The distribution and abundance of the estuarine crocodile, Crocodylus porosus, in Queensland

Abstract

A total of 6444 Crocodylus porosus (4303 non-hatchlings and 2141 hatchlings) were recorded during 196 vessel-based surveys of 103 waterways to determine the distribution and abundance of Crocodylus porosus in Queensland. The surveys, conducted from January 1994 to December 2000, covered 4174.3 km of waterway. Population structure was biased towards immature crocodiles, with 91% of all animals sighted being less than the minimum breeding size for individuals in the Northern Territory. The mean relative density of non-hatchling C. porosus was highest in waterways of north-western Cape York Peninsula and Lakefield National Park, and lowest for waterways along the populated east coast of Queensland. The highest numbers of hatchlings were recorded from waterways of north-western Cape York Peninsula, where nearly 74% of all hatchlings were recorded during the seven-year survey period. The C. porosus population in northern Queensland appears to be undergoing a limited recovery, with marginal increases in the mean relative density of non-hatchlings in seven of the eight crocodile biogeographic regions. On the basis of the distribution and abundance of hatchling and non-hatchling crocodiles, the north-western Cape York Peninsula region contains the best habitat for C. porosus in Queensland, particularly in the Wenlock River and Tentpole Creek area.