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 of a top predator, the dingo (Canis familiaris dingo), limits feral cat populations. We modelled feral cat and dingo site occurrence, to provide the first broad‐scale assessment of their distributional patterns and co‐occurrence within monsoonal Australia.
Location
About 370,000 km2 of monsoonal area in the Northern Territory.
Methods
We surveyed 376 sites using camera traps. We used single‐ and two‐species occupancy models to investigate feral cat and dingo site occurrence and the influence of dingoes on feral cat occupancy. We included predictor variables that relate to hypotheses of predator occurrence, including both environmental and disturbance‐related variables.
Results
Feral cat occurrence and dingo occurrence were best predicted by indices of habitat structural complexity; feral cat occurrence declined with increasing productivity, except in areas of relatively high fire activity (fire frequency and extent), and dingo occurrence declined with terrain ruggedness. We found no evidence that dingoes are spatially limiting feral cat occurrence.
Main conclusions
Our findings suggest the protection and enhancement of habitat structural complexity at both the local and landscape scale could enable conservation managers to reduce the exposure of small‐ and medium‐sized mammals to feral cats and dingoes. This can most likely be achieved through improved fire and feral herbivore management, which is a more feasible management option than lethal predator control.
Striking faunal turnover across Asia and Australasia, most famously along the eastern edge of the Sunda Shelf or ‘Wallace's Line’, has been a focus of biogeographic research for over 150 years. Here, ...we investigate the origins of a highly threatened endemic lizard fauna (four species) on Christmas Island. Despite occurring less 350 km south of the Sunda Shelf, this fauna mostly comprises species from clades centred on the more distant regions of Wallacea, the Pacific and Australia (more than 1000 km east). The three most divergent lineages show Miocene (approx. 23–5 Ma) divergences from sampled relatives; and have recently become extinct or extinct in the wild, likely owing to the recent introduction of a southeast Asian snake (Lycodon capucinus). Insular distributions, deep phylogenetic divergence and recent decline suggest that rather than dispersal ability or recent origins, environmental and biotic barriers have impeded these lineages from diversifying on the continental Sunda Shelf, and thereby, reinforced faunal differentiation across Wallace's Line. Our new phylogenetically informed perspective further highlights the rapid loss of ancient lineages that has occurred on Christmas Island, and underlines how the evolutionary divergence and vulnerability of many island-associated lineages may continue to be underestimated.
Monitoring is critical to assess management effectiveness, but broadscale systematic assessments of monitoring to evaluate and improve recovery efforts are lacking. We compiled 1808 time series from ...71 threatened and near‐threatened terrestrial and volant mammal species and subspecies in Australia (48% of all threatened mammal taxa) to compare relative trends of populations subject to different management strategies. We adapted the Living Planet Index to develop the Threatened Species Index for Australian Mammals and track aggregate trends for all sampled threatened mammal populations and for small (<35 g), medium (35–5500 g), and large mammals (>5500 g) from 2000 to 2017. Unmanaged populations (42 taxa) declined by 63% on average; unmanaged small mammals exhibited the greatest declines (96%). Populations of 17 taxa in havens (islands and fenced areas that excluded or eliminated introduced red foxes Vulpes vulpes and domestic cats Felis catus) increased by 680%. Outside havens, populations undergoing sustained predator baiting initially declined by 75% but subsequently increased to 47% of their abundance in 2000. At sites where predators were not excluded or baited but other actions (e.g., fire management, introduced herbivore control) occurred, populations of small and medium mammals declined faster, but large mammals declined more slowly, than unmanaged populations. Only 13% of taxa had data for both unmanaged and managed populations; index comparisons for this subset showed that taxa with populations increasing inside havens declined outside havens but taxa with populations subject to predator baiting outside havens declined more slowly than populations with no management and then increased, whereas unmanaged populations continued to decline. More comprehensive and improved monitoring (particularly encompassing poorly represented management actions and taxonomic groups like bats and small mammals) is required to understand whether and where management has worked. Improved implementation of management for threats other than predation is critical to recover Australia's threatened mammals.
Efectos de diferentes estrategias de manejo sobre las tendencias a largo plazo de los mamíferos amenazados y casi amenazados de Australia
Resumen
El monitoreo es fundamental para evaluar la efectividad del manejo, aunque faltan evaluaciones sistemáticas y a gran escala de este monitoreo para evaluar y mejorar los esfuerzos de recuperación. Compilamos 1,808 series temporales de 71 especies y subespecies de mamíferos terrestres y voladores amenazadas y casi amenazadas en Australia (48% de todos los taxones de mamíferos amenazados) para comparar las tendencias relativas de las poblaciones sujetas a diferentes estrategias de manejo. Adaptamos el Índice Planeta Vivo para desarrollar el Índice de Especies Amenazadas para los Mamíferos Australianos y así rastrear las tendencias agregadas de todas las poblaciones muestreadas de mamíferos amenazados y de los mamíferos pequeños (<35 g), medianos (35–5,500 g) y grandes (>5,500 g) entre 2000 y 2017. Las poblaciones sin manejo (42 taxones) declinaron en un 63% en promedio; los mamíferos pequeños sin manejo exhibieron las declinaciones más marcadas (96%). Las poblaciones de 17 taxones incrementaron 680% en los refugios (islas o áreas encercadas que excluían o eliminaban al zorro rojo Vulpes vulpes y al gato doméstico Felis catus, especies introducidas) Afuera de los refugios, las poblaciones sometidas al cebado constante de los depredadores en un inicio declinaron en un 75% pero después incrementaron al 47% de su abundancia para el 2000. En los sitios en donde los depredadores no fueron excluidos o cebados sino sometidos a otras acciones (manejo del fuego, control de herbívoros introducidos), las poblaciones de los mamíferos pequeños y medianos declinaron más rápido, pero los mamíferos grandes declinaron de manera más lenta que las poblaciones sin manejo. Sólo el 13% de los taxones contaron con datos para sus poblaciones con y sin manejo; las comparaciones entre índices para este subconjunto mostraron que los taxones con poblaciones en incremento dentro de los refugios declinaron afuera de éstos, pero los taxones con poblaciones sujetas al cebado de depredadores afuera de los refugios declinaron más lentamente que las poblaciones sin manejo y después incrementaron, mientras que las poblaciones sin manejo continuaron su declinación. Se requiere un monitoreo más completo y mejorado (particularmente el que engloba las acciones de manejo mal representadas y los grupos taxonómicos como los murciélagos y los mamíferos pequeños) para entender si ha funcionado el manejo y en dónde. La implementación mejorada del manejo para las amenazas distintas a la depredación es fundamental para recuperar a los mamíferos amenazados de Australia.
【摘要】
监测对于评估保护管理有效性至关重要, 但目前仍缺乏对监测的大尺度系统评估, 以评价和提高恢复工作。本研究整理了澳大利亚71种受威胁或近危的陆生及飞行野生哺乳动物物种和亚种(占所有受威胁哺乳动物的48%)的1808个时间序列, 以比较受到不同管理策略影响的种群的相对趋势。我们基于“地球生命力指数(Living Planet Index)”开发了“澳大利亚哺乳动物受威胁物种指数”, 并追踪了2000‐2017年所有采样的受威胁哺乳动物种群以及小型(<35克)、中型(35‐5500克)和大型哺乳动物(>5500克)的总体趋势。结果表明, 未受到管理的种群(42个类群)数量平均减少了63%;未受到管理的小型哺乳动物种群数量下降幅度最大(96%)。17个在避难所(驱除或消灭了外来赤狐Vulpes vulpe及家猫Felis catus的岛屿和围栏区)中生活的类群种群数量增加了680%。在避难所外, 受到持续捕食者诱捕管理的种群最初数量下降了75%, 但随后增加到2000年种群数量的47%。在没有驱除或诱捕捕食者, 但采取了其它行动(如火灾管理、引入食草动物控制)的位点, 小型和中型哺乳动物种群比没有受到管理的种群下降得更快, 但大型哺乳动物相比下降得更慢。只有13%的类群同时有未受到管理种群和受到管理种群的数据, 这部分数据的指数比较显示, 在避难所内种群增加的类群在避难所外种群有所下降, 但在避难所外受到捕食者诱捕的种群比没有管理的种群下降更慢且随后种群数量增加, 而未受到管理的种群则持续下降。未来还需要更全面和更好的监测工作(特别是纳入没有得到充分代表的管理行动及类群, 如蝙蝠和小型哺乳动物), 以了解管理的有效性以及有效的区域。进一步落实对捕食以外威胁的管理措施, 对于澳大利亚受威胁哺乳动物恢复至关重要。【翻译:胡怡思;审校:聂永刚】
Predation by feral cats (Felis catus) has caused the extinction of many native species in Australia and globally. There is growing evidence that the impacts of feral cats can be amplified in ...post‐fire environments, as cats are drawn to hunt in or around recently burnt areas and are also more effective hunters in open habitats. In 2018–2019, we established arrays of camera traps to estimate the abundance of feral cats on Kangaroo Island, South Australia. Much of the island (including five of our seven survey sites) was subsequently burnt in a severe wildfire (December 2019–February 2020). We re‐sampled the sites 3–8 months post‐fire (seven sites) and 11–12 months post‐fire (three sites). At two unburnt sites sampled post‐fire, it was possible to produce density estimates of cats using a spatially explicit capture–recapture approach. Where estimating density was not possible (due to low detections or individual cats not being distinguishable), the number of individuals and percentage of trap nights with detections was compared between the sampling periods. Some low‐level cat control occurred within 2 km of three of the seven arrays (all within the burn scar) within 3 months of the fire. Across the five burnt sites, there was a decline in cat detections post‐fire (including those without post‐fire cat control). At 3–8 months post‐fire, there was, on average, a 57% reduction in the number of individual cats, and a 65% reduction in the number of nights with cat detections, relative to pre‐fire levels. Although cat detections declined following the fire, reduced population sizes of prey species and reduced cover as a result of the fire might still mean that cat predation is a threat to some surviving prey species. Management that reduces feral cat predation pressure on wildlife following wildfire should enhance the likelihood of post‐fire wildlife persistence and recovery.
We examined the impact of a large, high‐severity fire on the abundance and detection of the feral cat on a temperate southern Australian island. The abundance and activity of the cat declined markedly following fire. Despite post‐fire reductions in feral cat populations, the species is likely to pose a considerable threat to the survival of native species.
The 2019–2020 Australian Black Summer wildfires demonstrated that single events can have widespread and catastrophic impacts on biodiversity, causing a sudden and marked reduction in population size ...for many species. In such circumstances, there is a need for conservation managers to respond rapidly to implement priority remedial management actions for the most‐affected species to help prevent extinctions. To date, priority responses have been biased towards high‐profile taxa with substantial information bases. Here, we demonstrate that sufficient data are available to model the extinction risk for many less well‐known species, which could inform much broader and more effective ecological disaster responses. Using publicly available collection and GIS datasets, combined with life‐history data, we modelled the extinction risk from the 2019–2020 catastrophic Australian wildfires for 553 Australian native bee species (33% of all described Australian bee taxa). We suggest that two species are now eligible for listing as Endangered and nine are eligible for listing as Vulnerable under IUCN criteria, on the basis of fire overlap, intensity, frequency, and life‐history traits: this tally far exceeds the three Australian bee species listed as threatened prior to the wildfire. We demonstrate how to undertake a wide‐scale assessment of wildfire impact on a poorly understood group to help to focus surveys and recovery efforts. We also provide the methods and the script required to make similar assessments for other taxa or in other regions.
The novel methods, outcomes, and implications are from analyses of the Black Summer wildfires on Australia's native bees. IUCN and EPBC categories are (L) Least Concern, (V) Vulnerable, (E) Endangered, and (CE) Critically Endangered. Silhouettes were either sourced from www.phylopic.org or created by the authors.
An emerging research program on population and geographic range dynamics of Australia's mammals illustrates an approach to better understand and respond to geographic range collapses of threatened ...wildlife in general. In 1788, Europeans colonized an Australia with a diverse and largely endemic mammal fauna, where many species that are now extinct or threatened were common and widespread. Subsequent population declines, range collapses and extinctions were caused by introduced predators and herbivores, altered land use, modified fire regimes and the synergies between these threats. Declines in population and range size continue for many Australian mammals despite legislative protection and conservation interventions. Here, we propose an approach that integrates museum data and other historical records into process‐explicit macroecological models to better resolve mammal distributions and abundances as they were at European arrival. We then illustrate how this integrative approach can identify the likely synergistic mechanisms causing mammal population declines across these and other landscapes. This emerging research approach, undertaken with fine temporal and spatial resolution, but at large geographic scales, will provide valuable insights into the different pathways to, and drivers of, extinction. Such insights may, in turn, underpin conservation strategies based on a process‐explicit understanding of population decline and range collapse under alternative scenarios of impending climate and environmental change. Given that similar information is available for other regional biotas, the approach we describe here can be adapted to conserve threatened wildlife in other regions across the globe.
For successful conservation of biodiversity, it is vital to know whether protected areas in increasingly fragmented landscapes effectively safeguard species. However, how large habitat fragments must ...be, and what level of protection is required to sustain species, remains poorly known. We compiled a global dataset on almost 2000 bird species in 741 forest fragments varying in size and protection status, and show that protection is associated with higher bird occurrence, especially for threatened species. Protection becomes increasingly effective with increasing size of forest fragments. For forest fragments >50 ha our results show that strict protection (International Union for Conservation of Nature IUCN categories I–IV) is strongly associated with higher bird occurrence, whereas fragments had to be at least 175 ha for moderate protection (IUCN categories V and VI) to have a positive effect. This meta‐analysis quantifies the importance of fragment size, protection status, and their interaction for the conservation of bird species communities, and stresses that protection should not be limited to large pristine areas.
Contemporary fire patterns are considered the most likely cause for regional population decline amongst small to medium mammals in northern tropical Australia. Here we assess the extinction risk ...faced by a vulnerable north Australian native rodent, the Brush-tailed Rabbit-rat
Conilurus penicillatus in relation to fire frequency. This species has recently suffered a significant contraction in range. We provide the first quantitative evidence to demonstrate the immediate threat destructive wildfires and regular annual fire pose to the long-term population persistence of
C. penicillatus. We show that late-dry season fires cause a reduction in both juvenile and adult survival probabilities. However, abundance declined at the unburnt as well as a frequently burnt site, suggesting that fire exclusion alone does not guarantee the species’ long-term persistence. Our model projections indicate that the remaining populations of
C. penicillatus on the Northern Territory mainland risk extirpation within the next ten years. Conservation requires decisive management action to ameliorate extensive and destructive fires. A multi-faceted management plan needs to focus on restoring a fire management regime which generates a fine-scale mosaic of burnt and unburnt habitat, and the release of captive bred animals into fenced reserves free of exotic predators.
Mammals comprise the bulk of the diet of free‐ranging domestic cats Felis catus (defined as including outdoor pet cats, strays, and feral cats) in most parts of their global range. In Australia, ...predation by introduced feral cats has been implicated in the extinction of many mammal species, and in the ongoing decline of many extant species.
Here, we collate a wide range of records of predation by cats (including feral and pet cats) on Australian mammals and model traits of extant, terrestrial, native mammal species associated with the relative likelihood of cat predation. We explicitly seek to overcome biases in such a continental‐scale compilation by excluding possible carrion records for larger species and accounting for differences in the distribution and abundance of potential prey species, as well as study effort, throughout each species’ range.
For non‐volant species, the relative likelihood of predation by cats was greatest for species in an intermediate weight range (peaking at ca. 400 g), in lower rainfall areas and not dwelling in rocky habitats. Previous studies have shown the greatest rates of decline and extinction in Australian mammals to be associated with these traits. As such, we provide the first continental‐scale link between mammal decline and cat predation through quantitative analysis.
Our compilation of cat predation records for most extant, terrestrial, native mammal species (151 species, or 52% of the Australian species’ complement) is substantially greater than previously reported (88 species) and includes 50 species listed as threatened by the IUCN or under Australian legislation (57% of Australia's 87 threatened terrestrial mammal species). We identify the Australian mammal species most likely to be threatened by predation by cats (mulgaras Dasycercus spp., kowari Dasyuroides byrnei, many smaller dasyurids and medium‐sized to large rodents, among others) and hence most likely to benefit from enhanced mitigation of cat impacts, such as translocations to predator‐free islands, the establishment of predator‐proof fenced exclosures, and broad‐scale cat poison baiting.
Aim
Species range contractions are increasingly common globally. The niche reduction hypothesis posits that geographic range contractions are often patterned across space owing to heterogeneity in ...threat impacts and tolerance. We applied the niche reduction hypothesis to the decline of a threatened marsupial predator across northern Australia, the northern quoll (Dasyurus hallucatus).
Location
Northern Australia.
Methods
We assembled a database containing 3,178 historic and contemporary records for northern quolls across the extent of their distribution dating between 1778 and 2019. Based on these records, we estimated changes in the geographic range of the northern quoll using α‐hulls across four main populations. We then examined how range contractions related to factors likely to mediate the exposure, susceptibility, or tolerance of northern quolls to threats.
Result
The extent of range contractions showed an east–west gradient, most likely reflecting the timing of spread of introduced cane toads (Rhinella marina). There were clear changes in environmental characteristics within the contemporary compared to the historic geographic range, with the most substantial occurring in populations that have suffered the greatest range contractions. The contemporary range is comprised of higher quality habitats (measured using environmental niche models), characterized by higher topographical ruggedness and annual rainfall, and reduced distance to water, compared to the historic range.
Main conclusions
Changes to range and niche likely reflect the capacity of complex habitats to ameliorate threats (namely predation and altered fire regimes), and access to resources that increase threat tolerance. This study highlights the multivariate nature of ecological refuges and the importance of high‐quality habitats for the persistence of species exposed to multiple threats. Our methods provide a useful framework which can be applied across taxa in providing valuable insight to management.
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