|Scientific Name:||Sarcophilus harrisii (Boitard, 1841)|
Ursinus harrisii Boitard, 1841
|Taxonomic Notes:||Sarcophilus laniarius has also been used recently in light of comparisons between a fossil specimen, S. laniarius (named prior to the naming of S. harrisii), and the extant species (Werdelin 1987).|
|Red List Category & Criteria:||Endangered A2be+3e ver 3.1|
|Assessor(s):||Hawkins, C.E., McCallum, H., Mooney, N., Jones, M. & Holdsworth, M.|
|Reviewer(s):||Hoffmann, M. & Chanson, J. (Global Mammal Assessment Team)|
Listed as Endangered as standardized surveys indicate that the global Tasmanian Devil population has declined by more than 60% in the last 10 years (Hawkins et al. 2006, McCallum et al. 2007). Research indicates that an invariably fatal infectious cancer, Devil Facial Tumour Disease (DFTD), is responsible for the decline. DFTD currently occurs across the majority (estimated 60%) of the geographic range of the devil and continues to spread at variable rates (depending on location) in the range of 7-50 km/y (McCallum et al. 2007). Mark-recapture data from the most intensively studied population at Freycinet National Park estimated a decline in total population size of 30% in the first 3 years after disease arrival, with an annual decline in the adult (2+) population of 50% (Lachish et al. 2007). Both projections from these observed results and an epidemiological model predict local extinction at this site within 10 years of disease arrival (McCallum et al. 2007). At a second site, Mt William, where DFTD signs were first reported 10 years ago, mark-recapture methods estimate a decline of 90% over 10 years. There is no evidence either of a reduction in disease prevalence or of the rate of population decline as devil abundance reduces. On current information, we therefore project at least 90% population decline over the next 10 years across the 60% of the devil's distribution currently occupied by disease, with at least a 100 km extension of the disease distribution. Together, this would amount to a further decline (in excess of the 50% already observed) of at least 70% in the next 10 years, with widespread local extinctions. Whilst the cause of decline (DFTD) is understood, it has not ceased and its effects are not reversible with current knowledge.
|Previously published Red List assessments:|
|Range Description:||The Tasmanian Devil is found throughout mainland Tasmania, Australia, an area of 64,030 km2. The species disappeared from the Australian mainland 430 +/-160 years ago (Archer and Baynes 1972), possibly through competition with dingos (Guiler 1982) and Aboriginals (Johnson and Wroe 2003). Tasmanian Devils were introduced to the small offshore Badger Island in the mid-1990s, but as of August 2007 all Tasmanian Devils were thought to have been removed from this island (N.Mooney unpubl.).|
Tasmanian Devils were present on Bruny Island (a large inshore island off south-eastern Tasmania) in the early 1800s, but there are no confirmed records from after 1900. Tasmanian Devils also occur on Robbins Island, a large inshore island to the north-west, semi-connected to mainland Tasmania.
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||In the early to mid-1990s, the total population estimate was 130,000–150,000 individuals (M. Jones pers. comm.; N. Mooney pers. comm.; DPIW unpubl.), based on extrapolations of population density estimates according to habitat. Systematic statewide spotlighting surveys have been carried out since 1985. Spotlighting sightings of Tasmanian Devils across the state have declined significantly since emergence of Devil Facial Tumour Disease (DFTD) in the mid-1990s: by 27% by early 2004, by 41% by early 2006, by 53% by early 2007 (Hawkins et al. 2006; McCallum et al. 2007), and by 64% by early 2008 (C. Hawkins et al. unpubl.). The decline was significantly sharper in regions where DFTD had been reported earliest, such that in north-east Tasmania, mean sightings have declined by 95% from 1992-1995 to 2005-2007, with no indication of recovery or plateau in decline. Comparison of mark-recapture results in the same area from the mid-1980s and 2007 supports this finding (McCallum et al. 2007). At the Freycinet peninsula, on the east coast of Tasmania, where the population has been monitored through trapping from 1999 to the present, the population has declined by at least 60% since the disease was first detected in 2001 and the adult population still appears to be halving annually (Lachish et al. 2007). Other indicators of devil abundance, such as roadkills, predation on stock, and carrion removal, also support this conclusion of a substantial decline.|
If a 64% decline based on spotlighting surveys is applied to the population estimates from the mid-1990s, the 2007 population size would have been an estimated 25,000 mature individuals (50,000 individuals total). Another method generated an estimated total population size in 2004 of approximately 21,000 mature individuals (C. Hawkins, unpubl.). This estimate was derived from mark-recapture density estimates from ten sites (four disease-free sites, six diseased sites) in the highest density areas (north-east and south-east Tasmania) and from one disease free site outside the high density area. The population estimate at each trapping site incorporated 95% confidence intervals of +/-c. 25%. A standard buffer was placed around each trap site to calculate the area from which Tasmanian Devils are trapped during a survey, and this area varies between sites, affecting density calculations. If this estimate is of a population that had declined by 27% of the pre-disease population size, then the 2007 population (estimated to have declined by 64%) would be 10,000 mature individuals.
For both estimates, the potential error is high and still under discussion. The estimation of mature individuals is particularly subject to error since the disease has so reduced the proportion of older individuals: in disease-free sites, half of all individuals trapped are typically mature, but this proportion is much less in diseased sites (varying locally according to time since disease emergence). Acknowledging these provisos, the best estimate of total population size based on current evidence thus lies within the range of 10,000-25,000 mature individuals.
While Tasmanian Devil distribution across the state appears to be continuous, two management units have been identified, with devils in north-western Tasmania being genetically distinct from those found across the rest of the State (Jones et al. 2004; Farmer 2006).
North-western. Jones et al. (2004) identified a genetically distinct management unit in northwestern Tasmania, across approximately 13,400 km², west of the Forth river and south to Macquarie Heads (Farmer 2006). This region encompasses four sites intensively surveyed by the Devil Disease Team since 2004, and one surveyed by C. Hawkins (unpubl.) in 2003. One of the Devil Disease Team sites, Woolnorth, holds the highest population density of Tasmanian Devils found in any of the Team's surveys, which is more than double that at the other sites. Extrapolating from the resulting density estimates, this management unit may currently consist of between 3,000 and 12,500 mature individuals. This management unit is not currently declining, but DFTD is expected to continue to spread into it.
Eastern/South-western. The remaining 50,630 km² area covers nine sites surveyed by the Save the Tasmanian Devil Program since 2004. The mean of the density estimates for each of these sites applied to this area (separating formerly high eastern areas and from long term low density southeastern areas as described above) indicates an approximate population size of 7,000 - 12,500 mature individuals.
Jones and Rose (1996) related statewide survey results to environmental and climatic features, generating a CORTEX spatial model predicting distribution and relative densities across the state (Figure 1). Findings from mark-recapture trapping surveys and other trapping work by the Department of Primary Industry and Water (DPIW) Save the Tasmanian Devil Program broadly support these predictions for DFTD-free regions. However, in central and eastern regions, marked population declines have been detected, in association with the earlier reports of Devil Facial Tumour Disease (DFTD) (Hawkins et al. 2006; McCallum et al. 2007), subsequent to the time of the Jones and Rose survey. The north-west region is thus now thought to support the highest population densities.
The general population trend for the entire species is a decline (McCallum et al. 2007; Hawkins et al. 2006; DPIWE, 2005).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Tasmanian Devils are found throughout Tasmania, in all native terrestrial habitats, as well as in forestry plantations and pasture, from sea level to all but the highest peaks of Tasmania (Jones and Rose 1996, Jones and Barmuta 2000). Densities are lowest in the buttongrass plains of the south-west and, prior to Devil Facial Tumour Disease (DFTD) emergence, highest in the dry and mixed sclerophyll forests and coastal heath of Tasmania's eastern half and north-west coast (Jones and Rose 1996). Open forests and woodlands are preferred, while tall or dense wet forests are avoided (Jones and Rose 1996; Jones and Barmuta 2000). The highest population densities are found in mixed patches of grazing land and forest or woodland. Relative trapping success and spool-and-line tracking indicate that Tasmanian Devils travel through lowlands, saddles and along creeks, avoiding steep slopes and rocky areas, and favouring predictably rich sources of food such as bush/pasture mosaics on farms, carcass and rubbish dumps, and roads (Jones and Barmuta 2000, Pukk 2005; N. Mooney and D. Pemberton pers. comm.). Tasmanian Devils are able to reach very high densities, even in suboptimal habitat, if sufficient food and den sites are available. The 14 km² Badger Island at one time supported 120 Tasmanian Devils.|
Seabird colonies, such as Short-tailed Shearwaters (or muttonbirds, Puffinus tenuirostris), are thought to have traditionally been a preferred habitat for Tasmanian Devils, providing an important food source. These are now much reduced along the east coast, but some sites remain along the west coast (D. Pemberton pers. comm.).
Dens are typically underground burrows (such as old wombat burrows), dense riparian vegetation, thick grass tussocks and caves. Adults are thought to remain faithful to their dens for life so den disturbance is destabilizing to populations (Owen and Pemberton 2005). In settled areas, dens are often under buildings which may be occupied by people.
Tasmanian Devils are the sole host to the only threatened invertebrate parasite, a tapeworm, Dasyurotaenia robusta, which is currently listed as Rare under the Tasmanian Threatened Species Protection Act 1995.
Tasmanian Devils are considered to be generalist predators and specialized scavengers; prey comprise primarily medium- to large-sized mammals, although they will eat large invertebrates such as bogong moths (Agrotis infusa) and the carcasses of any dead vertebrates, leading them to focus on areas where lambing, calving or wallaby shooting are in progress (Guiler 1970a, Jones and Barmuta 2000, Jones 2003, Owen and Pemberton 2005). Tasmanian Devils solitarily and actively hunt prey up to about 20 kg in size (including Bennett's Wallabies, Macropus rufogriseus rufogriseus, and Common Wombats, Vombattus ursinus) using a combination of ambush and short, moderate-speed pursuits (Jones 1998, 2003; Owen and Pemberton 2005).
Devils are usually nocturnal. There are no data to suggest seasonal changes in pattern of movement, apart from reduced activity of females with young in their dens (Pemberton 1990), although longer range movements (see below) are observed more frequently in winter. Tasmanian Devils occupy several different dens, changing dens every 1-3 days, and travelling a mean nightly distance of 8.6 km (Pemberton 1990). However, individuals have occasionally been observed to move up to 50 km in a single night (M. Jones pers. comm.).
Home ranges are found to overlap considerably. A typical home range across a two to four week period is estimated to be 13 km², ranging from 4-27 km² (Pemberton 1990). Different breeding females may be caught outside the same den site (Badger Island, N. Mooney unpubl.).
The Tasmanian Devil is promiscuous and breeds once a year during February to June (Hesterman et al. 2008; M. Jones pers. comm., Save the Tasmanian Devil Program unpubl.). In earlier studies the mating season was found to occur over a much shorter period, primarily during February-March (Guiler 1970b; D. Pemberton pers. comm.).
The majority of individuals mature at two years old; in DFTD-free areas, 5-10% of females typically mature at one year (Guiler 1970b; Hughes 1982; Pemberton 1990; Jones et al. in review; Hesterman et al., in prep.).
Reproductive success is high in wild, non-diseased populations, with nearly all females of breeding age (2-4) bringing the full complement (n = 4) of pouched young through to weaning (Pemberton 1990; H. Hesterman unpubl.). Success to maturity of post-weaning individuals is unknown.
Tasmanian Devils are thought to breed and raise their young in traditional dens (Owen and Pemberton 2005), but new sites (e.g. under buildings) are also used.
Longevity in the wild is 5-6 years (Guiler 1978; Jones 2001; Jones et al. in press). The sum effect of mortality and emigration at Mount William (pre-disease) was estimated as 80% between the first and second year, followed by 20% in subsequent years (Pemberton 1990).
Increased contact between individuals in breeding season results in higher injury rates as a result of intra/inter-sexual aggression. DFTD is thought most likely to be most easily transmitted between Tasmanian Devils through biting (AUSVET 2005; Pearse and Swift 2006; Hamede 2007), therefore this is a time of higher potential for disease spread.
The major threat to this species at present is Devil Facial Tumour Disease (DFTD), compounded by roadkills, dog kills and persecution.
Devil Facial Tumour Disease (DFTD)
Current evidence suggests that DFTD is an infectious, widespread disease (McCallum et al. 2007), so that any attempt to delineate boundaries between affected and unaffected locations is likely to be outdated swiftly. DFTD has been associated with local population declines of up to 89% since first reported (Hawkins et al. 2006, McCallum et al. 2007), indicated by long-term spotlighting data, widespread trapping and laboratory results. The declines, and the prevalence of the disease, have not eased off in any monitoring sites, and DFTD is present even in very low density areas. It is estimated that the adult population is approximately halving annually on the Freycinet peninsula (Lachish et al. 2007) with extinction predicted at this site 10-15 years after disease arrival (McCallum et al. 2007). Declines were most marked in areas where the disease had been reported earliest, in north-eastern and central eastern Tasmania.
Mean spotlighting sightings of Tasmanian Devils per 10 km route, obtained from across the core Tasmanian Devil range (eastern and north-western Tasmania), have declined by 53% since the first report of DFTD-like symptoms in 1996 (McCallum et al. 2007). The most immediately threatened location is thought to be the region where DFTD was reported prior to 2003: across 15,000 km² of eastern Tasmania. By 2005, the Devil Disease Project Team had confirmed DFTD in individuals found across 36,000 km² of eastern and central Tasmania (Hawkins et al. 2006). DFTD is now confirmed across more than 60% of the devil's overall distribution (C. Hawkins unpubl.), and there is evidence for continued geographical spread of the disease (Hawkins et al. 2006), so that Tasmanian Devils across between 51% and 100% of Tasmania may be, or have already been, subject to >90% declines in a ten-year period. The currently affected region covers the majority of the formerly high-density eastern management unit, involving what was perhaps around 80% of the total population.
DTFD has resulted in the progressive loss of first the older adults from the population and then the younger adults (Lachish et al. 2007) so that populations are comprised of one and two year olds (Jones et al. in press, Lachish et al. submitted). As female devils usually breed for the first time at age two, they may not successfully raise a litter before they die of DFTD (Lachish et al. submitted). An increase in precocial breeding indicates some compensatory response, but as yet this appears to have been insufficient to counter mortality (Jones et al. in press, Lachish et al. submitted).
DFTD behaves like a frequency-dependent disease, probably because the majority of the injurious biting, which is the type of contact most likely to lead to disease transmission, occurs between adults during the mating season (Hamede et al. in press). Frequency-dependent diseases, which are typically sexually transmitted, can lead to extinction (McCallum and Jones 2006). Because transmission occurs between the sexes at mating irrespective of population density, these types of diseases lack a threshold density below which they become extinct.
Cannibalism is considered fairly common in Tasmanian Devils and renders the species particularly vulnerable to disease transmission (Pfennig et al. 1998; Jones et al. 2007). However, modes of transmission of DFTD are not as yet known.
A recent three-year study of roadkill frequency on the main roads of Tasmania estimated 2,205 Tasmanian Devils are killed on roads annually (Hobday and Minstrell submitted). This suggests that 2-3.% of the total Tasmanian Devil population are killed on roads (based on an estimated population of 60,000–90,000 individuals at the time of the survey). The roaded parts of Tasmania closely match the core distribution area for Tasmanian Devils.
Roadkill was attributed as the cause of up to 50% and 20% of Tasmanian Devil death during a recording period of 17 months at Cradle Mountain and 12 months at Freycinet National Parks, respectively (Jones 2000; M. Jones pers. comm.). Local extinction and a similar rate of population decline at Cradle Mountain indicates that roadkill can cause local extinction, in which the road becomes a local sink (Jones 2000). Future impact is likely to remain at the same level.
Reports of about 50 devils killed per year by poorly controlled dogs are served from about 20 dog owners. There is no obligation or incentive for such reports, and generally some hesitance even among those providing them, so the real figures are more likely of the order of several hundred devils killed by dogs each year.
There have been spasmodic, small-scale introductions of the Red Fox (Vulpes vulpes) into Tasmania since early European colonisation. Early incursions were sometimes efforts at acclimatisation and others for short-term hunting. More recently, there has been at least one accidental incursion (from a container ship in 1998) and credible reports of a concerted, malicious campaign of introduction. Hard evidence (confirmed scats, carcasses) of foxes has been found in the north-west and northern and southern midlands. Credible sighting reports have come from most of the eastern half of the State including the central highlands and the far north-west (Fox Free Tasmania 2006), mostly areas where Tasmanian Devil populations are suppressed by DFTD.
A commonly held view has been that the abundance of Tasmanian Devils has prevented fox establishment through interference competition, either aggressive exclusion or predation on denned juveniles (Jones et al. 2007). Red Foxes and Tasmanian Devils share preferences for den sites and habitat, and are of a similar size. Tasmanian Devils abundance is likely to slow, if not prevent, fox establishment. It is possible that foxes have been present in Tasmania for many decades at sub-detectable levels, and that a degree of ecological release has occurred due to DFTD, with foxes increasing to detectable numbers. The current impact of the Red Fox has been quantified (N. Mooney pers. comm.), and it is unlikely that fox numbers are currently at a level to impose a measurable impact.
A decline in Tasmanian Devils number may create a short to medium-term surplus of food, for example carrion; ideal for fox establishment. Fox establishment may cause both direct and indirect effects on Tasmanian Devils. Direct effects include (reciprocal) killing by then abundant foxes of then rare juvenile devils at dens while the female forages (Jones et al. 2007). Fox establishment may also cause ecosystem disruptions through changes in other species (Jones et al. 2007) - a feature of foxes on mainland Australia (e.g. Saunders et al. 1995) and something that might then also indirectly affect Tasmanian Devils. Tasmania has the potential to hold up to 250,000 foxes (based on modelling of habitat preferences and densities in south-east mainland Australian) which could replace most medium- to large-sized marsupial carnivores (N. Mooney unpubl.).
In the past, persecution of the Tasmanian Devil has been very high throughout settled parts of Tasmania, and is thought to have brought about very low numbers at times. Through the 1980s and 1990s, systematic poisoning in many sheep-growing areas (particularly fine-wool with its reliance on merinos) was widespread and probably killed in excess of 5000 devils per year (N. Mooney unpubl., from interviews with landowners). In the 1990s, control permits were occasionally issued to individuals who were able to argue that Tasmanian Devils were pests (e.g. killing valuable lambs).
Current persecution is much reduced, but can still be locally intense with in excess of 500 devils thought to be killed per year (N. Mooney pers. comm.). However, this is reducing since devil numbers have declined. While the small amount of current persecution is likely to persist it is unlikely to constitute a major threat unless the Tasmanian Devil population becomes extremely small and fragmented.
Low genetic diversity
Jones et al. (2004) found the genetic diversity of Tasmanian Devils to be low relative to many Australian marsupials as well as placental carnivores. This was consistent with an island founder effect, but previous marked reductions in population size may also have played a role. Low genetic diversity can reduce population viability (Eldridge et al. 1999) and resistance to disease (Acevedo-Whitehouse et al. 2005).
As of May 2008, the Tasmanian Devil is listed as Endangered under the Tasmanian Government's Threatened Species Protection Act 1995. It is also listed as Vulnerable under the Australian Government Environment Protection and Biodiversity Conservation Act 1999.
At the end of 2003, the Tasmanian State Government's Department of Primary Industries, Water and Environment (now Department of Primary Industries and Water) launched the Tasmanian Devil Disease Program to investigate and respond to the threat of Devil Facial Tumour Disease. This program, now called the Save the Tasmanian Devil Program, has attracted many collaborative researchers. A forum exclusive to those directly involved in DFTD research in February 2007 was attended by approximately 80 people. The mission of the Save the Tasmanian Devil Program is "to maintain the Tasmanian Devil as an ecologically functional species in the wild" (AUSVET 2005). Conservation actions, including research directed towards improving conservation management, are driven by three future scenarios that have the potential to turn the epidemic around and bring devils back into the landscape as an ecologically functional species (Jones et al. 2007). These are extinction in the wild and reintroduction, the evolution of resistance, and the broad-scale application of a vaccine. Four management actions can therefore potentially be employed: establishing insurance populations; disease suppression in wild populations; selection for disease resistance; and development of a vaccine (McCallum and Jones 2006). Each of these is included in the current Strategic Plan of the Save the Tasmanian Devil Program.
The highest priority is to establish insurance populations of healthy devils in places isolated from the disease, firstly to avoid total extinction and, secondly, as a source for reintroduction to the wild if devils, and therefore also the disease, become extinct. Because these populations will possibly carry the species for 25-50 years and because devils already have low genetic diversity, a conservative retention of genetic diversity of 95% is recommended (Jones et al. 2007; Save the Tasmanian Devil Program Insurance Population Strategy 2007). A large founder base of 150 individuals is recommended, to be built up to an effective population size of 500 individuals. This would mean maintaining an actual population size of about 1700 individuals, if they were all maintained in captivity where breeding is closely managed, or 5,000 individuals if they were all wild-living (Jones et al. 2007; Save the Tasmanian Devil Program Insurance Population Strategy 2007).
Insurance populations would ideally be managed as a metapopulation of multiple captive and wild populations with managed migration between populations to maintain genetic diversity (Jones et al. 2007). Maintenance of wild as well as captive insurance populations is important because wild-living animals retain natural behaviours and natural suites of parasites, pathogens and commensals, all of which are progressively lost in captive animals (Jones et al. 2007). The options for wild insurance populations are offshore islands, and fenced enclosures on mainland Australia and disease free areas on mainland Tasmania. There are a number of issues to be considered with these possible types of insurance populations, including the number of potential sites, the number of devils that could be held, balancing the conservation value of the sites for other purposes, ecological functionality, biosecurity risk, whether the site is currently disease-free or whether disease eradication would be required (see disease suppression below), cost of establishment and maintenance, stakeholders and timescale.
To date, there have been three intakes of founders for captive insurance populations from the wild: 26 devils from eastern (n=13) and north-western (n=12) genetic provenances in 2005, 25 north-western founders in 2007, and 63 north-western founders in 2008. Founders were collected from as wide a geographic area as assurity of disease-free status permitted at the time (established though intensive and extensive surveys and including a buffer zone). This intake area gets smaller each year as DFTD spreads, and is currently the north-west corner and a strip down the west coast. Founder devils were accepted for collection according to a strict set of protocols: recently weaned and likely to be pre-dispersal, no biting injuries and no signs of sexual maturity / oestrus in females. The first two intakes were maintained in quarantine in Tasmania for 20 months and 8 months, respectively, in facilities where there are no wild devils on the outside (e.g. suburban, island). The current intake will be maintained in quarantine for a shorter period. These founder devils are transferred to mainland zoos where they are managed by the Australasian Regional Association of Zoological Parks and Aquariums (ARAZPA).
A risk reduction document has been distributed to wildlife park operators and the zoological industry (DPIW 2005; Tasmanian Devil Facial Tumour Disease Management Strategy) outlining biosecurity measures to maintain the health of current captive populations. These measures include adaptation of husbandry protocols to include use of footbaths, employ appropriate waste disposal principles or secure enclosures to prevent contact between wild and captive Tasmanian Devils. Actions have been moderately successful in terms of increasing biosecurity at existing wildlife parks. An intra-state movement guideline was established requiring special permits to transfer Tasmanian Devils between parks.
Updates on the disease and quarantine protocols are regularly disseminated to all stakeholders.
Disease suppression adaptive management trial
The only technique currently available to manage or even eradicate the disease in wild populations is detection and removal (euthanasia) of infected individuals. This comes lower in the decision tree than establishment of insurance populations (McCallum and Jones 2006), but is also part of an insurance strategy (McCallum and Jones submitted). If this technique works, it is a means of eradicating the disease in isolatable areas. If eradication is not achievable, disease suppression is still potentially a cost-effective way of protecting wild devil populations (per devil cost per annum of A$1,000 cf. A$12,000 to maintain a devil in captivity). Disease suppression has other uses as well, such as maintaining buffer zones around fenced enclosures and eradicating incursions (McCallum and Jones submitted).
An adaptive management trial in disease suppression commenced in January 2006 (after an 18-month pilot study) on the Forestier peninsula, where the disease has newly arrived and prevalence was low, and where movement of diseased Tasmanian Devils across a bridge and canal can be restricted. Work is underway with the state road authority and an engineering consulting firm to construct a barrier to devils on the bridge. Diseased Tasmanian Devils are being removed from the peninsula population through intensive trapping, in the hope of reducing or extirpating the disease there and to learn more about possibilities of controlling DFTD elsewhere. If it is not possible to eradicate or even control the disease in this isolated site, it is probably not possible to do so elsewhere. The suppression has succeeded in limiting the extent of the population decline, age structure changes and geographic spread and the size of the tumours now being detected is smaller (Jones et al. 2007, unpubl.). In late 2006, the rate of transitions to new disease cases peaked and prevalence is now in decline (Lachish et al. in prep.). It is too early to say whether eradication is possible (M. Jones unpubl.).
Selection for resistance
Research is in progress to identify resistant genotypes, in the MHC gene complex associated with tumour recognition (Siddle et al. 2007), and in the peri-centric inversion in chromosome 5 (Pearse and Swift 2006). If resistant individuals are found, management could be directed towards artificial selection in captive or wild populations, or in translocating resistant individuals to depleted parts of the devil's range.
Current evidence suggests that lack of diversity at the major histocompatibility complex (MHC) is responsible for the disease being able to transmit between devils (Siddle et al. 2007). There is evidence that some individuals from the as yet uninfected West Coast have MHC profiles that differ from those found in the infected Eastern populations (Belov pers. comm). Whether these differences are sufficient to be protective is currently unknown, but it is an area of active research.
Vaccine and treatment research
Vaccine research is ongoing and potentially promising, but is expected to take many years to achieve success. To be effective for disease control in wild populations in Tasmania, much of which is rugged and inaccessible by vehicle, a vaccine would need to be orally delivered, preferably by aerial baiting.
Research into treatment using cytotoxic drugs is underway. Treatment could be a viable option for saving captive individuals with valuable bloodlines but is too intensive and expensive to ever be useful for conserving wild populations (Stephen Pyecroft pers. comm. in Jones et al. 2007).
Currently, approximately 40% of the state of Tasmania is protected, but this is unlikely to counter the effects of DFTD.
|Citation:||Hawkins, C.E., McCallum, H., Mooney, N., Jones, M. & Holdsworth, M. 2008. Sarcophilus harrisii. The IUCN Red List of Threatened Species 2008: e.T40540A10331066.Downloaded on 16 July 2018.|
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