Age classes of the greater bilby (Macrotis lagotis) based on track and faecal pellet size

Abstract

The gait length and width and faecal pellet diameter of bilbies were examined to determine whether these measures could be used to accurately identify different age classes of individuals in the field. There was a good relationship between gait width+length and animal size that allowed the identification of three age classes: immature–independent individuals <500 g, mature females and small males 500–1200 g, and large males >1700 g. The relationship between pellet diameter and animal size was not as strong and faecal pellet diameter was suitable to identify only immature–independent individuals. An application of these measurements to a bilby population in the Tanami Desert indicated that immature individuals were limited to the central half of their current distribution whereas medium-sized individuals were distributed throughout.