The majority of Australian bandicoot species (Peramelidae) are considered threatened. The northern brown bandicoot Isoodon macrourus is one of the more common bandicoots but studies have shown it to be prone to sudden declines in abundance, possibly linked to intense fires. This present study examined the impact of four experimental fire management regimes on northern brown bandicoot survival during a large-scale, 6-year experiment conducted within 300 km² of savanna and open eucalypt woodland at the Kapalga Research Station in Kakadu National Park, Northern Territory.
Fire regimes: Experimental compartments (each 15-20 km²) were assigned randomly to one of four fire treatments each applied every year for 5 years (1990 to 1994). Prior to 1990, no fires had occurred since September 1987. The treatments (simulating landscape fires occurring in the region) were:
Unburnt - protected from fire;
Early - burnt early dry season (May–June), as practiced widely in Kakadu and other reserves;
Late - burnt late dry season (September–October), as occurs extensively due to wildfires;
Progressive - burnt early, mid- and late dry season (May, July and September);
Bandicoot monitoring: Live-trapping occurred bimonthly over 6 years (July 1989 to May 1995; total of 92,160 trap nights). Bandicoots were sexed, weighed, marked with a small numbered ear tag, and released at site of capture. Mark–recapture data were collected and analysed.
Over the 6 years, 658 individual bandicoots (418; 64% males) were captured and tagged, 317 were subsequently re-trapped at least once. A decline in survival took place over the 6 years i.e. a sudden collapse did not occur at the onset of burning. Relative abundance was highest in 1991 (3.89 captures/100 trap nights), declining in 1993 (1.09) to a low in May 1995 (0.03).
Unburnt and early burnt areas experienced the least overall decline: bimonthly survival rate in unburnt areas dropped from 0.756 in July-August 1989 to 0.549 in March-April 1995; in early burnt areas from 0.748 to 0.590.
Burning in the late dry season resulted in substantially more severe declines (from 0.783 to 0.187). Progressive burns caused an almost complete collapse in bandicoot survival (0.782 to 0.058).
All fire treatments trialled (including unburnt) were associated with declines in northern brown bandicootsurvival, thus none appear appropriate for their conservation. Repeated burning reduced habitat suitability (e.g. reduced the ground cover and habitat heterogeneity). Adult bandicoots have static home ranges and tend not to move far in response to local environmental changes; dense patches of understorey vegetation and litter are required for construction of grass nests (daytime refuges). Other factors e.g. rainfall and season, had comparatively little influence on survival rates.
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