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Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories ('pyrodiversity'), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of ≥4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the north Kimberley. A managed fire mosaic that reduces large scale and intense fires, including the retention of ≥4 years unburnt patches, will clearly benefit savanna mammals. We also highlighted the importance of fire mosaics that retain sufficient shelter for mammals. Along with fire, it is clear that grazing by introduced herbivores also needs to be reduced so that habitat quality is maintained.

We construct a state-and-transition model for mammals in tropical savannas in northern Australia to synthesize ecological knowledge and understand mammalian declines. We aimed to validate the existence of alternative mammal assemblage states similar to those in arid Australian grasslands, and to speculate on transition triggers. Based on the arid grassland model, we hypothesized that assemblages are partitioned across rainfall gradients and between substrates. We also predicted that assemblages typical of arid regions in boom periods would be prevalent in savannas with higher and more regular rainfall. Data from eight mammal surveys from the Kimberley region, Western Australia (1994 to 2011) were collated. Survey sites were partitioned across rainfall zones and habitats. Data allowed us to identify three assemblage states: State 0:--low numbers of mammals, State II:--dominated by omnivorous rodents and State III:--dominated by rodents and larger marsupials. Unlike arid grasslands, assemblage dominance by insectivorous dasyurids (State I) did not occur in savannas. Mammal assemblages were partitioned across rainfall zones and between substrates as predicted, but-unlike arid regions-were not related strongly to yearly rainfall. Mammal assemblage composition showed high regional stability, probably related to high annual rainfall and predictable wet season resource pulses. As a consequence, we speculate that perpetually booming assemblages in savannas allow top-down control of the ecosystem, with suppression of introduced cats by the dingo, the region's top predator. Under conditions of low or erratic productivity, imposed increasingly by intense fire regimes and introduced herbivore grazing, dingoes may not limit impacts of cats on native mammals. These interacting factors may explain contemporary declines of savanna mammals as well as historical declines in arid Australia. The cat-ecosystem productivity hypothesis raised here differs from the already-articulated cat-habitat structure hypothesis for mammal declines, and we suggest approaches for explicit testing of transition triggers for competing hypotheses.

Despite substantial investment in prescribed burning for biodiversity conservation there has been surprisingly little demonstration of its efficacy in achieving intended conservation aims for fauna. In the case of northern Australia’s threatened mammal fauna, most studies have reported negative responses to fire. We used satellite-derived fire scar imagery and small mammal survey data to compare fire regimes and threatened mammal abundance before and after implementation of broad-scale prescribed burning in north-western Australia. Specifically, we tested: (1) whether prescribed burning was effective in changing fire regimes; (2) whether all mammal species and functional groups responded to prescribed burning; and (3) what regional fire and environmental variables explained changes in mammal status. Low-intensity, patchy prescribed burning in the early dry season reduced the extent of high intensity late dry season wildfires. In sandstone habitats the abundance of all mammals, and the large marsupials and specialist rodent functional groups, increased concurrently with early dry season prescribed burning. All mammals and the small dasyurid functional group in woodland habitats also increased during this period. Early dry season prescribed burning extent was the strongest explanatory variable for mammal increases. Early dry season burning was also the strongest explanatory variable for woodland mammal abundance, but these mammals also had a positive association with extent of large patches of old growth vegetation (> 4 years since fire). Generalist rodents did not respond to prescribed burning and two other species declined following prescribed burning in one habitat. Generalist rodents and the two declining species had a negative association with extent of late dry season fire and a positive association with old growth vegetation (interacting with patch size). These results suggest an increased application of patchy early dry season prescribed burning of up to ca. 30% of the area will benefit positive fire responder species of threatened mammals including large specialist rock/arboreal rodents and most marsupial species. For mammals such as generalist terrestrial rodents with predominantly negative associations with fire, managers should seek to increase the size and extent of old growth vegetation.

Predators are fundamentally important in regulating many global ecosystems, and perturbations of predator populations through impacts by invasive species are frequently implicated in the degradation of these ecosystems. In considering recent declines of native critical weight range (35–5500 g) mammals in northern Australia, most attention has focused on predator–prey interactions between a mammalian invader, the feral cat ( Felis catus ), and these mammals. Little consideration has been given to the possible implications of changed reptilian predator assemblages resulting from invasion by another vertebrate, the toxic cane toad ( Rhinella marina ). We used reptile removal records from licenced reptile catchers in three widely spaced towns in the savannas of northern Australia to explore potential impacts of toads on apex and meso-predatory snakes and large lizards. In addition, simultaneous fauna survey data from one town with reptile removal records were used to identify cascading faunal impacts associated with toad invasion. Intervention analyses revealed empirical linkages between toad invasion, apex predator declines, meso-predator increases and declines of critical weight range mammals and other prey groups. Based on the timing and strength of intervention we postulate a novel hypothesis and supporting conceptual model linking recent mammal declines with trophic cascades following toad invasion. The conceptual model is discussed in relation to the prevailing feral cat focussed hypotheses regarding northern Australia’s dramatic small mammal declines. Future studies will need to test putative interactions and their importance so that appropriate management can be implemented to stem ongoing mammal losses.

The remote and sparsely populated Kimberley region is a major centre of endemism in the Australian monsoonal tropics that is threatened by uncontrolled fire following the disruption of Aboriginal burning practices. A recent study of the ant fauna of the Mitchell Falls area of the northern Kimberley revealed that 44 % of the species are known only from the Kimberley region. The fauna appeared to be highly resilient in relation to fire. Levels of endemism in the Mitchell Falls region are likely to be particularly high because it occurs in a high rainfall zone (>1,200 mm per year) that is isolated from similar zones elsewhere in northern Australia. In contrast, the lower rainfall eastern and southern Kimberley form part of continuous climatic bands that extend right across northern Australia, and so species from these areas might be expected to be more widely distributed. Here we describe the ant fauna of Mirima National Park in the eastern Kimberley, in the context of a broader biogeographic analysis of the Kimberley ant fauna and an understanding of its response to wildfire. We specifically test two hypotheses: first, that the ant species of Mirima tend to be more widely distributed across northern Australia than those of Mitchell Falls; and, second, that Mirima ant communities are highly resilient in relation to fire, as revealed by a weak relationship with time-since-fire. Analysis of distributional ranges revealed that 24 % of Mirima ant species are known only from the Kimberley, which, as hypothesized, is substantially lower than at Mitchell Falls (44 %). Also as we hypothesized, the Mirima ant fauna shows little relationship with time since fire, with no systematic variation in ant species richness between sites with 1–4 years since fire, and no relationship between time since fire and site similarity based on overall ant species composition. Although our study indicates that levels of endemism in the ant fauna of the eastern Kimberley are lower than those in the northern Kimberley, they are still extremely high. It seems that at least a quarter of all Kimberley ant species are endemic to the region. This confirms the Kimberley as a highly significant region for ant biodiversity. We have also shown that the regional ant fauna is highly resilient in relation to the key threatening process in the region.

Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories ('pyrodiversity'), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of greater than or equal to 4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the north Kimberley. A managed fire mosaic that reduces large scale and intense fires, including the retention of greater than or equal to 4 years unburnt patches, will clearly benefit savanna mammals. We also highlighted the importance of fire mosaics that retain sufficient shelter for mammals. Along with fire, it is clear that grazing by introduced herbivores also needs to be reduced so that habitat quality is maintained.

We construct a state-and-transition model for mammals in tropical savannas in northern Australia to synthesize ecological knowledge and understand mammalian declines. We aimed to validate the existence of alternative mammal assemblage states similar to those in arid Australian grasslands, and to speculate on transition triggers. Based on the arid grassland model, we hypothesized that assemblages are partitioned across rainfall gradients and between substrates. We also predicted that assemblages typical of arid regions in boom periods would be prevalent in savannas with higher and more regular rainfall. Data from eight mammal surveys from the Kimberley region, Western Australia (1994 to 2011) were collated. Survey sites were partitioned across rainfall zones and habitats. Data allowed us to identify three assemblage states: State 0:- low numbers of mammals, State II:- dominated by omnivorous rodents and State III:- dominated by rodents and larger marsupials. Unlike arid grasslands, assemblage dominance by insectivorous dasyurids (State I) did not occur in savannas. Mammal assemblages were partitioned across rainfall zones and between substrates as predicted, but-unlike arid regions-were not related strongly to yearly rainfall. Mammal assemblage composition showed high regional stability, probably related to high annual rainfall and predictable wet season resource pulses. As a consequence, we speculate that perpetually booming assemblages in savannas allow top-down control of the ecosystem, with suppression of introduced cats by the dingo, the region's top predator. Under conditions of low or erratic productivity, imposed increasingly by intense fire regimes and introduced herbivore grazing, dingoes may not limit impacts of cats on native mammals. These interacting factors may explain contemporary declines of savanna mammals as well as historical declines in arid Australia. The cat-ecosystem productivity hypothesis raised here differs from the already-articulated cat-habitat structure hypothesis for mammal declines, and we suggest approaches for explicit testing of transition triggers for competing hypotheses.