Predation and Hybridisation by Feral Dogs (Canis lupus familiaris) - key threatening process listing
NSW Scientific Committee - final determination
The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Predation and Hybridisation by Feral Dogs (Canis lupus familiaris) as a KEY THREATENING PROCESS in Schedule 3 of the Act. Listing of Key Threatening Processes is provided for by Part 2 of the Act.
The Scientific Committee has found that:
1. Domestic Dogs (Canis lupus familiaris) first became feral in Australian ecosystems soon after the arrival of Europeans. The magnitude of this invasion accelerated as Australia’s interior was inhabited by graziers and then agriculturists, bringing with them Domestic Dogs that escaped or were abandoned. Concurrently, the widespread destruction of the native Dingo (Canis lupus dingo) by poisoning and shooting removed the main competitor to Feral Dogs.
2. Both Domestic Dogs and Dingoes are considered subspecies of the wolf C. lupus. The Dingo originated in southern Asia and arrived in Australia about 4000–5000 years ago, most likely being transported by Asian seafarers (Corbett 1995; Savolainen et al. 2004). At the time of European settlement the Dingo was present throughout mainland Australia (Glen and Short 2000) although numbers are thought to have been low (Corbett 2001).
3. Domestic Dogs, both those that are feral and some that are associated with human habitation, can exert a high intensity of predation pressure on native fauna, especially medium to large macropods (Mitchell and Banks 2005). Unlike the Dingo, whose low population densities are responsive to widespread environmental constraints such as drought, there is a continual influx of Domestic Dogs into the wild, which maintains a more constant feral population. This means that Feral Dog population densities are not as strongly controlled by limiting environmental factors, persist at higher densities than a carnivore of their size would typically be able to sustain, and can rapidly recolonise habitats where dogs are eliminated by starvation or intentional poisoning. Modification of habitat and increased prey availability after European settlement have contributed to increases in canid populations (Corbett 2001), for example through the construction of artesian bores that allowed livestock to forage in arid areas, thus providing water and prey during droughts. These factors indicate that predation pressure from canids in some areas is higher than was the case prior to European settlement.
4. Even some Domestic Dogs can be a serious problem to native fauna if uncontrolled. For example, Domestic Dogs exterminated a colony of Little Penguins near Eden in a single night (Woodford 2005). Furthermore, some Domestic Dogs that are heavily reliant on humans for sustenance nonetheless hunt native fauna in nearby bushland and nature reserves.
5. There is a growing body of evidence that Dingoes play an important role as ‘trophic regulators’ in natural ecosystems, and that they can protect native species by controlling the density of Red Foxes, Cats, Goats and other feral species (e.g. Glen et al. 2007; Johnson et al. 2007; Wallach and O’Neill 2008). The role of Feral Dogs and hybrids in replacing Dingoes as trophic regulators remains uncertain (Daniels and Corbett 2003; Glen and Dickman 2005; Mitchell and Banks 2005), in part due to the potential differences between the taxa in their density, hunting behaviour, social structure and body size.
6. As with two other introduced carnivores, the Cat and Red Fox, predation pressure on native fauna by Feral Dogs threatens a number of species, including the following threatened fauna:
Spotted-tailed Quoll Dasyurus maculatus Vulnerable
Koala Phascolarctos cinereus Vulnerable
Southern Brown Bandicoot Isoodon obesulus obesulus Endangered
Eastern Ground Parrot Pezoporus wallicus wallicus Vulnerable
Pied Oystercatcher Haematopus longirostris Endangered
Hooded Plover Thinornis rubricollis Critically Endangered
Little Penguin Eudyptula minor Endangered Population
‘Predation by the European Red Fox Vulpes vulpes (Linnaeus, 1758)’ and ‘Predation by the Feral Cat Felis catus (Linnaeus, 1758)’ are listed as Key Threatening Processes under the NSW Threatened Species Conservation Act 1995.
7. All breeds of Domestic Dogs can interbreed with Dingoes, and the spread of Feral Dogs across NSW has led to widespread hybridisation between the two taxa. Dingo/dog hybrids now occur across mainland Australia but are most common in the east, southeast and southwest regions (Newsome and Corbett 1985; Corbett 1995; Wilton et al. 1999). As protection of Dingo populations from genetic introgression by Feral Dogs is difficult and expensive, the Dingo taxon is under serious decline as a consequence of hybridisation which may lead or has already led to the Dingo becoming threatened (Dickman and Lunney 2001). The IUCN elevated the global (Asia–Australia) status of Dingoes to Vulnerable in 2004 (Corbett 2008). In 2008 the Dingo was listed as threatened in Victoria under the Flora and Fauna Guarantee Act 1988 (Victorian Scientific Advisory Committee 2008). The Dingo is not listed as threatened in other states or territories.
8. There is currently no reliable field method for distinguishing pure Dingoes from hybrids (Elledge et al. 2006) although several behavioural and reproductive characteristics can help identify the subspecies. For example, Dingoes do not bark, and are seasonal breeders, producing one litter each winter, whereas most Domestic Dogs bark and have two oestrus periods per year (Catling et al. 1992). External body characteristics are unreliable for classification of hybrids even when applied by experienced Dingo experts (Corbett 1995). Skull measurements on dead animals can separate pure Dingoes from pure Domestic Dogs but are less reliable for distinguishing hybrids (Newsome and Corbett 1985; Corbett 1995, 2001; Wilton 2001).
9. Microsatellite techniques are now being used to distinguish hybrids through laboratory analysis (Wilton et al. 1999; Wilton 2001). Survey results from NSW indicate that hybrids exist in all populations tested and their proportion in these populations appears to be increasing (Wilton et al. 1999; Corbett 2001). Estimates of the proportion of hybrids in some populations are as high as 78% (Corbett 1995). To date, genetic surveys have been limited and future systematic analysis may detect Dingo populations that have a higher level of purity than others (e.g. Sturt National Park).
10. The degree of hybridisation that may significantly compromise the ecological roles and the genetic and behavioural integrity of Dingo populations is not yet understood. Such knowledge is required to support management operations directed at the control of Feral Dogs and conservation of Dingoes (Claridge and Hunt 2008). This will be predicated upon improved understanding of how observable morphological and behavioural characteristics relate to the genetic composition and ecological roles of hybrids.
11. Feral Dogs are regarded as pests and their control in NSW is legislated by the Wild Dog Destruction Act 1921 and Rural Lands Protection Act 1998. These Acts require owners and occupiers of land to continuously suppress or destroy wild dogs (including Dingoes). In eastern NSW, control since the mid-1960s has been conducted primarily through aerial baiting, with continuous annual or biannual applications. However, due to the constant influx of Domestic Dogs into natural ecosystems, lasting eradication of even local populations of Feral Dogs is difficult and thus predation pressure by Feral Dogs is seldom eliminated for long periods.
12. At present the most realistic approach to reducing the threat of hybridisation between Domestic Dogs and Dingoes is to quarantine ‘pure’ or relatively pure Dingoes from Domestic Dog genes by establishing dog-free buffers around key Dingo populations. The current management policy of the Department of Environment and Climate Change aims to meet the joint objectives of Dingo conservation and agricultural protection (NPWS 1997; Davis 2001) by protecting core Dingo populations while controlling all wild dogs outside these areas. However, recent research on the long-range movement patterns of Dingoes/wild dogs, and their relatively low densities in the centre of large reserves (Claridge and Mills 2007), suggests that individual animals may range across very large areas. The non-selective removal of animals by baiting has unknown impacts on the social structure and territoriality of Dingoes. A core-and-buffer approach will therefore need to be rigorously designed and implemented to secure core Dingo populations from gradual hybridisation and the impacts of Feral Dog control in the buffer. In some areas, relatively pure dingo populations that include some hybrids may still represent the most suitable candidates for conserving or recovering the Dingo genotype and its ecosystem function.
13. Predation and Hybridisation by Feral Dogs (Canis lupus familiaris) is eligible to be listed as a Key Threatening Process as, in the opinion of the Scientific Committee:
(a) it adversely affects threatened species, populations or ecological communities, or
(b) could cause species, populations or ecological communities that are not threatened to become threatened.
Dr Richard Major
Proposed Gazettal date: 31/07/09
Exhibition period: 31/07/09 - 25/09/09
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