A checklist of mammals with historical records from Darjeeling-Sikkim Himalaya landscape, India

A region-specific species checklist is an important resource for biodiversity documentation and conservation. This review provides an updated mammal species checklist for the biodiversity hotspots of the Darjeeling-Sikkim landscape in Eastern Himalaya. The list was compiled by systematically reviewing 94 available publications spanning 178 years from 1841 to 2019, for mammals from the region. The species checklist is envisioned to aid in understanding the current status of mammal records, historical distribution, ranked conservation status of mammals, and research gaps. A total of 173 mammal species under 11 orders and 33 families, including the recently upgraded taxon, Sikkim Pika Ochotona sikimaria was enlisted. There are 25 species included in the IUCN threatened categories, 58 species listed in the CITES Appendices, and 112 species included in the schedules of the Wildlife (Protection) Act, 1972 in India. Although mammals receive the maximum research attention in the landscape, small mammals and bats have rarely been subjected to systematic studies in recent years.

This necessitated a methodological literature review of mammal species recorded so far to compile a species list of mammals recorded in the landscape. The reviewed species list is envisioned as a precursor to initiate systematic documentation of mammals in the Darjeeling-Sikkim Himalaya landscape. The reviewed species list aims to aid in understanding the current status of mammal records, their distribution and ranked conservation status, and patterns emerging from these records, along with other knowledge gaps in the region. The compiled species list would also be a reference for systematic field surveys to establish new detection localities, distribution range, and catalogue any new species records. The completeness of any inventory from such field surveys could also be compared against this generated species list.
Darjeeling and Sikkim are rich repositories of valuable biodiversity, which always have interested naturalists and natural scientists from as early as the 19 th century, as a result of which there is a body of literature which records mammals and other taxa from the region.
A thorough literature survey, both offline and openaccess online, of published articles (67), books (17), book section (4), report (4), thesis (1), and news article (1), which include archived literature from various issues of very old journals available at the libraries of Darjeeling

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Natural History Museum and Darjeeling Government College, articles from the Journal of the Bombay Natural History Society and Journal of the Asiatic Society of Bengal available in the Biodiversity Heritage Library was done and then used to prepare a checklist of mammals recorded so far from Darjeeling-Sikkim Himalaya. To update this checklist, necessary corrections from previous publications were made, which include synonyms reported as two different species, subspecies elevated to species, revised nomenclature, and inclusion of new species recorded and not recorded previously. Exclusion of historical species records from singular grey literature not supported by IUCN Red List distribution range and inclusion of species, whose distribution was found to not overlap with IUCN distribution range but supported by peer-reviewed literature were also included. The nomenclature and taxonomic arrangement of the species of the mammals in the checklist are based on the checklist of mammals of southern Asia by Nameer (2015) and cross-checked with the IUCN Red List of Threatened Species for updated nomenclature (IUCN 2020). The present status of each species was also determined at the landscape level based on records updated until 2019, and categorized as Extinct (based on subsequent studies revealing species absence in previously recorded sites or no reports for more than 20 years), Present (species reported within the last 20 years), and Uncertain (reported more than 20 years ago and needs further exploration to confirm species presence). The spellings of location names are kept,as-is from the cited literature.

RESULTS
A total of 94 relevant pieces of literature from available sources for mammalian diversity in Sikkim-Darjeeling Himalayan landscape were reviewed. The majority of literature available pertains to cataloguing, species records, new sightings, and reports accounting for 54 sources. Some studies, however, relate to taxonomy (15), ecology (12), pathology (6), genetics &evolution (2), ethno-zoology (2), and conservation (3). This review covered a span of 178 years dating from 1841 to 2019 and revealed a historical record of 173 species representing 11 orders and 33 families in this landscape

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(Appendix 1). A total of 153 and 145 mammalian species were listed from Sikkim and Darjeeling, respectively. Of the 173 species with historical records in 168  The available literature, when grouped as <1900 and a decade each after, showed that the number of publications peaked at two points, first during 1911-1920 (n=13) followed by a general decline until1980. After that, the trend showed a rise in publications from 1981 onwards ( Figure 2). The other peak was during 2010-2019 (n=19), however, it is expected that the number of publications is likely to increase by the end of the decade. A closer look at recent studies from [2000][2001][2002][2003][2004][2005][2006][2007][2008][2009][2010][2011][2012][2013][2014][2015][2016][2017][2018][2019]44 literature in total, showed that the maximum number of studies pertain to medium and large-sized mammals (56.8%) followed by mammals in general (18.2%), bats (13.6%) and small mammals (11.34%). Only one empirical study based on fieldwork for small mammals, 11 for medium and large-sized mammals, four for mammals in general were carried out. However, no study on bats was conducted during during this period.
Order Chiroptera represents the maximum number of species (n=54 species) followed by order Carnivora According to the IUCN Red List, of the 173 species of mammal recorded from Darjeeling-Sikkim Himalayan landscape, 25 species belong to threatened category (2 Critically Endangered(1.2%), 10 Endangered (5.8%), and 13 Vulnerable(7.5%)); 14 species (8.1%) are Near Threatened; 129 species (74.6%) are Least Concern; four species (2.3%) are Data Deficient; and one species (0.6%) not assessed (Appendix 1). The total number of species falling under various appendices of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) accounts for more than one-fourth (n=54 species) of the total species found in Darjeeling-Sikkim Himalaya, of which 24 species are listed under Appendix I, 15 underAppendix II, and 19 underAppendix III. Almost two-thirds of the total species recorded J TT are protected under the schedules of the Wildlife (Protection) Act, 1972 in India, of which 36 species are listed in Schedule I, 38 in Schedule II, five in Schedule III, four in Schedule IV, and 29 in Schedule V (Appendix 1).

DISCUSSION
The review of biodiversity research trends (Kandel et al. 2016) showed that mammal studies contributed to 45% of total faunal studies in Eastern Himalaya comprising Nepal, Bhutan, and India ( Darjeeling-Sikkim). The bulk of mammal documentation in Darjeeling-Sikkim Himalaya was done half a century ago which is likely to have changed in their distribution records and status due to various factors, including the rapidly changing land-use patterns, urbanization, climate change, and other anthropogenic pressures such as hydroelectric projects and road construction (Banerjee et al. 2019) The resultant checklist from this review is inconsistent with the mammal list of India (Sharma et al. 2014), where the maximum representation is of the orders Chiroptera and Rodentia. This observation could be due to the lack of research in some of the mammal orders like Rodentia in Darjeeling-Sikkim Himalaya. The number of mammal species in Darjeeling and Sikkim also differed, with Sikkim having more number of records than Darjeeling, perhaps due to the considerable altitudinal variation in Sikkim.
This checklist provides for necessary corrections from previous literature, such as the Tarai Gray Langur Semnopithecus entellus ssp. hector,which is now considered a separate species Semnopithecus hector, Greater Hairy-winged Bat Harpiocephalus mordax now synonymized with Lesser Hairy-winged Bat Harpiocephalus harpia (Matveev 2005) and Rufous Horseshoe Bat Rhinolophus rouxii is now synonymized with Chinese Rufous Horseshoe Bat Rhinolophus sinicus. New scientific nomenclatures were also incorporated; replacing the old nomenclature such as Cadorna's Pipistrelle Pipistrellus cadorna is now Hypsugo cadornae (Bates et al. 2019). The present species list also includes a recently upgraded taxon Sikkim Pika Ochotona sikimaria .
The previous records confirming the presence of Rohu's Bat Philetor brachypterus in Sikkim (Molur et al. 2002; were that of misidentified Joffre's Pipistrelle Hypsugo joffrei (Saikia et al. 2017). Previous records of Forrest's Pika Ochotona forresti in Sikkim were also merged with records of Large-eared Pika Ochotona macrotis in light of the new J TT taxonomic assessment of specimens of Forrest's Pika from Eastern Himalaya  which considers it as a new subspecies of Large-eared Pika in Eastern Himalaya based on phylogenetic analysis and morphometric measurements. Forrest's Pika was not recorded in subsequent studies as well (Dahal et al. 2020). Therefore, Rohu's Bat and Forrest's Pika are not included in this checklist.
Historical species records based on singular grey literature    (Gompper & Vanak 2006), is not included in Sikkim species list due to the absence of supporting primary evidence, its distribution range not overlapping as per the extant (resident) shown in the IUCN geographic distribution range and subsequent literature (Menon 2014). The Tibetan Antelope/Chiru was confirmed to be locally extirpatedin Sikkim by Chanchani et al. (2010) as they had assumed the species' presence in the region based on Hooker's account. Joseph Dalton Hooker, however, had not reported the species' sighting in Sikkim and had stated that he "found the horns of this animal on the southern side of Donkia Pass, but (I) never saw a live one except in Tibet" (Hooker 1854, p 157). Hence, there is neither concrete and definitive historical evidence, nor subsequent accounts of this species that suggests its presence in Sikkim (Dawson 1934). Therefore it has been excluded from the species checklist.
Similarly, Tibetan Shrew Sorex thibetanus Kastschenko, 1905, and Southeastern Asian Shrew Crocidura fuliginosa (Blyth, 1856) were also not included. These species, however, had been mentioned in a nonpeer-reviewed report from an ecological study in Teesta Basin ). Besides, these species were also not reported in subsequent literature , and the IUCN geographic distribution range does not overlap with the study area.
A few species records from singular grey literature from Sikkim  but whose geographical distribution range are found to overlap with the IUCN distribution range were considered as being present. These include the Northern Tailless  Another notable inclusion is the Pygmy Hog Porcula salvania. The Pygmy Hog is still included in the checklist, although the current geographic distribution range does not overlap due to empirical research Sclater 1891) confirming historical presence. Although the Blue Sheep or Bharal Pseudois nayaur recorded in (Dutt-Mazumdar 1955 is now considered locally extinct in Darjeeling , it also is included due to its presence within the landscape.

CONCLUSION
The present review of literature, updated till 2019, for records of mammal species in Darjeeling-Sikkim landscape compiles an updated mammal list which generates an overview of mammals in different taxonomic orders, families, and genera which allows an analysis on areas requiring focus on survey, monitoring, and research in the region.
Small mammals:Three orders of mammalian taxa, namely Rodentia, Scandentia, and Eulipotyphla form the small mammals. Globally, these three orders comprised of more than 2,800 species, of which 437 (15%) of them are considered to be threatened with extinction by the IUCN (IUCN SMSG 2018). The small mammals, however, are also inadequately studied, with many hundreds of species never being photographed in the wild and even their basic ecology unknown (Gomez et al. 2017). Moreover, they also serve as model organisms for a better understanding of ecosystem and landscape processes due to their short life cycles and smaller areas of land use (Barrett & Peles 1999). Pradhan et al. (2018) reported large-and medium-sized mammals from the agroecosystems of Darjeeling but not the small mammals. The recent species inventory of mammals in protected areas (PAs) of Sikkim also does not include small mammals . The fact that small mammals have less representation in recent research studies as compared to large-and medium-sized mammals calls for a priority survey and focus on small mammals in Darjeeling-Sikkim Himalaya.

Bats (Order Chiroptera)
Order Chiroptera has a large number of species in the Darjeeling-Sikkim landscape, but there are minimal systematic surveys and monitoring of bats in the context of changes in land use and agroecosystems.

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The most recent study on bats in the region was in 2012 in Kalimpong . The species list for bats requires an update for other parts of Darjeeling and Sikkim, and their status needs to be understood for further long term research on bat ecology and monitoring in the region.

Areas outside of protected areas
There is growing recognition of agroecosystems as repositories of significant biodiversity (Altieri 1999;Bali et al. 2007;Bhagwat et al. 2008;Perfecto & Vandermeer 2008;Chazdon et al. 2009;Chettri et al. 2018), which requires serious conservation attention (Perfecto et al. 2005). For instance, there is no record of threatened species such as the Critically Endangered Chinese Pangolin in the recent study by the Forest Department, Sikkim in the protected areas  although there were records of its presence in Sikkim Sathyakumar et al. 2011b; The Statesman 2019).
Besides the above three major concerns, the findings from this review also give rise to questions as to what is the current distribution and status of the four Data Deficient species-Hairy-footed Flying Squirrel Belomys pearsonii, Millard's Rat Dacnomys millardi, Sombre Bat Eptesicus tatei, and Joffre's Pipistrelle Hypsugo joffreione not assessedspecies Sikkim PikaOchotona sikimaria, and 17 endemic mammals in the region. It is also important to know the present status and understand the ecology of mammals in the agroecological matrix, a prerequisite for their conservation and co-existence with humans in the socioecological landscapes. Future research should be directed to address these gaps in the mammal survey and ecological studies in the region. Darjeeling Gurung & Agarwal 1969;Chatterjee et al. 1970;Bandyopadhyay & Dasgupta 1984b;Dey et al. 1984;Banerjee et al. 1996), Ghoombhanjan ), Darjeeling and Ghoom (Molur et al. 2005) 13. Petaurista nobilis (Gray,