Large snakes in a mosaic rural landscape: the ecology of carpet pythons Morelia spilota (serpentes: Pythonidae) in Coastal Eastern Australia

How can large pythons coexist with human beings in highly modified habitats throughout the eastern coastal region of Australia, when the same species has undergone rapid declines in other parts of the country? To investigate this question, we surgically implanted miniature temperature-sensitive radiotransmitters into 19 adult carpet pythons Morelia spilota (body lengths 1.3-2.8 m; 1.4-7.0 kg) from two study sites near Bangalow and Mullumbimby, NSW. We located the snakes every few days for the next 32-567 days (mean = 308 days), to obtain data on their movements, habitat use, postures, thermal biology, and food habits. Radio-tracked snakes were primarily arboreal (45% of locations), and generally selected trees with a dense covering of vines. Arboreality was more common in males than females, and more common in winter than in other seasons. The snakes generally avoided open areas, but frequently used artificial shelter (e.g. roof spaces in buildings; thickets of nonnative tree species). Distances moved were generally small (mean <15 m/day; mean home range = 22.5 ha), and larger in males than in females. Population densities were high, especially in small forested areas that penetrated orchards (>6 snakes/ha; >20 kg/ha). The success of carpet pythons in these areas reflects their inconspicuousness (due to their selection of densely vegetated arboreal habitats, their sedentary nature, and their cryptic coloration), and their preparedness to utilise 'artificial' habitats (such as roof spaces) and non-native prey species (mainly, commensal mammals). Prolonged immobility is possible because of the snakes' reliance on ambush predation, and their large body size facilitates thermoregulation without overt shuttling behavior. Pythons are vulnerable to predators (especially canids) when they move across large open areas, but generally avoid such habitats. Morelia spilota have declined in regions of Australia where agricultural practices have left no thickly vegetated habitats. Patches of such habitat (even if small, and composed of introduced plant species) appear to be vital for the continued presence of large pythons in the agricultural landscape.