Movement and Dispersal Patterns of Crocodylus porosus in some Rivers of Arnhem Land, Northern Australia

Abstract

The dispersal of juvenile C. povosus hatched in the Liverpool River is described. Of those initially caught when hatchlings, 1-y-olds and 2–4-y-olds, and recaught 1 year later, 93 %, 73% and 57% respectively were within 10 km of the original capture site. Movements of up to 21 km in one direction in 1 year could be followed by a similar movement in the opposite direction the following year. Relocated C. povosus demonstrated a homing instinct. A possible explanation for the long distances travelled by some juveniles (up to 81 km in a year), is that chance wandering placed them in the mouth of another stream, and attempts to 'home' in the new stream took them further away from their original capture site. The distribution of C. povosus in other rivers can be explained by dispersal patterns similar to those found in the Liverpool River. Some rivers seem to have supported successful C. povosus breeding for a number of years, others seem to have been sporadically successful, and still others unsuccessful. Movement of juveniles from 'successful' to 'unsuccessful' rivers could account for older juveniles found in the latter type of river.