This week I’d like to give you an introduction to the history and ecology of the dingo (Canis lupus dingo), but I’m not sure how thorough I can be here- one of the things that struck me in my reading was how many opinions there are about dingoes. And people with differing conclusions seem to be responding to each other in print- one study says one thing, the next study says that the first did not collect data properly, a third says the second did not use the most appropriate process for analysis; an article is published, and then someone else publishes a letter in response. So it would seem that dingoes are controversial subjects- I am neither a dingo expert nor a statistician, but I’ve had to make decisions about what to include here; hopefully I’m offering a reasonably accurate account of this canid species.
Dingo (Canis lupus dingo)
Basic dingo ecology. These 30-35 lb. predators can be solitary or found in groups, and the size of the group is related to how big the prey is (which makes sense- if your prey is big, like a large kangaroo, you may want some help to ensure a successful kill and there will be plenty of food to share at the end of the day, but if you are going after a rabbit, you may not want dinner company) (Vernes et al. 2001). Dingoes are flexible predators who eat a wide variety of prey species and can alter their behaviors to take advantage of changes in food supply, such as focusing on rodent species during population booms and then diversifying their diet when the boom is over (Pavey et al. 2008).
What does dingo family history look like? There is general agreement that dingoes arrived in what is today mainland Australia between 5000 and 3500 years ago (Johnson & Wroe 2003, Stephens 2011), probably as a semi-feral, semi-commensal element of Aboriginal society- based upon the low genetic diversity of dingoes, it’s likely a few individuals founded the entire population. Dingoes have been given responsibility for the extinction of a number of native Australian species on the mainland (and there is also a debate about whether to consider dingoes native or exotic animals), including the thylacine and Tasmanian native hen, but researchers have begun to question those claims, partly because the thylacine was a predator that could take down larger prey than a dingo while the hen was likely the prey of neither predator, and partly because the dingo’s arrival coincided with a drier climate that would have put stress on many species (Johnson & Wroe 2003). With the arrival of Europeans and, specifically, European livestock, dingo-human conflict became a big issue. In 1885 dingoes were officially labeled pests and a bounty system implemented (Allen & Sparkes 2001). To-date more than 1.5 million bounties have been claimed; baiting with poison and shooting trapped animals were and are the most common methods of population control. Do they deserve this treatment? Well, that is the crux of the dingo debate in many ways. There is no question that dingoes have killed and continue to kill sheep, which is damaging to people’s livelihood. They also prey upon some of Australia’s threatened and endangered species- although that may have been normal behavior for several thousand years, it tends to get different reactions when the prey species is in danger of extinction. There are other viewpoints which say that dingoes are beneficial in the environment because they keep other pest populations down (Allen & Sparkes 2001) or because their presence helps small mammals by keeping their predators away (Letnic et al. 2009) (more about this in a later post).
What does the dingo’s world look like today? The species’ range is smaller, and across Australia dingoes are treated differently in different locations (Levy 2009)- in some places they are protected and in others rural landowners are required to kill them. Starting in 1945, the Dingo Barrier Fence (DBF) was constructed along part of the border between New South Wales, South Australia, and Queensland with the idea of keeping dingoes out of sheep ranching lands (Allen & Sparkes 2001). This 2-m tall fence has been the subject of many dingo studies because it offers the chance to examine the differences between areas with dingoes and areas without them (and this is where I found a variety of contradictory opinions). Keeping dingoes out of sheep areas has reduced sheep-predation, but people have also noticed that there are more red and grey kangaroos on the dingo-free side of the fence (Caughley et al. 1980; Pople et al. 2000); the opposite is true for rabbits and rodents (Letnic & Koch 2010). One of the big dingo debates centers around why this is so: according to Pople et al. (2000) and Letnic & Koch (2010), dingoes are keeping the roo numbers down through direct predation; according to Newsome et al. (2001) the differences are caused by fewer watering holes and less preferred kangaroo habitat; and according to Caughley et al. (1980) high rabbit densities give dingoes adequate alternate prey to keep predator numbers high enough to depress kangaroo populations (I had to think about that one for a while before I understood what they were saying: normally when a predator hunts a species until the prey numbers drop substantially, the predator has just lost its main food source and it also declines, like the mink downstream from me who spent a lot of time fishing in one section of river until bigger fish became scarce and then had to pack up camp, but the rabbits in Australia gave dingoes another food source, so the dingo population didn’t decline when kangaroos did). There are also concerns about dingoes hybridizing with feral dogs, especially along coastal areas in the southeast (Stephens 2011), so researchers aren’t sure exactly what percentage of the dingo population is ‘pure’, which can complicate how we approach dingo roles and management in the future. Why is this important? Well, if people are already lukewarm about an animal whose numbers have declined and then someone claims that the remaining population genetically isn’t that species anymore, you tend to lose support for conservation measures.
I recognize that the information above is a lot to take in, and I haven’t even scratched the surface in some respects, but hopefully I’ve given you a better sense of the dingo’s history and possible ecosystem roles. Next week I’d like to look at how the dingo may or may not fit into Australia’s conservation plans, and also peek into how the dingo’s situation relates to that of other wild dogs around the world. The presence of any wild dog in an ecosystem can be very controversial, so I have no doubt that there will be multiple viewpoints about those as well.
Works cited:
Allen, LR & EC Sparkes. 2001. The effect of dingo control on sheep and beef cattle in Queensland. Journal of Applied Ecology 38: 76-87.
Caughley.G, Grigg, GC, Caughley, J, & GJE Hill. 1980. Does dingo predation control the densities of kangaroos and emus? Aust. Wildl. Res. 7: 1-12.
Johnson, CN & S Wroe. 2003. Causes of extinction of vertebrates during the Holocene of mainland Australia: arrival of the dingo, or human impact? The Holocene 13: 941-948.
Letnic, M, Crowther, MS, & F Koch. 2009. Does a top-predator provide an endangered rodent with refuge from an invasive mesopredator? Animal Conservation 12: 302-312.
Letnic, M & F Koch. 2010. Are dingoes a trophic regulator in arid Australia? A comparison of mammal communities on either side of the dingo fence. Austral Ecology 35: 167-175.
Levy, S. 2009. Dingo dilemma. BioScience 59: 464-468.
Newsome, AE, Catling, PC, Cooke, BD, & R Smyth. Two ecological universes separated by the dingo barrier fence in semi-arid Australia: interactions between landscapes, herbivory and carnivory, with and without dingoes. Rangel. J. 23: 71-98.
Pavey, CR, Eldridge, SR, & M Heywood. 2008. Population dynamics and prey selection of native and introduced predators during a roden outbreak in arid Australia. Journal of Mammalogy 89: 674-683.
Pople, AR, Grigg, GC, Cairns, SC, Beard, LA, & P Alexander. 2000. Trends in the numbers of red kangaroos and emus on either side of the South Australian dingo fence: evidence for predator regulation? Wildlife Research 27: 269-276.
Stephens, D. 2011. The molecular ecology of Australian wild dogs: hybridization, gene flow and genetic structure at multiple geographic scales. PhD thesis: University of Western Australia.
Vernes, K, Dennis, A & J Winter. 2001. Mammalian diet and broad hunting strategy of the dingo (Canis familiaris dingo) in the wet tropical rain forests of northeastern Australia. Biotropica 33: 339-345.