A game of cat-and-mouse: microhabitat influences rodent foraging in recently burnt but not long unburnt shrublands

We investigated the influence of vegetation structure and fire history on the foraging behavior of small rodents (Notomys mitchellii, Pseudomys hermannsburgensis, and Mus musculus) by conducting giving-up density (GUD) experiments in recently burnt (9–13 years since last fire) and long unburnt shrublands (> 40 years), and open and sheltered microhabitats, in a semiarid region of Western Australia. We predicted that rodents would spend less time foraging in recently burnt shrublands and open microhabitat and that the influence of microhabitat would be weaker in long unburnt compared to more recently burnt vegetation. Our findings show that fire history and microhabitat structure influence the foraging behavior of the study species and that the influence of microhabitat varies between fire histories. GUDs were higher in long unburnt vegetation and in open microhabitats. There was a microhabitat effect in recently burnt vegetation, but not in long unburnt. Rodents foraged more in sheltered microhabitats probably because predator encounters are less likely to occur there and it provides them with greater refuge from predation. The presence of a microhabitat effect in recently burnt, but not long unburnt vegetation suggests that understory vegetation density is more important in mediating predation risk than canopy density. Future studies of small mammal responses to land management actions should include behavioral, as well as population-level responses to differing fire regimes.

Dietary overlap between sympatric dingoes and feral cats at a semiarid rangeland site in Western Australia

Abstract. The diet of sympatric dingoes and feral cats was studied in the semiarid southern rangelands of Western Australia. A total of 163 scats were collected over a period of 19 months. Rabbit remains were the most common food item in cat scats, followed by reptiles, small mammals and birds. Macropod remains were the most common food item in dingo scats, followed by rabbits and birds. Dingo scats did not contain small mammal remains, and infrequently contained arthropod and reptile remains. Cat and dingo scats contained remains from 11 and six mammal species, respectively. Of the small mammals, cat scats contained rodent remains more frequently than those of dasyurids. Dietary diversity of cats was higher than for dingoes and dietary overlap between the two species was relatively low.

Effects of a fox removal program on small and medium-sized mammal population dynamics within the Anglesea Heathlands, Victoria

This thesis assessed the diet of foxes within the ALCOA lease area of Anglesea to determine which native and introduced species foxes were eating. Results showed that Swamp Wallaby was regularly eaten but many other mammals, birds, insects and reptiles were also consumed. The response of native mammals to seasonal fox removal was also determined.

Ecological fire regimes for the recovery and management of threatened small mammals in southern Australia

The application of fire to fauna management, particularly for endangered species, is a significant issue for wildlife managers. Mammals respond to fire regimes including intensity, frequency and season of occurrence, and changes in fire-regimes are implicated in detrimental effects on mammal communities. For many species temporal habitat change is a key factor affecting the persistence of populations. These species require the option of colonising the shifting habitat mosaic. There is substantial evidence that species such as the native rodents New Holland Mouse (Pseudomys novaehollandiae) and Heath Rat (Pseudomys shortridgei) are early successional species dependent on such temporal habitat changes. In conrast species such as the dasyurid marsupial, Swamp Antechinus (Antechinus minimus) are late successional species, which may take up to 20 years to recolonise. In many situations ecological fire regimes need to be implemented to increase areas of suitable habitat for population expansion and reintroductions. This paper assesses research findings and the development of management actions incorporating ecological fire regimes for the recovery of Pseudomyine rodents and the Swamp Antechinus. Spatially explicit models are required to determine changes and patterns at the landscape level. The prospect of global climate change also is of significance and needs to be assessed.

Habitat fragmentation disrupts the demography of a widespread native mammal

Fragmentation theory predicts that population persistence should be positively correlated with the size of habitat fragments. The patterns of occurrence of many species are consistent with this prediction, but the demographic processes that determine how species respond to fragmentation are poorly understood. In addition, habitat quality may interact with fragment size as an influence on demographic performance. We investigated these predictions for the native bush rat Rattus fuscipes by testing the following hypotheses: 1) population performance (i.e. viability as determined by various demographic parameters) is positively correlated with fragment size; and 2) population performance is positively correlated with habitat quality. Populations of R. fuscipes were censused in two large (>49 ha) and eight small (<2.5 ha) forest fragments in an agricultural region of southeastern Australia. Fragments with high and low quality habitat were included in each size category. Fragment size influenced multiple aspects of population demography; populations in large fragments had higher densities, older age structures, received more potential immigrants, and were more likely to recruit adults than those in small fragments. Reproductive patterns were more predictable in large fragments. Habitat quality per se had less marked effects; adult females were heavier and subadults more prevalent in fragments with high quality habitat. However, high quality habitat enhanced population performance in small fragments more so than in large ones. Despite being widespread in the study area, R. fuscipes populations are profoundly impacted by habitat fragmentation, with population performance declining with fragment size. Studies based on patterns of species occurrence should be interpreted with caution as they may mask critical processes occurring at the population level. For a thorough understanding of the effects of habitat fragmentation, population-level studies are required.

Fire and climatic extremes shape mammal distributions in a fire-prone landscape

Aim: Extreme climatic events and large wildfires are predicted to increase as the world's climate warms. Understanding how they shape species' distributions will be critical for conserving biodiversity. We used a 7-year dataset of mammals collected during and after south-east Australia's Millennium Drought to assess the roles of fire history, climatic extremes and their interactions in shaping mammal distributions. Location: Grampians National Park, south-eastern Australia.

Methods: We surveyed mammals at 36 sites along a ~50-year post-fire chronosequence in each of the 7 years. We modelled ten mammal species in relation to fire history, productivity and recent rainfall. Next, we examined the consistency of species' fire response curves across each of three climatic phases relating to the Millennium Drought. Finally, we identified the optimal distribution of fire ages for small and medium-sized mammal conservation in each of the three climatic phases.

Results: The majority of species were influenced by fire history, and all native species were negatively associated with recently burned vegetation. Seven of ten species responded positively to the end of the Millennium Drought, but six of these declined quickly thereafter. Species' responses to fire history differed depending on the climatic conditions. However, the optimal distribution of fire-age classes consistently emphasized the importance of older age classes, regardless of climatic phase. This distribution is in stark contrast to the current distribution of fire ages across the study region.

Main conclusions: Mammals in the study region face an uncertain future. The negative impact of drought, the short-lived nature of post-drought recovery and, now, the possibility of a new drought beginning forewarn of further declines. The stark contrast between the optimal and current fire-age distributions means that reducing the incidence of further fires is critical to enhance the capacity of native mammal communities to weather an increasingly turbulent climate.