Reticulated pythons in Sumatra: biology, harvesting and sustainability

Abstract

Hundreds of thousands of giant snakes ( Python reticulatus) are taken from the wild to be killed for their skins each year, raising doubts about the longterm sustainability of this offtake. We visited four locations in northern Sumatra (Medan, Seisuka, Rantauprapat and Cikampak) at four times of year and gathered information on the sizes, sexes, reproductive status and food habits of 784 slaughtered pythons. Pythons in northern Sumatra mature at larger body sizes than do those studied previously in southern Sumatra (Palembang). Their seasonal timing of reproduction is shifted appreciably, presumably because the two areas lie on opposite sides of the equator. The slaughtered animals are mainly adult males and adult plus juvenile females. Females attain larger sizes than males, but very large females are rarely captured. This bias may reflect size-related shifts in habitat selection; smaller snakes (including adult males of all sizes, and recently-matured females) feed primarily on commensal rats and hence are abundant in disturbed (agricultural and village) habitats. Female pythons produce large clutches (mean=24.2) of large eggs (mass>250 g), but reproduce only once every 2 to 4 years. The apparent ability of reticulated python populations to withstand high levels of offtake may reflect their demography (rapid growth rates, early maturation, high fecundity), their flexibility in diets and habitat use, and their ability to evade detection (because neither foraging nor thermoregulation require extensive movements).