Contrasting responses of small mammals to fire and topographic refugia

Bush rat

Agile antechinus

Unburnt patches are expected to provide an important resource for fauna, potentially acting as a refuge from the direct effects of fire, and allowing animals to persist in burnt landscapes.  Nevertheless there is little information about the way refugia are used by fauna and how populations may be affected by them. 

In our new paper, we tested three alternative hypotheses relating to the abundance of two small mammal species, bush rat (Rattus fuscipes) and agile antechinus (Antechinus agilis), after a planned fire at Henderson Creek in the Otway Ranges: 

1. Active refugia – increased abundance in unburnt patches due to a post-fire shift of individuals from burnt to unburnt areas
2. Passive refugia – abundance in unburnt patches would remain similar to pre-fire levels, and,
3. Limited or no refugia – reduced abundance in unburnt patches related to the change induced by fire in the wider landscape. 

We surveyed small mammals using Elliott Traps, and found that the two species responded differently to the presence of unburnt refugia in the landscape. Whilst fire resulted in reduced abundance of bush rats on burnt slopes, there was no change in gullies, suggesting that their use of refugia is passive.  In contrast, agile antechinus abundance increased in gullies immediately post-fire, consistent with a shift of individuals from burnt parts of the landscape and suggesting active use of refugia.

Our work highlights that different species' responses to patchy disturbances are likely to be influenced by factors such as site fidelity, habitat use and intraspecific competition.

Find the paper in Early View:

Swan, M., Galindez-Silva, C., Christie, F., York, A. & Di Stefano, J. (in press). Contrasting responses of small mammals to fire and topographic refugia. Austral Ecology.