Tracking movement, home range, and microhabitat use in a small terrestrial breeding frog using harmonic direction-finding technology

Context Tracking the movements of an animal increases our understanding of its behaviour and ecological preferences. Aims This study aimed to assess the movements, home range, nesting sites, and microhabitat use of a very small, cryptic, terrestrial microhylid frog species (Austrochaperina robusta) in an upland rainforest, during the breeding season. Methods We used harmonic direction-finding (HDF) technology with ultra-light harnesses/tag combinations of two sizes (small 0.023 g and large 0.033 g) to track male A. robusta. These are substantially lighter than all tag/harness combinations previously used in amphibian tracking studies and represented a small proportion (1.8–2.58%) of the body mass of the very small study species, A. robusta (1.27 ± 0.20 g). Key results Both tag sizes were effective for tracking, and tag size did not change the distance moved or time until an individual was found. Males did not move far between surveys (average 58.2 ± 24.7 cm) and had small home ranges (0.46 ± 0.20 m2) over the 5-day tracking period. Implications Our study highlights that HDF can be used to track very small vertebrates in structurally complex environments. This method has the potential to fill important knowledge gaps regarding the ecology of small terrestrial breeding amphibians, providing insights that can inform conservation measures and population assessments for vulnerable species.