The Oriental Rat Snake

The Oriental Rat Snake (Ptyas mucosa) is a medium-sized, active, diurnal snake associated with open habitats including agricultural systems; much of the diet consists of amphibians and commensal rodents. The species has a wide distribution through much of Asia, from Iran to China and Southeast Asia, and has been commercially harvested for the international skin trade since the early 20th century. From west to east, it occurs in Iran, Turkmenistan, Afghanistan, Pakistan, India, Sri Lanka, Nepal, Bangladesh, Myanmar, China, Thailand, Laos, Cambodia, Vietnam, Malaysia, Singapore, and Indonesia. The Oriental Rat Snake is not strongly associated with wetland habitats. In the wet season, the species shifts to drier areas that do not flood.

The species is also used in the illegal meat trade in China. Under Indonesian legislation, only the harvest of live specimens and skins of the Oriental Rat Snake is permitted – the trade in meat of this species is therefore illegal. During the 1980s most specimens in trade originated from Java (Indonesia) and Thailand. However, the trade has banned the harvest of the species in 1985, and the distinct decline in export volumes after 1986 from Indonesia was the result of a decreased market demand rather than any negative impact on populations of the Oriental Rat Snake.

General biological and life history characteristics of the species

• The Oriental Rat Snake is a medium-sized, active, non-venomous, diurnal snake associated with open habitats including agricultural systems.
• Medium-sized snake, reaching about 2.5 m in length and 5-10 cm in girth.
• Males grow longer than females and have larger heads, longer tails, and greater body mass than females of the same length
• Reaches maturity at 9 months 120 cm for females  
• Clutch size average 13 
• May lay 2 clutches per year.
• Widespread generalist thrives in a human-modified environment
• Unknown density and population trends
• No major threats known

Arboreal behavior is believed to be largely associated with resting. Parts of the range of the Oriental Rat Snake overlap with the Indo-Chinese Rat Snake (Ptyas korros) and where they overlap both species may share the same habitat. Both species search paddy fields for prey and hide beneath dense vegetation along riverbanks. However, the Indo-Chinese Rat Snake is more closely associated with habitats along watercourses than the Oriental Rat Snake.

This species is a predator of rodents and amphibians, and to a lesser extent lizards, insects, birds, and even insects.  Rodents are reportedly the favored food, however; amphibians were the predominant prey of Oriental Rat Snake populations in Central Java.  Snakes are either captured by experienced harvesters or opportunistically by seasonal rice farmers. Snake capture is secondary to farming activities and appears to be carried out in an ad hoc manner. According to several traders, the harvesting activity levels increase with the onset of the wet season (the first heavy rains after the dry season).

In East Java the wet season typically occurs between December and April, and in Central Java between October and December and February to April, depending on the geographical location. During the dry season (May to August) the species is extremely scarce, and another collector estimated that the capture of the Oriental Rat Snake decreases by 50-60% in the dry season. 

During the dry season, the people work in the rice fields so that less manpower is available to capture snakes during the rice harvest, and so the study species is less common in trade during the dry season. The species occurs on other Indonesian islands, including Sumatra and Sulawesi. Furthermore, Increased enforcement is needed to reduce illegal trade.