Status, distribution and threats of kraits (Squamata: Elapidae: Bungarus) in Bangladesh

Review

introduction

Kraits (genus Bungarus: Elapidae) are venomous elapid snakes. They inhabit most of the Oriental Region with the exception of the Philippines (Kuch et al. 2005). There are 16 species of Bungarus known (Abtin et al. 2014; Wallach et al. 2014) and 15 are restricted to the southern and southeastern Asia (Slowinski 1994; David & Ineich 1999; Kuch et al. 2005), and one in Iran (Abtin et al. 2014). Five species of kraits are known to occur in Bangladesh (e.g., Ahsan 1998; Kabir et al. 2009; Khan 2015) but their status and distribution in the country are not well understood. This study was designed to evaluate the countrywide status and to compile the distribution and point out threats to these five species.

 

 

Materials and Methods

The status and distribution of kraits in Bangladesh have been compiled from both primary and secondary sources for 15 months (January 2014 to March 2015). Different books (e.g., Khan 1982, 1992, 2008, 2010, 2015; Sarker & Sarker 1988; Kabir et al. 2009; Hasan et al. 2014), national and international journals, websites, literatures, reports (both published and unpublished) (e.g., Sarker 1975; Husain 1977; Montaquim 1979; Montaquim et al. 1980; Rashid 1982; Sarker & Sarker 1985; Khan 1987; Sarker & Hossain 1997; Ahsan 1998) were consulted, personal visits were also conducted in the fields. Eighteen protected areas were visited during the study period (Table 1). Data were collected through direct field observations along the existing trails or streams during 1–3 visits for each area. Searching involved in turning rocks, logs and leaf litters from twilight to early night (17:00–20:00 hr) by three persons. Preserved snake specimens in the collections of 36 different institutes and museums throughout the country were verified (Table 2). The results of all possible sources have been compiled and a distribution map has been depicted but not by GPS readings (Fig. 1). Possible threats were noted and questionnaires were made to find out major threats. The status of these species has been assessed based on the chance of being encountered during its most active period during the field visits, the availability of specimens in collections and the comments on the species in old literature records. Species that were observed more than 15 times (75%, of the total observation days), are considered very common (VC); those that were seen 10 to 14 times (50–74 %, of the total observation days) common (C); as fairly common (FC) were regarded those spotted 5 to 9 times (25–49 %, of the total observation days); uncommon (UC) for those that were noticed 1 to 4 times (1–24 %, of the total observation days); and no sighting of the species in the field but availability in collections as preserved specimens were regarded as rare species in this list (Ahsan et al. 2015).

 

 

 

 

 

Results

 

 

Bungarus caeruleus (Schneider, 1801) (Image 1)

The Common, Indian or Blue Krait (B. caeruleus) is recorded from greater Kushtia (Montaquim 1979) and Dhaka (Rashid 1982) districts. Sarker & Sarker (1988) reported it from the Sundarbans area. Khan (1992) mentioned a distribution all over the country except Madhupur and Saint Martin’s Island. Gieson & Rashid (1997) reported it from the Tanguar haor of Sunamganj District. It is rarely found in Chittagong region (Parvin 1999) and Chowdhury et al. (2011) confirmed it from Sylhet. It has also been reported from Dudpukuria-Dhopachari Wildlife Sanctuary (WS) (Feeroz et al. 2012), Carmichael College of Rangpur (Kabir 2013), northwestern (Rangpur) Bangladesh (Sharma et al. 2013), Teknaf WS (Hasan et al. 2013) and Rema-Kalenga WS (Feeroz et al. 2011). There are two specimens (106CU, 124CU) in the museum of the Department of Zoology, University of Chittagong, Chittagong, which were collected from the Chittagong University Campus. A good number of specimens have been preserved in the Department of Medicine at Khulna Medical College and Department of Zoology, Brajalal (BL) College, Khulna, which were collected from Khulna. Specimens were also found in Rajshahi District in 2013 and in Rangpur District in 2010 (M. Farid Ahsan pers. obs.). In this study we report it from Barisal, Comilla, Jessore, Jhalokathi, Habiganj, Khulna, Pirojpur, Sirajganj and Tangail districts. The global distribution of the species includes Afghanistan (Kral 1969), Myanmar (Chakma 2009a), India, Nepal, Pakistan and Sri Lanka (Wallach et al. 2014). It ranges from the plains up to an elevation of 1,646m (5,400ft) (Smith 1943).

 

 

Bungarus fasciatus (Schneider, 1801) (Image 2)

Banded Krait (B. fasciatus) was reported from Rajshahi Town (Sarker 1975). Montaquim (1979) and Rashid (1982) also reported it from Tangail (Madhupur) and Mymensingh districts. Sarker & Sarker (1988) commented that it is fairly common and widely distributed. Khan (1992) mentioned it is widely distributed in the country and very common in Chittagong region (Parvin 1999). It has been reported from Madhupur National Park (NP) (Reza 2007); Nijhum Dweep NP (Rabbi 2009); Sylhet (Chowdhury et al. 2011) and Tanguar haor of Sunamganj (Alam et al. 2012). Rahman et al. (2012) have confirmed it from the adjacent area of the Padma River, Rajshahi. One specimen is preserved in the Zoological Museum of the Dinajpur Govt. College (M. Farid Ahsan pers. obs. in 2003). It is recorded from the Dudpukuria-Dhopachari WS (Feeroz et al. 2012), Teknaf WS (Hasan et al. 2013), Rema-Kalenga WS (Feeroz et al. 2011), and Baraiyadhala NP (Karim 2014). In this study we report it from Chittagong University Campus, Fashiakhali WS and Bagerhat, Barisal, Comilla, Jessore, Patuakhali, Pirojpur and Rangamati districts. This common elapid snake’s worldwide distribution includes Bangladesh, Bhutan, Brunei Darussalam, Cambodia, China, India, Indonesia, Lao PDR, Malaysia, Myanmar, Singapore, Thailand, Vietnam (Stuart et al. 2013), Macau, Nepal (Wallach et al. 2014), and Sri Lanka (Günther 1864). It ranges from 20–2,300 m (Stuart et al. 2013).

 

 

 

 

 

 

 

Bungarus lividus Cantor, 1839 (Image 3)

Lesser Black Krait (B. lividus) is reported by Smith (1943) and Khan (1992) from Rangpur District of Bangladesh. Recently, it was recorded from Carmichael University College of Rangpur (Kabir 2013) and Dinajpur (Sharma et al. 2013). Two specimens (BD 410, BD 411) are preserved in the collection of the Zoological Museum of the Dinajpur Govt. College in 2003 (M. Farid Ahsan pers. obs.). One specimen was collected from Mymensingh District in 2008 and one from Feni District in 2009 through Chittagong Medical College Hospital (M. Farid Ahsan pers. obs.). During this study period we found two specimens in the museum collections of the Department of Zoology, Govt. Sohrawardi College, Pirojpur and Govt. Prafulla Chandra (PC) College, Bagerhat. Globally, B. lividus occurs in Bangladesh, India, Nepal and ranges up to 340m (Wallach et al. 2014).

 

 

Bungarus niger Wall, 1908 (Image 4)

An individual of the Greater Black Krait (B. niger), from unknown origin in Bangladesh was kept for a brief period in Dhaka Zoo in the 1990s (Sarker & Sarker 1985). Khan (1992) reported a skin of this species in the market in Dhaka and commented that it might be present in Mymensingh and Sylhet districts. It is recorded from the Sundarbans and is expected that the species might occur in other plain lands (Islam 2009). It is also recorded from Chandanaish, Fatikchari, Chittagong University Campus in Chittagong as well as from Dighinala (Khagrachhari) and Khagrachhari districts in the Chittagong Hill Tracts (Faiz et al. 2010). Faiz et al. (2010) also commented that its distribution is country-wide. Recently, it has been reported from Dudpukuria-Dhopachari WS (Feeroz et al. 2012), Teknaf WS (Hasan et al. 2013) and Baraiyadhala NP (Karim 2014). It was found from Chittagong Hill Tracts (Bandarban, Khagrachhari, Rangamati and Kaptai NP), Sherpur, Jamalpur, Habiganj, Moulavibazar (including Lawachara NP), Sylhet, Chittagong, Cox’s Bazar (M. Farid Ahsan pers. obs. [1990–2013]) and Savar (Dhaka) during this study. Its worldwide distribution includes Bangladesh, Bhutan, Nepal, Northeastern India (Wallach et al. 2014), and Myanmar (Faiz et al. 2010). It is recorded from Kaski District in Nepal at 1,450m altitude (Sharma et al. 2013).

 

 

Bungarus walli Wall, 1907 (Image 5)

Wall’s Krait (B. walli) is distributed in Rangpur and Dinajpur districts of Bangladesh (Khan 1992). One live specimen was collected by a snakebite victim from Ramgoti Upazila of Noakhali District through Chittagong Medical College Hospital in 2006 and another dead specimen from Rajshahi Medical College Hospital in 2010 (M. Farid Ahsan pers. obs.). In 2007, one dead specimen was brought to Dhaka Medical College Hospital by a snakebite victim from Gazipur (M. Farid Ahsan pers. obs.). Recently, the species was recorded from Laksmipur (Laxmipur) District (Sharma et al. 2013). In this study we report from Barisal, Jessore, Khulna, Sirajganj and Tangail districts. The species is supposed to be an endemic snake of the Indian subcontinent (Chakma 2009b). It has been reported from Bangladesh, India and Nepal (Wallach et al. 2014) and is recorded up to 100m above sea level (Wall 1907).

 

 

 

 

 

 

 

 

Discussion

The five Bungarus species (B. caeruleus, B. fasciatus, B. lividus, B. niger and B. walli) are distributed in Afghanistan, Bangladesh, Bhutan, Brunei Darussalam, Cambodia, Indonesia, India, Lao PDR, Macau, Malaysia, Myanmar, Sri Lanka, Nepal, Pakistan, Singapore, southern China, Thailand and Vietnam (Slowinski 1994; David & Ineich 1999; Kuch et al. 2005; Wallach et al. 2014). It is evident from the above discussion that kraits are in general southern, southeastern and middleeastern Asian snakes. Two species (Common Krait and Banded Krait) are common in Bangladesh, one species (Greater Black Krait) is uncommon, and the remaining two (Lesser Black Krait and Wall’s Krait) are rare; IUCN Bangladesh (2015) mentioned the status of B. caeruleus and B. fasciatus as “Least Concern”, and B. lividus, B. niger and B. walli as “Near Threatened”. B. fasciatus is the commonest among the five native Bungarus species in Bangladesh. Both B. caeruleus and B. fasciatus are widely distributed in the country, but the former is very common in Khulna and the latter in Chittagong districts. B. lividus is the rarest one and confirmed reports on it reveal that the species occurs in the northern, northwestern, southeastern and southwestern parts of Bangladesh. This species may be absent in mixed evergreen forests of northeastern and southeastern parts of the country. B. niger is widely distributed all over the country except western and northwestern parts, and commonly found in northern, northeastern and southeastern parts of the country. B. walli is another rare species and dispersed in the central, northwestern, southeastern (partly) and southwestern parts of the country. It is mostly found in the belts of rivers and canals especially sandy ‘char’ [Bengali: sand bank] areas. The species may also be absent in the districts of western side of the Padma River and mixed evergreen forests of northeastern and southeastern parts of the country. It is a common species in Tangail and Sirajganj districts.

Kraits have great medicinal and ecological value in Bangladesh but the survival of these species is threatened due to the direct or indirect impacts of the ever-increasing human population of the country. Habitat destruction through forest clearing and alteration, infrastructure development, agricultural expansion, spreading out of human settlements, road kill, killing due to fear, and illegal exports as well as the misconceptions of human beings about snakes are the major threats for these species. Illegal capturing of B. fasciatus is reported for use in traditional medicines. Generally, specimens with a weight above 2kg are captured for illegal markets.

Kraits are key components of the natural ecosystem and should be conserved. We hope that this study will support any further study on this medically important, timid and often docile snakes and facilitate development of conservation strategies.

 

 

 

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