Source: Photograph courtesy of Nick Mooney
Source: Photograph courtesy of Nick Mooney
This SoE Issue Report focuses on the known changes to the population and abundance of Tasmania's fauna and the threatening processes that affect them. A number of other Issue Reports provide information on the environmental changes that have affected Tasmania's fauna over the past 5 years, including: Internal linkHabitat Change, Internal linkAnimal Pests and Native Animal Diseases, Internal linkClimate Change and Natural Values and Internal linkNative Vegetation. In the Water Chapter, relevant issue reports include Internal linkWater Quantity and Use and Internal linkWetlands. Tasmania's Threatened Fauna Handbook provides a detailed review of threatened species and their habitats (Internal linkDPIW 1999), although it is now in need of an update in the light of new and emerging threats. On-line resources include Tasmania's Wildlife (Internal linkDPIW 2008) and Mammals of Tasmania (Internal linkPWS 2008).
There are indications of increasing pressures and threats affecting the State's unique fauna including the impacts of pests and diseases, ongoing habitat change and the effects of climate change on specific habitats such as wetlands, rivers and dry eucalypt forest. The condition of Tasmania's fauna provides important information about how particular species are faring but also gives insights into the state of the habitats and environments that these species rely upon. The following section provides an overview for each of the key animal types.
Tasmanian devilinternal SOE link to larger image
Many species of native mammals are in a precarious state in Australia generally. Twenty-two species of mammals are extinct in Australia; a further eight species are found only on islands (Internal linkCork et al. 2006). Tasmania continues to provide a key refuge for a number of native mammal species. However, there are concerns over Tasmania's capacity to continue to provide this role due to a number of interrelated and emerging pressures.
Tasmania retains the most ecologically diverse group of large marsupial carnivores in Australia—the eastern quoll (Dasyurus viverrinus), the spotted-tail quoll (Dasyurus maculatus) and, despite its parlous state, the Tasmanian devil (Sarcophilus harrisii). Several species that are extinct, or nearly so, on mainland Australia maintain viable populations in Tasmania, including the eastern barred bandicoot (Perameles gunnii), Tasmanian bettong and the Tasmanian pademelon (Thylogale billardierii). The following table details mammal species listed under the External link: LegislationThreatened Species Protection Act 1995.
Mammals listed under the Threatened Species Protection Act 1995 and example habitat
Mammals listed under the Threatened Species Protection Act 1995 and example habitat
Biodiversity is often considered at three levels: genetic diversity, species diversity and ecosystem diversity. Genetic diversity refers to the variation in genes within a species. A qualitative assessment of forest-associated species potentially at risk from isolation and the loss of genetic variation as a result of past human-induced events or natural events has been completed (Internal linkState of Tasmania 2007). A total of 270 vertebrate species and vascular plants were assessed as being potentially at risk ranging from moderate to high (104 species) to low (116 species) and unknown (50 species). As shown in the following table, five species of forest-dwelling mammal species have been assessed in terms of their risk from loss of genetic diversity or isolation (Internal linkState of Tasmania 2007).
Assessment of the risk to Tasmanian (forest dwelling) threatened mammals from loss of genetic diversity or isolation
Assessment of the risk to Tasmanian (forest dwelling) threatened mammals from loss of genetic diversity or isolation
The Devil Facial Tumour Disease (DFTD) promoted research into the genetic diversity of the Tasmanian devil. It found that devils in eastern Tasmania in particular, do not mount an immune response to DFTD due to a loss of genetic diversity in the most important immune region of the genome (Internal linkTasmanian Government and University of Tasmania 2009).
The introduction of the European red fox (Vulpes vulpes) is a major threat to Tasmania's native mammals and other native wildlife. The ability of the fox to form a viable breeding population in the State will continue to have serious implications for Tasmania's fauna due to predation unless eradication efforts are successful. It is suspected from evidence and collective knowledge that the density of the Tasmanian fox population might be as low as one fox per 500 km2 (Internal linkDPIPWE 2009). The impact of the fox on native wildlife at these densities is unknown, although even a single fox is estimated to eat about 400 gm of food each night, which is equivalent to one bandicoot (Internal linkDPIPWE 2009).
The presence of the European fox (Vulpes vulpes) in Tasmania is a significant threat to critical-size mammals as well as other native species. If the European fox were to become established in Tasmania, 78 native vertebrate species would be at risk. Of these, 34 species have locally restricted ranges, 16 are suspected to be already declining in distribution and 12 are listed as threatened in Commonwealth and State threatened species legislation (Internal linkDPIPWE 2009).
Due to their wide diet, foxes compete with many animals, such as Tasmanian devils and quolls. Species with a preference for dry, open forest such as the Tasmanian bettong (Bettongia gaimadi) and eastern quoll (Dasyurus viverrinus) are most at risk since foxes prefer this habitat above closed, wet forest. Other species are also at risk including the southern brown bandicoots, long-nosed potoroo, Tasmanian pademelon, brushtail possum, ringtail possum, small dasyurids, pygmy possums, quolls and small Tasmanian devils. The impact of the European fox and other pests and diseases affecting Tasmania's native wildlife is described in more detail in Internal linkAnimal Pests and Native Animal Diseases.
Habitat change, habitat fragmentation and climate change are further significant threats affecting Tasmania's wildlife. Further information is provided in Internal linkHabitat Change and Internal linkClimate Change and Natural Values.
Tasmania has 12 species of endemic birds. There are also a number of species that are endemic at the subspecies level, such as the threatened wedge-tailed eagle (Aquila audax), and a number of species which are known as breeding endemics. Breeding endemics breed only in Tasmania and migrate to mainland Australia outside the breeding season. The swift parrot (Lathamus discolor) and the orange-bellied parrot (Neophema chrysogaster) are two of these species.
As well as being important in their own right, changes in the number and distribution of birds can also tell us about changes in environmental condition. Areas with healthy bird populations are most likely to be those where the other elements of biodiversity (such as vegetation, mammals, reptiles and insects) are thriving. The presence of birds gives an indication of the ecological health at a variety of scales. For example, numerous species of migratory waders use Tasmanian wetlands (e.g. curlews, whimbrels, godwits). A number of birds migrate as far as the northern hemisphere, including the short-tailed shearwater (Puffinus tenuirostris), red-necked stints (Calidris ruficollis), curlew sandpipers (C. ferruginea) and greenshanks (Tringa nebularia). A few Tasmanian off-shore islands are the only Australian breeding sites of the shy albatross (Diomedea cauta).
The global range of many of these species only just reaches Tasmania, so that changes in the annual numbers of these birds provide a useful index of environmental pressures elsewhere. Macquarie Island is a major breeding site for subantarctic birds, including four species of penguins, four species of albatrosses and many other seabirds.
Among the birds, about 50 species migrate to the Australian mainland, including the swift parrot (Lathamus discolor), four cuckoo species, the striated pardalote (Pardalotus striatus), the orange-bellied parrot (Neophema chrysogaster), and the grey fantail (Rhipidura fuliginosa).
Some changes in migratory species are occurring. There are indications that climate change is restricting habitats for breeding and food sources for some bird species. Migratory sea and shore birds leave and return to Australia earlier because of earlier breeding seasons in warmer Arctic areas. They are placed at higher risk because the timing of Arctic food supply does not coincide with the breeding cycle resulting in the loss of young birds (Internal linkWolcott and Tzaros 2008).
A general global trend is occurring with shorebirds and their wetland habitats under threat worldwide. More than half of all shorebird populations with known trends are declining (Internal linkWetlands International 2006).
Climate may also be a factor in the population decline of the swift parrot as a result of changes in the availability of flowering Eucalyptus globulus or Eucalyptus ovata on the east coast of Tasmania (Internal linkWebb 2008). However, it is difficult to separate the impacts of climate change from other threatening processes that are outlined in this SoE Report such as habitat change and weeds, pests and diseases. Clearing of mature and old-growth forest in Tasmania has been a major factor in causing the decline of the forty spotted pardalote, swift parrot, wedge-tailed eagle and grey goshawk.
While there are very few long-term datasets on populations of birds in Tasmania that would allow trends and changes to be identified, selected data are included in the indicators on Internal linkPopulation Distribution and Trends of Representative Bird Species and Internal linkWaterbird Population Trends. The limited available long-term monitoring is a concern as population declines have a significant risk of being undetected.
The presence of the European fox ( Vulpes vulpes ) in Tasmania is a significant threat to Tasmania's native birds. Evidence of a population of European fox in Tasmania (the discovery of carcasses and scats as opposed to other indicators such as reported sightings) has been increasing since 2005. Due to their wide diet, foxes compete with many animals, such as raptors and ravens. The masked owl, brown goshawk, and the wedge-tailed eagle are some of the species that will be threatened as they compete with the fox for food (Internal linkState of Tasmania 2007).
The Threatened Tasmanian Eagles Recovery Plan has identified that a population decline of the Tasmanian wedge-tailed eagle is inferred due to loss of nesting habitat, nest disturbance from land clearance and other inappropriate land management practices and from unnatural mortality, including persecution and collisions with commercial wind turbines (Internal linkThreatened Species Section 2006). Available data indicate a high proportion of inactive nests and elevated adult mortality leading to a reduction in the mean age of the population and a subsequent reduction in breeding success. High levels of disturbance of breeding habitat also contributes to increasing changes of nest sites, the movement being away from optimal (first choice) sites. The proportion of juvenile birds within the population appears to be decreasing due to a lack of recruitment (Internal linkBell and Mooney 1998). Any further decline in the rate of recruitment may not become apparent for some years, as adult wedge-tailed eagles are long-lived (probably up to 20–25 years in the wild).
Pedder galaxias (Galaxias pedderensis) Source: Inland Fisheries Service
Pedder galaxias (Galaxias pedderensis)internal SOE link to larger image
Source: Inland Fisheries Service
While birds are important indicator species for the condition of Tasmania's native vegetation and coastal habitats, Tasmania's native freshwater fish (together with other indicators such as aquatic invertebrates) are indicative of the health of freshwater aquatic habitat. Viable populations of freshwater fish are indicative that there are sufficient food sources such as crustaceans and aquatic insects, that habitat is relatively intact and that there is sufficient water for the life stages of a species. It also tells us that predation by introduced brown trout (Salmo trutta), brook trout (Salvelinus fontinalis) and rainbow trout (Oncorynchus mykiss) (see Internal linkThreatened Species Network, Australian Government and World Wide Fund for Nature Australia 2008), and other introduced species, such as the fish and frog egg-eating eastern gambusia (Gambusia holbrooki), are being managed effectively.
Many of Tasmania's native freshwater fish are in a precarious position. They are the most threatened animal group in inland waters. A number of species have been uplisted recently since the release of the Recovery Plan for Tasmanian Galaxiidae 2006–2010 (Internal linkThreatened Species Section 2006). An additional six species of freshwater fish have been listed under the External link: LegislationThreatened Species Protection Act 1995 since 1996, which brings the total number of listed freshwater fish to 11 of the 25 Tasmanian native species at the time of writing this SoE Report.
Threatened Tasmanian native species of Galaxiidae (freshwater fish) in Tasmania
Threatened Tasmanian native species of Galaxiidae (freshwater fish) in Tasmania
The major threatening processes affecting Tasmania's threatened fish are described in the Recovery Plan for Tasmanian Galaxiidae 2006–2010 (Internal linkThreatened Species Section 2006) and Tasmania's Threatened Fauna Handbook (Internal linkDPIW 1999). In brief, modifications of habitat through hydro impoundments or other hydrological impacts have been a historic factor in the threatened status of species including the native galaxias species (Pedder galaxias, swamp galaxias, saddled galaxias, Shannon paragalaxias and Great Lake paragalaxias). For example, habitat loss, vegetation clearance and fragmentation is a major cause of decline of the threatened and totally protected dwarf galaxias (Galaxiella pusilla), and swan galaxias (Galaxias fontanus) (Internal linkThreatened Species Section 2006). Wetland degradation is a major cause of decline of the dwarf galaxias. Available habitat has also been reduced by road culverts creating barriers to upstream movement in some of the streams occupied by swamp galaxias, resulting in its occurrence downstream of the culvert only (IFS unpubl. data). The following CFEV map provides one perspective on habitat issues that may arise for Tasmania's native freshwater fish, which is represented by the CFEV river naturalness index.
One of the most significant ongoing threats arises through predation and competition from introduced fish species, in particular brown trout. Brown trout has a significant impact directly through predation and in reducing the available habitat for native fish (populations are isolated by the presence of introduced fish). Brown trout in Lake Crescent feed almost exclusively on golden galaxias while other species such as the dwarf galaxias will rarely co-exist with trout (Internal linkThreatened Species Section 2006).
Stream flows and lake water levels are a significant issue. The driest years have occurred following the publication of the Recovery Plan for Tasmanian Galaxiidae 2006–2010 in 2006, suggesting the need for an update of the Recovery Plan to consider appropriate responses. Dry conditions for several years and low lake levels have caused deterioration in habitat quality and availability for species such as the golden galaxias. The drying of lakes over large areas serves to compound losses of habitat through the loss of shallow lakeside marshes and inflow streams, and exposure of rocky shore habitat. Predation by trout will increase as a result of the loss of the protective rocky shore habitat that may have otherwise provided protection for native freshwater fish.
There are an estimated 35,000 non-marine invertebrate species in Tasmania (Internal linkDPIW 1999). Invertebrates have a fundamental role in ecosystem functioning, which enables them to serve as indicator species in some environments. For example, assemblages of macroinvertebrates in rivers as assessed by AUSRIVAS (Australian River Assessment Scheme) are used to determine river health (see Internal linkAquatic Health and indicator=14!;). Aquatic macroinvertebrates include a range of insect, crustacean and molluscan groups, and include snails, water boatmen, dragonflies, stoneflies, mayflies and aquatic worms. Some invertebrates are also referred to as keystone species in natural ecosystems: changes in ecosystem processes can occur because of the displacement of some native invertebrates.
A significant amount of invertebrate research effort has occurred through the Warra Long Term Ecological Research site in southern Tasmania. A recent report by Forster and Grove (Internal link2008) has demonstrated the value of beetles as indicator species for environmental change and in detecting impacts of climate change on decomposition. Further information on the Warra Long Term Ecological Research site is available through the Warra website (External linkThe Warra Long Term Ecological Research (LTER)).
Some weed species are limited by a lack of suitable pollinators but the introduction of exotic pollinators can facilitate rapid spread (Internal linkJavorek no date). The bumblebee, Bombus terrestris is established in the most remote parts of Tasmania including throughout the Tasmanian Wilderness World Heritage Area (TWWHA) and is not dependent on introduced garden plants. It is likely to have negative impacts on native animals and plants and has the potential to enhance seed production in weeds (Internal linkKingston et al. 2002). In situations where nectar and pollen are in short supply, bumblebees may exhaust the available supplies before the native bees begin to fly (Internal linkHingston and McQuillan 1998).
The use of nectar and pollen resources by bumblebees also disadvantages birds such as honeyeaters and parrots. The endangered swift parrot ( Lathamus discolor) is largely dependent on the nectar and pollen of Eucalyptus globulus and Eucalyptus ovata for food while breeding. Flowers were virtually devoid of nectar when the introduced European honeybees and bumblebees were active (Internal linkHingston and Mallick 2003).
European wasps compete with native bees. They also predate on other native animals, especially invertebrates such as the vulnerable Ptunarra brown butterfly (Oreixenica ptunarra) and mussels. They are also predating on native tadpoles. In environments like the TWWHA, this species may compete with meat eating native animals such as the endangered wedge-tailed eagle (Aquila audax fleayi).
Invertebrate diversity and health is a key component of soil organic matter, which is widely regarded as a vital component of soil physical, chemical and biological fertility. The maintenance of soil organic matter is critical in the long-term management of Tasmanian soils because it binds soil particles into stable aggregates. It also comprises a critical link in the nutrient cycling processes that operate in soils, and contributes to the capacity of soils to hold water and exchange ions with the surrounding soil solution (Internal linkCotching 2006; Internal linkMcKenzie and Dixon 2006). Further information is provided in Internal linkSoil Diversity.
Beyond their fundamental role for ecosystem functioning and in the provision of ecosystem services such as pollination, many of Tasmania's invertebrates are unique and significant. Approximately one third of all invertebrates known in Tasmania are endemic and some groups such as the stag beetles (Lucanidae), geometrid moths (Lepidoptera) and primitive syncarid crustaceans (Anaspididae) are of immense biological significance because of their ancient origins and evolutionary links (Internal linkDPIW 1999).
Tasmania has Australia's richest diversity of temperate zone cave-dwelling invertebrates. The twilight zone of caves is occupied by a great diversity of animals including the giant cave spider ( Hickmania troglodytes ), various cave crickets (Micropathus), the Tasmanian glow worm ( Arachnocampa tasmaniensis ) and carabid beetles (Goedetrechus, Tasmanotrechus, Idacarabus spp.). In contrast to mainland Australia, there are no known bat colonies in Tasmanian caves.
The leaf litter on the forest floor is inhabited by an exceptional variety of detritus-feeding mites and springtails preyed upon by a multitude of tiny endemic beetles and arachnids (e.g. spiders). In one square metre of rainforest litter there can be over 20,000 invertebrates, including as many as 7,000 springtails and 8,000 mites (Coy et al. 1993).
The External link: LegislationThreatened Species Protection Act 1995 currently lists 119 invertebrate species, which includes beetles, butterflies, moths, snails, spiders and crayfish. The giant freshwater lobster Astacopsis gouldi is one example. It occurs only in rivers across northern Tasmania. Having the distinction of being the largest freshwater invertebrate in the world, this creature is threatened by pollution of waterways, loss of stream vegetation, and recreational fishing.
Tasmanian tree frog, Birches Inlet Source: Matthew Pauza
Tasmanian tree frog, Birches Inletinternal SOE link to larger image
Source: Matthew Pauza
Eleven species of frog occur throughout Tasmania, three of which are endemic: Tasmanian tree frog ( Litoria burrowsae ), moss froglet ( Bryobatrachus nimbus ) and Tasmanian froglet ( Crinia tasmaniensis ). Two frog species are currently listed under the External link: LegislationThreatened Species Protection Act 1995, namely: striped marsh frog ( Limnodynastes peroni) and green and golden frog ( Litoria raniformis ). The striped marsh frog is listed as rare and the green and golden frog is listed as vulnerable. The full list of eleven Tasmanian frog species is available on the Parks and Wildlife External linkFrogs of Tasmania website.
Due to their sensitivity to environmental change, frogs are often referred to as biological indicators for aquatic environments. Many species of frogs throughout the world are in decline due to a variety of threatening processes. Change processes include habitat loss, and the loss of wetlands, pools and ponds. The long-term effect of drought on frog populations is likely to be severe, although some species may fare better than others.
The consequences of the drying out of breeding habitat for the Green and Golden Frog were noted in the Listing Statement in 2001. It was noted that frog activity had declined significantly because of the drought (Internal linkThreatened Species Unit 2001). The Listing Statement notes that declines have been reported from all areas in the last 15 years. Populations have been lost from areas in the Midlands, Derwent Valley and the northwest coast. The distribution on the mainland was unclear at the time the Listing Statement was prepared in 2001, however, it noted that it has disappeared from the Australian Capital Territory and the southern tablelands of New South Wales and has only patchy distribution in Victoria and South Australia.
The following eight years—with the possible exception of 2005—have all been very dry in Tasmania. However, it is unknown how the Green and Golden Frog has fared in the subsequent period.
Global warming and increased ultra-violet radiation have been cited as causal agents (Internal linkTyler 2006). An assessment of the impact of climate change on global amphibian species found that about half of them were susceptible to climate change, including Australian ground frogs (Limnodynastinae), tree frogs (Hylidae) and (Myobatrachidae) (Internal linkFoden et al. 2008). All of Tasmania's 11 species occur in these families.
Climate change may be threatening frog populations in Tasmania as a result of changes to streamflows, the loss of wetlands (see indicator Internal linkExtent and Condition of Wetlands) and through a shift towards optimal temperature regimes for an emerging infectious disease known as chytridiomycosis (Internal linkPounds et al. 2006 referenced in Internal linkPauza and Driessen 2008).
Chytridiomycosis is caused by a pathogenic fungus, Batrachochytrium dendrobatidis . The disease is a problem in four regions across Australia, including Tasmania, and is thought to be the agent of a global pandemic in amphibian populations (Internal linkDEH 2006 and Internal linkDPIW 2007). Amphibian chytrid has been linked to the decline and extinction of several frog species on the mainland of Australia since the 1970s (see Internal linkDEH 2006). Infection of amphibians with amphibian chytrid fungus is listed as a key threatening process under the EPBC Act (Internal linkDEH 2006). Seven species of frog have shown visible lesions of chytridiomycosis during the tadpole stage of development: the Brown Tree Frog (Litoria ewingii), Tasmanian Tree Frog (Litoria burrowsae), Eastern Banjo Frog (Limnodynastes dumerilii), Spotted Marsh Frog (Limnodynastes tasmaniensis), Tasmanian Froglet (Crinia tasmaniensis), Common Froglet (Crinia signifera), and the Green and Gold Frog (Litoria raniformis) (Internal linkDPIW 2007).
A recent study of chytridiomycosis in the TWWHA found that the majority of the TWWHA is currently free of the pathogen despite the region providing what appear to be optimal conditions (Internal linkPauza and Driessen 2008). Further information on chytridiomycosis is provided in Internal linkAnimal Pests and Native Animal Diseases.
The Tasmania Natural Values Atlas (NVA) is the State's primary repository for animal distribution records, particularly threatened species records and observations by State Government scientific staff. The following table and maps summarise observation counts of frog species and the date of the most recent observation. Some observations were unavailable due to restrictions for threatened species. While the record of frog observations held on the NVA does not allow changes in the distribution and abundance of frog species to be identified, the information can be used by scientists to plan survey work from which information on changes may be gleaned.
Observations of Tasmanian frog species under the Natural Values Atlas (public records only) The table excludes some observations of restricted frog species. Source: Internal linkDPIPWE 2009
Observations of Tasmanian frog species under the Natural Values Atlas (public records only)
The table excludes some observations of restricted frog species.
Source: Internal linkDPIPWE 2009
Knowing how Tasmania's native animals are faring is broadly dependent on programs relating to wildlife health and distribution (including monitoring of diseases, population distribution and abundance) and programs directed towards understanding habitat changes and availability.
For threatened species, listing statements typically define recommended monitoring priorities and programs. For example, the listing statement for the Green and Golden Frog recommends conducting a survey for unrecorded populations, particularly on the Bass Strait Islands and to establish a database of records, which includes population and habitat data (Internal linkThreatened Species Unit 2001). There is no statutory requirement that a recommended monitoring approach for a threatened species, as outlined in a listing statement, is implemented.
A recent DPIW review of wildlife monitoring priorities noted that 40% (18 species out of 49) of Priority 1 and 22% (6 species out of 27) of Priority 2 threatened species are currently subject to some level of monitoring (Internal linkDriessen and Hocking 2008).
There are gaps in knowledge of specific type of species because many species are difficult to detect. For example, information remains very limited on the distribution and management needs of invertebrates and marine species. There are also gaps in knowledge of species in particular environments. For example, large areas of Tasmania's coastline and many offshore islands have not been surveyed.
There are a number of constraints on the capacity to monitor and report on population numbers and trends for many bird species. Overall, there are significant challenges in identifying trends for highly mobile species, such as the orange-bellied parrot and the swift parrot. There are very few long-term data sets on which to base management decisions. Given that birds tend to be long-lived, data needs to be collected and managed over the long-term to ensure that population changes are observed. Sporadic survey work can fail to identify episodic population changes. While there have been efforts to survey bird populations these are often limited to count results only and do not attempt to estimate populations.
While there are particular problems in monitoring small birds such as the forty-spotted pardalote, the status of population monitoring programs is only marginally better for more conspicuous birds such as the wedge-tailed eagle. The Threatened Tasmanian Eagles Recovery Plan has identified a number of limitations with white-bellied sea-eagle monitoring such as the limited data on nest condition (Internal linkThreatened Species Section 2006). Current unpublished research through the Forest Practices Authority is identifying some shortfalls in the available information for the wedge-tailed eagle. Previous studies have been too coarse to determine critical habitat requirements. Satellite tracking of wedge-tailed eagles to better understand habitat requirements together with a more comprehensive program checking of nesting sites by air would assist in providing the information needed by land managers to make better management decisions.
In the absence of reliable data, populations for some bird species could decline to critical levels with insufficient warning to allow management action to be undertaken, thereby adding to the risk of extinction. The following table lists current monitoring programs for threatened bird species in Tasmania.
Integration of datasets is a further difficulty. Where bird population or nest data are collected, it is held in a variety of formats on desktop computers with limited integration that may allow broader patterns of change to be identified. In some cases, it is important that sensitive data such as on nesting sites is not made publicly available at high levels of spatial accuracy. Nevertheless, it is important both for conservation decision-makers and the wider community to be able to gain regular updates on population trends and changes for threatened Tasmanian bird species. This is not presently possible. DPIW has indicated that recommendations have been made to respond to this issue in DPIW's Wildlife Monitoring Strategy (Internal linkDPIW 2008).
An emerging challenge due to climate change is that protection of habitat no longer provides any guarantee that species contained within these habitats will survive. Monitoring of additional priority species—such as those at the lower end of threatened species status (rare or vulnerable species)—may increasingly be justified to keep an eye on those species that would have not have previously required monitoring. However, as noted in the DPIW review of Wildlife Monitoring Priorities, there is already far more species that would justify monitoring than there are resources available to support these programs (Internal linkDriessen and Hocking 2008). Nonetheless, there is a case to identify species that should be monitored as sentinel or indicator species.
Wildlife health and other species programs
Long-term information on the population trends of key mammal species may provide an indication of the changing relative abundance of native and non-native species in the Tasmanian environment. Subject to sampling issues, population surveys provide a measure of changes in the population and abundance of a species. Some of this information is collected spatially, which allows the analysis of changes in the distribution of monitored species. These data may also be used to complement other data to present a perspective on how a species is responding to changes in its environment.
Spotlight surveys are conducted annually by DPIW for many mammal species in Tasmania. These surveys provide estimates of population trends rather than quantitative counts. Spotlight survey records extend back to 1975 for most species and locations, though not all areas have been monitored since this time.
DPIW ensures that spotlight surveys are conducted only under suitable weather conditions (e.g. nothing more than a light wind, no or very little rain, no fog, etc.) and that as much as possible, human-induced variability is controlled (e.g. observer experience, driver speed, etc.) (Internal linkHocking 2008). The data collected through spotlight surveys are therefore standardised as much as practicable and are considered a very valuable record of medium- to long-term population trends for the species monitored. It is inevitable that some general biases are introduced by the methodology itself, however, as spotlight surveys necessarily rely on counts being conducted along roadsides. Drought conditions cause many species of both herbivores and carnivores to be drawn to roadsides in search of food and this can lead to population numbers being overestimated. In this way, observed population declines may be underestimated and population increases overestimated in drought conditions.
Although little is known of the abundance or population trends of small marsupials such as pygmy possums (Cercartetus spp.), spotlight surveys provide information on some of the more conspicuous native species. It can provide valuable information about medium- to long-term trends in species abundance, particularly if this information is spatially referenced.
Spotlight surveys were designed for monitoring harvested species and are established in areas where most harvesting takes place. As a result, population monitoring records are often heavily influenced by previous harvesting pressures. For this reason, monitoring data for harvested species may not necessarily be indicative of natural fluctuations in population dynamics.
Regions surveyed by DPIW in annual spotlight surveys are shown in the following map.
Spotlight transects used for mammal population surveys Source: Map production by SoE Unit using spotlight transect location data supplied by Internal linkHocking 2008. Base topographic data provided by the LIST.
Spotlight transects used for mammal population surveysinternal SOE link to larger image
Source: Map production by SoE Unit using spotlight transect location data supplied by Internal linkHocking 2008. Base topographic data provided by the LIST.
In the following example from the Internal linkPopulations of Selected Mammal Species indicator, spotlight survey data show declining survey counts for the Tasmanian devil and eastern quoll in recent years. Care is needed in interpreting these data as, over the longer-term, there has been a high level of data variability. The data suggests that from the mid 1990s Tasmanian devil counts had started to decline and, by 2000, both the Tasmanian devil and eastern quoll show decreasing counts. Coinciding with these recent decreases in counts, feral cat population counts have shown an increase of comparable magnitude. The spotted quoll numbers are also too low to make any useful conclusions, other than that they are still present. Although there is a general decrease in the population counts of ring tail possums, the numbers are quite low, and therefore susceptible to troughs which appear to plummet towards zero.
It is not possible to state any interconnectedness between any of the declines and increases, as there is a complex number of factors affecting each population. It cannot be stated simply that the cats are filling the Tasmanian devil's niche, nor can it be stated that eastern quolls are aligned with devils food source as the devil population decline is predominately resultant from DFTD, not a loss of resource such as food. It is unknown whether the increase in feral cat numbers is causally related to the decline in Tasmanian devils and eastern quolls – the environmental and ecological processes that would allow this to occur are unknown. The Statewide drought, which intensified around 2002, would have some effect on food availability and changes to habitat that would help or hinder access to food sources. What these effects would be cannot be stated from this information, but it would be remiss not to draw the conclusion that it would be a significant factor impacting all the observed species.
Wildlife monitoring by DPIW is directed towards the following key priority areas: species that are subject to harvesting and culling, threatened species, monitoring of potential threats, monitoring of introduced animals and long-term ecological research. In practice, there are overlaps, and programs such as monitoring of harvesting and culling also provide insights into long-term environmental change. Some species that are not currently threatened but are monitored include the little penguin, leopard seal, Macquarie Island penguin and Australasian gannet.
Species subject to harvesting and culling
There are 20 species of wildlife in Tasmania that are subject to harvesting and culling, of which 16 are monitored. Information gained from this monitoring has been used to identify trends in the abundance of the harvested or culled population and to guide decisions in relation to restrictions on harvesting and culling. Trends in abundance are monitored using a variety of methods ranging from systematic surveys by DPIW staff to sighting records provided by hunters (Internal linkDriessen and Hocking 2008).
Monitoring of threatened species
Wildlife monitoring priorities also include some threatened species. Monitoring of threatened species provides information on the status of species. It also enables the outcomes of management processes to be assessed. For example, threatened mammal species such as the Tasmanian devil are monitored through the DPIW Spotlight Survey program.
Monitoring of potential threats
A program to monitor species at risk from the European fox—such as eastern barred bandicoots, eastern quolls and Tasmanian bettongs—is being established by DPIW. This program will guide management of the species should attempts to eradicate the fox from Tasmania fail. This will complement current monitoring of species through the annual spotlight survey program, which includes some species that are at risk from the European fox such as the brown bandicoot and bettong.
A program to monitor the ecological impacts of the Devil Facial Tumour Disease (DFTD) on a range of species that may be affected by a decrease in devil numbers is also in the process of being established. These programs are funded by both State and Commonwealth governments and undertaken by DPIW (Internal linkDriessen and Hocking 2008).
The Tasmanian Tree Frog is being monitored because of the threat posed by chytrid fungus. Invertebrate and bird communities are being monitored along an altitudinal gradient in southern Tasmania in an effort to detect changes in species distribution in relation to future climate change. The latter is part of the Warra Long Term Ecological Research project.
Introduced Animal Species
Three introduced animal species are specifically targeted for monitoring by the Resource Monitoring and Conservation Division of DPIW. Monitoring is undertaken to detect the presence of foxes and to direct control efforts. European rabbits are monitored at Strathgordon to measure the success of an eradication program and on Macquarie Island to assess the impacts of rabbit and cat control programs. Fallow deer are monitored in the Central Plateau Conservation Area to determine their status and to determine whether control is required. Several other introduced animals that are monitored as part of the spotlight survey program are rabbits, fallow deer and hares.
Habitat monitoring programs are reviewed in more detail in the Internal linkHabitat Change Issue Report. Broadly, these programs can be grouped in relation to terrestrial vegetation programs, marine programs and freshwater aquatic programs. The key programs are summarised as follows:
Environmental indicators help track changes in the environment. Indicators can help in gaining an appreciation of conditions and trends and changes in the environment without having to capture the full complexity of the system, which is typically unknowable for most ecosystems: it is inherently complex and always changing, as is human interaction with the environment.
Indicators may be physical, chemical, biological or socio-economic that provide useful information about the whole system. In SoE reporting, indicators are also often classified as to whether they relate to the condition of the environment, pressures caused by people on the environment or management responses (in seeking to reduce pressure and improve condition).
In the 2009 SoE website, an indicator may be used across more than one issue report or chapter. For example, measures of water quality in Tasmania's rivers and streams tell us about the condition of these aquatic systems and are used in this part of the SoE Report (condition of freshwater). They may also tell us about pressures on estuaries receiving water from these rivers and catchments (pressures on estuaries).
Index of native animals indicators Control or culling of some species may be undertaken for land management purposes such as to prevent land degradation due to over-grazing by native animals. There are also a variety of commercial and recreational requirements for harvesting, control and culling.
Index of native animals indicators
Control or culling of some species may be undertaken for land management purposes such as to prevent land degradation due to over-grazing by native animals. There are also a variety of commercial and recreational requirements for harvesting, control and culling.
Populations of Selected Mammal Species - at a glance
This indicator presents the results of spotlight surveys conducted in Tasmania each year from 1985 for selected native and non-native mammal species (Internal linkHocking and Dawson 2008). These surveys provide invaluable long-term information on the population trends of key mammal species. This dataset provides an indication of the changing relative abundance of native and non-native species in the Tasmanian environment. Information from these population trend estimates are also used to dictate the permissable levels of harvesting for each species in subsequent years. Changes since the 2003 SoE Report are highlighted.
The following table shows trends in population numbers of selected mammal populations between 1985 and 2008. In the table, species are ranked in order of the magnitude of their decline or increase. For further information on how this table was created, refer to the in depth version of this Indicator.
Population trends of selected mammal species, 1985 to 2008 Animal numbers recorded by roadside spotlight survey may be subject to bias in times of drought, such as the conditions experienced in recent years, as both herbivorous and carnivorous species can be drawn to roadsides in search of food. This bias may have caused the declines in some populations to appear less severe than they actually are. Similarly, increases in other populations may be slightly over-represented here. Source: Data analysis by SoE Unit using spotlight survey data from Internal linkHocking and Dawson 2008.
Population trends of selected mammal species, 1985 to 2008
Animal numbers recorded by roadside spotlight survey may be subject to bias in times of drought, such as the conditions experienced in recent years, as both herbivorous and carnivorous species can be drawn to roadsides in search of food. This bias may have caused the declines in some populations to appear less severe than they actually are. Similarly, increases in other populations may be slightly over-represented here.
Source: Data analysis by SoE Unit using spotlight survey data from Internal linkHocking and Dawson 2008.
Population Distribution and Trends of Representative Bird Species - at a glance
This indicator is a broad measure of the conservation and population status of selected threatened and non-threatened bird species across a variety of habitats. Trends and changes in key bird populations are an important indicator not only of the health of the species themselves but potentially of biodiversity health in general.
This indicator provides information on the status of selected bird species across a number of habitats, including: forest and woodland birds, shorebirds and seabirds.
There are a number of constraints on the capacity to monitor and report on population numbers and trends for many bird species: birds are often inconspicuous and difficult to monitor, there are limited data (whether short- or long-term), different measures of population abundance and conservation status are used, and monitoring programs are typically short-term and ad hoc.
Information for this indicator draws from a number of sources, including: the External link: LegislationThreatened Species Protection Act 1995; population counts and trends data from the Biodiversity Conservation Branch of DPIW; and Birds Tasmania data.
Care is needed in making general inferences from population trends for species. Because birds are wide-ranging across a variety of habitats or migratory (on global scales for some species), population trends tell us about the cumulative pressures faced by a species across their entire range and at different stages in their life-cycles. The following analysis is subject to the data availability and limitations that are detailed within the indicator.
Wedge-tailed eagle (Aquila audax fleayi)
Swift parrot (Lathamus discolor)
Forty-spotted pardalote (Pardalotus quadragintus)
Scarlet Robin (Petroica multicolor) and Dusky Woodswallow (Artamus cyanopterus)
Waterbird Population Trends - at a glance
This indicator reports on the trends and changes in waterbirds. Population trends tell us about the cumulative pressures faced by a species across their entire range and at different stages in their life-cycles.
Five species of native duck namely; black duck, mountain duck (shelduck), wood duck, chestnut teal and grey teal are hunted in Tasmania during an open season usually held from early March to early June. DPIW monitors their population trends. While the primary purpose of these counts is to monitor the harvest, they also provide invaluable long-term data on population trends.
A significant limitation is the absence of information on the distribution and mobility of populations both within Tasmania (and its islands) and between Tasmania and the Australian mainland. There is currently no systematic national survey that would account for movements between states in response to favourable or unfavourable conditions. It is possible that Tasmania is serving as a refuge for mainland Australia waterbirds following the drying of significant river, lake and wetland habitat on the mainland. However, little is known about this because banding of species halted in the 1970s. The survey technique used in Tasmania is able to provide an indication of trends in relative abundance not absolute population numbers.
Animal Pests and Diseases - at a glance
This indicator describes the number of introduced animals identified as pests in Tasmania. It also highlights a number of native animal diseases in the State that affect Tasmania's native animals. The indicator is divided into two parts: (1) native animal pests; and (2) native animal diseases. Data was sourced from DPIW and the Inland Fisheries Service (IFS). Additional information was also sourced from a range of government and research agencies including the Department of Environment, Parks, Heritage and the Arts (DEPHA), Forestry Tasmania and CSIRO Marine and Atmospheric Research. A ranking score on priority feral animals that has been developed by the Tasmanian Threatened Species Network is also included. Data availability and limitations are reviewed in the indicator.
The first section focuses on the number of animal pests declared under relevant Tasmanian legislation, the number of animals considered as pests by management authorities, and a review of the animal pests for which management control actions are being undertaken. The second section focuses on native animal diseases identified by management authorities as management priorities. It provides examples of the distribution of three key native animal diseases and their known distribution in Tasmania.
Roadkill - at a glance
This indicator reports on the number of native and non-native animals killed on Tasmanian roads. The number of animals killed on Tasmanian roads provides an indication of human impacts on native and non-native animal populations. In addition, roads can cause fragmentation of populations that result in the loss of habitat and reduced habitat ranges. This indicator is based on research conducted by Alistair Hobday and Melinda Minstrell from the University of Tasmania between June 2001 and November 2004. Data was collected by an observer in a moving vehicle using a GPS (Internal linkHobday and Minstrell 2008). More information on their survey can be found through External linkRoadkilltas website. Some of the summary findings from their research includes the following:
Harvesting, Control and Culling of Terrestrial Animal Species - at a glance
This indicator details the level of harvesting and culling of native fauna for crop protection and wildlife management, commercial enterprise, mammal browsing control, and recreation. It also includes harvesting details for some non-native animals that have become established in Tasmania. DPIW data on crop protection permits were made available for the SoE Report. Some figures of 'non-commercial shooting' of wallabies—including those killed for crop protection and recreation—were published in the Sustainability Indicators for Tasmanian Forests 2001–2006 report (Internal linkState of Tasmania 2007), though these numbers do not reflect the full complement of harvesting for crop protection in Tasmania.
Terrestrial Protected Areas - at a glance
This indicator reports on the area by vegetation type in protected area categories as defined by the IUCN, in hectares and as a percentage of the pre-1750 area, by IBRA. Information on the reserve system in Tasmania and the vegetation contained within these reserves is readily available and regularly updated. The information for this indicator was drawn from unpublished data provided by DPIPWE and published sources. The published sources used include the Sustainability Indicators for Tasmanian Forests 2001–2006 (Internal linkState of Tasmania 2007).
The following section provides an overview of programs that have implications for native animals in Tasmania. More information is provided in the following issue reports: Internal linkAnimal Pests and Native Animal Diseases, Internal linkHabitat Change, Internal linkEstuarine and Marine Pests and Diseases and Internal linkNative Vegetation. Management responses relating to native animals may be grouped under the broad categories of animal pest and disease management, habitat retention and listing under the External link: LegislationThreatened Species Protection Act 1995. Some of the key responses, including policies and strategies and other related programs, projects, frameworks and initiatives are listed below.
Management policies and strategies
Other programs, projects, frameworks and initiatives
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