Resource Limitation Shapes Platypus Spatial Ecology in Urban Streams

As urbanisation accelerates, freshwater ecosystems face growing threats, particularly for species reliant on riparian zones, like the platypus (Ornithorhynchus anatinus). This study examines platypus presence, distribution and habitat use along Moggill Creek in Queensland across an urban-rural gradient. Using environmental DNA (eDNA) sampling, live trapping and radio tracking, we assessed urban development influences on platypus home range and habitat preferences. Over six nights of trapping, we captured six adult platypuses (four males, two females). Cross study analysis of radiotracking data revealed that platypuses in urban environments maintain home ranges approximately 2.36 times larger than those in rural habitats (95% CI: 1.58 to 3.63, P<0.001), with the model explaining 57.5% of variance. Net type emerged as the dominant predictor of capture rates, with fyke nets capturing platypuses at 72% lower rates than mesh nets (P<0.001), representing a critical methodological consideration for comparative studies. We confirmed platypus DNA at 13 of 14 sites through eDNA sampling, with notable absence at the most downstream urban site suggesting potential habitat limitations. Analysis of macroinvertebrate communities revealed significant differences between urban and rural sites, driven by environmental factors including elevation and riparian vegetation, which correlated with higher biodiversity and water quality in rural areas. These findings underscore platypus capacity to persist in urban environments whilst revealing ecological costs, including substantially expanded home ranges likely driven by resource limitation. This research, the first to radio track platypuses in Queensland, emphasises the urgent need for conservation strategies targeting urban waterways to maintain habitat quality and support platypus populations amidst accelerating urbanisation pressures.