The response of terrestrial mammals and arboreal marsupials to past burning history as well as a year prior to, and then for 4 years after, a major wildfire in 2003 at Booderee National Park, Jervis Bay Territory was quantified. The present study encompassed extensive repeated surveys at a set of 109 replicated sites stratified by vegetation type and fire history. It was found that most species exhibited significant differences in presence and abundance between major vegetation types. Detections of long-nosed bandicoot (Perameles nasuta) increased significantly in all vegetation types surveyed, in both burnt and unburnt areas. Temporal patterns in captures of three species of small mammals (bush rat (Rattus fuscipes), swamp rat (Rattus lutreolus) and brown antechinus (Antechinus stuartii)) showed a trend for lower numbers of captures on burnt sites compared with unburnt sites. Three species of arboreal marsupials, common ringtail possum (Pseudocheirus peregrinus), greater glider (Petauroides volans) and common brushtail possum (Trichosurus vulpecula), were moderately common and all showed marked differences in abundance between vegetation types. Whereas P. peregrinus and P. volans exhibited a temporal decline between 2003 and 2006, T. vulpecula exhibited a general increase from 2003 levels. However, arboreal marsupial responses did not appear to be directly fire related.
Predation by European red foxes is believed to be the major cause of the extinction and decline of a large number of native medium-sized terrestrial mammals in Australia. We examined the impact of poisoning of foxes on the relative abundance of a group of medium-sized mammals in an experiment conducted in three large forest blocks in south-eastern Australia. The blocks consisted of paired sites, as follows: one site where poison baiting was used to control foxes (treatment site) and one where foxes were not controlled (non-treatment site). At all six sites, the population responses of a range of mammals were measured, and compared between treatment and non-treatment sites. The relative fox abundance, as indexed by bait-take, declined during the course of the study at treatment sites and to a lesser extent at non-treatment sites. The decline in bait-take at non-treatment sites was most likely due to treatment sites acting as ecological traps, so that reduced intra-specific competition attracted foxes from non-treatment to treatment sites, where they were subsequently poisoned. There was a significant treatment effect for the abundances of total mammals, long-nosed potoroos, southern brown bandicoots and common brushtail possums, with higher abundances at treatment sites than at non-treatment sites. Common ringtail possums increased in abundance during the course of the study, with no significant difference between treatment and non-treatment sites. There was no significant effect of time or treatment on the abundance of long-nosed bandicoots. The increase in the abundance of native mammals at treatment sites was most likely due to a lower predation pressure by foxes brought about by fox control, and the smaller increase in abundance in non-treatment blocks was likely due to the ecological-trap effect because of fox baiting at treatment sites. The present study demonstrated that broad-scale fox control can lead to increases in the abundance of native mammals in forested habitats, without recourse to aerial baiting or fences. The study also demonstrated that the influence of fox control on the fox abundance can extend well beyond the perimeter of the area baited.
Over-abundance of native herbivores is a problem in many forests worldwide. The abundance of native macropod wallabies is extremely high at Booderee National Park (BNP) in south-eastern Australia. This has occurred because of the reduction of exotic predators through an intensive baiting program, coupled with the absence of other predators. The high density of wallabies at BNP may be inhibiting the recruitment of many plant species following fire-induced recruitment events. We experimentally examined the post-fire response of a range of plant species to browsing by wallabies in a forest heavily infested with the invasive species, bitou bush Chrysanthemoides monilifera. We recorded the abundance and size of a range of plant species in 18 unfenced (browsed) and 16 fenced (unbrowsed) plots. We found the abundance and size of bitou bush was suppressed in browsed plots compared to unbrowsed plots. Regenerating seedlings of the canopy or middle storey tree species Eucalyptus pilularis, Acacia implexa, Allocasuarina littoralis, Breynia oblongifolia and Banksia integrifolia were either smaller or fewer in number in grazed plots than treatment plots as were the vines Kennedia rubicunda, Glycine tabacina and Glycine clandestina. In contrast, the understorey fern, Pteridium esculentum increased in abundance in the browsed plots relative to unbrowsed plots probably because of reduced competition with more palatable angiosperms. Twelve months after plots were installed the community structure of the browsed and unbrowsed plots was significantly different (P = 0.023, Global R = 0.091). The relative abundance of C. monilifera and P. esculentum contributed most to the differences. We discuss the possible development of a low diversity bracken fern parkland in Booderee National Park through a trophic cascade, similar to that caused by overabundant deer in the northern hemisphere. We also discuss its implications for broad scale fox control in southern Australian forests.
Agencies charged with nature conservation and protecting built-assets from fire face a policy dilemma because management that protects assets can have adverse impacts on biodiversity. Although conservation is often a policy goal, protecting built-assets usually takes precedence in fire management implementation. To make decisions that can better achieve both objectives, existing trade-offs must first be recognized, and then policies implemented to manage multiple objectives explicitly. We briefly review fire management actions that can conflict with biodiversity conservation. Through this review, we find that common management practices might not appreciably reduce the threat to built-assets but could have a large negative impact on biodiversity. We develop a framework based on decision theory that could be applied to minimize these conflicts. Critical to this approach is (1) the identification of the full range of management options and (2) obtaining data for evaluating the effectiveness of those options for achieving asset protection and conservation goals. This information can be used to compare explicitly the effectiveness of different management choices for conserving species and for protecting assets, given budget constraints. The challenge now is to gather data to quantify these trade-offs so that fire policy and practices can be better aligned with multiple objectives.
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