Varanus bengalensis (Bengal Monitor Lizard)
The common name of this Monitor Lizard in English is commonly called Bengal Monitor Lizard , Clouded Monitor, Common Indian Monitor and Thai name called ตะกวด (Ta-guuad), ตะกวดเบงกอล (Ta-guuad Bengal), ตะกวดอินเดีย (Ta-guuad India), แลน (Lan).
ตะกวดเบงกอล : Varanus bengalensis (Daudin, 1802)
Varanus bengalensis is a species of the Monitor Lizard Genus (Varanus) within the Monitor Lizard Family (Varanidae), Superfamily Platynota, in the Lizard and Snake Order (Squamata), in the Reptile Class (Reptilia), in the Chordate Phylum (Chordata) in the Animal Kingdom (Animalia).
Published in Daudin, F. M. Histoire Naturelle, génerale et particulièredes reptiles, ouvrage faisant suite, a l'histoiure naturelle, générale et particulière composée par LECLERC DE BUFFON, et redigée par C. S. SONNINI, vol. 3. F. Dufart, Paris, 452 pp. (1802).
Varanus irrawadicus Yang & Li, 1987 and V. vietnamensis Yang & Liu, 1994 were previously described as nominal species, but both were synonymized with V. bengalensis by Böhme and Ziegler (1997).
The same authors raised V. bengalensis nebulosus (Gray, 1831) to full species status based on a V. b. bengalensis specimen obtained from a market in Phuket (exhibiting characters within the range of V. b. nebulosus), which was thought to prove sympatry between the two forms, together with differences in hemipenial structure.
It is widely accepted that this specimen instead represents a geographic race of V. bengalensis, based on a very detailed study of geographic variation in V. bengalensis across its range (Auffenberg 1994).
The Phuket locality is also considered doubtful, as this is an extensively-visited area where no nebulosus-morph monitors have otherwise been recorded, and the specimen recorded in the market may have been collected further north (D. Bennett pers. comm. 2017). Consequently V. nebulosus is treated here as a junior synonym of V. bengalensis.
The specific epithet 'bengalensis' meaning its occurrence in Bengal (but note the original erroneous type locality).
Subspecies
- Varanus bengalensis bengalensis (Daudin 1802)
- Varanus bengalensis irrawadicus Yang & Li 1987
Geographic Range
This is a wide ranging monitor lizard found in Afghanistan, Pakistan, Bangladesh, Nepal, India, Sri Lanka, southern China (Daudin 1802, Zhao and Adler 1993), Myanmar, Viet Nam (Nguyen et al. 2009, Das 2010), Lao PDR (Duckworth et al. 1999), southeastern Iran, and as far as Java and the Anambas Islands in Indonesia.
In Lao PDR, it has been reported from Nakai Plateau and is considered to have been locally extirpated in recent years in one area of Phou Louey NBCA (Stuart 1998c, Duckworth et al. 1999).
In China, it is only known from the Wanding Valley, in Yunnan Province (Zhao and Adler 1993). It has an upper elevation limit of 2,150 m asl (though has been reported up to 2,600 m asl. in Afghanistan - Clark 1990).
Varanus bengalensis nebulosus is present in Myanmar, Lao PDR, Thailand, Cambodia, Malaysia, Singapore, Indonesia, Viet Nam, and various islands in the South China Sea between Peninsular Malaysia and Sumatra and Borneo (Gray 1831, Nguyen et al. 2009, Das 2010, Grismer 2011, Chan-ard et al. 2015).
In Viet Nam, it has been recorded from the provinces of Quang Tri (Dak Rong, Dong Tam Ve, Huong Hoa), Thua Thien-Hue (A Luoi, Loc Hai), Da Nang (Son Tra), Quang Nam (Nam Giang, Tay Giang), Kon Tum (Kon Plong, Bo Y), Gia Lai (K Bang), Dak Lak (Chu Yang Sin, Dak Phoi, Yok Don), Lam Dong (Lang Bian Plateau), Binh Phuoc (Nghia Trung), Dong Nai (Cat Tien), Ba Ria–Vung Tau (Con Dao) and Kien Giang (Phu Quoc) (Nguyen et al. 2009).
In Indonesia, it has been recorded from Java and its occurrence on Sumatra has been suggested (Gray 1831, De Lisle 1996, Smith 1935, Das 2010).
Although there are some old specimens purportedly from Sumatra, no recent records seem to exist from the mainland (e.g. Auffenberg 1994), but it has been recorded on at least three islands in the Riau Archipelago close to the coast of Sumatra (E. Arida pers. comm. 2019, Arida et al. 2015).
Javan records are from the west and east, but the only recent records are photographs of a dead and a live animal from Baluran National Park and from Meru Betiri National Park (Auliya and Koch 2020), both taken in East Java two or three years ago (E. Arida pers. comm. 2019). Captive animals have been seen in West Java (D.T. Iskandar pers. comm. 2019).
In Malaysia, it is known from the states of Perlis (Wang Kelian), Kedah (Ulu Muda, Pulau Langkawi), Terengganu (Jertih, Hutan Lipur Sekayu, Tasik Kenyir, Perhentian Besar, Gunung Tebu), Perak (Batang Padang and Beruas, Selangor (Kepong), Negeri Sembilan (Pasoh), Endau-Rompin (Kampung Relau, Johor (Gunung Panti, Pulau Aur), Penang (Pulau Jerejak) and Pahang (Pulau Tioman, Krau Wildlife Reserve), and the foot of Gunung Lawit in Sungai Padang and Batang Padang (Cantor 1847, Boulenger 1903, Hendrickson 1966, Dring 1979, Sharma et al. 2001, Grismer et al. 2001, Norsham and Ong 2001, Daicus and Hashim 2004, Norsham et al. 2005, Ibrahim et al. 2006, Chan et al. 2009, 2010, Grismer 2011, Nurulhuda et al. 2014, Sumarli et al. 2015).
In Thailand, it is present in forested areas throughout the country, although rare in the northeast (Chan-ard et al. 2015). In Cambodia, it has been found in the northern Cardamom Mountains (Daltry and Chheang 2000, Swan and Daltry 2002).
In Lao PDR, the species is sometimes referred as V. nebulosus, which has been reported from Nakai Plateau and considered as locally extirpated in recent years in one area of Phou Louey NBCA (Stuart 1998c, Duckworth et al. 1999). It ranges up to 350 m asl (Grismer 2011).
The species is naturally absent from the Chao Phraya River Central Flood Plain in Thailand, a historically swampy area unsuitable for this typically dry forest species. It may be absent from naturally swampy areas in the Mekong Delta, but there are too few records for Myanmar to clarify its occurrence in this area (G. Wogan pers. comm. 2017).
In China this species is distributed in Ruili River watershed in western Yunnan (Yang and Li 1987, as Varanus irrawadicus). The highest elevational record is 3,000 m asl (Singh et al. 2020).
Habitat and Ecology
This diurnal and largely terrestrial species inhabits forests and forests edges, as well as plantations (Das 2010), including oil palm, and agricultural areas (Auffenberg 1994). It has been recorded from a variety of habitats, both arid and moist, and from scrubland to forests, at moderate to high elevations (Auffenberg 1994, Pianka 2004), although it is absent from swampy areas.
It feeds on insects, spiders, snails, crabs, frogs, small mammals, birds, lizards and snakes; also known to scavenge (Das 2010). Clutches comprise 8–32 eggs, with 1–2 clutches laid per year (Auliya and Koch in press), which may be laid in termitaria (Das 2010); hatchlings measure 94 mm (Das 2010). The average age at reproduction may be 11 years, as the species has an age at maturity of three and maximum longevity of 20 years (M. Cota pers. comm. 2017).
This species is harvested for a number of uses: the skins are commercially valuable, the meat is eaten, and the fat is used in traditional medicine (Papenfuss et al. 2010). In India there is an illegal trade in hemipenes of the Bengal and Yellow Monitors (termed "hatha jodi"), which are marketed as plant roots with magical powers (D'Cruze et al. 2018; Sharma et al. 2019).
It is hunted for food and sold to traders in Lao PDR, Viet Nam and Thailand (Baird 1993, Stuart 1998b, 1998e, 1998d, Duckworth et al. 1999), and it has been estimated that a single village in Dong Khanthung PNBCA annually harvested 100 individuals for consumption and sale to Lao army soldiers and Lao traders (Stuart 1998e, Duckworth et al. 1999).
International trade is prohibited, however, this species appears to be in regional trade between Lao PDR, Viet Nam and China (S. Phimmachak pers. comm. 2017), and trade from China appears to have declined or ceased since the 1990s (D.Q. Rao pers. comm. 2019).
Synonym
- Lacerta tigrina Linnaeus 1754: 41
- Lacerta monitor Linnaeus 1758: 201 (Nom. Reject.)
- Tupinambis bengalensis Daudin 1802: 67
- Tupinambis cepedianus Daudin 1802: 43 (Fide Mertens 1963)
- Lacerta argus Daudin 1802 (In Part)
- Varanus bengalensis Bengalensis (Daudin 1802)
- Tupinambis bengalensis Daudin 1802: 67
- Tupinambis bengalensis Daudin 1802: 67
- Varanus punctatus Merrem 1820: 59
- Varanus taraguira Merrem 1820 (In Part)
- Monitor gemmatus Guérin-méneville 1829
- Monitor heraldicus Gray In Griffith 1831: 27 (Fide Mertens 1963)
- Varanus bengalensis Duméril & Bibron 1836: 480
- Monitor inornatus Schlegel 1839: 72
- Varanus bibronii Blyth 1842: 869
- Uaranus lunatus Gray 1845: 10
- Varanus dracaena Theobald 1868: 22
- Varanus lunatus Anderson 1871: 155
- Varanus dracaena Anderson 1871: 156
- Varanus bengalensis Boulenger 1885: 310
- Varanus monitor Bahl 1937
- Varanus (Varanus) Bengalensis Mertens 1942: 184
- Varanus monitor Swan & Leviton 1962: 112
- Varanus (Indovaranus) Bengalensis Mertens 1963: 4
- Varanus bengalensis Irrawadicus Yang & Li 1987
- Varanus irrawadicus Yang & Li 1987
- Varanus irrawadicus Zhao & Adler 1993
- Varanus irriwadicus [Sic] Auffenberg 1994
- Varanus bengalensis Irrawadicus De Lisle 1996: 119
- Varanus bengalensis Cox et al. 1998: 106
- Varanus bengalensis Bonetti 2002: 179
- Varanus (Empagusia) Bengalensis Koch et al. 2013
- Varanus (Empagusia) Bengalensis Bucklitsch et al. 2016: 50
- Varanus benghalensis Sahi & Koul 2020 (In Error)