Investigating the effects of landscape productivity on the spatial ecology of a threatened marsupial inside feral predator exclosures

Abstract

Landscape productivity and resource dispersion are key drivers of the movement patterns of many species. In less productive environments, home ranges are generally larger as individuals travel further to access resources. The greater bilby (Macrotis lagotis) has been reintroduced to several feral predator exclosures to reduce their extinction risk. Understanding how landscape productivity and resource dispersion influence bilby space use is critical to enable effective management of populations in exclosures. At two exclosures, we tested three hypotheses: 1. Bilbies would preferentially utilize habitats with sandy substrates (<20% clay content), as they are suitable for digging burrows and foraging pits; 2. Home ranges would be larger at the arid site compared to the semi-arid site due to lower productivity and patchier distribution of preferred habitats; and 3. Bilbies would travel further each night at the arid site to access preferred habitats. Rainfall was used as an indicator of productivity, and dispersion of preferred habitats as an indicator of resource dispersion. The study was undertaken during average rainfall conditions and under similar bilby population densities at both sites. GPS loggers recorded home ranges and movements of 10 bilbies at the arid site, and 11 bilbies at the semi-arid site. Seventeen of the 21 bilbies preferentially utilized habitats with sandy substrates, which were less abundant at the arid site. There were no significant differences in home range size or nightly movements between the sites for either sex. We suggest the average rainfall conditions at both sites, and the dietary flexibility of bilbies, supported the maintenance of relatively small and stable home ranges (particularly for females). The effects of landscape productivity and resource dispersion on bilby space use are more likely to be evident during extended periods of below average rainfall. Bilby home range studies during low rainfall conditions (e.g. drought) are required for the effective, long-term management of exclosure populations.