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A survey of blue sheep was carried out in four major valleys of Kangchenjunga Conservation Area (KCA) to determine the distribution and population status during the months of September to November 2007. Blue sheep is the major prey species of snow leopard in Nepal KCA. The fixed point count method from vantage point was used to determine the population status and distribution. The result showed the uneven distribution of blue sheep in KCA. The highest number of blue sheep were recorded from the Yangma valley (n=570) followed by Ghunsa (n=419), Olangchungola (n=113) and Yamphudin (n=32). Livestock grazing, habitat degradation and disturbance appear to be the most significant threats for the survival to species in the areas surveyed.
Keywords: Blue sheep, population, KCA, herd size, threats
The blue sheep is considered as the lower risk or near threatened species by IUCN (Harris 2008). They are widely distributed in the Himalaya of Central Asia extending into Nepal, Bhutan, India, China and Pakistan. The animal is primarily found in the northern portion of Nepal bordering to Tibetan Autonomous Region, China. Blue sheep typically prefer plateau, alpine barren rock, and inter-valley grassland (Schaller 1977). In Nepal, the blue sheep inhabits in the main Himalayan chain along the Tibetan border. Its distribution seems to be localized in some protected areas of the Nepal Himalayas and presence has been confirmed in mountain protected areas; Shey Phoksundo National Park, Makalu-Barun National Park, Annapurna Conservation Area, Kangchenjunga Conservation Area, Dhorpatan Hunting Reserve and Manaslu Conservation Area (Khatiwada and Chalise 2006, Jackson 1996, Shrestha et al. 2005, Shah 1986) and outside the protected areas; Darchula and Humla districts of Far western Nepal (Khatiwada and Ghimire 2009). Although the Blue sheep is one of the most widely studied mountain ungulate in Nepal; it has been little studied in Eastern Nepal. Most of the information available consists only of competition with livestock and other wild ungulates and prey-predator relationship (Wilson 1981, Shah 1986, Oli 1996, Shrestha et al 2005, Shrestha and Wegge 2006, Shrestha and Wegge 2008a, Shrestha and Wegge 2008b). Recent surveys have clarified that Kangchenjunga Conservation Area has the important habitats and strongholds for the blue sheep in Nepal. We report here on studies carried out during September-November 2007 to assess the population status and distribution of the Blue sheep, and identify the existing threats to their existence in the area.
MATERIAL AND METHODS
The survey of Blue sheep was carried out in the four major valleys of Kangchenjunga Conservation Area (hereafter KCA). The KCA is situated in between 27028'48" N' to 270 56'24" N and87039'00" E to 88012'00' E in the Taplejung district in North eastern comer of the country (Fig. 1). The KCA covers an area of 2,035 km2 between the altitudes 1,200m and 8,586 at the top of Mt. Kangchenjunga, the third highest mountain in the world. The area is established in 1997 as a conservation area, is adjoining to the Qomolongma Nature Preserve in Tibet, and Kanchenjunga Biosphere Reserve in Sikkim, India. Because of its location directly to the north of the Bay of Bengal, it receives higher rainfall than other parts of Nepal. It is an extraordinary landscape with unique floral and faunal diversity, breath-taking scenery, and rich cultural heritage. Biogeographically, it lies in eastern Himalayas (Olson and Dinerstein 1998). The Conservation Area supports about 3000 species of plants (BPP 1995), species of flora that are characteristic of the eastern Himalaya. The vegetation ranges from subtropical to alpine (Rastogi et al. 1997). The KCA is important for number of threatened mammals (e.g. Musk Deer Moschus chrysogastor, Snow Leopard Uncia uncia, Red Panda Ailurus fulgens, Serow Capricornis sumatraensis, Assamese Macaque Macaca assamensis, Himalayan Black Bear Selenarctos thibetanus and Clouded Leopard Neofelis nebulosa). As many as 279 bird species have so far been recorded in the Conservation Area, but many more are likely to occur (Thapa and Karki 2006).
Figure 1: Map of four major valleys of Kangchenjunga Conservation Area
The fieldwork was carried out between September and November, 2007 in four different valleys; Olangchungola, Yangma, Ghunsa and Yamphudin of Kangchenjunga Conservation Area. Blue sheep were observed at designated vantage point (Jackson and Hunter 2005). The observations were done from 07h00 to 11h00 and 15h00 to 18h00 by using 8x40 binoculars and 15-45X spotting scope as visual aids. In each point, the observers waited for at least 30 minutes before proceeding to other locations. Whenever a herd of blue sheep was observed, we recorded the time, date, number, age and sex of animal as well as habitat characteristics with GPS coordinates. The classification of blue sheep was done in six different categories modified from Schaller (1977) and Wilson (1981) (Table 1). The age and sex were determined by horn length and shape, intensity of the black markings on the legs and chest, as well as body size of the sheep.
The descriptive statistics were performed to show the age-sex categories in different blocks. F-test was used to show overall distribution pattern in survey blocks. Comparisons are expressed mean ±standard error. Overall, analysis was done using SPSS version 13.
Table: 1 Classification of age and sex categories of blue sheep
Fully grown male with an estimated horn length of at least 45-50cm, horns curving noticeably backwards, animals mostly older than 7 yrs.
Males with horn longer than 30-35cm but curving backward slightly, presumably consisting 7, 4, 5 and 6 year olds.
Horn size between 15-35cm and 2, 3 year old small size males.
Female with an estimated horn length of 15-25cm and 3 years
Young ones up to 2 years old
Born in the current year
Population structure of Blue sheep
A total of 1167 Blue sheep were recorded from the four major survey blocks; Olangchungola, Ghunsa, Yangma and Yamphudin of KCA. This comprised 28% adult female, 16% lamb, 11% yearling, 8% young male, 7% sub-adult male, 13% adult male and 17% unidentified blue sheep (Fig. 2). Out of the total 1167 blue sheep from 43 herds; only 966 blue sheep were classified as per age and sex category which revealed 34% adult female, 20% lamb, 13% yearling, 10% young male, 8% sub-adult male and 15% adult male blue sheep (table 2). The number of blue sheep was vary in survey blocks (F=2.674 DF=3, P=0.062). The highest number of blue sheep was recorded from Yangma (31.66±5.62, N=570 from 17 herds) followed by Ghunsa (24.64 ± 5.27, N=419 from 17 herds), Olangchungola (14.125±3.02, N=113 from 8 herds) and Yamphudin (16.25±4.83, N=32 from 4 herds).
Figure 2: Percentage of blue sheep encountered in four different survey blocks of KCA
There was considerable variation in herd sizes in four different blocks which ranged from three (n=1) to 88 (n=1) in Ghunsa, three (n=1) to 28 (n=1) in Olangchungola, six (n=1) to 99 (n=1) in Yangma and six (n=1) to 24 (n=1). The most commonly observed herds were 1-10 animals (n=9), 10-20 animals (n=11) and 20-30 (n=14) animals. The survey result revealed that some of the herds of more than 99 individuals were also encountered, signifying in large part the pre-rut period of blue sheep during which data was collected. The average herd sizes were ranged from (mean 32 ± 5.62) in Yangma, (mean 17 ± 3) in Ghunsa, (mean 14 ± 3.02) in Olangchungola and (mean 16 ± 9) in Yamphudin block. Unlike the Yangma and Ghunsa in Olangchungola and Yamphudin blocks, the areas were relatively disturbed from livestock grazing and high degree of poaching.
Habitat utilization and distribution
Majority of blue sheep were recorded in the grassland (or alpine meadow) (65%) followed by scrub (24%) and barren land/cliff (11%). Most of the herds were observed between the altitude of 4400m- 4700m (n =35) (Fig. 3). Similarly herds were found on average 320 Slope (n=.31) and 1450 aspect (n=32). The estimated average mean distance to cliff for the blue sheep herds were 150m (n=35).
Figure 3: Landform type used by blue sheep in KCA
The landform ruggedness utilized by the average blue sheep herds were 47% on rolling terrain, 5% were on cliff, 33% were on broken terrain, 10% very broken and 5% were found on the flat land respectively (Fig. 4). Among the total herd observed, 60% blue sheep were observed in hill slope followed by 20% in cliff, 13% valley floor and 7% in the ridgeline. Most of the herds were observed in remote areas, showing that the species are probably staying away from areas with human activity.
Figure 3: Overall landform type used by blue sheep in KCA
The blue sheep is principal prey species of Snow leopard Nepal Himalaya (Jackson 1996). The survey result reveled that a total of 43 herds consisting of 1167 individuals of blue sheep were observed from the entire survey blocks and also the major wild ungulate prey of snow leopard in KCA. The herd size and composition of Blue sheep varies because of habitat structure, disturbance and food availability. During the study period the blue sheep population amongst the blocks was higher in the Yangma block. The area is relatively less disturbed than other survey blocks. The livestock keeping is the main activity of the local people in living in area. The Yamphudin and Olangchungola blocks are heavily affected by disturbance, illegal hunting and overgrazing. Locals report indicated that once blue sheep were plentiful in Olangchungola and Yamphudin areas. Illegal hunting on blue sheep and musk deer is still prevalent in the areas from locals and even from the Tibetan people because the area closer to Sino-Nepalese broader. During the survey period six blue sheep trap caves and several leg snares were found from the Olangchungola and Yamphudin areas.
Blue sheep is most important prey species that determine the population of the snow leopard in the KCA. A predation rate of about 10% of a population represents a limiting equilibrium state for large predators and large mammalian prey (Emmons 1987). An adult snow leopard requires 2030 blue sheep annually. i.e. 150230 blue sheep are needed to support a single adult snow leopard with 13% harvesting rate (Jackson 1996). Schaller (1998) suggested a similar figure, i.e. a blue sheep population with 150200 animals and an annual increment of 15% could support one wolf or one snow leopard if the population lacked other mortality causes such as poaching.
Status of pasture, trend of their livestock type and number in the particular area is directly related to the abundance of native local ungulates. There is high grazing pressure on the snow leopard's habitats in KCA. Secondary impacts of grazing, particularly reductions of wild prey through competition, may negatively influence snow leopard range use (Ale 2006). No data available on competition between livestock and blue sheep in the KCA. However, Shreshtha and Wegge (2008 b) reported the high pattern of resource-use overlap between blue sheep with livestock in Manang. Similarly, Mishra et al (2004) found low population of blue sheep in heavily grazed areas in India and showed poorer performance (lower young: adult female ratio). Bagchhi (2004) also reported forage competition between livestock and native prey species. Livestock found to be removed large amounts of forage from the pastures.
The blue sheep were never recorded as crop depredator in the Yangma earlier. However, all respondents from Yangma village strongly condemned the ungulate's crop damaging activity. Firstly, decline in the population of natural predator like snow leopard has attributed in some extent rise of blue sheep population in the area. Secondly, in the valley, as the areas adjoining to the agricultural lands are religiously protected no hunting activities are allowed due to religious sentiments. However, these areas are also main livestock grazing areas for the villagers therefore; food competition might have compelled the sheep to raid the crops.
We are thankful to the WWF Nepal program for providing financial support for this study. Field assistants Tashi Sherpa and local communities of KCA made this study possible. We are also grateful to anonymous reviewer for critical comments on the manuscript.