Bangladesh is a country of rich biodiversity, including herpetofauna, across diverse ecosystems. This study reviews snake diversity and distribution patterns in Bangladesh, identifying 141 species in the existing literature. However, we confirmed the presence of 89 species based on documentation in literature, research-grade data in online repositories, and verified photographs on social media. Among them, the family Colubridae comprises 35%, followed by Elapidae (26%), Natricidae (13%), and others. Regarding envenomations, 70% of the species are non-venomous and 30% are venomous. Three species (Acrochordus granulatus, Boiga westermanni, and Dieurostus dussumieri) were considered regionally extinct in the absence of sightings in the past five decades. Sixteen species were deleted due to unreliable reports or misidentifications, while Ahaetulla sahyadrensis and Rhabdophis helleri were added. Additionally, we hypothesize that 33 species may inhabit Bangladesh, considering their ecological distribution. We illustrated the geographical distribution patterns of confirmed species using kernel density estimation (KDE), identifying the mixed evergreen forests in the southeast and northeast and the mangrove forests in the southwest as densely populated habitats. This study enhances the understanding of snake diversity and distribution in Bangladesh and underscores the need for further research and conservation efforts to prevent species extinction.

checklist, Chittagong Hill Tracts, conservation efforts, herpetofauna, kernel density estimation, Sundarbans, zoogeography

Bangladesh is a South Asian country that occupies an area of about 147,570 km², located along the Bay of Bengal to the south, with India to the west, north, and east, and Myanmar to the southeast (Rashid 2019). The country is characterized by a predominantly low-lying landscape with vast floodplains, lakes, marshlands, and the lower delta of crisscrossing rivers (e.g., Padma, Meghna, and Jamuna) and estuaries, making it the largest river delta in the world (Chowdhury et al. 2022). The country’s topography is mostly flat, with extensive waterways and coastal areas, including the Sundarbans, the world’s largest mangrove forest (Rogers and Goodbred 2014). The terrestrial habitats in Bangladesh include the evergreen forest of the Chittagong Hill Tracts in the southeastern part featuring hilly terrain, mixed evergreen low hill forest patches in the northeast (Sylhet) and northern (Mymensingh) regions, moist deciduous forests in the central and northwest regions, and the mangrove forest, the Sundarbans, in the southwest (Reza et al. 2019). In addition, bushy, grassy, and bamboo-dominated unclassified state forests, or classified forest patches, namely Kunjaban at plains and Paraban at hill tracts, as well as homestead vegetation, make up the diverse terrestrial habitat (Alam 2011). Except for some wide rivers, there are no dominant physical barriers across the country—that is why it serves as a connecting bridge for the faunal diversity of the Indo-Burma hotspot, the Gangetic plains, and the Deccan plateau (Chandra and Gupta 2022).

The first systematic research on the wildlife in this region was initiated by Sir William Jones (1746–1794) in the 18^th century, while herpetological research began with the collection of type specimens for the museum of the Asiatic Society of Bengal by Theodore Edward Cantor (1809–1860) and John MacClelland (1805–1875) during the British colonial period in the early 19^th century (Das et al. 1998). Later, Edward Frederick Kelaart (1819–1860), Colonel Arthur Purves Phayre (1812–1885), Brian Houghton Hodgson (1800–1894), William Lutley Sclater (1863–1944), and Sunder Lai Hora (1895–1955) also made noteworthy contributions to herpetological research by collecting type specimens from British India, including Bengal (Mahendra 1935; Das et al. 1998). In addition to the collection and curation of specimens, Edward Blyth (1853), Thomas Claverhill Jerdon (1853, 1870), Albert C. Günther (1864), William Theobald (1868, 1876), Ferdinand Stoliczka (1870, 1872), William Thomas Blanford (1870, 1878, 1890, 1898, 1901), John Anderson (1871), George-Albert Boulenger (1890, 1893), William L. Sclater (1891), Alfred Alcock (1896), Frank Finn (1896), Nelson Annandale (1904, 1905, 1912), Captain Frank Wall (1906), and Malcolm Arthur Smith (1943) made significant contributions to herpetology by publishing formal works on the reptiles (including snakes) of British India (Mahendra 1935). In those references, “Bengal” was frequently designated as the type locality for reptilian species, creating ambiguity about whether the species’ range lies within the current political borders of Bangladesh or the neighboring West Bengal state of India.

In present-day Bangladesh, numerous studies have significantly contributed to our understanding of snake diversity over the years, with several comprehensive lists compiled by various researchers. Montaquim et al. (1980) were among the first to document the region’s snake diversity, listing 28 species. This was followed by Khan (1982), who compiled a checklist of 78 species. Subsequent studies by Sarker and Sarker (1985) and Khan (1987) further expanded the list, reporting 72 and 79 species, respectively. Over the following years, more detailed research was conducted by Sarker and Sarker (1988), noting 88 species in a book on wildlife. Khan (1992) accumulated 81 species in a Bengali book on snakes, and Ahsan (1996) presented a list of 77 species at a conference. As research progressed into the 21^st century, the number of reported species grew substantially. In 2007, Asmat and Hannan (2007) compiled a checklist of 94 species, while Khan (2008) reported 98 species in a field guide. Kabir et al. (2009) compiled a list of 91 species in the encyclopedia of country fauna. Khan (2010) produced a checklist of 94 species and again compiled a list of 106 species in a field guide in 2015 (Khan 2015). Recently, Khan (2018) provided a list of 105 species in a photographic guide. Besides these reports, IUCN Bangladesh assessed the conservation status of 28 species in 2000 and 100 species in 2015 as part of the Red Listing program (IUCN Bangladesh 2000, 2015). However, these studies exhibit inconsistencies both in the reported taxa and in the number of species. These discrepancies may arise from differences in research methodologies applied during taxonomic revisions. Such inconsistencies create confusion among herpetologists, snake rescuers, conservation activists, snakebite-related health care providers, and policymakers by complicating the understanding of snake diversity in the country.

Besides the above country checklists, several studies have explored regional snake diversity in Bangladesh. Notable contributions include research on wildlife, including snakes, in the mangrove ecosystem (Khan 1986), coastal wildlife (Sohrab and Sarker 1986; Sarker and Hossain 1997), and herpetofauna in the Chittagong Hill Tracts (Mahony and Reza 2008). Other significant studies have focused on cataloging amphibians and reptiles at the zoological museum of Jahangirnagar University (Mahony et al. 2009), examining the herpeto-mammalian fauna of the Padma River (Rahman et al. 2012), studying snake activity patterns in Lawachara National Park (Rahman et al. 2013), and documenting snake abundance at Rangpur Carmichael College (Kabir 2013). Additional research has explored the herpetofauna of Baraiyadhala National Park (Karim and Ahsan 2014), snake diversity at the Chittagong University campus (Ahsan et al. 2015), and bycatch sea snakes in Cox’s Bazar (Sarker et al. 2017). More recent studies have focused on the diversity of herpetofauna in Lawachara and Nijhum Dwip National Parks (Hakim et al. 2020; Rabbe et al. 2022) as well as wildlife diversity in the northern deciduous forests (Jaman et al. 2023).

At the beginning of the 21^st century, several publications described new country records of snake species from Bangladesh. Notable examples include the documentation of Ptyas korros (Ahsan and Parvin 2001), Boiga ochracea (Ahsan and Parvin 2004), Lycodon zawi (Reza 2010a), Oligodon albocinctus (Hasan et al. 2013), Sinomicrurus macclellandi (Rahman et al. 2017), Psammophis condanarus (Haidar et al. 2020), Hydrophis lapemoides (Chowdhury et al. 2021), Oligodon kheriensis (Romon et al. 2021), Fowlea schnurrenbergeri (Mahamud et al. 2022), Hydrophis stricticollis and H. obscurus (Sarker et al. 2023), and Smithophis atemporalis (Mahamud et al. 2023).

Being cold-blooded, slithering animals, snakes are an integral part of culture, religious beliefs, mythos, folklore, and superstitions in this region, often resulting in snake–human conflicts. This conflict is bipartite: the intentional or unintentional killing of snakes by humans and snakebite envenoming causing human deaths. To focus on the first aspect, several studies have been conducted on the anthropogenic impacts on snakes (Quamruzzaman et al. 2016; Datta et al. 2018; Rabbe et al. 2021), the traditional practice of snake charming (Karim 1988; Ahmed et al. 2013; Kabir 2018), the behavioral ecology of snakes (Shihan and Kabir 2015; Moktadir and Hasan 2016), and the habitat utilization patterns and distribution of snakes across this tropical country (Chowdhury et al. 2011; Rahman et al. 2013; Shome and Jaman 2021; Haidar et al. 2023; Hasan et al. 2025). Focusing on the second aspect, several studies have also been conducted to understand the dynamics of snakebite, which is a significant concern in rural Bangladesh (Rahman et al. 2010; Rashid et al. 2022; Ghose et al. 2023). Among these, the clinical management of snakebites in Bangladesh has been extensively studied in the last few decades (Faiz et al. 2010; Mondal et al. 2012; Hasan et al. 2016; Haidar et al. 2023; Chowdhury et al. 2024a). This also includes multiple studies on the proteomic analysis of snake venom of native venomous species (Pla et al. 2019; Alam et al. 2023; Haidar et al. 2024) and the efficacy of antivenoms in preclinical and clinical settings (Faiz et al. 2017; Deka et al. 2019). Researchers have also carried out studies on the genomics and molecular taxonomy of snakes in the country (Kundu et al. 2020; Islam et al. 2022). Along with the literature on the diversity and new distribution records of snakes, these publications also provide valuable insights into the country’s snake diversity and distribution over time.

In modern information flow, online databases such as GBIF, iNaturalist, and IUCN portals are invaluable tools for studying snake diversity (Uetz et al. 2025). In recent times, the use of smart mobile devices and access to social media have also played a significant role in studying snake diversity, as people from every corner of the country regularly post photos and occurrence information of snakes. With proper scrutiny, these vast sources of information can be used for scientific research (Marshall and Strine 2019), including biodiversity studies (Chowdhury et al. 2024b). Additionally, records in the country’s institutional museums provide valuable information on snake distribution and play a crucial role in understanding snake diversity (Guedes et al. 2020). Including all the aforementioned sources, we conducted a systematic review through an extensive survey of literature on snake diversity and distribution, new records, habits, habitat ecology, human perceptions, snake charming traditions, snake genomics and proteomics, venomics and antivenomics, and snakebites and their management. This review also outsourced information from scientific publications, online repositories, and social media to decide the confirmation, elimination, and anticipation of the occurrence of snake species, ultimately creating a comprehensive confirmed list of snake species in the country. We also estimated the species richness, population density, and geographical distribution patterns of snakes in Bangladesh.

A systematic review is a critical analysis that combines secondary information from published sources with primary data generated through reproducible methods (Pollock and Berge 2018). This review critically analyzed published references, obtained research-grade data from authentic online repositories (Saran et al. 2022), and incorporated data from social media after cross-verification (Chowdhury et al. 2024b) to confirm species occurrence and compile a comprehensive list of snakes in the country.

This systematic review and analysis of ophidian species in Bangladesh provides an updated and comprehensive overview of the species diversity and distribution patterns of snakes in the country, highlighting significant regions that need to be conserved as habitats. This study reveals Bangladesh as home to diverse ophidian fauna, confirming the presence of 89 snake species and emphasizing the importance of specimen-based taxonomic research to discover more species. Therefore, species eliminations from the country list underscore the significance of continuous taxonomic revision and reassessment of snake specimens. Additionally, habitat-specific distribution patterns of venomous and non-venomous snakes indicate the potential of habitat diversity in the country for in situ conservation.

The predominance of non-venomous species aligns with findings from other tropical regions, both in terms of diversity and population density (Luiselli et al. 2020). The families Colubridae and Natricidae account for the largest proportion of non-venomous species diversity. Additionally, the families Typhlopidae, Pythonidae, Sibynophiidae, Erycidae, Pareidae, and Calamariidae are entirely comprised of non-venomous snakes. Two venomous families, Elapidae and Viperidae, constitute 29.2% of the total snake species. The Elapidae family is the most significant contributor to the venomous species pool, with both terrestrial and marine species (Chippaux 2017). The Viperidae family consists of all terrestrial venomous snakes, found in habitats ranging from lowland mangroves to high-elevation hills (Maritz et al. 2016). In addition to these venomous families, the Natricidae family includes a single species known for being rear-fanged venomous, with a poison gland located behind the eye (David and Vogel 2021).

This study also identifies three species (Acrochordus granulatus, Dieurostus dussumieri, and Boiga westermanni) as regionally extinct in Bangladesh. The most recent confirmed sighting of the marine file snake, A. granulatus, was in 1970 (Khan 1987). Since then, no further records of this species have been reported. The holotype of the Kerala mud snake, D. dussumieri, was collected from “Bengal” and designated as Eurostus dussumieri but was lost or destroyed during World War II (Das et al. 1998). There have been no subsequent records of this species in Bangladesh, and it is now considered endemic to Kerala, India (Kumar et al. 2012). Similarly, the holotype of the Indian egg-eating snake, B. westermanni, was collected from Rangpur in 1863 and originally designated as Elachistodon westermanni (Wallach et al. 2014). However, there have been no further confirmed sightings of this species in Bangladesh since that time. The absence of these species may reflect changes in habitat suitability, climate shifts, or anthropogenic pressures, underscoring the importance of long-term monitoring and the need for conservation actions to mitigate further losses.

Furthermore, 16 species have been removed from the country’s snake list. Nine species—Xerotyphlops vermicularis, Pareas margaritophorus, Homalopsis buccata, Echis carinatus, Trimeresurus purpureomaculatus, T. stejnegeri, Dendrelaphis punctulatus, Herpetoreas sieboldii, and Sibynophis subpunctatus—were originally listed without specimen-based documentation or confirmed sightings and have thus been excluded. Four species have been eliminated based on taxonomic revisions. For example, Trimeresurus albolabris, once considered the most abundant pit viper in Bangladesh, is now believed to be absent in the Indian subcontinent, including Bangladesh. In these regions, it may be replaced by Trimeresurus salazar (Vogel et al. 2022; Haidar et al. 2023). Similarly, the long-nosed vine snake, Ahaetulla nasuta, once thought to be widely distributed in Bangladesh (IUCN Bangladesh 2015), is now confirmed to be endemic to Sri Lanka (David et al. 2021). The brown vine snake, Ahaetulla pulverulenta, recorded from the Sundarbans (Denzau and Denzau 2010), has since been reassigned to A. sahyadrensis (Mallik et al. 2020). The population of Dendrelaphis pictus in Bangladesh has been revised as D. proarchos (Vogel and van Rooijen 2011). A specimen of Boiga from the University of Chittagong Museum was initially tagged as B. cynodon (Nootpand 1971). Later taxonomic revision clarified the distribution of B. siamensis in Bangladesh, India, Myanmar, Thailand, Cambodia, Laos, and Vietnam, while B. cynodon is restricted to Thailand, Malaysia, Indonesia, and the Philippines (Pauwels et al. 2004). The Chin Hills keelback, H. venningi, was reported from Bangladesh by Reza (2010b); however, re-examination of photographs and morphological data confirmed the specimen as H. xenura. Consequently, there is no confirmed record of H. venningi from Bangladesh, and the species is restricted to northeastern India and western to northwestern Myanmar (David et al. 2015). Lastly, the population of Rhabdophis subminiatus helleri in Bangladesh has been elevated to full species status and is now recognized as R. helleri (David and Vogel 2021). Revising species lists by removing unconfirmed species and reassessing taxon status contributes to accurate and reliable inventories, which are essential for proper conservation planning to protect biodiversity.

The species richness map and KDE analyses revealed specific regions of Bangladesh that are particularly important for snake diversity. The southeastern and northeastern regions, characterized by mixed evergreen forests in Chattogram and Sylhet, emerge as hotspots for ophidian diversity. In addition, the southwestern mangrove forests and central deciduous forests are considered regions of abundance for non-venomous species. These areas are critical conservation zones with high species richness and potential species abundance. The presence of terrestrial venomous species in mixed evergreen forests, deciduous forests, and lowland wetlands highlights the ecological significance of these habitats. Alternatively, the southeastern seashore and coastal mangrove forests had higher probability values for the occurrence of marine venomous snakes. These coastal areas represent critical marine habitats that require high conservation attention given threats from fishing, trawling, vehicle traffic, and habitat destruction (Udyawer et al. 2018).

Beyond their ecological role in maintaining ecosystem balance, venomous snakes have significant medical importance, particularly in snakebite management. Bangladesh is recognized as one of the most snakebite-prone countries globally, largely due to its diverse ecosystems that harbor a variety of venomous species (Ghose and Faiz 2014). Identifying regions with high richness of venomous snake species is critical, as this knowledge can inform effective management strategies for both the conservation of these species and the mitigation of public health concerns associated with snakebites (Haidar et al. 2023). Such information is invaluable for developing targeted interventions in snakebite prevention, as well as enhancing both preclinical management and clinical treatment. Understanding the distribution patterns, regional diversity, and abundance of these snakes allows healthcare providers to better anticipate and respond to snakebite incidents, ensuring timely and appropriate medical care. Furthermore, insights into the venom composition of local species are essential for improving antivenom production and advancing treatments that can save lives in areas where snakebites are a common threat (WHO 2016).

Considering the significant habitat-specific variation in species richness and distribution, conservation efforts should be prioritized for protecting regions with high species diversity. Particularly, the mixed evergreen forests in the southeastern and northeastern parts of the country are at high risk of habitat destruction (Reza and Hasan 2019). Moreover, the analysis suggests that regions such as the Sundarbans mangrove forests and coastal wetlands are critical areas for marine venomous species, which face high risk from anthropogenic activities and natural calamities, including climate change (Mahendra 1935). Conservation strategies should also account for species that may inhabit Bangladesh but have not yet been confirmed through direct sightings or specimen-based documentation. Their inclusion in the anticipated species list suggests that further exploration of their potential habitats is warranted.

This research provides detailed data on the ophidian fauna of Bangladesh, revealing species distribution patterns and potential areas for conservation priority. The incorporation of the latest taxonomic revisions, identification of regional extinctions, and anticipation of future species occurrences highlight the dynamic state of the country’s snake diversity. This study underscores the importance of maintaining diverse ecosystems, particularly semi-evergreen rainforests in the southeast and northeast, coastal mangrove forests in the southwest, deciduous forests in the east-central region, and low-plain wetlands in the northwest, as key snake habitats. Our findings enhance the understanding of the ecological requirements of snakes and provide a foundation for future ecological research and conservation initiatives aimed at protecting the country’s ophidian fauna.

We are grateful to the diligent researchers, wildlife biologists, and enthusiastic field herpetologists who have significantly contributed to the herpetology of Bangladesh. Their knowledge of snake identification and documentation of new country records from various geographical regions of Bangladesh has aided in assembling a comprehensive and authenticated checklist of the country’s snake fauna. We are also thankful to the social media groups working to create public awareness about snakes and for providing geographical locations of encountered snakes to help mitigate snake–human conflict nationwide. Their rapid response to rescue operations reduces snake–human conflict and supports the conservation of snakes throughout Bangladesh.