Spatial-Organization and Movement Patterns of Adult Male Platypus, Ornithorhynchus-Anatinus (Monotremata, Ornithorhynchidae)

Abstract

Home-range size and overlap and movement patterns of adult male platypus, Ornithorhynchus anatinus, occupying streams in southern Victoria were investigated near the start of the breeding season using radio-tracking techniques. On the basis of a sample of males monitored for four or more complete activity periods, home-range size varied from 2.9 to 7.0 km, with individuals (n = 4) moving a mean net distance of 2.0 +/- 1.4 km per activity period. Longer-range movements were also observed, with one male travelling at least 15 km from one stream catchment to another via an intervening stretch of river. Some home ranges of males were mutually exclusive whereas others overlapped substantially; in the latter case, males largely avoided each other, spending most of their time in different parts of the shared area. All home ranges of males apparently overlapped those of two or more adult females. Three patterns of travel over complete activity periods were recognised, including unidirectional travel (point A to B), return travel (A to B to A) and multidirectional travel with multiple, relatively short-range backtracking. Males occupying overlapping areas often moved multidirectionally and rarely undertook unidirectional travel, whereas the converse applied to males occupying exclusive areas.