Source: Photograph courtesy of Paul Ovenden © Australian Museum
Source: Photograph courtesy of Paul Ovenden © Australian Museum
An introduced animal is any species of animal that is not native to an area. An animal pest is an introduced animal that is not native to an area. It has an established self-supporting population in the wild (also known as feral or naturalised) that is a threat, for example, to human health, primary production and/or the natural environment. Animal pests that specifically impact upon environmental values (such as on native plants and animals) are termed environmental pests.
In the past, pest species have arrived in Tasmania by natural means such as on wind currents or across water. However, since the early days of European settlement many animals from interstate and overseas have been introduced, either deliberately or accidentally, into the State. Significantly, animal pests are inadvertently introduced into Tasmania via air and sea transport routes such as those that 'hitch a ride' in vehicles that are transported through ports from Devonport from Melbourne on Spirit of Tasmania I and II (Internal linkTT-Line Company Pty Ltd 2008; and also Internal linkWardlaw 2008).
The following maps provide broad information on the overall density of nine key vertebrate animal pests (animals with a backbone) in Tasmania that are included in the Australian Natural Values Atlas (Internal linkBRS 2007). Vertebrate animal pests detailed are the European fox (Vulpes vulpes), feral cats (Felix spp.), European rabbits (Oryctolagus cuniculus), fallow deer (Dama dama), feral pigs (Sus scrofa), feral goats (Capra hircus), wild dogs (Canis spp.), European carp (Cyprinus carpio) and common starlings (Sturnus vulgaristhat). The relationship between the density of these pest species and damage to our natural resources is often unknown. Information presented here is based on a national collation of data compiled for standard 1:100,000 map sheets with the base topographic data provided by the LIST. More information on animal pests is provided in the embedded document Internal linkAssessment of animal pests in Tasmania that details a range of introduced animals that have become established in Tasmania and are now considered as pests.
Animal pests can cause a range of environmental and economic impacts depending on the species and the environment in which they live. There is uncertainty about the total number of introduced animals in Tasmania and whether they have become naturalised and/or environmental pests. In the 2003 SoE Report, animal pests were identified as representing serious threats to Tasmania's biodiversity both on land and in water. It was estimated that a total of 1,012 (60 vertebrates and 952 invertebrates) known naturalised animal species were present in the State (Internal linkRPDC 2003). At the time, 32 of the 60 recorded introduced vertebrate species were recognised as environmental pests (including foxes, rabbits, ferrets, cats, rats and carp). Of the 952 introduced invertebrate species (animals without a backbone) recorded in Tasmania, 74 were recognised as animal pests and 12 were recognised as environmental pests.
In 2004, it was estimated that at least 80 species of introduced vertebrate and invertebrate animals were known to occur in Tasmania (including 8 mammal species, 11 bird species, 4 fish species and 16 introduced invertebrates species) (Internal linkPWS 2004). In 2005, a revised estimate identified that there were 44 introduced vertebrate animals known to occur in Tasmania and its immediate offshore islands (Driessen et al. in Internal linkTSN 2005). Birds accounted for nearly half of the introduced species (21 species – with the redpoll (Carduelis flammea) also being recorded at Macquarie Island), over one quarter were mammals (13 species) and one fifth were fish (9 species). The only known introduced reptile recorded in 2005 was the semi-aquatic long-necked tortoise (Chelodina longicollis). No introduced amphibians (frogs) were recorded.
There are more introduced invertebrates in Tasmania than introduced vertebrates. In 2005, it was estimated there were possibly over 350 invertebrate species in the State. Most introduced invertebrates such as weevils, mealybug, lice, fleas and aphids are associated with, or dependant upon, introduced plant or animals species (Driessen et al. in Internal linkTSN 2005). In addition, 23 species of introduced vertebrates and 42 introduced invertebrates were identified in 2005 as being present in the Tasmanian Wilderness World Heritage Area (TWWHA) although this figure may be an under-estimate. Of particular concern are those that have become more widespread including feral cats, rabbits, rats, sugar gliders, blackbirds, starlings, introduced fish, introduced wasps and bees, and the hedgehog slug. Other introduced animals could also affect native plants and animals including goats in the WWHA, the superb lyrebird (Menura novaehollandiae) in wet forests, and fallow deer in the Central Plateau Conservation Area.
In 2005, the Department of Primary Industries, Water and Environment (DPIWE now the Department of Primary Industries, Parks, Water and Environment) identified that 56 offshore islands (which were >20 ha or larger) have pests and/or introduced animals (Internal linkDPIWE 2005). This report did not include the largest offshore islands including King Island, Flinders Island, Cape Barren Island and Clarke Island in Bass Strait and Bruny Island in the southeast because they are considered to have the same characteristics as mainland Tasmania in terms of introduced and/or pest animals. When this data is combined with data from other sources, a total of 69 offshore islands are suspected of harbouring pests and/or introduced animals. European rabbits are the most common animal pest found, followed by cats, rats, mice, cattle, sheep, horses, goats, fallow deer, pigs and hares. Twenty-five offshore islands (>20 ha) were found to be free of pests and/or introduced animals. The majority of these islands were in the southwest of the State. Islands with feral animals were more common around areas of human settlement, particularly in the northeast and southeast of the State. More information on pests and/or introduced animals on Tasmanian offshore islands can be found in the Internal linkIntroduced Species on Offshore Islands Indicator.
It is noted that bumble bees (Bombus terrestris) and European wasps (Vespula germanica) are now present on most of the islands that were assessed as pest free in 2003. While the impact of these species is poorly understood they are a risk to biodiversity values.
The variations in these figures highlight the difficulty in determining accurate lists of introduced species and whether these species are environmental pests. In 2008, it was further estimated that about 447 introduced species were present in the State. This figure comprises 49 vertebrate animals (including 16 mammal species, 23 bird species, 9 fish species and 1 reptile) and 398 introduced invertebrate species. Of these introduced animals 63 species were estimated as being present in the WWHA (including 8 mammals, 11 birds, 4 fish and 40 invertebrates). It was not possible to determine if these figures represent a change in the actual number of introduced species in Tasmania or a change in reporting criteria used to calculate the numbers. The information available confirms that there are a substantial number of introduced vertebrate and invertebrate animals in Tasmania and more research is required to determine their status and impacts on the Tasmanian ecosystem.
Further information on the 49 introduced vertebrate animals and 398 invertebrate animals in Tasmania, including lists of species known to occur in the State, can be accessed in the Internal linkAnimal Pests and Diseases Indicator and through the Department of Primary Industries, Parks, Water and Environment (DPIPWE) External linkWhat can be done about introduced animals? website.
Significance of animal pests
Of the most important animal pests in Tasmania, European foxes, feral cats, feral rabbits, feral pigs and feral goats have an impact on a wide range of native species and with the potential of causing adverse changes in ecological communities in Tasmania. Predation by European foxes and feral cats are listed key threatening processes under the Commonwealth External link: LegislationEndangered Species Protection Act 1992, whilst competition with native species and land degradation by rabbits, pigs and goats are also key threatening processes under the External link: LegislationEnvironment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Populations of a few exotic species have also been established in the wild to support recreational hunting. Whilst they are not considered environmental pests, they are managed to minimise any adverse impacts to the Tasmanian environment. The principal species that have been released in the State to support hunting and sporting interests are the fallow deer (Dama dama) and the 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).
Other species such as introduced invertebrates also pose a significant but largely unknown threat to Tasmania's plants and animals. Since the last SoE Report in 2003, eight invertebrate species including the Thorell redback spider (Latrodectus hasselti) and Argentine ant (Linepithema humile) have become well established and widespread in Tasmania, but have also been de-listed as declared animal pests under Section 10 (List B) of the External link: LegislationPlant Quarantine Act 1997. List B pests and diseases are declared under the Act as being present in the State, although they may not be widespread and are usually contained or managed. Paradoxically, the de-listing of species from List B does not necessarily indicate that they pose a reduced environmental threat. The delisting of species from List B can be indicative of the species becoming well established and it may pose a potentially greater environmental threat. Despite the de-listing of these invertebrates, their affects on native species is largely unknown. More information on animal pests in Tasmania is detailed in the Internal linkAnimal Pests and Diseases Indicator and Internal linkIntroduced Species on Offshore Islands Indicator.
Many introduced animals in Tasmania have become self supporting in the wild and now affect native plants and animals and potentially ecosystems. Of the 447 introduced animal species recorded as being present in Tasmania in 2008, 47 (34 vertebrates and 13 invertebrates) are identified as being 'key' environmental pests. In the previous SoE Report in 2003, 44 'key' environmental pests were identified (32 vertebrates and 12 invertebrates). Although there appears to be an increase in the number of 'key' environmental pests in the State, the source information remains inconclusive and uncertainty remains about the accuracy of the trend. The following table outlines a number of environmental pests and their distribution in Tasmania.
Examples of environmental pests and their distribution in Tasmania Source: DPIPWE; IFS
Examples of environmental pests and their distribution in Tasmania
Source: DPIPWE; IFS
Despite the substantial number of introduced animals known to occur in Tasmania, very little is known about their pest status or their impacts upon native species or ecosystems. However, it is known that introduced species that have become environmental pests prey upon and compete with native animals for food, destroy habitat and interfere with natural environmental processes. For example, feral cats are suspected of having a profound effect on Tasmanian native animals. However, there is little documented evidence that evaluates the impacts of cats on prey animals and ecological community structure. In addition, the presence of brown trout has been linked with the decline of several native fish species and some invertebrate species. Environmental pests can also potentially spread disease or environmental weeds, and cause economic losses to agricultural and tourism industry sectors. Generally, our knowledge is limited to monitoring and research conducted for a small number of pest animals. Examples of impacts from these pests in the State are detailed in the following table.
Examples of impacts from animal pests in Tasmania Further information on marine pests is available within the Marine Pests Issue Report. Source: DPIPWE; IFS; CSIRO Marine and Atmospheric Research
Examples of impacts from animal pests in Tasmania
Further information on marine pests is available within the Marine Pests Issue Report.
Source: DPIPWE; IFS; CSIRO Marine and Atmospheric Research
The distribution of vertebrate animal pests in Tasmania is species dependent. More information on key environmental pests and their distribution in Tasmania is detailed in the Internal linkAnimal Pests and Diseases Indicator and Internal linkIntroduced Species on Offshore Islands Indicator. Some species, such as the feral cat and common starling are widespread.
Since 2000, there has been an increasing amount of evidence (i.e. carcasses, scats, footprints and blood) of a small number of European foxes in the State (see, for example, Internal linkDPIPWE 2009; Internal linkDPIWE 2002). The establishment and predation of foxes is the most significant threat to the State's native mammals and birds. Although not yet established in the TWWHA, the fox also represents the biggest potential threat to native animals in the area. This 'key' environmental pest is listed as a national threat under the EPBC Act.
Given that Tasmania has been recognised as a national and international haven for native land-based animals due to the lack of foxes, if this pest animal became established native wildlife would be at substantial risk from predation. Due to their wide diet, foxes also compete with many animals, such as raptors and ravens. The masked owl (Tyto novaehollandiae), brown goshawk (Accipiter fasciatus), wedge-tailed eagle (Aquila audax) and Tasmanian devil (Sarcophilus harrisi) are some of the species that will be threatened as they compete with the fox for food (Internal linkState of Tasmania 2007). In addition, given that the nature-based tourism is a valuable industry to the State, the loss of our unique native wildlife to foxes could cause a reduction in the number of tourists being attracted to the State and jeopardise jobs within this industry. Further information on the European fox is available through the Internal linkDPIPWE website. Some key issues are provided in the embedded document Internal linkEuropean foxes in Tasmania and locations of hard evidence reports and sightings confirming the presence of this species in the State is detailed in the Internal linkAnimal Pests and Diseases Indicator.
Alternatively, some animal pests, such as feral pigs that are found on Flinders Island, are restricted in their distribution. Other examples include the introduction of the European carp in Lake Crescent and Lake Sorell (located on the Tasmanian Central Plateau), and the fish and frog egg-eating eastern gambusia (Gambusia holbrooki) located in the Tamar River and isolated farm dams in the south of the State. The distribution of invertebrate animal pests in Tasmania can also be species dependent. For example, yabbies (Cherax spp.) were initially released into farm dams, bur have now become widespread. European wasps were also once restricted to the Hobart area but are now widespread and common.
This SoE Report does not focus on the impact of native animals that have become pests in Tasmanian although they have been introduced to other areas in the State or the offshore islands. There is considerable uncertainty surrounding this issue, particularly regarding the impacts of native animals such as the 'over-abundance' of brushtail possums (Trichosurus vulpecula). Other examples of native animal introductions is the establishment of Bennetts wallabies (Macropus rufogriseus) and Forester kangaroos (Macropus giganteus) on Maria Island and Bennetts wallabies on Deal Island (Internal linkDPIWE 2005).
Other native animal pests that invade young native forests include invertebrates such as chrysomelids, scarabs, psyllids, sawflies, moths and weevils. The chrysomelids, (Chrysophtharta bimaculata) and (C. agricola), remain the major insect defoliators in young Eucalypt spp. plantations (Internal linkWardlaw 2008). Damage to these plantations from defoliating insects generally showed a sharp increase in 2004–05 and 2005–06 from previous years, particularly in lowland areas of southern Tasmania (Internal linkState of Tasmania 2007). However, according to Forestry Tasmania in the Draft Forest Management Plan 2008–17, 'native species of weeds, pests and diseases, by and large, pose minimal threat to values being managed on State Forest' (Internal linkForestry Tasmania 2008).
Native Animal Diseases
From the mid-1990s, 13 new wildlife diseases have emerged in Australia and their introduction highlights an unprecedented global trend (Internal linkPhillips 2008). Many of these wildlife diseases are found in Tasmania. The ability to prepare and respond to unusual deaths resulting from native animal disease introductions into the State can only be based on prior knowledge and understanding of disease incidents that have occurred and an understanding about the environmental conditions associated with a disease outbreak (Obendorf and Woods in Internal linkAWHN 2004). The occurrence and localisation of a native animal disease is determined by various factors including those relating to the host, the causative agent and the environment. Environmental factors include complex interactions between climate, topography, soil, water and biotic features such as the overall composition of other animals (and plants), the location of the disease and more broadly, climate change. Other human centred factors contribute to the emergence of diseases including habitat destruction, urbanisation, change in agricultural practices, chemical usage, water distribution and human disturbance.
There are several known diseases affecting populations of native animals in Tasmania including the following:
DFTD, amphibian chytridiomycosis (that affects frogs), platypus mucormycosis and Psittacine Circoviral Disease (PCD) currently have the highest priority for research and management in the State given the significant threats they pose to native animals. More information is provided in the embedded document Internal linkAssessment of other native animal diseases in Tasmania and it details a range of other diseases that have the potential to affect native animals in Tasmania. More information on native animal diseases in Tasmania is detailed in the Internal linkAnimal Pests and Diseases Indicator.
Tasmanian Devil Facial Tumour Disease
DFTD is a neoplastic disease fatal to the Tasmanian devil. The disease appears to be a new infectious disease that affects only adult Tasmanian devils. Small lumps in and around the mouth develop into large tumours on the face and neck. Once the tumour becomes visible, the animal usually dies within months. Given that Tasmanian devils are endemic and restricted to Tasmania, the impact of this disease has been devastating on the total population.
Although Tasmanian devils were first photographed in 1996 in the northeast of the State with what appeared to be large facial tumours, the first clear indications of the impact and wide distribution of DFTD emerged in 2003 (Internal linkHawkins et al. 2006). By 2006, scientists estimated the wild devil population had fallen to 80,000 individuals, from around 140,000 in the 1990s, due to the spread of this disease. The best estimate based on December 2006 data puts Tasmanian devil numbers at between 20,000–50,000 mature individuals, which is assumed to be about half the overall numbers (Internal linkTasmanian Government and University of Tasmania 2009). In 2007, Dr Hamish McCallum estimated that Tasmanian devil numbers were around 15,000 to 20,000 individuals (Internal linkPickrell 2007). Irrespective of estimates of the remaining population, it is clear that the disease is having a catastrophic affect on the Tasmanian devil population as it spreads across the State.
The Tasmanian devil was first protected by law in 1941. Given the significant threat of DFTD on the total population, in 2006 the species was listed as threatened (classed as 'vulnerable') under the Tasmanian External link: LegislationThreatened Species Protection Act 1995 and the Commonwealth's External link: LegislationEndangered Species Protection Act 1992. It is also listed as a protected species under the Tasmanian External link: LegislationNature Conservation Act 2002. After a recent review of Tasmania's Threatened Species Protection Act 1995 the status of the Tasmanian devil was raised in May 2008 from 'vulnerable' to 'endangered'. The endangered listing was based on expert advice that this species may be extinct in the wild within 20 years.
Amphibian chytridiomycosis (chytrid fungus)
Tasmania's native amphibian population (including frogs) is under threat from the pathogenic fungus, Batrachochytrium dendrobatidis. The fungus is known as amphibian chytrid fungus, and it causes the infectious disease known as chytridiomycosis (Internal linkDPIPWE 2009; Internal linkObendorf 2005). The disease is a problem in four regions across Australia, including Tasmania, and is thought to be the cause 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). A Threat Abatement Plan for this disease has been developed by the Australian Government in consultation with the state and territory governments.
The fungus was first detected in Tasmania in 2004 (but was probably introduced to Tasmania much earlier) and has subsequently been found in free-living frog populations of Tasmania in a range of urban and rural habitats, particularly in the eastern and northern parts of the State (Internal linkPauza and Driessen 2008 and Internal linkDriessen and Hocking 2008). It is likely that frogs carrying the fungus were accidentally introduced from mainland Australia into Tasmania (e.g. via fresh food produce such as banana boxes).
Amphibian chytrid can be transferred across a landscape through movement of freshwater and aquatic substrates, plants and organisms; infected amphibian carriers; and contaminated wet soil (Internal linkDPIW 2007). Other human activities such as bushwalking or recreational fishing can also transfer the fungus to new locations via contaminated equipment or the unintentional or intentional movement of frogs and tadpoles. Because amphibian chytrid is readily transferable, there is a significant threat to all susceptible frog populations across the State, particularly endemic, vulnerable wild frog populations such as the Tasmanian tree frog (Litoria burrowsae) and threatened frog species such as the green and gold frog (Litoria raniformis). Further information on chytridiomycosis in Tasmania can be accessed through the External linkDPIPWE website.
The resilience of amphibians in Tasmania to changes in climate could be severely compromised. In a paper in the leading international journal Nature in 2006, researchers contend that 'the climate-linked epidemic hypothesis predicts amphibian declines in unusually warm years, because shifts in temperature or related variables often influence disease dynamics ... as temperatures rise, climate fluctuations may cross thresholds for certain pathogens, triggering outbreaks' (Internal linkPounds et al. 2006). If this occurs, diseases (including amphibian chytrid) are expected to become more lethal, or spread more readily, as the Earth warms. In Tasmania, warmer or dryer conditions may stress amphibians, possibly increasing their susceptibility to disease. Warm years could also favour chytridiomycosis. This lethal combination could potentially result in the extinction of Tasmania's amphibian populations.
Platypuses are quite common across Tasmania but there are concerns for their population health due to the presence of the debilitating mucormycosis fungal disease, which is caused by the Mucor amphibiorum fungus. This disease is also a threat because platypuses are highly cryptic and if it were to become firmly established, this water-based animal would be difficult to locate and manage.
The disease can cause skin lesions or ulcers on various parts of their body (i.e. backs, tails and legs) and possibly further problems with the underlying muscles and internal organs. It can also lead to death from secondary infection and an inability to control body temperature (Internal linkDPIW 2007). Information from DPIPWE indicates that mucormycosis is acquired naturally by free-ranging platypuses in Tasmania (Internal linkDPIW 2007). An unusual feature of this fungal disease is that 'it affects platypuses only in Tasmania and not on the Australian mainland where the same pathogen infects frogs and toads' (Internal linkDPIPWE 2009). There is limited knowledge about how much impact the disease is having on the platypus population, how it is transmitted or how widespread it is across the State.
Platypus mucormycosis fungal disease was first detected in platypuses in 1982 in the Elizabeth River near Campbell Town in the north of Tasmania (Internal linkDPIPWE 2009). The disease appears to have spread widely from this region in the subsequent 25 years. Speculation remains about how the fungus was introduced into the State, although it may have been were accidentally introduced via fresh food produce (such as banana boxes). The 1997 SoE Report reported that this disease was restricted to the broad river valleys of the South Esk and Macquarie rivers in northern Tasmania (Internal linkSDAC 1997).
Psittacine Beak and Feather Disease
Psittacine Beak and Feather Disease (PCD) is a virus that affects psittacine species (parrots and related species) such as the critically endangered orange-bellied parrot (Neophema chrysogaster) and the endangered swift parrot (Lathamus discolor). It was first confirmed in Tasmania in 1987 in the orange-bellied parrot population (Internal linkDEH 2004). This disease does not appear to threaten the survival of non-endangered parrot species as larger populations can sustain the losses from the disease and some birds build up immunity. Although this disease is believed to occur naturally, it is often fatal to more vulnerable bird species and is considered one of the threatening processes contributing to the pressures on the orange-bellied parrot population. PCD is listed as a key threatening process under the EPBC Act (see Internal linkDEH 2004).
Broader concerns and climate change
Animal pests and diseases introduced into Tasmania from mainland Australia or overseas could unexpectedly threaten native plants and animals. A local example of an unexpected disease threat in the State is the spread of amphibian chytrid fungus. In addition, we know very little about other diseases impacting native animals in the State. One example of a poorly understood native animal disease is the avian pox virus infection. This disease was identified in the shy albatross (Thalassarche cauta) population breeding on Albatross Island in the late 1990s. Shy albatrosses breed in three colonies on Albatross Island, Pedra Branca and the remote Mewstone Island (this disease does not appear to be present at Pedra Branca or Mewstone islands). While the effect of this avian pox virus infection vary inter-annually, breeding success can be reduced to 10% in some colonies in some years due to chick deaths (Woods in Internal linkAWHN 2004 and Internal linkACAP 2006). Almost nothing is known about the shy albatross disease although it has the potential to have a significant effect upon the overall population dynamics of this species.
Adding to the known pressures that pests and/or introduced animals and native animal diseases have on Tasmania's native animals and plants is the potential threat of climate change. It is important to note that the Intergovernmental Panel on Climate Change have warned that globally, climate change appears to be associated with the spread of many animals and diseases.
It is possible that many native animals in Tasmania could be negatively impacted by changes in climate, particularly if the new conditions favour the survival of animal pests and native animal diseases. Climate change could alter not only the composition and distribution of animal pests and native animal diseases; it could alter their growth rate and abundance or may affect the ecosystem sensitivity to threats. If this eventuated, environmentally stressed species could become more susceptible to pests, diseases and pathogens or less able to compete for resources (Internal linkDunlop and Brown 2008). Further information on climate change is available within the Internal linkClimate Variability and Change Issue Report.
DPIPWE has developed the Review of Wildlife Monitoring Priorities, 2008 (Internal linkDriessen and Hocking 2008). The document identifies six species of introduced animals as Priority 1 species for monitoring. They are European foxes across Tasmania, feral cats on offshore islands, rabbits at Strathgordon, black rats (Rattus rattus) and rabbits on Macquarie Island, Indian myna birds (Acridotheres tristis) across Tasmania and common starlings at Birches Inlet and Melaleuca. Ten introduced animals are also identified as Priority 2 species. Monitoring priorities and Priority 1 and 2 species identified by DPIPWE for animal pests are detailed in the Internal linkAnimal Pests and Diseases Indicator.
The impacts of intentionally and unintentionally introduced animals and diseases into Tasmania are significant threats that are poorly understood. An introduced animal or disease is often brought into the State by human agency or into areas of human disturbance. However, they can also be introduced on other animals (such as parasites of pets, crops and stock), and on various vehicles of transport (such as planes, cars, ships and bikes). One emerging threat is the importation of reptiles and amphibians (such as snakes and turtles) into Tasmania. These animals are either being illegally brought into the State as exotic pets or they are inadvertently being transported via freight cargo. Recent examples have involved the illegal importation into Tasmania of the semi-aquatic long-necked freshwater tortoise, and the highly invasive semi-aquatic North American slider turtle (Trachemys scripta elegans) that was imported from Italy (Glenn Atkinson, pers. comm. 2008). This aggressive turtle, with its distinctive red facial markings, has no known predators and therefore has the potential to displace native species.
Abandoned animals can also establish themselves as feral introduced species. When these animals become feral they compete with native animals for food and can spread disease into new areas. A number of non-native mammals, birds and fish are already present in Tasmania as pets (including cats, dogs, ferrets, galahs and goldfish). For example, ferrets (Mustela furo) pose a significant threat to Tasmania's wildlife because they prey upon small native mammals and birds. In the past, feral populations of this species have been found at South Arm near Hobart, to the south of Launceston and potentially on King Island.
Native Animal Diseases
DFTD, amphibian chytridmycosis, platypus mucormycosis and PCD have been given priority with respect to their assessment, monitoring and management in Tasmania. Information is provided below on the status of these diseases and the programs and processes that have been implemented for their assessment and measurement. The DPIW (now DPIPWE) report on Wildlife Health in Tasmania: Disease Information (Internal linkDPIW 2007) provides an important source of information on these diseases and other 'diseases of concern' in relation to their impacts on native fauna.
Tasmanian Devil Facial Turmour Disease
By October 2008, DFTD had spread to 64 confirmed locations covering over 60% of Tasmania (Internal linkTasmanian Government and University of Tasmania 2009). Although wildlife diseases rarely cause extinction, no evidence to date suggests that this disease will stop spreading across Tasmania, or that Tasmanian devil populations can recover once infected (Internal linkState of Tasmania 2007). No local extinctions have yet been detected in Tasmania and this animal still exists throughout the State. Locations where the DFTD has been confirmed are detailed in the Internal linkAnimal Pests and Diseases Indicator.
Across Tasmania, there has been between a 64% and 70% decline in average sightings of Tasmanian devils over the last decade (Internal linkDPIPWE 2009). In the northeast, where signs of DFTD were first reported, there has been a 95% (approximately) decline of average spotlighting sightings of this species from 1992–95 to 2002–05 (Internal linkTasmanian Government and University of Tasmania 2009). Areas where Tasmanian devils have declined below carrying capacity due to the impact of the disease are also especially at risk from European foxes (Internal linkState of Tasmania 2007).
It is now known that the disease is transmissible between Tasmanian devils, so new cases continue to occur in areas where the disease had not previously been recorded. New sites include Guilford and Upper Natone both to the south of Burnie in the northwest of Tasmania. The proportion of animals displaying signs of the disease at any one site has reached up to 83% of trapped adults.
In November 2007, populations in the western third of the State appeared to have remained healthy and viable. However, given that research indicates the DFTD is transmissible, it is believed that the disease will spread across the range of the Tasmanian devil population within 5 to10 years. Researchers are also concerned that if the population is diminished, and if fox numbers increase, it may be increasingly difficult, if not impossible, for this species to recover.
Amphibian chytridiomycosis (chytrid fungus)
The report titled: Wildlife Health in Tasmania, 2007, highlights that there are seven species of frog that have shown visible lesions from the fungus during the tadpole stage of development (confirmed by analysis and/or histology) (Internal linkDPIW 2007). These species include the Tasmanian tree frog, green and gold frog, brown tree frog (Litoria ewingii) and common froglet (Crinia signifera). The Review of Wildlife Monitoring Priorities, 2008 also lists the southern toadlet (Pseudophryne semimarmorata), smooth froglet (Geocrinia laevis) and moss froglet (Bryobatrachus nimbus) as being at risk (Internal linkDriessen and Hocking 2008). Some of these species may be carriers of the disease and not succumb to infection.
Two studies conducted between 2004 and June 2007 confirmed that the amphibian chytrid fungus is established across Tasmania. The fungus has been verified in and around Hobart including Seven Mile Beach and the Mount Wellington Park. It has also been verified in and around Launceston and in the Nunamara and St Mary's areas to the east of the State. Other locations where this fungus has been verified include the Arthur-Pieman Conservation Area, Cradle Mountain, Mole Creek and Elizabeth Town in the northwest. The WWHA was found to be largely free of the disease (Internal linkDPIPWE 2009). Given that the majority of the WWHA is not readily accessible by humans and is largely free of the fungus, and that Tasmanian frogs reproduce in ponds rather than streams, it may be possible to control the spread of the disease in remote areas (Internal linkPauza and Driessen 2008). Locations where the amphibian chytrid fungus has been verified are detailed in the Internal linkAnimal Pests and Diseases Indicator.
Disease eradication is not possible due to the widespread distribution of amphibian chytrid fungus. Targeted eradication in strategic areas may become an option as research progresses (see, for example, Internal linkDEH 2006). The key objective for management of the disease is to control its spread into uninfected areas.
Since 1982, the platypus mucormycosis fungal disease appeared to have spread to a range of sites located in 11 catchments through the north central part of the State including the Supply, Meander, Liffey, South Esk and Elizabeth rivers, and Brumbys Creek. Other anecdotal reports suggest that the fungus may have spread to other southern and north western river systems, including the WWHA. The DPIPWE Platypus Fungal Disease website (Internal linkDPIPWE 2009) provides an important source of information on mucormycosis disease.
Although this disease has been present in Tasmania for more than 25 years, its impact on platypus populations is not well known due to limited monitoring and research (Internal linkDriessen and Hocking 2008). Many aspects of the epidemiology of the mucormycosis disease also remain to be established. Locations where the platypus mucormycosis disease has possibly occurred are detailed in the Internal linkAnimal Pests and Diseases Indicator.
Through 2008–09, DPIPWE conducted 32 field surveys across Tasmania to assess the current distribution and prevalence of mucormycosis (Internal linkDPIPWE 2009). Seven of the 179 animals examined were ulcerated with infected platypuses captured being from the Meander, Brumby's-Lake, South Esk and North Esk catchments. Disease prevalence (the infected proportion of the population) appears to have declined since the mid to late 1990s.
Psittacine Beak and Feather Disease
The Tasmanian Orange-bellied Parrot Recovery Plan, 1998–02 (Internal linkOrange-bellied Parrot Recovery Team 1999) suggests that since 1990 the mortality of captive-bred birds due to PCD had been practically eliminated with the relocation of the Hobart breeding facility to a warmer, more sheltered site. Evidence of exposure to the disease was detected at low prevalence in both wild and captive populations of orange-bellied parrots. A small incursion of clinical disease among captive birds during the 2007–08 breeding season resulted in increased monitoring and targeted management.
The presence of the disease within captive (breeding) orange-bellied parrots populations for increasing the numbers of birds in the wild add to the pressure on this species. Any individual bird loss is significant and captive birds that survive could spread the disease if they are released into the wild. There is currently no formalised monitoring of PCD in swift parrot populations.
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 animal pests and native animal diseases indicators
Index of animal pests and native animal diseases indicators
Fox sightings, March 2008
Fox sightings, March 2008internal SOE link to larger image
A: Carp in Lake Crescent
A: Carp in Lake Crescentinternal SOE link to larger image
B: Carp in Lake Sorell
B: Carp in Lake Sorellinternal SOE link to larger image
Tasmanian devils and feral cats
Tasmanian devils and feral catsinternal SOE link to larger image
Rabbits and hares
Rabbits and haresinternal SOE link to larger image
Fallow deerinternal SOE link to larger image
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 DPIPWE 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.
Offshore islands with known introduced vertebrate pests
Offshore islands with known introduced vertebrate pestsinternal SOE link to larger image
Introduced Species on Offshore Islands - at a glance
This indicator describes the number Tasmanian offshore islands where introduced vertebrate pests (e.g. cats, rabbits, rats, mice, goats) have been recorded, and the islands where management plans or actions provide information on the management of animal pests. Data was sourced from DPIPWE. Data availability and limitations are reviewed in the indicator.
The impact of introduced animals on Tasmania's offshore islands can be devastating. On some islands, they have caused major declines and extinctions of native species, especially seabirds. The maintenance of island ecosystems is essential to ensure the survival of native species, but also to maintain genetic diversity. This is because islands often support species that are genetically distinct from their mainland counterparts and their survival may depend upon maintaining the niche island ecosystem.
Tasmanian offshore islands may also increasingly offer important safe havens for the protection and preservation of native species that may otherwise become threatened or extinct on mainland Tasmania due to the predation or competition from environmental pests.
Density of Road Networks and Walking Tracks - at a glance
This indicator reports on the density of roading in a region (e.g. catchments) by providing a measure of the length of roading in each area. It also reports on the density of walking tracks in a region and provides a number of illustrative examples on where key walking tracks are found in the State. The data included in this indicator has been sourced from a number of sources including the DPIPWE Road Infrastructure Dataset (2008) and PWS Bushwalking Tracks Dataset (2008).
Roading and walking tracks provide access which gives rise to a range of pressures on the natural environment (e.g. ecosystems and other undisturbed or fluvial and coastal systems). They are often a precursor to changes in land use and land cover, which in turn, affect the potential of animal pests and native animal diseases being able to access new areas. Changes (which will normally be increases) in roading and walking track density within a region will imply a higher likelihood of adverse impacts on the natural environmental processes within that region.
For example, the hard evidence indicates that European foxes have become established in areas associated with human settlement and roading (Internal linkDPIW 2008). They have been sighted across the north of Tasmania, down the east coast and throughout the Midlands to the south. There have also been credible reports of foxes in the Huon Valley area and around Geeveston and Franklin in the south of the State.
In addition, a $23 million Tarkine tourist loop road in an area of Forest Reserve was approved by the Tasmanian Government in early 2009 to promote tourism on the north-west coast (Internal linkDEDT 2009). The project involves the upgrading of 127 km of existing gravel roads and tracks and completing a 7.6 km link of which 5.4 km will require new roading. It will extend from the Wynyard area, through forest reserves, accessing the 447,000 ha Tarkine Wilderness Area and connecting with the end of the Great Nature Trail at Arthur River. Some critics of the loop road point out that road developments such as these have the potential to hasten the transfer of unwanted organisms such as feral animals, weeds and other disease-causing pathogens (Open Letter of Concerned Scientists in Internal linkTasmanian Times 2009; see also Internal linkMilne 2009). For example, there are concerns that DFTD-infected Tasmanian devils and amphibian chytridiomycosis may be spread into this disease-free Tarkine area.
There have been a number of management responses and changes since the 2003 SoE Report that are relevant to managing and controlling animal pests and native animal diseases in Tasmania. In this regard, DPIPWE continues to engage with other government agencies, NRM regions, industry bodies (such as Forestry Tasmania and Hydro Tasmania) and the general community to increase knowledge and awareness about the abundance, distribution and environmental impacts of animal pests and native animal diseases in the State. Some of the key responses, including policies and strategies and other related programs, projects, frameworks and initiatives are listed below.
Animal pest and disease management legislation
Management policies and strategies
Other programs, projects, frameworks and initiatives
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