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Australia's recent mammal declines have been most severe in the arid regions, with at least 14 species extinctions occurring therein. The common brushtail possum (Trichosurus vulpecula) is a semi-arboreal marsupial that historically occurred widely across arid Australia but has disappeared from much of this region. We surveyed the last known sites for the species in central Australia. In 2012, we detected possum scats from 3 of 19 sites in Tjoritja National Park in the Northern Territory. Presence sites were separated by <4 km and characterised by extreme ruggedness. Further scat surveys in 2016–17, and 10 499 camera-trap nights of targeted survey in 2020–21, resulted in no possum detections. Moreover, no possums were detected during >60 000 camera-trap nights at nearby monitoring sites targeting other species in 2016–22. The contraction of common brushtail possums to rugged refuges by 2012 is consistent with a decline driven by mammalian predators. The possible extirpation also coincided with or followed record years of high temperatures. The culturally significant common brushtail possum is a priority candidate species for reintroduction to parts of central Australia. Reintroduction attempts must manage mammalian predators and consider the suitability of source populations and translocation sites in the face of a rapidly warming climate. We surveyed the last known sites for the common brushtail possum in central Australia. Our data suggest that possums were extirpated from their last refuges in the MacDonnell Ranges after 2012. Any reintroduction attempts must manage mammalian predators and consider the suitability of source populations and translocation sites in the face of a rapidly warming climate. [ABSTRACT FROM AUTHOR]

The long-term persistence of Z. palatalis is threatened by altered fire regimes, grazing by feral animals and stock, weed intrusion, and the stochastic hazards associated with small, fragmented populations. Based on the best existing data a population and habitat model was developed to assess the relative importance of these threats and develop practical management options.

This study records and documents the most severe and notable instance ever reported of sudden and widespread dieback of mangrove vegetation. Between late 2015 and early 2016, extensive areas of mangrove tidal wetland vegetation died back along 1000 km of the shoreline of Australia's remote Gulf of Carpentaria. The cause is not fully explained, but the timing was coincident with an extreme weather event; notably one of high temperatures and low precipitation lacking storm winds. The dieback was severe and widespread, affecting more than 7400 ha or 6% of mangrove vegetation in the affected area from Roper River estuary in the Northern Territory, east to Karumba in Queensland. At the time, there was an unusually lengthy period of severe drought conditions, unprecedented high temperatures and a temporary drop in sea level. Although consequential moisture stress appears to have contributed to the cause, this occurrence was further coincidental with heat-stressed coral bleaching. This article describes the effect and diagnostic features of this severe dieback event in the Gulf, and considers potential causal factors. [ABSTRACT FROM AUTHOR]

Context. Translocation is widely used to help avoid extinction of species from threatening processes. A fundamental objective of translocation is to establish self-sustaining populations; estimating demographic parameters is critical to assessing success of these programs and can also be used to support future management actions. Aims. We estimated demographic parameters to evaluate the success of translocating the northern quoll Dasyurus hallucatus to two islands (Astell and Pobassoo), in response to the threat posed by the introduced cane toad Rhinella marina on the Australian mainland. Methods. We used capture-mark-recapture methods to monitor both populations at regular intervals from initial release in 2003 until 2009 and a one-off survey in 2014. Key results. Relative abundance (trap success) increased exponentially in the first 4 years, declined, and then stabilised in subsequent years. The population of female northern quolls on Astell Island peaked in 2006 with an estimate of 3640 (95% CI 3022-4257), and on Pobassoo Island the peak was 2007 with 617 (95% CI 531-703) females. In 2014 the population had decreased to 2193 (95% CI 1920-2467) on Astell and 451 (95% CI 359-543) on Pobassoo. Apparent survival and body condition decreased significantly following the population peak, possibly related to density dependence. Conclusion. Both populations of northern quolls reached their regulation phase after going through establishment and growth phases, which included exceeding carrying capacity. The pattern was similar between the populations. Implications. Increased survival and recruitment at threat-free translocation sites contributes to successful establishment of self-sustaining populations. [ABSTRACT FROM AUTHOR]

The challenges of sampling rare fauna limit efforts to understand and mitigate the factors that restrict their distribution. Camera traps have become a standard technique for sampling large mammals, but their utility for sampling small, rare species remains largely unknown. The central rock-rat ( Zyzomys pedunculatus ) is critically endangered and restricted to rugged range country in central Australia. Using Z. pedunculatus as a focal species, we sought to evaluate the effectiveness of camera trapping for sampling small mammals in this environment and to better understand the factors driving the occurrence of this species. We installed baited camera traps at 50 sites across 1795 ha of core refuge habitat for Z. pedunculatus . We recorded all six species of small mammals known previously from this area, including the highly detectable Z. pedunculatus at five sites. Occupancy modelling showed that distance to the nearest occupied site was the most important predictor of Z. pedunculatus occurrence, suggesting that this rodent occurs in discrete sub-populations within the matrix of refuge habitat. Fire history and ruggedness may also influence occupancy of Z. pedunculatus at the landscape-scale and could assist in locating additional sub-populations. At the site-scale, occupancy of Z. pedunculatus was high and there was no clear influence of any site-scale variables. Management of Z. pedunculatus will require protection and expansion of known sub-populations. We conclude that camera trapping provided useful and cost-effective insight into the factors limiting rock-rat distribution, and predict that it will become a standard tool for sampling rare small mammals in difficult-to-access environments. [ABSTRACT FROM AUTHOR]

Patch-mosaic burning is a widely accepted practical approach to managing biodiversity, whereby spatial and temporal diversity of fire is manipulated to benefit biotic diversity. We use simulation experiments based on stochastic population viability analysis to evaluate the implications of contrasting patch-mosaic burning scenarios for the population dynamics and risk of decline of four species of small mammals in northern Australia. Our results, based on models developed from detailed mark-recapture data, suggest that fire frequency has more influence on small-mammal persistence than fire extent. Risk of extinction increased for all four species when fire frequency exceeded once every five years. Under current ambient fire regimes most Australia tropical savannas burn more frequently and therefore seem to have unfavourable consequences for this faunal group and risk precipitating severe future declines. [ABSTRACT FROM AUTHOR]

Fire is a natural disturbance that exerts an important influence on global ecosystems, affecting vegetation distribution and structure, the carbon cycle and climate. However, human-induced changes to fire regimes may affect at-risk species groups such as small mammals. We examine the effect of fire on small mammals and evaluate the relative sensitivity to fire among different groups using a systematic review methodology that included critiquing the literature with respect to survey design and statistical analysis. Overall, small mammal abundance is slightly higher, and demographic parameters more favourable, in unburnt sites compared to burnt sites. This was more pronounced in species with body size range of 101 -- 1000 g and with habitat requirements that are sensitive to fire (e.g. dense ground cover): in 66.6 and 69.7% of pairwise comparisons, abundance or a demographic parameter were higher in unburnt than burnt sites. This systematic review demonstrates that there remains a continued focus on simple shifts in abundance with regards to effectoffire and small mammals, which limits understanding of mechanisms responsible for change. Body size and habitat preference were most important in explaining variation in small mammal species' responses to fire. [ABSTRACT FROM AUTHOR]

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 constrained by the sparse information base across this region. Disconcertingly, the decline has similarities with the earlier phase of mammal extinctions that occurred elsewhere in Australia. We considered four proximate factors (individually or interactively) that might be driving the observed decline: habitat change, predation (by feral cats), poisoning (by invading cane toads), and novel disease. No single factor readily explains the current decline. The current rapid decline of mammals in Kakadu National Park and northern Australia suggests that the fate of biodiversity globally might be even bleaker than evident in recent reviews, and that the establishment of conservation reserves alone is insufficient to maintain biodiversity. This latter conclusion is not new; but the results reported here further stress the need to manage reserves far more intensively, purposefully, and effectively, and to audit regularly their biodiversity conservation performance. [ABSTRACT FROM AUTHOR]

A high diversity of rock-dwelling macropod species inhabit the tropics of the Northern Territory, Australia. Within this region, individual species have varied distributions, with ranges variously being widespread, restricted, or geographically disjunct with variable levels of sympatry between them. The cause of these patterns is unknown and little is known of the ecology of these rock-dwelling macropods. We hypothesized that differences in the habitat requirements is the key to understanding the biogeography and sympatry of the species. We examined this hypothesis at both regional and local scales. We analysed records of occurence of Petrogale brachyotis, P. concinna, Macropus bernardus and M. robustus and environmental correlates (such as geology type, vegetation type, distance to drainage and distance to ‘rugged’ terrain) throughout the monsoon tropics using geographic information systems and generalized linear modelling. We surveyed 80 sites across the tropics of the Northern Territory and collected presence-absence data using scats and environmental correlates to examine fine-scale habitat requirements. From the regional scale analysis, it was clear that distance to rugged terrain strongly influences presence of all four species. Responses to this variable suggest M. bernardus and P. concinna have greater requirements for rugged terrain, whereas M. robustus and P. brachyotis are found across a broader range of habitats. The local scale analysis suggested presence of M. robustus is primarily driven by vegetation type, M. bernardus by the cover of outcrops, boulders and large rocks, and P. brachyotis by the density of caves. Although these species overlap in their use of habitats, there are also differences in their habitat requirements that are likely to play a role in their niche separation and in some cases their biogeography. However, it is apparent that the distributions of the species have also been influenced by historical factors given the absence of these species from some apparently suitable sites. [ABSTRACT FROM AUTHOR]

Throughout the world, there are imperatives and opportunities to develop sustainable enterprises based on plants and animals to alleviate poverty. This is true for indigenous people across northern Australia, although to date there has been very limited commercial use of wildlife within indigenous Australian communities. In this study, we examine factors affecting the establishment of enterprises utilising animal species in remote indigenous communities and suggest ways of improving uptake. We found four major areas affecting the progress of these enterprises: a lack of comprehensive market information and dissemination of that knowledge; a lack of basic infrastructure and training; a need for more appropriate and flexible government policy and regulation; and adverse public perceptions. Commercialisation of native species is at a relatively early stage compared to tropical Asia, Africa and South America, and development of these enterprises has the potential to benefit indigenous livelihoods in remote and marginal areas in Australia. [ABSTRACT FROM AUTHOR]

Introduced into Australia in 1935, the cane toad (Chaunus [Bufo] marinus) threatens native vertebrate predators. However, there have been few rigorous quantitative studies on species threatened by this toxic invasive species. This study examines the changes in abundance and proportion of sites occupied by Merten's water monitor (Varanus mertensi) at a site in the Northern Territory following invasion by cane toads. The study was located at Manton Dam Recreation Area, 70 km south of Darwin, and ran for 18 months. Cane toads were first detected at the study site in February 2005, three months after the first survey, and their abundance remained low until February 2006, when an increase was observed. The abundance of V. mertensi declined substantially 8 months after the arrival of cane toads and remained low. The probability of detection of V. mertensi varied considerably within and among surveys, and was higher in the wet season surveys. The proportion of sites occupied by V. mertensi at the start of the study was 0.95 0.03. Site occupancy remained high for 6 months after the arrival of cane toads, but declined gradually to a low of 0.15 0.16 within 12 months. There has been demonstrable change in the abundance and proportion of sites occupied by V. mertensi following the colonisation of cane toads, but the population has been able to persist. Monitoring of populations impacted by cane toads may provide unique opportunities to understand processes underlying local extinction and colonisation of native predators following the impact of invasive species. [ABSTRACT FROM AUTHOR]

Aboriginal people in remote Australian communities have limited opportunity to participate in the market economy. The Aboriginal arts and craft industry offers an important option to generate cash income and the sustained supply of native plants used in production is vital. We assessed the current harvest of a rainforest tree species commonly used for sculpture, Bombax ceiba. Information from field surveys, a regional rainforest inventory and sales figures from the Maningrida region were used to estimate the population size and structure of B. ceiba, the harvest intensity of patches and the economic value of the harvest. We estimate the density of B. ceiba to be 105.10±12.32 stems ha−1 and a regional population of 76615±14063 stems. A cumulative harvest over 20 years of 6% suggests approximately 4596 stems harvested, and the harvest was worth about $200,000 over the last three years. The majority (80%) of harvested stems coppiced and were suitable for harvesting. Logistic regression suggests both distance to outstation and township influence harvesting intensity, with some localised over-harvest. Rainforests provide a valuable resource to Aboriginal artists in Maningrida and their maintenance provides important conservation benefits to the Australian community. [Copyright &y& Elsevier]

Abstract The impact of SO2 dry deposition from mining emissions on cricket abundance, diversity and composition was investigated at Mount Isa in the semiarid tropics of northern Australia. Seventy-one sites were sampled, stratified at two levels: sulphur deposition zones (high, medium, low, and background zones) and habitat (rocky ridge, rocky plain and alluvial plain). The three habitats did not support distinctly different cricket assemblages. Crickets responded to SO2 emissions, but impacts were largely restricted to the high-sulphur zone. Generalised linear modelling showed significant reductions in the probability of presence in the high-sulphur zone for the three genera Eurepella, Salmanites and Endacusta , and the subfamily Eneopterinae. In ordination space, the three high-sulphur zone by habitat combinations were clearly separated from all other combinations, and vector fitting of environmental variables showed soil SO4 to be a primary correlative factor of this separation. Crickets are sensitive to SO2 emissions and they appear to be a good indicator group in this context. [ABSTRACT FROM AUTHOR]

Abstract The impact of dry deposition of SO2 emissions on ant abundance, diversity and composition was investigated at Mount Isa in the semiarid tropics of northern Australia. Forty plots were sampled, stratified at two levels: sulfur deposition zones (high, medium, low, and two control zones) and habitat (Ridge and Plain). The two habitats supported distinctly different ant communities. Ants had clear responses to SO2 emissions. Ant abundance was lowest in the high and medium sulfur zones in both habitats. Species richness in high SO2 plots (up to 5 km from the source) was approximately half that of control plots in Ridge habitat, and was substantially less than controls in the Plain habitat. Ant community composition in the high sulfur zone was clearly separated from those of other zones in ordinations. Vector fitting showed soil SO4 concentration as a primary correlative factor in this separation. Ant abundance and richness were both negatively correlated with soil SO4 concentration, and positively correlated with plant species richness and distance away from the smelters. The abundance of 10 of the 21 most common species showed significant responses to emissions. Five species showed positive responses, and all belong to species-groups known to be abundant at disturbed sites throughout northern Australia. Relative abundance and richness of Eyrean (arid adapted) taxa collectively responded positively to sulfur, and Torresian (tropical) and Widespread species responded negatively. Despite large changes in species composition and abundances, there was relatively little change in the abundance of functional groups that have been widely used in studies of Australian ant communities. Ants are sensitive to SO2 emissions and appear to be good candidates as an indicator group in this context. However, an alternative functional group framework is required for the identification of recurrent responses of... [ABSTRACT FROM AUTHOR]

Aerial survey methods for census of wildlife populations are widely used to manage species. There has been considerable research to develop methods to cope with imperfect detection during aerial surveys, however misidentification remains an unresolved but significant issue. Using data from a comprehensive dugong aerial survey of the coastline of the Northern Territory, Australia, we assessed the influence of observer, sighting and environmental variables on probabilities of both observers in double-count, dual-observer teams detecting dugongs and dolphins ('duplicate sighting probability'), the confidence with which observers could distinguish between dugongs and dolphins, and the reliability of post-detection observations by comparing data between observers. Dolphin duplicate sighting probability varied dependent on group size, Beaufort sea state and the lateral position inside the strip-width transect in relation to the aircraft. Dugong duplicate sighting probability varied across dual-observer teams. Counts of individuals in dugong and dolphin groups were unreliable past ≈5 individuals. Observer confidence in taxon identification varied by individual observer and throughout the duration of the survey (dolphin sightings) and potentially by the lateral position inside the transect strip-width in relation to the aircraft (dugong sightings). The probability of taxon identification disagreement between observers for duplicate dugong and dolphin sightings varied with group size, and markedly if one observer was uncertain (i.e. not 100% confident) of their assigned taxon. We believe this is predominately due to the presence of Australian snubfin dolphins (Orcaella heinsohni) in the survey area, which look like dugongs when seen from a distance, momentarily. We further show that application of different data filtering scenarios for uncertain taxonomic identifications and taxon identification disagreements between dual observers produces highly variable estimates of observer-specific dugong detection probability (ranging from 0.26 to 0.80 in a single observer) and dugong abundance (x̅ ± S.D., 40% ± 25%: difference between highest and lowest estimate, relative to the lowest estimate, across different data filtering scenarios). These results are particularly relevant not only to researchers conducting dugong aerial surveys, but also for other marine mammal aerial surveys in passing mode that target sympatric, morphologically similar species. We recommend development of operating procedures and analytical methods to quantify and adjust for misidentification and uncertain taxon identifications. • Accurate species identification (ID) and counts are essential for aerial surveys. • Species detection and accurate ID varies between observers and with other variables. • Detection & Abundance estimates vary depending on how ambiguous data are filtered. • Surveys of sympatric, morphologically similar species may be similarly affected. [ABSTRACT FROM AUTHOR]