J. Bio. & Env. Sci

Small mammals have multiple ecological roles and are important components of the terrestrial ecosystems. They are important ecological indicators of changes in the natural surroundings. However, little is known about the small mammals in Bhutan. We conducted this study in the Bumdeling Ramsar Site in eastern region of Bhutan, aimed at enhancing our understanding of the species composition, abundance, and seasonal diversity of small mammals. We laid linear transects, each measuring 500 m in six different habitat types: agriculture land (AG), fallow land (FL), Alnus sp. forest (AF), open grassland (OG), riparian forest (RR), and oak forest (OF). We placed 17 collapsible Sherman live traps (23x9x8cm) in each transect to capture both ground dwelling and arboreal small mammals. We conducted the trapping exercise twice in the year 2016 (28 March to 28 April during the wet season and 1 to 30 October during the dry season), amounting to a total of 1,224 trap nights. We trapped a total of 135 individuals of small mammals, yielding seven species of rodents (90 individuals; 66.7%) and four of insectivores (45 individuals; 33.3%). We found significant difference in the number of individuals trapped among the six different habitats (X2=66.43, df= 5, P<0.05) with the highest in AG (59 individuals, 43.7%) and the lowest in OG (1 individual; 0.7%) during the dry and wet season, respectively. In order to promote diversity of small mammals in the Ramsar site, we recommend reducing free-range cattle grazing and restraining domestic dogs in the vicinity of the Ramsar site. *Corresponding Author: Lam Norbu  lam.norbu@ymail.com Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online) Vol. 15, No. 3, p. 36-45, 2020 http://www.innspub.net J. Bio. & Env. Sci. 2019 37 | Norbu et al. Introduction Small mammals (rodent, shrew and lagamorph ≤ 500g or 1kg) form a majority of the mammalian fauna, and they are an important component of most natural and semi-natural ecosystems (Ofori et al., 2015). They perform ecological roles in dispersal of seeds (Aplin et al., 2003; Garshong et al., 2013) and fungal spores (Gupta, 2011), nutrient cycling (Sieg, 1987; Klerk, 2014), and decomposition and mediation of energy flow through consumption and shedding of vegetation (Hoffmann et al., 2010). They also often dubbded as environmental engineers because of their role in soil aeration through digging and burrowing, and in extreme cases, altering the whole landscape (Garshong et al., 2013; Gyeltshen, 2015). They also serve as essential prey for many mammals, birds and reptiles (Garshong et al., 2013; Chane and Yirga, 2014). They are, thus, known to play an important role in determining forest structure, composition and succession of vegetation (Ofori et al., 2015). Their abundance and composition in turn, are influenced by habitat structure, productivity and other important environmental factors (Demeke and Afework, 2014; Tuyisingize et al., 2014; Assefa and Srinivasulu, 2019). Small mammals are considered to be good bioindicators of habitats because of their short lifespan, rapid population dynamics, and low level of hunting pressure in comparison to larger mammals (Karuaera, 2011, Chane and Yirga, 2014). Most small mammals are prolific breeders; hence, they represent significant amount of the animal biomass in forest and other natural ecosystem (Aplin et al., 2003). They are also the major agricultural pests, causing substiantial damage to crops and stored farm produce (Karuaera, 2011; Ofori et al., 2015). Further, they also serve as parasitic host and disease reserviors (Avenant and Cavallini, 2008; Bantihun, 2012). On a gobal scale, there are approximately 5,416 species of mammals (Bantihun and Bekele, 2015) of which 2,706 (50%) are small mammals (Wolff and Sherman, 2007; Molur and Singh, 2009; Datiko and Bekele, 2013). South Asia alone has recorded 185 species of small mammals of which 62 are endemic to the region (Molur et al., 2005). Among the South Asian countries, India has 120 species of small mammals representing 66% of Indian mammal records (Walker, 2003; Gyeltshen, 2015). Similarly, Nepal has 158 species of small mammals representing more than 60% of mammal records, and one species being endemic to Nepal (Katuwal and Koirala, 2012). In Bhutan, there is very few documentations of small mammals, and hence, little is known about them with respect to their species diversity, distribution, conservation status, and ecology. This is largely attributed to limited explorations and studies conducted so far in the country. In fact, documentation of small mammals was initiated only in 1993, following which a few studies were conducted in the recent years. Wangmo et al., (2014) listed four species of small mammal from Royal Manas National Park (RMNP) in south-central region of Bhutan. Gyeltshen (2015) conducted an exploration in Jigme Dorji Nation Park (JDNP) in western Bhutan where he recorded six species of rodents. In the same year, Dorji (2015) added seven species of high-altitude rodents and shrews in the wetlands of Phobjikha, which is the third Ramsar Site in Bhutan. All of these studies are concentrated in the western region of the country, and there is no exploration from the eastern region. Therefore, we conducted this study in the eastern region of Bhutan, aimed at enhancing our understanding of the species composition, abundance, and seasonal diversity of small mammals. Materials and methods Study area We conducted the study in the Bumdeling Ramsar Site (27°39’33.86” N, 91°25’47.73” E), which is situated inside the Bumdeling Wildlife Sanctuary (BWS; Fig.1), in north-eastern part of Bhutan. Our study site was designated as a Ramsar Site in 2012 in recognition of the conservation significance of the charismatic and ‘Vulnerable’ black-necked crane (Grus nigricollis) which winters annually in the area. On an average, about 90 individuals of this bird arrive J. Bio. & Env. Sci. 2019 38 | Norbu et al. and reside in the area every year. It covers an area of 1.42 km2. The elevation of the adjacent forest ranges from 1,900 to 2,050 m above sea level (a.s.l.). The wetland has 160 species of plants, 73 of birds, 38 of snakes, seven of lizards, seven of fishes and 12 of mammals (UNESCO, 2012). Among the large predators, the globally threatened and flagship species such as the Bengal tiger (Panthera tigris) is known to coexist with Himalayan black bear (Ursus thibetanus), dhole (Cuon alpinus), and red panda (Ailurus fulgens). Bhutan’s national butterfly (Bhutanitis ludlowi) is also recorded in the study area (UNESCO, 2012; Poel, 2013). The mean annual temperature recorded is 20.20C and the mean annual rainfall is 1,065 mm (UNESCO, 2012). People residing in the vicinity of the study site follow subsistence farming which consists of crop cultivation, livestock rearing, and sale of non-timber forest produce. They also collect firewood, house construction timber, and NWFPs (such as bamboo, barks of daphne (Daphne bholua), fiddle heads, mushrooms, and many other wild vegetables) from the nearby forests. We selected six habitat types based on the dominant species composition: agriculture land (AG), fallow land (FL), Alnus forest (AF), open grassland (OG), riparian forest (RR), and oak forest (OF). Fig. 1. Map showing study location in Bumdeling Ramsar Site (Trashiyangtse, Bhutan). Live trapping of small mammals At the outset, we conducted a preliminary survey in order to be able to appropriately select the trapping sites. Relevant site information such as topography, climatic conditions, and the associated flora and fauna were gathered. We conducted the trapping exercise twice in the year 2016 to compare seasonal diversity of small mammals: first round from 28 March to 28 April during the wet season and the second from 1 to 30 October during the dry season. This amounted to a total of 1,224 trap nights. Transect lengths varying from 400 to 500 meters have been used in small mammal surveys (Klerk, 2014; Dorji, 2016). We laid linear transects, each measuring 500 m in six different habitat types of the study area. We placed a total of 17 collapsible Sherman live traps (23x9x8cm) in each transect, spaced by an interval distance of 15 m to capture both ground dwelling and arboreal small mammals. We kept the traps for three consecutive days to capture all possible small mammals. As recommended by Cunningham and Moors (1996) and Hoffmann et al., (2010), we placed the traps in areas with high likelihood of small mammal visitation, such as proximity to rocks, caves, burrows, log side, bushes, fences, sheds, tree buttresses, coarse woody debris, visible droppings, food remains and runway. The traps were covered with litters, foliage and hays to camouflage and provide insulation (Barnett and Dutton, 1995; Pearson and Ruggiero, 2003). This also prevented the local people, cow herders, and stray dogs from being attracted by the shiny surfaces of the traps. We baited each trap with locally made flour dough mixed with ground nuts, apples, grapes, bananas, wheat biscuits, dry salty fish, bread, canned fish and fresh carrot following the baiting method of Barnett and Dutton (1995). In order to be able to relocate the traps, we marked each trap location with red cloth tagged on a stick or a branch of a nearby tree or shrub. We inspected each trap twice a day: once in early morning from 7:00 hrs to 9:00 hrs and once in the late afternoon from 17:30 hrs to 19 hrs. This was to capture both diurnal and nocturnal animals (Bantihun and Bekele, 2015). During each inspection visit, we checked the baits and replenished them wherever necessary to increase trapping success and to avoid loss of animal lives J. Bio. & Env. Sci. 2019 39 | Norbu et al. from hunger. We cautiously removed each trapped animal, placed in a polythene bag, and weighted using Pesola ® spring balance of 200g capacity. Next, we measured each animal using the standard morphol