Owl Pellet Content Analysis Proves an Effective Technique to Monitor a Population of Threatened Julia Creek Dunnarts (Sminthopsis douglasi) Throughout a Native Rodent Plague

Logistical, environmental and temporal considerations can limit the effectiveness of long-term live trapping for small mammals in remote environments. Owl pellet content analysis offers a low-cost, non-invasive alternative to live trapping, as it is generally reflective of prey abundance within the broader small mammal community. One species to which this detection technique could be readily applied is the threatened Australian dasyurid, the Julia Creek dunnart, Sminthopsis douglasi. Most population information is outdated, and the species is notoriously difficult to monitor. Here, we aimed to monitor S. douglasi and other small terrestrial vertebrates over time and in relation to a native long-haired rat (Rattus villosissimus) plague, assessing their occurrence as dietary items in eastern barn owl (Tyto javanica delicatula) pellets collected at Toorak, north-west Queensland, Australia. A total of 1007 individual vertebrates were identified from 706 barn owl pellets spanning 3 present-day collections (2023–2024), with further analysis incorporating a prior published historical dataset (1994–2001, 210 pellets). We demonstrated a shift in Toorak small mammal community structure both over time and in response to an active R. villosissimus plague. Despite declines across present-day pellet collections, S. douglasi was always detected in high abundance, peaking at 30.75% of all individuals. Cumulative probability of detection indicated that analysis of owl pellets was highly effective at detecting S. douglasi (within 20 pellets) despite the ongoing rodent plague, which has undermined the effectiveness of parallel live trapping efforts across the region. Owl pellet analysis is thus an effective methodology for rapidly assessing S. douglasi populations and should be incorporated into both S. douglasi and other small mammal species monitoring regimes.