported two road kills; a porcupine and a macaque.
The population of Phayre's langur in the Sepahijala Wildlife Sanctuary was estimated at seven troops comprising 95 individuals (eight of them infants). This is higher than that of the forest department census report (2009), which recorded 45 individuals in four groups. In 1993, however, Gupta estimated the Phayre's langur population in the Sepahijala Wildlife Sanctuary to be 17 groups, with group sizes ranging from 8 to 22 individuals. The reasons for the decline of the population are unclear. No poaching or deaths were recorded during the study period. The decline might be due to inbreeding or disease, which need to be investigated in future longterm studies. Disturbance from logging, firewood collection, bamboo collection, road kill (accidents by vehicles) and other anthropogenic pressures may also be indirect causes for the population decline. The Sepahijala Wildlife Sanctuary is a small but important protected area for Phayre's langur, and ecological studies and long-term monitoring of the population are needed.
Doki Adimallaiah particularly thanks the Forest Department, Government of Tripura, for providing permission to carry out this study. We are also thankful to Mr. Nirod Baran Debnath, Wildlife Warden, Mr. Gautam Karmakar, Forest Ranger and Assistant Wildlife Warden, Mr. Biswajit Datta, and Mr. Lari Mohan Tripura, foresters of the Sepahijala Wildlife Sanctuary, for their kindness and support during the field work. Our gratitude goes to Mr. Maranko, Wildlife Crime Control Bureau, for his support in many ways. Special thanks also to N. Swapna and R. Deepak for their help during the study.