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Context: Masked water snakes (Homalopsis buccata , Homalopsidae) thrive in the muddy edges of agricultural ponds and canals in densely populated areas of West Java, Indonesia, and are harvested by local farmers to protect fish stocks and to provide meat, skins, and medicines for commercial use. Aims: Here, we aimed to quantify sexual dimorphism and reproductive biology of H. buccata , so as to deepen our knowledge of the species' inherent ability to withstand commercial harvests. Methods: We examined carcasses of 4286 snakes at six processing sites to quantify biological attributes (e.g. sexual dimorphism in body size and shape, seasonality of reproduction, fecundity, reproductive frequency), with emphasis on traits that affect the ability of snake populations to withstand this intensive harvesting. Key results: The snakes we examined were primarily adults (<1% juvenile), with approximately equal numbers of males and females except in January (when females comprised >90% of specimens). Females grow larger than males, and they are more heavy-bodied but shorter-tailed than are males of the same snout–vent length. Reproduction is seasonal in both sexes, with testis volumes decreasing to a minimum over the period August to November (late dry season) when most adult-size females were gravid. Litter sizes ranged from 1 to 37 (mean 12), increasing with maternal body size, with ~75% of females reproducing each year. Conclusions: On the basis of these results, we infer that the life history of H. buccata (viviparity, high fecundity, frequent reproduction, rapid maturation) renders it inherently resilient to harvesting, especially because that offtake is based on males as well as females. Because a lack of sustainability is evident only in hindsight, regular monitoring of the trade could assure that any problems are detected rapidly. Implications: To further buffer these populations from the impact of harvest, hunting could be restricted during January (a time when gravid females are disproportionately vulnerable) and the largest snakes (females, with high fecundity and reproductive frequency) could be excluded from harvests. Although it is impossible to prove sustainability of any wildlife harvest, except in hindsight, studies of commercially exploited taxa can provide a basis for prediction. Our data on commercially harvested masked water snakes in Java, Indonesia, suggest that these snakes possess ecological and life-history attributes likely to make them resilient to harvesting, consistent with the species' continuing abundance, despite a long history of intense exploitation. Photograph by Alamsyah Herlambang. [ABSTRACT FROM AUTHOR]

Large (>3 m) slender-bodied rat snakes are abundant in agroecosystems of southern Asia and are heavily exploited for their skins and meat. We examined 216 specimens killed at commercial facilities in Cirebon, West Java, to quantify morphological and reproductive traits and evaluate harvest sustainability by comparing this sample to one taken 25 years previously. The snakes we examined were mostly adults, and mostly male. Females were less heavy-bodied than males of the same body length, matured at a larger size than males, but attained smaller maximum sizes. Reproduction and energy (fatbody) storage was seasonal in both sexes, with females containing oviductal eggs primarily during the annual wet season. Clutch size averaged 12.6 eggs and increased with maternal body size. Comparison of the two samples taken 25 years apart revealed strong similarity in sex ratio, the numerical preponderance of adults, body sizes at sexual maturation and mean adult body sizes, sexual dimorphism in body length and mass, reproductive seasonality in females, mean fecundity, and the relationship between fecundity and maternal body size. That consistency suggests that commercial harvesting over the intervening period has not affected the biological traits of rat snake populations, consistent with a sustainable level of offtake. The heavily exploited oriental rat snake is common across much of Asia. Despite its economic and ecological importance, little is known about its biology or the sustainability of the harvest. Dissection of 216 commercially collected snakes from West Java and comparison with a sample taken 25 years previously shows that the harvest is based mainly on adults and is likely sustainable. Sustainability is enhanced by the snake's rapid growth, early maturation, high reproductive output, and ability to exploit available resources. Photograph by Nathan Rusli. [ABSTRACT FROM AUTHOR]

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. Thousands of rainbow mudsnakes are captured and killed for trade in Indonesia each year, questioning the sustainability of this offtake. We examined the reproductive biology of Enhydris enhydris collected from disturbed landscapes in West Java. Collected snakes are mostly adults, quick to mature, reproduce frequently and have large litters. These traits render this species resilient to intensive harvesting. Photograph by Alamsyah Elang Nusa Herlambang. [ABSTRACT FROM AUTHOR]