In March 2014 the Indonesian Ministry of Forestry announced they had given permission to two East Javan companies to export captive-bred rat snakes specifically as pets, with an annual quota of 1,850 Ptyas mucosa allocated to the Kediri-based UD Bina Usaha Mandiri and 125,000 Ptyas korros and 50,000 P. mucosa allocated to the Sidoarjo-based CV Karya Albadi Reptil Mulia. These quotas are considerably larger than previous quotas of up to 3,000 for P. mucosa and 1,000 for P. korros. Both companies are large-scale exporters of dried geckos and snakes to East Asia, and there are no indications that either of them have ever been involved in the trade of live animals or that they are experienced in breeding reptiles. Auliya (2010, Conservation Status and Impact of Trade in the Oriental Rat Snake in Java, TRAFFIC, Petaling Jaya) gives a detailed account of the trade in rat snakes in Central and East Java, confirming the absence of their trade for pets in or from Java, and including data on reproduction, growth rates, and prices. These data allow us to evaluate whether captive breeding of rat snakes is economical.
Rat snakes are predominantly terrestrial and on Java can be found in a range of habitats, and are abundant in agricultural areas such as rice fields. The snakes are collected in large numbers either opportunistically by farm workers or by professional harvesters, and passed on to middlemen who sell them to large-scale traders. International trade in P. mucosa is regulated through CITES, with > 90% of the trade comprising skins and meat. After having been banned from exporting P. mucosa for 12 years, Indonesia now sets an annual export quota of 90,000 wild-caught individuals for P. mucosa (89,500 to be exported for their skins, 500 as pets) and 4,500 wild-caught individuals for P. korros (1,800 skins, 2,700 pets) but captive-bred individuals can be traded above and beyond this quota.
A rat snake's value increases with size, with the maximum values attached to skins of 140 cm length and live snakes of 800 g or more; at these sizes rat snakes have retail values for Indonesian exporters of USD 2.85–2.96 when sold alive and USD 3.03 when the skin and meat are sold separately.
Oriental rat snake females become sexually mature in 9 months, gestation and incubation last 5 months, and mean clutch size on Java is 15 eggs. Males and females have slightly different growth rates but they reach their economically optimal size in 15–20 months. If under optimal conditions females can produce two clutches per year, all 30 eggs hatch and there is no mortality of the young, then to produce 176,850 rat snakes per year one has to maintain a breeding stock of almost 4,000 adult females.
Given the low price rat snakes command and their apparent abundance, especially in Central and East Java, it cannot be economical to breed rat snakes for commercial purposes. Maintaining breeding stock, taking care of eggs and feeding young for over a year, only to be able to sell them on for < USD 4, suggests that wild-caught individuals are probably being exported as captive-bred to circumvent the quota system for wild-caught individuals. I urge the Indonesian CITES Scientific Authority, which sets these quotas, to reconsider its decisions and for importers to carefully check whether or not animals (or their parts) declared as captive-bred have indeed been bred under controlled conditions.
