Alaric Fisher

Alaric Fisher
Department of Enviroment and Natural Resources (DENR)

PhD

About

98
Publications
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Publications

Publications (98)
Article
Full-text available
The likelihood of extinction within the next 20 years was determined for 47 Australian mammal, bird, reptile, frog and freshwater fish taxa previously identified as being highly imperilled. A 14-member expert elicitation panel, consisting of a mix of taxon experts and government managers of threatened species, estimated that there was a > 50% chanc...
Article
Assessments of ecosystem restoration have traditionally focused on soil and vegetation, often with little consideration of fauna. It is critical to include fauna in such assessments, not just because of their intrinsic biodiversity value but also because of the many ecological roles that animals play in restoration processes. However, a widely acce...
Article
Full-text available
ContextInvasive predators are a key threat to biodiversity worldwide. In Australia, feral cats are likely to be responsible for many extinctions of native mammal species in the south and centre of the continent. AimsHere we examine the effect of feral cats on native rodent populations in the second of two translocation experiments. Methods In a wil...
Article
Context Small and medium-sized native mammals have declined precipitously across northern Australia. Feral cats have been implicated in causing declines and ongoing suppression of populations. Aims The aim of the present study was to evaluate the response of small and medium-sized native mammal populations when cat predation was removed. Methods A...
Article
Full-text available
Aim An interaction between reduced habitat structural complexity and predation by feral cats (Felis catus) has been hypothesized as the primary driver of mammal decline in northern Australia. However, we have a limited understanding of the drivers of the distribution and abundance of feral cats at a landscape scale, including whether the occurrence...
Article
In recent decades severe mammal declines have occurred in the vast and uncleared tropical savannas of northern Australia. Mounting evidence suggests that feral cats (Felis catus), large feral herbivores and increased frequency of high-severity fires, are all contributing to declines; however, the respective influence of each threat remains unclear....
Technical Report
Full-text available
A major rehabilitation program is underway at Ranger Uranium Mine in the Northern Territory, where mining ceased in 2012. To meet national and international standards of ecosystem restoration the rehabilitation area must support a diversity of characteristic flora and fauna species, with high similarity to adjacent areas of lowland woodland in Kaka...
Article
Full-text available
Assessing the statistical power to detect changes in wildlife populations is a crucial yet often overlooked step when designing and evaluating monitoring programs. Here, we developed a simulation framework to perform spatially explicit statistical power analysis of biological monitoring programs for detecting temporal trends in occupancy for multip...
Article
Full-text available
Understanding where species occur and how difficult they are to detect during surveys is crucial for designing and evaluating monitoring programs, and has broader applications for conservation planning and management. In this study, we modelled occupancy and the effectiveness of six sampling methods at detecting vertebrates across the Top End of no...
Data
Mapped climatic, topographic and fire covariates used to model species occupancy and detectability. Covariates (scaled) at 1 km resolution used to model occupancy and detectability of 242 birds, mammals and reptiles recorded at 333 sites across the Top End of northern Australia. (TIF)
Data
Number of covariates included in occupancy and detectability models for 136 species. Proportion of models per animal group with 1–8 covariates included in the best model. Note, maximum covariate count for detectability models is 3, and method was included in detectability models for species with multiple methods of detection, but was not included i...
Data
Sampled environmental domains across the Top End of northern Australia. Frequency histograms of covariate values occurring within the truncated (i.e., not the full extent of the Top End) mapping region, showing the representativeness of sampling sites for birds (red), mammals (blue), and reptiles (orange) in comparison to the spectrum of environmen...
Data
Model coefficients for the occupancy component of the reptile models. Model coefficients for the occupancy component of the reptile models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Data
Model coefficients for the occupancy component of the mammal models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Data
Estimates of occupancy and detectability for each mammal species with alternative sampling methods. Occupancy and detectability for 20 mammals modelled using live trapping and spotlighting averaged across 326 sites, and camera trapping averaged across 168 sites in northern Australia. Detectability estimates for live trapping and spotlighting is ove...
Data
Reptile occupancy maps across the Top End of northern Australia. Occupancy maps for reptiles with covariates in the best model. Occupancy maps for reptiles with covariates in the best model. Light grey represents zero occupancy, while blue represents an occupancy probability of 1. (PDF)
Data
Bird occupancy maps across the Top End of northern Australia. Occupancy maps for birds with covariates in the best model. Occupancy maps for birds with covariates in the best model. Light grey represents zero occupancy, while blue represents an occupancy probability of 1. (PDF)
Data
Sampling methods applied at monitoring sites across the eight conservation reserves. Summary of the method of detection pooled to generate detection histories per animal group per location: Djelk Indigenous Protected Area (DIPA); Fish River Station (FRS); Garig Gunak Barlu National Park (GGBNP); Gregory National Park (GNP); Kakadu National Park (KN...
Data
Mammal occupancy maps across the Top End of northern Australia. Occupancy maps for mammals with covariates in the best model. Light grey represents zero occupancy, while blue represents an occupancy probability of 1. (TIFF)
Data
Estimates of occupancy and detectability for each bird species. Occupancy and detectability estimates (over one day/night) for 83 birds modelled using diurnal active searches and spotlighting averaged across monitoring sites. (PDF)
Data
Estimates of occupancy and detectability for each reptile species. Occupancy and detectability (over one day/night) estimates for 33 reptiles modelled using pitfall trapping and/or spotlighting data averaged across monitoring sites. (PDF)
Data
Pairwise correlation matrix for candidate predictor variable. Covariates with a Spearman’s correlation coefficient greater than 0.7 are shown in bold, with one of a pair excluded from the analysis. (PDF)
Data
Model coefficients for the occupancy component of the bird models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Data
Model coefficients for the detection component of the reptile models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Data
Model coefficients for the detectability component of the bird models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Data
Model coefficients for the detectability component of the mammal models. Note, species containing only dashes were recorded during surveys but were unable to be modelled. (PDF)
Article
Feral cats have been responsible, in part, for the extinction of many species of mammal, bird and reptile globally, especially on islands. Whilst there is extensive evidence of the predatory impacts of cats on mammals and birds, far less is known about their ecological impacts on reptiles, especially in continental situations. We conducted a field...
Article
Context Small-and medium-sized native mammals have suffered severe declines in much of northern Australia, including within protected areas such as Kakadu National Park. Several factors have been implicated in these declines but predation, particularly by feral cats (Felis catus), has been identified as potentially the most direct cause of decline...
Technical Report
Full-text available
Monitoring and evaluating patterns of change in biodiversity are essential to inform land managers, policy-makers and planners about the condition of biodiversity and ecological responses to management and environmental change. Over the past 24 years the Northern Territory Government, in conjunction with Parks Australia and traditional owners, has...
Article
Full-text available
Australia has experienced dramatic declines and extinctions of its native rodent species over the last 200 years, particularly in southern Australia. In the tropical savanna of northern Australia significant declines have occurred only in recent decades. The later onset of these declines suggests that the causes may differ from earlier declines in...
Article
Full-text available
Introduction: Recent studies at sites in northern Australia have reported severe and rapid decline of several native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic group...
Article
Full-text available
Introduction: Recent studies at sites in northern Australia have reported severe and rapid decline of several native mammal species, notwithstanding an environmental context (small human population size, limited habitat loss, substantial reservation extent) that should provide relative conservation security. All of the more speciose taxonomic group...
Article
Full-text available
Small mammal (<2kg) numbers have declined dramatically in northern Australia in recent decades. Fire regimes, characterised by frequent, extensive, late-season wildfires, are implicated in this decline. Here, we compare the effect of fire extent, in conjunction with fire frequency, season and spatial heterogeneity (patchiness) of the burnt area, on...
Article
Full-text available
The recent commentary by Woinarski (2014, Global Ecology and Biogeography, doi: 10.1111/geb.12165) disagreed with our conclusions on the correlates of decline in the marsupials of tropical Australia (Fisher et al., 2014, Global Ecology and Biogeography, 23, 181–190). We compared traits of species that were associated with range decline in southern...
Article
Small mammal species are declining across northern Australia. Predation by feral cats Felis sylvestris catus is one hypothesised cause. Most evidence of cat impacts on native prey comes from islands, where cat densities are often high, but cats typically occur at low densities on mainland Australia.We conducted a field experiment to measure the eff...
Article
Full-text available
This study examines whether there is a biodiversity benefit (“dividend”) associated with the existence and management of conservation reserves in the extensive and largely natural landscape of northern Australia. Species richness and abundance of vertebrate fauna and the intensity of a range of disturbance factors were compared across a set of 967...
Article
Full-text available
A third of all modern (after 1500) mammal extinctions (24/77) are Australian species. These extinctions have been restricted to southern Australia, predominantly in species of ‘critical weight range’ (35–5500 g) in drier climate zones. Introduced red foxes (Vulpes vulpes) that prey on species in this range are often blamed. A new wave of declines i...
Technical Report
Full-text available
This project investigated the potential for pastoral intensification in the Victoria River District (VRD) of the NT to increase the profitability of the northern beef industry in the face of rising costs. The results suggested that intensification can increase a property’s profitability without adverse effects on land condition or biodiversity in t...
Conference Paper
Full-text available
This project investigated the potential for pastoral intensification in the Victoria River District (VRD) of the NT to increase the profitability of the northern beef industry in the face of rising costs. The results suggested that intensification can increase a property’s profitability without adverse effects on land condition or biodiversity in t...
Article
Full-text available
Context. Aprevious study reported major declines for native mammal species from Kakadu National Park, over the period 2001-09. The extent to which this result may be symptomatic of more pervasive biodiversity decline was unknown. Aims. Our primary aim was to describe trends in the abundance of birds in Kakadu over the period 2001-09. We assessed wh...
Article
Australia has lost more native mammal species than any other country in the past two centuries, and this record of loss looks likely to worsen over the next few decades. Small- to medium-sized mammals are declining in both distribution and density across large tracts of northern Australia's tropical savannas, including within protected areas. The m...
Article
Full-text available
Birds with restricted geographical distributions are particularly vulnerable to environmental change. In order to evaluate their conservation status it is necessary to have accurate records of their distribution and how that distribution has changed over time. The determinants of the distribution and abundance of the Carpentarian Grasswren (Amytorn...
Article
Full-text available
This article provides a context to, attempts an explanation for, and proposes a response to the recent demonstration of rapid and severe decline of the native mammal fauna of Kakadu National Park. This decline is consistent with, but might be more accentuated than, declines reported elsewhere in northern Australia; however, such a comparison is con...
Article
Full-text available
The need for broad-scale, long-term biodiversity monitoring to support evidence-based policy and management in the Australian rangelands is clear and pressing but, despite protracted discussion of this need, there has been little progress towards implementation. To prompt real progress, we propose a framework of spatially hierarchical and complemen...
Article
Full-text available
Context: Australian islands have provided a major conservation refuge for many native mammals; however, conversely, island populations may also be highly susceptible to the introduction of novel threats. Nearby islands subject to different arrays of threats or different timing of arrival of those threats may provide a natural experiment, offering p...
Article
Full-text available
The invasion of exotic pasture species into intact woodlands has the potential to affect native fauna by altering habitat structure and ecosystem function. The spread of these weeds is generally in concert with cattle grazing, so that fauna or habitat change is due to multiple interrelated causes. In this study we investigated whether the spread of...
Article
Full-text available
Context. Australia has a lamentable history of mammal extinctions. Until recently, the mammal fauna of northern Australia was presumed to have been spared such loss, and to be relatively intact and stable. However, several recent studies have suggested that this mammal fauna may be undergoing some decline, so a targeted monitoring program was estab...
Article
Forty-four species of terrestrial reptiles and eight species of frogs were recorded from 60 continental islands of the Wessel and English Company groups off northeastern Arnhem Land, Northern Territory. Two gecko species, Oedura rhombifer and Heteronotia binoei, were present on the most islands (34 and 31, respectively), and occurred on islands < 5...
Article
Full-text available
Change is a constant in Australia’s rangelands. Appropriate management,of this change,requires a sound knowledge of drivers (e.g. climate variability, livestock grazing), their impacts on natural resources (state and trend), socio-economic outcomes, and how these feed back through learning and adaptive management to affect drivers and their impacts...
Article
The bird faunas of the adjacent Wessel and English Company island chains were sampled at two scales (0.25 ha quadrats and entire islands). Ninety-six species were recorded from 226 quadrats, with the most frequently recorded species being mistletoebird Dicaeum hirundinaceum, brown honeyeater Lichmera indistincta, silver-crowned friarbird Philemon a...
Article
Achieving more uniform grazing at landscape and paddock scales is seen as an important management objective by pastoralists in northern Australia, but it is difficult to attain in practice. This paper presents a brief review of some key factors to be considered in attempts to modify grazing distribution in extensive rangelands by drawing on the pre...
Article
Full-text available
Generalised linear modelling (GLM) was used to develop habitat models for 25 of the 28 microchiropteran bat species that occur in the wet–dry tropics of the Northern Territory (the ‘Top End’). Based on these models, a geographic information system (GIS) was used to derive probability of occurrence maps for each species. Almost all of the models ide...