The influence of European Rabbits, Oryctolagus cuniculus, on diel activity patterns of native marsupials in the absence of apex predators

Context: European Rabbits (Oryctolagus cuniculus) are ubiquitous across Australia and have the capacity to influence native species populations both directly and indirectly. Despite this, limited research has focused on interspecific interactions between invasive pests and native marsupials, yet these interactions could be important for conservation efforts. Aims: To determine how the site occupancy, detection probability, and temporal activity periods of native mammals changed in response to the presence or absence of European Rabbits. Methods: I monitored three native mammal species using passive, outward-facing trail cameras, in a predator-barrier fenced reserve. Two distinct areas (an area with rabbits and an area without rabbits) were monitored. Vegetation surveys were conducted at each camera site to measure vegetation density as a possible influence on site occupancy and detection probability. Temporal kernel density analyses were run to consider how activity periods differed between rabbit presence and absence areas. Key Results: Bettongs (Rufous and Eastern), Eastern Barred Bandicoots and Southern Brown Bandicoots had a na�ve site occupancy of 78%, 46% and 48%. Detection probability was strongly influenced by vegetation parameters and prevented the interpretation of trends in site occupancy. High proportions of clumping grass resulted in a lower detection probability for all three focal species. Rabbits reduced detectability for Southern Brown Bandicoots and bettongs, however increased Eastern Barred Bandicoot detections. The temporal patterns of Eastern Barred Bandicoots and Southern Brown Bandicoots were earlier and shorter in areas without rabbits in comparison to areas with rabbits. Conclusions: Vegetation density explained large proportions of the variation in detection probability and limited my capacity to identify trends in site occupancy, a regular challenge for assessing the impacts of rabbits due to their indirect effects on vegetation. Both bandicoot species may switch their activity in the presence of rabbits, suggesting some temporal partitioning between rabbits and bandicoot species. Implications. The presence of rabbits influences bandicoot diel activity, although may be mediated by habitat. This study demonstrated the challenges in identifying the impacts of rabbits with the confounding nature of vegetation response. Future studies should focus on areas containing a wider variety of vegetation densities at different stages of rabbit influence and ensure they account for detection probability.