Unravelling predator–prey interactions in response to planned fire: a case study from the Tanami Desert

Context

Introduced predators pose a significant threat to biodiversity. Understanding how predators interact with other threats such as fire is crucial to developing effective conservation strategies.

Aims

We investigated interactions between the greater bilby (Macrotis lagotis) and two introduced predators, the European red fox (Vulpes vulpes) and feral cat (Felis catus), in response to fire management in a remote part of the Tanami Desert, Australia.

Methods

We used motion-sensor cameras and non-invasive genetic sampling to monitor bilbies and predators. We compared activity profiles to determine the level of temporal overlap among species, and used generalised linear modelling to assess the correlation between activity and average normalised difference vegetation index (NDVI; as a proxy for fire-associated environmental change). Finally, we used spatially explicit capture–recapture modelling to estimate cat and bilby densities before and after fire.

Key results

Cat and bilby activity declined following fire, whereas fox activity increased (despite only a small proportion of the study area being burnt). Bilbies and foxes showed the greatest overlap in temporal activity (76%), followed by bilbies and cats (71%) and cats and foxes (68%). Bilbies and cats were more likely to be captured in areas with a lower NDVI, whereas foxes were more likely to be captured in areas with a higher NDVI. Bilby density declined significantly following fire, whereas cat density remained constant through time.

Conclusions

Declines in bilby activity and density following fire may be attributed to emigration from the study area and/or increases in fox activity. Post-burn emigration could be due to wide scale destruction of important food resources. However, given much of the study area where bilbies were detected remained unburnt, it is more likely that observed declines are related to increases in fox activity and associated increases in predation pressure. Improved understanding may be gained by experimentally manipulating both fire and predator densities.

Implications

Increases in fox activity following fire are likely to have devastating consequences for the local bilby population. It is thus vital that appropriate management activities are put in place to protect bilbies from foxes. This may be achieved through a combination of lethal control and indirect methods.