Ptyas mucosus has been among the main snake species being harvested in India for the illegal trade in snake skins. A challenge in controlling this trade is the difficulty in confidently identifying skins. Dubey et al. (2009) developed PCR primers for the identification of three snake species, Indian Rock Python, (Python morulus), Indian Cobra (Naja naja), and Rat snake (Ptyas mucosus).They report that their method allows rapid and cost effective discrimination of these commercially exploited snakes based on multiplex amplification of species-specific PCR fragments of different sizes.
The Dhaman or Indian rat snake (Ptyas mucosus)is a large (up to 3.5 m) colubrid that is found throughout most of southern Asia and western Indonesia. It is often described as a nervous snake, both quick to strike and prone to defensive displays, including the production of a distinctive low frequency sound. As part of its defensive display, this snake mediolaterally compresses the anterior portion of its body and expands its throat region ventrally. During this display, the snake produces a deep, rumbling defensive growl.
There is substantial overlap between the geographic distribution and ecological preferences of the Indian Rat Snakea and the King Cobra (Ophiophagus hannah). There are several accounts in the literature describing the Indian Rat Snake as resembling or mimicking the King Cobra, especially with respect to its defensive behavious anddefensive sounds. As part of its defensive display, the King Cobra passes an exhalent airstream over a series of tracheal diverticula which act as resonating chambers, acoustically modifying the hiss into a low frequency growl (Young 1991). While similar tracheal diverticula are found in some other snakes, including a congener of the Indian Rat Snake, P. korros, they are lacking in the Indian Rat Snake (Young 1992). Young et al. (1999) examined the morphological basis of sound production in the Indian Rat Snake in an effort to document the acoustic properties of this defensive sound, the Their analysis confirmedthe acoustic similarities between the growls produced by these two species and yielded some hypotheses regarding the production of these sounds. Given that these sounds are produced only during defensive displays, that these snake species have considerable overlap in geographic range and habitat preference, and that the King Cobra has a highly toxic venom, Young et al. suggest that the defensive growl may indeed be an example of acoustic Batesian mimic.
(Young et al. 1999 and references therein)
Ptyas mucosa, commonly known as the oriental ratsnake,[2] Indian rat snake,[4] darash or dhaman,[2] is a common non-venomous species of colubrid snake found in parts of South and Southeast Asia. Dhamans are large snakes. Typical mature total length is around 1.5 to 1.95 m (4 ft 11 in to 6 ft 5 in) though some exceed 2 m (6 ft 7 in). The record length for this species was 3.7 m (12 ft 2 in), second only to their cousin Ptyas carinata among living colubrid snakes.[5][6] Despite their large size, oriental ratsnakes are usually quite slender with even a specimen of 2 m (6 ft 7 in) commonly measuring 4 to 6 cm (1.6 to 2.4 in) only around in diameter.[7] Furthermore, the average weight of ratsnakes caught in Java was around 877 to 940 g (1.933 to 2.072 lb), though larger males of over 2.3 m (7 ft 7 in) (which average mildly larger of the two sexes in the species) may easily weigh over 2.5 kg (5.5 lb).[8] Their color varies from pale browns in dry regions to nearly black in moist forest areas. Rat snakes are diurnal, semi-arboreal, non-venomous, and fast-moving. Rat snakes eat a variety of prey and are frequently found in urban areas where rodents thrive.
Found in Afghanistan, Andaman and Nicobar Islands, Bangladesh, Myanmar, Cambodia, China (Zhejiang, Hubei, Jiangxi, Fujian, Guangdong, Hainan, Guangxi, Yunnan, Tibet, Hong Kong), Taiwan, India, Sri Lanka, Indonesia (Sumatra, Java, Bali), Iran, Laos, West Malaysia, Nepal, Myanmar, Pakistan (Sindh area), Thailand, Turkmenistan and Vietnam.[9][10]
Adult rat snakes have no natural predators, although younger specimens are the natural prey of King cobras that overlap them in their range. Juveniles fear birds of prey, larger reptiles, and mid-sized mammals. They are wary, quick to react, and fast-moving.[11]
Rat snakes and related colubrids are aggressively hunted by humans in some areas of their range for skins and meat. Harvesting and trade regulations exist in China and Indonesia, but these regulations are often ignored.[12]
Description from Boulenger's Fauna of British India: Reptilia and Batrachia volume of 1890:
Snout obtuse, slightly projecting; eye large; rostral a little broader than deep, visible from above; suture between the internasals shorter than that between the prefrontals; frontal as long as its distance from the end of the snout, as long as the parietals or slightly shorter; usually three loreals; one large preocular, with a small subocular below; two postoculars; temporals 2+2; 8 Upper labials, fourth and fifth entering the eye; 5 Lower labials in contact with the anterior chin shields, which are shorter than the posterior; the latter in contact anteriorly. Dorsal scales in 17 rows at midbody, more or less strongly keeled on the posterior part of the body. Ventrals 190–208; anal divided; subcaudals 95–135, divided. Brown above, frequently with more or less distinct black crossbands on the posterior part of the body and on the tail; young usually with light crossbands on the front half of the body. Lower surface yellowish; the posterior ventral and the caudal shields may be edged with black.[13]
It is the second largest snake in Sri Lanka, after the Indian rock python.
Rat snakes, though harmless to humans, are fast-moving, excitable snakes. In captivity, they are territorial and may defend their turf aggressively, attempting to startle or strike at passing objects. Rat snakes are diurnal and semi-arboreal. They inhabit forest floors, wetlands, rice paddies, farmland, and suburban areas where they prey upon small reptiles, amphibians, birds, and mammals. Adults, unusually for a colubrid, prefer to subdue their prey by sitting on it rather than by constricting, using body weight to weaken prey.[11][14]
Rat snakes mate in late spring and early summer, though in tropical areas reproduction may take place year round. Males establish boundaries of territory using a ritualised test of strength in which they intertwine their bodies. The behaviour is sometime misread by observers as a "mating dance" between opposite-sex individuals.[14] Females produce 6–15 eggs per clutch several weeks after mating.[11][14]
Adult members of this species emit a growling sound and inflate their necks when threatened. This adaptation may represent mimicry of the king cobra or Indian cobra which overlaps this species in range.[15] The resemblance often backfires in human settlements, though, as the harmless animal may be mistaken for a venomous snake and killed.[11][14]
The International Code for Zoological Nomenclature (ICZN) directs that the grammatical gender of any given species name should follow logically from the gender of its associated genus name. As Ptyas is a feminine word form (from πτυάς, a Greek word for a venom-spitting snake), the proper form of the species name is mucosa (a Late Latin word meaning "slimy"). Reference materials older than 2004 often show the masculine form, mucosus, and the CITES list continues to list the species this way.[16][17][18]
Head with open mouth
Top view of head
View of temporals
Underside of head
Belly of snake
Body and scales
Body and scales
Body and scales
Long tail of oriental rat snake
Temporals indicated
Scale patternPtyas mucosa, commonly known as the oriental ratsnake, Indian rat snake, darash or dhaman, is a common non-venomous species of colubrid snake found in parts of South and Southeast Asia. Dhamans are large snakes. Typical mature total length is around 1.5 to 1.95 m (4 ft 11 in to 6 ft 5 in) though some exceed 2 m (6 ft 7 in). The record length for this species was 3.7 m (12 ft 2 in), second only to their cousin Ptyas carinata among living colubrid snakes. Despite their large size, oriental ratsnakes are usually quite slender with even a specimen of 2 m (6 ft 7 in) commonly measuring 4 to 6 cm (1.6 to 2.4 in) only around in diameter. Furthermore, the average weight of ratsnakes caught in Java was around 877 to 940 g (1.933 to 2.072 lb), though larger males of over 2.3 m (7 ft 7 in) (which average mildly larger of the two sexes in the species) may easily weigh over 2.5 kg (5.5 lb). Their color varies from pale browns in dry regions to nearly black in moist forest areas. Rat snakes are diurnal, semi-arboreal, non-venomous, and fast-moving. Rat snakes eat a variety of prey and are frequently found in urban areas where rodents thrive.
