Predation and Hybridisation by Feral Dogs (Canis lupus familiaris) - proposed key threatening process listing

NSW Scientific Committee - preliminary determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Preliminary Determination to support a proposal 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, 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 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. The role of Feral Dogs in replacing Dingoes as ‘trophic regulators’ in the natural ecosystem remains uncertain (Glen and Dickman 2005; Mitchell and Banks 2005; Daniels and Corbett 2003), in part due to the potential differences between the taxa in their density, hunting behaviour and social structure.

5. As with two other introduced carnivores, the Cat and Red Fox, predation pressure on native fauna by Feral Dogs threatens a large number of species, including the following threatened fauna:

 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 Endangered
 Little Penguin Eudyptula minor Endangered Population

‘Predation by the European Red Fox Vulpes vulpes (Linnaeus, 1758)’ and ‘Feral Cat Felis catus (Linnaeus, 1758)’ are listed as Key Threatening Processes under the NSW Threatened Species Conservation Act 1995.

6. All breeds of Domestic Dogs interbreed readily 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 extremely 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).

7. There is currently no reliable field method for distinguishing pure Dingoes from hybrids although several behavioural and reproductive characteristics can help identify Dingoes. For example, Dingoes do not bark, and are seasonal breeders, producing one litter each autumn, whereas Domestic Dogs and hybrids may have two oestrus periods per year with pups born in spring and autumn (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).

8. 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 may have a higher level of purity than others (e.g. Sturt National Park and the Limeburners Creek region).

9. 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 frequent and continuous applications. However, due to the constant influx of Domestic Dogs into natural ecosystems, lasting eradication of even local populations of Feral Dogs is extremely difficult and thus predation pressure by Feral Dogs is seldom eliminated for long periods.

10. The most realistic approach to reducing the threat of hybridisation between Domestic Dogs and Dingoes is to quarantine ‘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 wild dogs, and their relatively low densities in the centre of large reserves (Claridge and Mills 2007 suggests that even intensive management of core habitat is unlikely to protect Dingo populations from gradual hybidisation.

11. 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.

Professor Lesley Hughes
Chairperson
Scientific Committee
Proposed Gazettal date: 29/08/08
Exhibition period: 29/08/08 – 24/10/08

References:

Catling PC, Corbett LK, Newsome AE (1992) Reproduction in captive and wild dingoes (Canis familiaris dingo). Australian Journal of Zoology 27, 939-944.

Claridge AW, Mills DJ (2007) Dogs in space. Abstract in ‘Proceedings of a workshop on remote monitoring of wild canids and felids.’ http://www.invasiveanimals.com/downloads/Final-Remote-sensing-workshop_edited_18_11_07_press-res.pdf accessed on 1 July 2008.

Corbett LK (1995) ‘The dingo in Australia and Asia.’ (UNSW Press: Sydney)

Corbett LK (2001) The conservation status of the dingo Canis lupus dingo in Australia, with particular reference to New South Wales: threats to pure dingoes and potential solutions. In ‘A Symposium on the Dingo’. (Eds CR Dickman and D Lunney) pp 10-19. (Royal Zoological Society of New South Wales: Mosman)

Daniels MJ, Corbett L (2003) Redefining introgressed protected mammals: when is a wildcat a wild cat and a dingo a wild dog? Wildlife Research 30, 213-218.

Davis E (2001) Legislative issues relating to control of dingoes and other wild dogs in New South Wales. I. Approaches to future management. In ‘A Symposium on the Dingo’. (Eds CR Dickman and D Lunney) pp 39-41. (Royal Zoological Society of New South Wales: Mosman).

Dickman CR, Lunney D (2001) (Eds) ‘A Symposium on the Dingo’. (Royal Zoological Society of New South Wales: Mosman)

Glen AS, Short J (2000) The control of dingoes in New South Wales in the period 1883-1930 and its likely impact on their distribution and abundance. Australian Zoologist 31, 432-442.

Glen AS, Dickman CR (2005) Complex interactions among mammalian carnivores in Australia, and their implications for wildlife management. Biological Reviews 80, 387-401.

Mitchell BD, Banks PB (2005) Do wild dogs exclude foxes? Evidence for competition from dietary and spatial overlaps. Austral Ecology 30, 581-591.

Newsome AE, Corbett LK (1985) The identity of the dingo. III. The incidence of dingoes, dogs and hybrids and their coat colours in remote and settled regions of Australia. Australian Journal of Zoology 33, 363-375.

NPWS (1997) ‘Wild Dog Policy.’ NSW National Parks and Wildlife Service, Hurstville, NSW.

Savolainen P, Leitner T, Wilton AN Matisoo-Smith E, Lundeberg J (2004) A detailed picture of the origin of the Australian dingo, obtained from the study of mitochondrial DNA. Proceedings of the National Academy of Sciences 101, 12387-12390.

Wilton AN (2001) DNA methods for assessing dingo purity. In ‘A Symposium on the Dingo’. (Eds CR Dickman and D Lunney) pp 49-56. (Royal Zoological Society of New South Wales: Mosman)

Wilton AN, Steward DJ, Zafiris K (1999) Microsatellite variation in the Australian dingo. Journal of Heredity 90, 108-111.

Woodford J (2005) ‘Just east of Eden a hill once alive to the sound of penguins.’ Sydney Morning Herald. http://www.smh.com.au/news/national/just-east-of-eden-a-hill-once-alive-to-the-sound-of-penguins/2005/07/28/1122143966685.html accessed on 1 July 2008.

Page last updated: 28 February 2011