Population size, demography and diet of the Siamese crocodile, Crocodylus siamensis (Schneider, 1801) in the Mesangat Swamp in Kalimantan, Indonesia

Abstract

A study of the distribution, abundance and diet of the critically endangered Siamese crocodile (Crocodylus siamensis) was undertaken during 2010 and 2011 in the Mesangat wetland, East Kalimantan, Indonesia. It provides the first hard data concerning the ecology of the species outside of mainland Indochina. Crocodiles were captured if possible, weighed, measured and tagged subcutaneously with a Passive Integrated Transponder (PIT tag). Forty-three (43) non-hatchling C. siamensis were identified, of which seven were adults. An estimate of total non-hatchling population size was calculated from individuals marked in 2010 and re-captured in 2011, extrapolated to the area of all locations where C. siamensis were seen. The total population size in the survey area was estimated to be approximately 75 individuals. Ninety-one percent (91%) of all C. siamensis detections (n= 77) occurred outside the forest-type habitat, adjacent to or within two meters of floating grassy mats. The first investigation on stomach contents of the species was undertaken in this study. Diet samples from 13 C. siamensis were obtained from stomach lavage and analysed individually. Prey found in stomach contents contained insect remnants, snail shells, fish bones, bird feathers, snake scales and small mammal fur and varied considerably between individuals. The presence of necrophagic ants suggested that C. siamensis consume carrion. The current study confirmed at least one healthy breeding population of C. siamensis outside of the mainland of Indochina and provides important data for the species’ long-term conservation in Kalimantan.

Agata Staniewicz

Research scientist