Reproductive biology of the rainbow mudsnake (Enhydris enhydris) in West Java, Indonesia

Context: Unsustainable harvesting can threaten wildlife populations and jeopardise the livelihoods of people relying on wildlife resources. Although millions of rainbow mudsnakes (Enhydris enhydris) are harvested from wetland agroecosystems in tropical Asia each year, few detailed studies have been conducted on the biology of this species. 

Aims: We aimed to address this knowledge gap by examining the reproductive biology and resilience to harvesting of E. enhydris, collecting from agricultural landscapes in West Java, Indonesia. 

Methods: We measured and examined 1731 specimens that had been collected and killed for skins and meat near the city of Cirebon in West Java. 

Key results: Most snakes that we examined were adults (94% of females, 88% of males), with females outnumbering males overall (69% female). Sex ratios varied seasonally and among processing facilities. Females attained larger body sizes than males, were more heavy-bodied, and had shorter tails relative to snout-vent length. Reproductive traits varied among months, with two peaks in the incidence of gravid snakes occurring in March and September. Litter sizes averaged 11.2 (range 2-31) and increased with maternal body size. About half of the adult females were reproductive (vitellogenic or gravid) at the time of collection. This proportion increased with maternal body size, such that 60-70% of large females were reproductive at the time of collection, suggesting that some females may produce two litters per year. 

Conclusions: Rainbow mudsnakes remain exceptionally abundant in West Java, despite significant habitat modification and intensive harvesting. 

Implications: The ability of this species to exploit anthropogenic subsidies in disturbed agricultural landscapes gives it access to plentiful food, and the resultant early maturation, frequent reproduction, and high fecundity enable it to withstand high levels of commercial offtake.