Stemming the tide: progress towards resolving the causes of decline and implementing management responses for the disappearing mammal fauna of northern Australia

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 groups of mammals in northern Australia have some species for which their conservation status has been assessed as threatened, with 53 % of dasyurid, 47 % of macropod and potoroid, 33 % of bandicoot and bilby, 33 % of possum, 30 % of rodent, and 24 % of bat species being assessed as extinct, threatened or near threatened. However, the geographical extent and timing of declines, and their causes, remain poorly resolved, limiting the application of remedial management actions.\ud \ud Material and methods: Focusing on the tropical savannas of northern Australia, this paper reviews disparate recent and ongoing studies that provide information on population trends across a broader geographic scope than the previously reported sites, and examines the conservation status and trends for mammal groups (bats, macropods) not well sampled in previous monitoring studies. It describes some diverse approaches of studies seeking to document conservation status and trends, and of the factors that may be contributing to observed patterns of decline.\ud \ud Results and Discussion: Current trends and potential causal factors for declines. The studies reported demonstrate that the extent and timing of impacts and threats have been variable across the region, although there is a general gradational pattern of earlier and more severe decline from inland lower rainfall areas to higher rainfall coastal regions. Some small isolated areas appear to have retained their mammal species, as have many islands which remain critical refuges. There is now some compelling evidence that predation by feral cats is implicated in the observed decline, with those impacts likely to be exacerbated by prevailing fire regimes (frequent, extensive and intense fire), by reduction in ground vegetation cover due to livestock and, in some areas, by 'control' of dingoes. However the impacts of dingoes may be complex, and are not yet well resolved in this area. The relative impacts of these individual factors vary spatially (with most severe impacts in higher rainfall and more rugged areas) and between different mammal species, with some species responding idiosyncratically: the most notable example is the rapid decline of the northern quoll (Dasyurus hallucatus) due to poisoning by the introduced cane toad (Rhinella marina), which continues to spread extensively across northern Australia. The impact of disease, if any, remains unresolved.\ud \ud Conservation Management Responses. Recovery of the native mammal fauna may be impossible in some areas. However, there are now examples of rapid recovery following threat management. Priority conservation actions include: enhanced biosecurity for important islands, establishment of a network of feral predator exclosures, intensive fire management (aimed at increasing the extent of longer-unburnt habitat and in delivering fine scale patch burning), reduction in feral stock in conservation reserves, and acquisition for conservation purposes of some pastoral lands in areas that are significant for mammal conservation

Understanding evolutionary processes during past Quaternary climatic cycles: Can it be applied to the future?

Climate change affected ecological community make-up during the Quaternary which was probably both the cause of, and was caused by, evolutionary processes such as species evolution, adaptation and extinction of species and populations

How does naiveté affect co-existence between native and alien species?

Native populations that have been isolated from alien species for an extended period often have ineffective strategies for combatting alien threats due to a lack of evolutionary or lifetime experience. This “naiveté” can exacerbate the negative impacts of alien species when exposure does occur, as the native population struggles to recognise and respond appropriately to the novel threat. I hypothesised that live exposure to alien threats would either allow retention of pre-existing anti-alien strategies or would exert selective pressure on naïve species by removing the least fit individuals from the exposed population and “fast-tracking” evolution such that the skills, behaviours, and traits required to co-exist in the wild with alien species would be naturally selected for or learned. To test my hypothesis, I examined a population of freshwater crocodiles (Crocodylus johnstoni) co-occurring in the wild with invasive toxic cane toads (Rhinella marina), but I unexpectedly found that twelve years of cane toad exposure had not resulted in crocodile molecular or behavioural adaptations to avoid lethal interactions with cane toads along the pathways that we examined (Chapter 2). I also assessed a fenced population of greater bilbies (Macrotis lagotis) and conversely found that two years of controlled live exposure to alien feral cats (Felis catus) improved the survival and anti-predator behaviours of predator-exposed bilbies (Chapter 3). I then evaluated the conservation outcomes of an applied headstarting facility which exposed bridled nailtail wallabies (Onychogalea fraenata) to alien predators only during the adult life stage. This partial lifetime exposure facilitated population growth and juvenile retention (Chapter 4) without impacting long-term survival or anti-predator behaviour (Chapters 5 and 6) of headstarted wallabies. Overall, I discovered that live exposure to alien species can improve the survival and anti-alien characteristics of naïve native species, but that the “wildness” of the exposure may impact the success of the anti-alien strategy. Unmanaged live exposure in the wild can exert selection pressure on native populations but may not improve anti-alien characteristics (Chapter 2). However, controlled levels of alien pressure (Chapter 3) or partial lifetime exposure to alien species (Chapters 4 and 6) can instil—or facilitate retention of—aversive characteristics to allow the co-existence of native species with alien species

Fieldwork/fieldwalking: Art, sauntering and science in the walking country

fieldwork/fieldwalking is a contemporary art project exploring practices of walking and science in the field. 11 explores the themes of walking and-fieldwork in art, and as art. Whilst the. sociology of science in the laboratory has been well theorised, less has been said about the field in the natural sciences. And, equally, the most recent and provocative walking art is found in urban areas, in a fabric dominated by the patterns of human settlement. How could new walking art be made in non-urban places? The project set out to investigate how these two, fieldwork and walking, could be combined in artwork. The research question was: in the common ground shared between art and science, what are the connections between fieldwork and walking in the field? The project explored this and five sub-questions through photography, video, and the creation of installations and sound art walks. Much of the research revolved around one field location, the walkingcountry in the Kimberley of Western Australia that was visited six times over different seasons from 2004 to 2006. Activities included walking and general immersion in the place, scientific and artistic \u27fieldwork\u27 and the observation and documentation of the work of scientists at the site and in the Kimberley. Non-urban areas can offer intense and specific experiences with heightened materiality and direct engagement with nonhuman agents. This was borne out in the fieldwork undertaken in the project. However the artworks created are also set in contrast to the work of other walking artists such as Hamish Fulton and Richard Long that are often based on sublime wilderness experiences. Based on my experiences I formulated and applied the concept of \u27ordinary wilderness\u27: much of one\u27s time in the field is involved in pragmatic and bodily encounters. Some of the aesthetic experiences are local and ephemeral. Wildness and the delight of wonder are more appropriate than the fear and awe of the sublime. fieldwork/fieldwalking draws together threads from sources as diverse as recent scientific ecology, Ric Spencer\u27s (2004) conversational aesthetics and nonrepresentational theory in human geography to make art that questioned representational strategies and explored an expanded model of artworks where the relationships between the artist, the audience, the environment and the material art object are of equal importance. A significant issue was how to creatively transform the experience of elsewhere (the field) into artworks in a gallery. In the sound art walk To Meander and back (strange strolls, Moores Building Contemporary Art Gallery (MBCAG), 2005} the strategy was to fold and imbricate the walkingcountry, the gallery in Fremantle, and the space in-between together. This artwork also sought to reconcile the \u27emptiness\u27 of Euro-Australian belonging by encouraging via sound and silence an understanding of place that is more living, changing and performative. Other artworks included Zoo for the Species at the National Review of Life Art (Midland, 2003) , and works in the solo exhibitions Four Tales from Natural History (Perth Institute of Contemporary Art, 2004), Semi (Spectrum Project Space/Kurb Gallery, 2004} and fieldwork/fieldwalking (MBCAG, 2006)

Linking Husbandry and Behavior to Enhance Amphibian Reintroduction Success

Wildlife in captivity has a long history of benefiting global conservation goals. Captive animals can raise awareness and appreciation for the conservation of endangered species. Additionally, captive animals can be used as source populations to reintroduce animals back to the wild or to supplement existing wild populations. The rapid increase in amphibian species threatened with imminent extinction has necessitated the creation of dozens of captive-breeding programs. The focus of this dissertation has integrated topics across the spectrum of animals in captivity and the wild, and the results provide useful recommendations for conservation action. First, I describe how market pressures over a 28-year period are causing meteoric increases in the prices of amphibians sold in the pet trade, indicating a high risk of overexploitation. Pet amphibians may facilitate greater understanding and appreciation of amphibians, but the pet trade must be sustainable. Improving amphibian husbandry will increase the number of captive-bred animals available in the pet trade, and it will allow greater production of threatened species for reintroductions. Secondly, by performing a systematic review of husbandry for 289 amphibian species native to the US, I identified a critical lack in taxon-specific husbandry and developed husbandry research prioritizations. Next, I used a combination of laboratory and field studies to examine domestication processes in amphibians by comparing defensive behaviors in two species of captive-bred and wild poison frog. Captive-bred amphibians had significantly reduced defensive behaviors compared to wild conspecifics, likely resulting from habitation processes related to their husbandry. Finally, I performed three reintroductions of the critically endangered Wyoming Toad (Anaxyrus baxteri) in Wyoming, US. I demonstrated how providing a transitionary period, called a soft-release, to captive-bred toads moving to a novel, wild environment can improve reintroduction success. My work illustrates how improving our understanding of the nexus between captivity and the wild can improve conservation action for endangered species

Global economic costs of herpetofauna invasions

Biological invasions by amphibian and reptile species (i.e. herpetofauna) are numerous and widespread, having caused severe impacts on ecosystems, the economy and human health. However, there remains no synthesised assessment of the economic costs of these invasions. Therefore, using the most comprehensive database on the economic costs of invasive alien species worldwide (InvaCost), we analyse the costs caused by invasive alien herpetofauna according to taxonomic, geographic, sectoral and temporal dimensions, as well as the types of these costs. The cost of invasive herpetofauna totaled at 17.0 billion US$between 1986 and 2020, divided split into 6.3 billion US$ for amphibians, 10.4 billion US$for reptiles and 334 million US$ for mixed classes. However, these costs were associated predominantly with only two species (brown tree snake Boiga irregularis and American bullfrog Lithobates catesbeianus), with 10.3 and 6.0 billion US$ in costs, respectively. Costs for the remaining 19 reported species were relatively minor ( 99%), while for reptiles, impacts were reported mostly through damages to mixed sectors (65%). Geographically, Oceania and Pacific Islands recorded 63% of total costs, followed by Europe (35%) and North America (2%). Cost reports have generally increased over time but peaked between 2011 and 2015 for amphibians and 2006 to 2010 for reptiles. A greater effort in studying the costs of invasive herpetofauna is necessary for a more complete understanding of invasion impacts of these species. We emphasise the need for greater control and prevention policies concerning the spread of current and future invasive herpetofauna.info:eu-repo/semantics/publishedVersio

The genetic basis of behaviour during invasion

This study identified genes associated with range expansion and patterns of brain gene expression in cane toads across their invasive Australian range. Differences in gene expression were identified between toads from the core area and invasion front and between toads from the wild and toads kept under captive conditions

Phenotypic evolution in the invasive cane toad (Rhinella marina): adaptations for dispersal

Phenotypic evolution in the invasive cane toad (Rhinella marina): adaptations for dispersal Abstract Invasive species provide a rare opportunity to study how organisms adapt when colonising novel environments. Despite the negative ecological impacts caused by the introduction of alien species, biological invasions act as natural experiments that we can exploit for ecological and evolutionary research. This is particularly true for introductions with precise geographic and historical records, such as the cane toad (Rhinella marina) introduction to Australia. Arguably the most successful invasive anuran worldwide, the cane toad was first introduced to the Hawai’ian Islands in 1932, and subsequently to northeastern Queensland in 1935. Over the past 82 years, R. marina has spread rapidly and at an accelerating pace throughout northern and eastern Australia, causing massive ecological disturbances in its wake. This acceleration of dispersal capability is a well-documented phenomenon in invasive organisms that can occur via a combination of natural selection, and spatial sorting. Although the increasing rate of cane toad dispersal has been extensively researched, my thesis aims to address questions about the evolutionary changes that have taken place throughout the process. Namely, what morphological, behavioural, or physiological shifts in cane toad phenotypes are associated with increased dispersal ability? I began by taking gross morphological measurements from toads across a transect through their northern Australian range that included long-colonised and invasion-front populations. Additional populations from a prior invasion (Hawai’i), and the native range (French Guiana) were later added to compare the morphology of individuals from the source populations. I focused on the components of each limb (hand, radioulna, humerus [forelimb]; femur, tibiofibula, foot [hindlimb]), as limb morphology is strongly linked to locomotor ability, but also collected data on mass, snout-vent length, head width, and parotoid gland shape. A subset of Australian individuals were collected from the edges of the range, representing the oldest and newest toad populations to be used in a common-garden breeding experiment. These individuals, and their resulting offspring were held in captivity and subjected to a series of performance trials. A separate group of individuals from invasion-front and range-core populations was used for Computerised X-ray Tomography (CT) scanning for precise geometric morphometric comparison of skeletal structure. Captive breeding of cane toads from the invasion-front (in Western Australia) and long-colonised areas (in Queensland) allowed me to control for the influence of rearing environment on common-garden F1 individuals. This also enabled analyses on heritability of morphology and performance traits by comparing offspring to their parents, and siblings to each other. Common-garden F1 offspring were raised over a period of 27 months, and measured repeatedly throughout ontogeny. Performance trials consisted of climbing trials (where toads would have to escape from a mesh tube by climbing vertically) and anti-predator raceway trials (where toads were encouraged to hop down a raceway by prodding). These trials were conducted on wild and captive toads. Within this thesis I document reproductive differences between invasion-front and long-colonised populations, significant geographic variation in locomotor performance, regional changes to skeletal structure, shifts in sexual dimorphism with time since colonisation, and heritability of behavioural and morphological traits; and I demonstrate that these changes have arisen via the rapid evolution of a high-dispersal phenotype during the invasion process