Thylacines and Dingoes
By Branden Holmes
Early European maritime visitors to Australia recorded the close relationship between the aboriginal people and wolf-like dogs. The first known mention of dingoes appears to be that of Jan Carstenszoon in 1623 around Queensland's Cape Yorke Peninsula. Later early encounters include a "yellow Dog" near Jurien, Western Australia in 1697 (Abbott, 2008), William Dampier's crew (1699), the HMS Endeavour (1770), and the First Fleet (1788). An illustration of the "dog of New South Wales" was made by Arthur Phillip, first colonial governor of NSW, not long after the First Fleet landed in 1788. It was this illustration that was the basis, first of Robert Kerr's now abandoned name for the dingo Canis antarticus (Kerr, 1792; but see ICZN, 1957), and then of today's accepted name Canis dingo given by Friedrich Meyer in 1793. Though today more often referred to as Canis lupus dingo or Canis familiaris dingo, in order to emphasise its domestic origins.
Early European encounters with the thylacine on the other hand are much less clear. Paddle (2000:3) suggests a similar timeframe, the seventeenth and eighteenth centuries, for the first European encounters. The account of Abel Tasman's crew finding "tyger" footprints on Van Diemen's Land (now Tasmania) in 1642 (Rembrantse, 1682), is often reproduced. However, the footprints of a thylacine are decidedly more dog-like, and thus not likely to instill fear in those who come across them. The cute and cuddly wombat, however, has relatively long intractable claws that are likely to leave in fear those who are not familiar with the benign possesser of such fearsome hardware (Guiler & Godard, 1998; Mooney, 2014). It would be easy to mistake a complete print for that of a ferocious tiger-like creature. Thus the description of "tygers" in Tasmania, and the thylacine often being referred to as a tiger due to its stripes, is probably pure coincidence.
The safest of Paddle's suggested pre-1805 records of European contact with thylacines is that on 13 May 1792, by members of the French La Récherche expedition. Made more secure by a re-translation of the relevant phrase by Neil Murray (Paddle, 2000:3). While the earliest two post-1804 encounters seem to be those on 30 March 1805 (Anonymous, 1805) and 2 May of the same year (Nicholls, 1977; journal entry for 18 June). With a smattering of thylacine encounters over the first decade of settlement. Doubtless a product of both the small settler population and the relative rarity of top predators compared with their prey. In his scientific description of the species (read in London, 21 April 1807), George Harris mentions that only two specimens, both males, had been taken since settlement in 1803 (Harris, 1808). One being Paterson's specimen killed on the hill, an average of one every two years. A rate that would sadly climb and climb in years to come. Indeed it would appear to have taken 17 years before a specimen was taken alive (Anonymous, 1820).
The dingo din' go to Tasmania?
There is no evidence to suggest that the dingo ever occurred in Tasmania (contra Krefft, 1868; see Allport, 1868; Jones, 1968). Either it never arrived, or it died out. The adaptibility of the species is evident on the mainland, where it occupied every single habitat from the deserts to the snow-laden Australia Alps, until it was exterminated from much of its former range (Corbett, 1995a). A range greater even than that of the red fox (Vulpes vulpes), which even in good years does not extend to the top of the continent (Coman, 1995). There is therefore no good reason to suppose that Tasmania was ecologically closed off to the dingo. Moreover, if it did arrive it would undoubtedly have a close relationship with the aboriginals like European-introduced dogs later did (Anonymous, 1826), somewhat contrary to the situation on the mainland (A New Correspondent, 1835). Beyond the obvious logistical fact that it couldn't get there on its own, the relationship would have been mutually beneficial (e.g. hunting, companionship, security etc.1). A situation mirrored all over the Pacific, where now extinct breeds of dog thrived alongside their Polynesian seafaring owners on many Pacific islands (Williams et al., 2018). Thus creating an extra buffer against extinction.
So it appears that the dingo never reached Tasmania. On the face of it this is a curious fact. The dingoes ancestors probably came from South-East Asia through New Guinea and across the Torres Strait. The latter is about 150km wide at its narrowest, while the Bass Strait which separates Tasmania from the mainland is just under 200km at its narrowest. An extra 50km is certainly a substantial difference, even for skilled seafarers. However, both straits are conspicuously traversable by utilising islands dotted along the way. In the case of the Bass Strait, through the Kent and Furneaux Groups of islands. Thus neither journey would necessitate a strictly overwater affair, and hence each could avoid at least some of the dangers thereof. Thus geography alone cannot account for why the dingo never arrived in Tasmania.
The only conceivable major difference between the two straits is the sailing conditions. The famous Roaring Forties, which produce howling westerly winds in the region of the forties latitude. As well as the sheer ferocity of the waves at times. Which combined with gale-force winds and freezing temperatures (even above the water) made the 1998 Sydney to Hobart Yacht Race the deadliest of all time. Six sailors lost their lives as the 115-strong fleet headed into what can only be described as hell on Earth. Even with all of the modern technologies at their disposal, only 44 yachts crossed the finish line that year. While it is certainly possible to play up the dangerousness of the Bass Strait, evidenced by the rather mundane journey of the Spirit of Tasmania most days, such a ferry is huge and thus not as amenable to the influence of the ocean as much smaller vessels are. Its shallowness presents untold dangers, which aboriginal sailors and fisherman would have been well aware of.
Given the unfavourable sailing conditions, there are three basic hypotheses to consider. Any one of which in isolation could in theory explain the lack of contact between mainland and Tasmanian aboriginals. Although the real answer probably lies in a combination of them: a) there was no great need to sail far from the shore, since fish, turtles, dugong etc. would have been more than plentiful close to the coast, b) some kind of taboo against sailing in the direction of Tasmania, whether or not the people were aware of that distant land, and c) contact would more than likely have been accidental, thus not likely to result in enough dingoes in a short span reaching Tasmania for a viable population to arise. A fourth possibility, in the opposite direction, namely deliberate contact, is what I am arguing against by proxy of the evidence of the absence of the dingo from Tasmania. It is inconceivable that there would have been regular contact without dingoes being involved.
Aboriginal oral tradition, when properly understood and treated with respect, can provide us with evidence for hypotheses that would otherwise be almost impossible to make a case for (Burbidge et al., 1988; Abbott, 2008; Burbidge, 2017). Thus the seeming complete lack of evidence for dingoes in Tasmanian aboriginal oral tradition is evidence that it was at least largely absent from the island. It is of course possible that a tiny number of dingoes were brought to the island and either died out due to inbreeding, were consumed, killed by disease etc. Moreover, Tasmanian aboriginal oral tradition is less completely known than that of mainland aboriginals. While Tasmanian aboriginals survive today, descendents of their full-blood relatives, they have lost an untold wealth of knowledge (their languages have all been lost). Which might have included knowledge of the Australian dingo. So that its absence from known oral tradition is not strictly proof of its absolute absence.
In defence of the hypothesis that dingoes have (largely) been absent from Tasmania, we can also point to the cultural and technological differences between mainland and Tasmanian aboriginals which must have accumulated as a result of their physical isolation from each other. It is well known that Tasmanian aboriginals were more technologically primitive than their mainland counterparts at European contact. For example, they lacked the boomerang even though it would have been of great benefit in the last several thousand years, as the mammalian aspect of their diets increased significantly. A state of affairs that resulted in Victorian minds, gripped by thoughts of evolution, in seeing their demise as "natural". Nevermind the fact that they survived in such a "primitive" state without issue until European contact. Whatever the cause of their relatively primitive state, certain tools would have undoubtedly provided advantages to the Tasmanian aboriginals had they had them. So that their absence is something of a proxy for the absence of mainland influence on their culture.
The final reason to suppose that the dingo never arrived in Tasmania is the ecological results of European dogs being introduced to Tasmania. Feral packs became a problem starting in the late 1820's, resulting in livestock losses increasing dramatically, with the thylacine being falsely blamed. They also displaced thylacines, forcing the latter to retreat to the less inhabited and more mountainous areas of the island (Anonymous, 1884; Boyce, 2006,2008). Before canine distemper took hold and the feral packs slowly died out during the mid nineteenth century (Ibid.). The thylacine population thus began to increase again, albeit with a significantly smaller gene pool. Accounts of thylacine-dog encounters paint the thylacine in a somewhat favourable light, able to fend itself against one or two domestic dogs (Paddle, 2000). Which has led Paddle to conclude that "there is little evidence" that European dogs contributed directly to the thylacine's extinction, contradicting the above.
The evident bias in Paddle's case is that he does not take into account the relevant differences between dogs obeying their masters and a psychologically independent pack of hardened feral dogs. The latter have to be more ferocious and cunning than the former in order to eke out their existence. Moreover, displacement is just as valid a cause of extinction as predation, since both result in a population reduction. There is only so many thylacines that a given area can sustainably support before either fatal thylacine-thylacine competition or starvation starts occurring. Paddle notes that feral packs of dogs tend to arise when aboriginal people have been displaced or murdered. The genocide of the Palawa people certainly would have forced their dogs to adjust to feral life. Thus at least in part explaining the origins of the feral packs that were a serious pest on the Tasmanian sheep industry, and turned some farmers whole-heartedly against thylacines.
Post-European mainland thylacines?
The scientific consensus is that thylacines became extinct on the mainland around 3,000 years ago. Radiocarbon dated specimens vary greatly in age but increase towards a younger date, finally clustering at around the 3.5ka mark before petering out completely (White et al., 2018b). It must be pointed out that some bias is evident in the dataset used to infer an extinction chronology, as the fossil sites from which dates are taken are almost exclusively from southern Australia. Thus there is some potential for northern Australia to have been a refugium for the species, but future dating of northern Australian specimens will either support or disconfirm the currently accepted chronology. It must also be noted that there have been palaeontological claims of much more recent specimens (Gill, 1953; Archer, 1974), but these have been overturned as a result of re-dating (e.g. Gill, 1971).
There was also the extraordinary discovery of the mummified thylacine carcass (nicknamed "Old Hairy") in a Nullarbor cave2, by David and Jackie Lowry in October 1966 (Lowry & Lowry, 1967). The state of preservation lead both the discoverers and Atholl Douglas to suppose that its age was less than 2,000 years old, and possibly only several years old (Ibid.; Douglas, 1990). The true age of the specimen, established through radiocarbon dating, was in excess of 3,000 years old (Partridge, 1967; Lowry & Merrilees, 1969; Merrilees, 1971). However, Douglas persisted in his belief that the specimen was very recent, for several reasons, none of which hold up (Williams, 2014). There is also, of course, the many thousands of sighting reports from the mainland (e.g. Healy & Cropper, 1994; Heberle, 2004; Opit, 2014; Smith, 2014).
Although almost ubiquitously known today as the thylacine or Tasmanian tiger, the species had innumerable other names during the nineteenth and twentieth centuries (Guiler & Godard, 1998:15). These include variations on the term 'hyena', so that a very early newspaper report has been hypothesised by The Thylacine Museum (5th revision) to possibly refer to two instances of post-European mainland thylacines:
"Two animals of the hyena kind were seen at Campbell's Island by hunting parties belonging to the Mary and Sally ; from the description given of which they appear to have been of the same species with an animal killed at Port Phillip in 1803." (Anonymous, 1811)
Such an early report does not make one very confident that the thylacine is the only, or even most probable, identification. Especially when one realises that the Campbell's Island referred to is actually the subantarctic island belonging to New Zealand (Crowther, 1932). Nevertheless Robert Paddle has raised the possibility of at least two relict populations of thylacines on the mainland until at least the 1830's and 1840's (Paddle, 2000:22-23). One in South Australia and the other in the Blue Mountains (NSW), as he seems to implicitly dismiss the idea of them constituting a continuous population. His suggestion, however, is based upon a completely flawed case. He cites three lines of evidence: three articles by a naturalist called 'Cambrian' (Cambrian, 1855a,b,c), a lecture by Dr. John Palmer Litchfield (Anonymous, 1840), and aboriginal oral tradition (Tunbridge, 1991). None of these hold up to scrutiny, and worse still, other considerations render his bold claims even more objectionable.
The author Cambrian's true identity is unknown3, and thus the veracity of their writings about the thylacine cannot be ascertained. The significance of their claims means that we need positive evidence, not merely anonymous comments. Given Cambrian's use of a pseudonym, it seems impossible to check their background, thus rendering their comments moot. But Paddle claims that we may infer Cambrian's competence by "a frank apraisal of the accuracy of the non-marsupi-carnivore material...in light of European marsupial knowledge at the time" (Paddle, 2000:23). In reality, Cambrian's competence cannot be gauged by any such method. The juxtaposition of valid scientific observations with bold unverified claims does not render the latter more likely to be true. Especially since we simply do not know the source for their non-marsupi-carnivore material in the articles. And we can't start simply assuming Cambrian's reliability in order to take them at their word as having made the observations themselves.
But let's assume that Cambrian was a competent naturalist and that they did indeed examine two dead thylacines on the mainland. It is far more likely that the actual geographical origin of the specimens was Tasmania rather than the mainland4. Whether as a result of an accident or a lie at some point. Instances of wrong locality data being attached to specimens are certainly not unknown. In fact an excellent example of this (see appendix 1) is the claimed recent occurence of the echidna genus Zaglossus in the Kimberley region of Western Australia (Helgen et al., 2012). Historically thought to be confined to New Guinea, a specimen labelled as coming from the Kimberley region was re-discovered in a museum collection. They made a case based upon fossil remains, aboriginal rock art, the living memory of aboriginals, and of course the specimen labelled as originating from Australia (collected by a competent naturalist, John T. Tunney, then director of the Western Australian museum). Conservationist and WA mammal expert Andrew Burbidge evaluated their case and found it to be seriously flawed (see appendix 1), concluding that the "most plausible explanation is that the tag on the specimen came from another animal" (Burbidge, 2017).
Back to Paddle's own case, Cambrian cites both the explorer Charles Sturt and South Australian Governor Sir George Grey as sources relating to mainland thylacines. Unsurprisingly Paddle cannot find any such mention of mainland thylacines in the writings of either (Ibid.). Worse still, Paddle cites a lecture by Dr. John Palmer Litchfield, which claims that a bounty was placed upon thylacines in South Australia. Or at least according to Paddle, who has a penchant for interposing his own interpretation of other people's writings. The "province" referred to is completely ambiguous, but that doesn't stop Paddle from asserting that it is South Australia. If such were true, mainland thylacine research today would look very different. We would find newspaper reports lamenting the devastating effects of thylacines upon livestock, as we do in fact find in Tasmania. So that even if the bounty itself, like some in Tasmania, is scantly attested to (as Paddle himself has uncovered), the motivation for the bounty (i.e. claimed thylacine attacks on livestock) in the first place would be easy to find. Alas that is not the case.
In reality 'Dr.' John Palmer Litchfield was a notorious conman whose writings about the thylacine cannot be relied upon in any serious way5. A serial liar and pedagogical fraud. It is very worrying that Paddle is completely unaware of this fact. Since even a cursory look into Litchfield's background would establish that all is not right, such as via an internet search. Granted Paddle did not have access to many of the electronic resources we do almost two decades later, as the internet was still relatively new. But by the same token, his university studies and access to archival material would have more than made up for this, giving him access to information that we members of the public today still do not readily have access to. A background check of the author of a given source should be one of the (if not the first) early tasks of the researcher. Being taken in by a conman is a sign of severe intellectual myopia.
Paddle's last line of evidence is aboriginal oral tradition. The identification of the marrukurli of Flinder's Ranges aboriginal oral tradition with the thylacine is suggested as a possibility by (Tunbridge, 1991:48) because "several Adnyamathanha elders have believed them to be identical". She notes, however, that "there is no certainty" that this is so. Moreover, the marrukurli appears in both the Dreaming and other oral traditions which "suggest the possibility of their bodily existence in the region in the not-too-distant past" (Ibid.). Tunbridge's picture of the marrukurli does not pick out the thylacine as being the obvious match. If it is a single type of animal it is more likely referring to brindle and/or starving dingoes (with their ribs showing), hanging around settlements hoping for a meal. After all there are documented unprovoked fatal attacks on humans by healthy dingoes, while the several alleged instances of thylacines attacking people in Tasmanian are either of sick or injured animals, or it is hard to tell who the actual aggressor was.
The marrukurli comes across as more like a blend of fact and fiction, serving a deeper purpose: warning children not to stray too far from the adults at night. It is said, as is so often the case with large predators, that keeping up a fire wards them off. With the comforts and security of modern living it is easy to forget that Pleistocene people, indeed many people today, must have been so concerned for their safety. Until 50,000 years ago Australia was inhabited by Megalania (Varanus priscus), a giant goanna twice the size of a Komodo dragon. As well as other terrifying predators like the Marsupial lion, whose bite force is pound-for-pound the strongest known of any animal, living or extinct. Paddle (2000:23) thus ignores the serious doubt surrounding the identity of the marrukurli, and simply asserts that the two are identical. In summary it is clear that Paddle has unquestioningly pulled together any "fact" that props up his belief that thylacines survived on the mainland until after European colonisation.
A unique problem for Paddle
Paddle's problems are confounded by the idiosyncratic position that he finds himself in. On the one hand he "suggests the possibility" that at least two relict populations of thylacines existed on mainland Australia until at least the 1840's. But on the other hand he claims that they are definitely extinct today, not just in Tasmania and on the mainland, but also on New Guinea. He notes that the species disappears from mainland aboriginal oral tradition during the 1840's and 1850's, corroborated by its absence from contemporary species lists by scientists, which he seems to take as representing the near-terminal extinction chronology of the species (Paddle, 2000:22-23). A few individuals could in theory have lingered on in such low density that not even aboriginals were aware of their continued survival, but that would also lead to a lack of breeding. The overriding problem is that Paddle is largely bereft of a mechanism to explain the species' extinction on the mainland, especially since his inferred extinction chronology is much shorter than that on Tasmania.
For Paddle, the claim that dogs (whether dingoes on the mainland or European dogs in Tasmania) were a direct cause of the extinction of the thylacine is a symptom of placental chauvinism. The alleged superiority of the placental dingo, with its bigger brain, larger social structure, and broader diet, is a myth. Driven and perpetuated by an innate desire to rid ourselves of the guilt of driving the thylacine to extinction. Their real contribution to the extinction of the species in Tasmania is negligible, while on the mainland they were ancillary to the increased hunting activity that their co-operation with their aboriginal companions allowed. For Paddle then, there can be no valid case made that dogs helped significantly to cause the extinction of the species. In Tasmania it was the false persecution of the thylacine as a sheep killer, which led to several unmitigated bounties, and the appearance of an epizootic disease at the turn of the 20th century (Paddle, 2012), which ultimately led to the species' demise.
Paddle cannot apply either of these extinction causes to the mainland thylacine. The bounty that Paddle mentions can reasonably be said to have never taken place since its only source was a conman, and the epizootic disease that Paddle discusses arrived far too late. Moreover, Paddle needs one or more extinction causes that are even more acute than these two in conjunction. It is safe to say that if it were not for humans (whether directly or indirectly) the species would undoubtedly still exist today. Going back to the year 1800 on the mainland, the thylacine population would almost certainly have been relatively healthy. With no bounty on them, and no good reason to suppose that the population would have been unhealthy6, the two populations could have exceeded Tasmania in terms of total population size. But by the 1850's it was almost, if not already, extinct. A period of a mere 50 odd years.
If we take the Tasmanian thylacine situation from the years 1870-1920, encompassing both the 1888-1909 government bounty and the rise and spread of the epizootic disease, the species was already persecuted for decades beforehand and survived for at least another 16 years and 9 months. Thus Paddle needs an even more devastating tragedy to have visited the mainland than Tasmania. Whose scope is barely conceivable, if the systematic killing of thylacines combined with disease did not kill off the Tasmanian population as quickly as the mainland thylacine died out. Simply put, there just isn't any such possible extinction cause that has any documentary evidence for it.
Dingo-thylacine interactions: stiff competition, continental breakfast, or no bark, no bite?7
While the thylacine almost certainly didn't survive on the mainland until European colonisation, it undoubtedly existed there until at least several thousand years ago. Irrefutable evidence of this are the many securely dated fossils (White et al., 2018b). The question naturally arises, why did it persist in Tasmania so much longer? Three basic hypotheses exist8: climate, competition with the dingo, and human intensification (population size and technological advancements). Evidence suggests that New Guinea and Tasmania were less affected by global climatic changes taking place at the time we are talking. While Tasmania almost certainly lacked canids, and seems to have lacked the spike in technological evolution that took place on the mainland. Therefore, it is very difficult, if not impossible, to single out any one of these three hypotheses as the reason they survived in Tasmanian much longer. Moreover, geologically recent extinctions can be quite complex affairs. The Tasmanian thylacine population is a case in point. No sole extinction cause can be cited, even if one of them would have been sufficient had the others not arisen.
The dingo has long been held as a cause of the thylacine's extinction on the mainland, due to what we might ambiguously call the 'superiority hypothesis'. As already noted the larger brains, bigger social structure, and broader diet of the dingo, potentially have serious implications for any sympatry between the species. Aboriginal author Marie Munkara, however, suggests that they were in general not sympatric at all9. Contrary to Paddle, accepting the dingo as superior to the thylacine in the relevant sense only commits us to the view that thylacines would have been more negatively affected by sympatric dingoes than dingoes would have been by sympatric thylacines. Indeed Paddle seems unfazed at calling some dogs "stupid" (Paddle, 2000:21). While it is certainly true that a strong correlation between brain size and intelligence is somewhat wanting, the implication of his comment that brain size is rather irrelevant to intelligence is even less attested.
Ogilby (1841) was the first to suggest explicit competition between thylacines and dingoes, resulting in the loss of the thylacine from the mainland. A view contradicted by Gerard Krefft's claim that the thylacine was actually responsible for the extirpation of the dingo from Tasmania, which as (Allport, 1868) points out, is rather a bold claim since the dingo is not know to have ever occupied the Apple Isle. In his PhD thesis, Robert Paddle compiled a list of references from 1842-2000 which claimed that dingoes were responsible for the extinction of the thylacine on mainland Australia (Paddle, 1997). From 1842-1950 he found 19 references, while during the next 50 years he found 80. An increase from one every 5.5 years to one every 8 months (see Paddle, 2000:35f). While one needs to factor in such things as the increase in the rate at which literature is being written and published as the population of scientists grows, this is nevertheless an abrupt transition in the general thinking.
Paddle attributes it to the growing scientific realisation that the thylacine is probably extinct, which thus calls out for a cause of its extinction. Scientists being allergic to the notion of anthropic extinction, "desperate to attribute the thylacine's extinction to non-human causes", the superiority of the dingo was constructed (whether consciously or unconsciously) as a red herring to divert attention away from the fact that we only have ourselves to blame (Paddle, 2000:20). Well let's say that Paddle is right. What logically follows from this? Certainly not the impossibility, or even improbability, of the dingo's central role in the extinction of mainland thylacines. For that you need to have contrary evidence (which Paddle claims that he has). To suggest otherwise is to fall for the genetic fallacy. That is, ruling out a view based upon not its intrinsic merits, but because of the motivations and/or reasons ascribed to those for holding it in the first place. For example, if I believed the sun revolved around the Earth simply because that is what my father told me, that would not in itself disprove geocentrism. For that you would need evidence that geocentrism itself is false. At its most basic, conclusions are independent of any particular route to getting there: disproving a route does not disprove the destination.
Paddle himself doesn't fall for the genetic fallacy. He makes it quite clear that his problem with the notion of the superiority of the dingo is, at least in part, the dissonance involved in asserting the dingo's central role in the extinction of thylacines on the mainland, while simultaneously ignoring or trying to explain away their lack of such efficacy in Tasmania. As I have already discussed, this is itself at odds with the historical record as illustrated by (Boyce, 2006,2008). Indeed as noted, Paddle's observation that the destruction and displacement of aboriginal people led to a rise in the feral dingo population on the mainland, provides a cause for the emergence of the packs of feral dogs in Tasmania that proved such a problem for thylacines during the early-to-mid 19th century. The latter only getting a reprieve after canine distemper arose. At the same time, Paddle puts forward a good point. Even if we allow that dingoes are in general superior to thylacines, were there enough of them prehistorically to actually cause the extinction of the mainland thylacine? It seems like the literature has simply assumed that there were.
Only one species of the genus Thylacinus is known to have survived into the Late Pleistocene (126ka-11.7ka) anywhere on the planet. Although in the nineteenth century two or more species were often accepted for periods before one was synonymised with the living T. cynocephalus. Either a fossil species from the recent past (e.g. T. spelaeus), or two contemporaneous species in Tasmanian (e.g. T. breviceps). On the mainland fossil female thylacines are on average somewhat smaller than their Tasmanian counterparts, a fact long known (Ride, 1964) and which prompted (Lowry, 1972) to investigate the taxonomic status of the two populations. She found no justification for the recognition of two distinct taxa. Fillios et al. (2012) further argued for the small stature of female mainland thylacines, in conjunction with a discussion of the possible implications of this for thylacine-dingo competition. While also pointing to the larger brains of dingoes, concluding that dingoes "were likely a primary agent for the extinction of the thylacine from mainland Australia".
Letnic et al. (2012) was more specific, concentrating solely upon the potential for direct killing of relatively smaller female thylacines by larger dingoes. With a skewed sex ratio, reproductive oputput would have been severely constrained, thus potentially leading to other negative effects like inbreeding. This exploits a hypothetical difference between the trophic levels of male and female mainland thylacine when the dingo is potentially sympatric, due to their differential sizes as discussed above. That is, the level at which they sit with respect to the rest of the food chain. Males would be apex predators along with male and female dingoes (since their sexual dimorphism is less marked), while female thylacines would not be apex predators. When a new, larger predator moves into an area a trophic cascade is said to occur, whereby any change at the top of the food chain affects the lower levels. In this case the smaller native predator/s all slide down the trophic scale to a lower level. Here in Australia the red fox (Vulpes vuulpes) and feral cat (Felis catus) are said to be mesopredators, that is, predators which are mid-level on the trophic scale.
Female predators tend to move less within their smaller ranges than males of the same species. Thus even if females are smaller, they are also less mobile and hence less likely to encounter species at a higher trophic level. This fact seems not to have been covered much within the literature, at least in part because it does not seem to give the thylacine much of a reprieve if dingoes are generally superior. While if dingoes are not superior, then it is a moot point. A study lead by Marie Attard (Attard et al., 2011) argued that the stress placed upon the thylacine skull during biomechanical reconstructions pointed to the thylacine probably being capable only of killing prey smaller than itself. Due largely to its relatively narrow skull, compared with a Tasmanian devil and even a quoll (Dasyurus sp.). If true this has serious implications for even a male thylacine's ability to fend itself against lone dingoes, let alone survive an encounter with a whole pack.
Johnson & Wroe (2003) argued that competition from the dingo, as well as human intensification driven by population growth which fueled technological advancements, together could have driven the three vertebrate species conspicuously absent from the mainland but present in Tasmania (thylacine, Tasmanian devil, native hen) extinct. The most recent study to date has found that thylacines and Tasmanian devils both became extinct on the mainland about 3,275 years ago (White et al., 2018b). Which would constitute a temporal overlap of about 1,200-1,700 years between the species. Although the data set used is biased towards southern Australian fossil sites, and thus does not take into account the potential for reufgia in northern Australia. Nevertheless, the relatively short overlap between the two species in southern Australia is important, even though the terminal dates for thylacines (and Tasmanian devils) on the mainland also coincides with peak ENSO activity.
If the thylacine were alive today, even if only in Tasmania, the current debate over the role of the dingo in its mainland extinction would undoubtedly look very different. For example, we would have a far better idea whether it is a pursuit, pounce-pursuit or ambush predator (Jones & Stoddart, 1998; Jones, 2003; Figueirido & Janis, 2011; Janis & Figueirido, 2014). The thylacine's stripes are suggestive of a mode of camouflage, which lends itself to an ambush style of predation. However, reports of thylacines doggedly pursuing wallabies at a steady trot tend to portray a more cursorial habit, which is somewhat inconsistent with its elbows (Figueirido & Janis, 2011). Its senses seem to have been very sharp, for example an anecdote of a pet thylacine being aware of visitors long before they arrived. While the species was evidently rarely encountered in the wild, a testament not to its rarity (since so many were killed) but rather to its ability to evade humans. In the end, it seems to have had a rather unique generalist morphology (Janis & Figueirido, 2014), indicating its true dominon over the beautiful Tasmanian landscape, not having to be shoehorned into some tight ecological niche with little evolutionary breathing space.
Quantifying the pre-European dingo population
Human colonisers often have a bifurcating effect on the fortunes of the native plants and animals of a region. Some decrease in numbers as their habitat is altered and destroyed, while for others the changes bring new opportunities. Little if any research has been done into how European colonisation changed the fortunes of the dingo. Robert Paddle suggests that the displacement and destruction of mainland aboriginals over the last 200 years is largely responsible for the dingo's current situation: "existing by themselves at high population density levels throughout the Australian mainland" (Paddle, 2000:22). There is no doubt that dingoes forced to turn feral because their owners were killed or had to abandon them contributed to a rise in the wild population. Just as the introduction of livestock onto the continent brought a greater potential food supply and more watering holes, especially in arid regions. But without a pre-European wild population baseline, it is very difficult to quantify or even infer the impact of the dingo on mainland thylacines.
Early European accounts of the dingo are too sparse in detail and too few in number to help chart the pre-European wild dingo population. While subfossil remains contribute only a small piece of the overall picture, namely minimal geographical extent. For real data on population extent and density we need aboriginal knowledge. Unfortunately the loss of many aboriginal peoples and languages means that what information is left that can be compiled is very incomplete. This information, spread over the many aboriginal tribes, has not been adequately documented. It therefore remains to be seen exactly how extensive the pre-European dingo population was. But given the huge size of Australia, the longevity of the species here, inter-tribal warfare which left dingoes without owners, the dingoes' adaptibility, and finally the pre-European abundance of prey, there is every reason to suppose that the wild population was significant. Although this remains largely conjectural.
This state of affairs is quite surprising since the whole dingo-thylacine debate potentially hinges on this very question. Even if dingoes are conclusively shown to be superior in every way to thylacine (quality), without enough of them (quantity) they could not have caused the species' extinction from the mainland. Or at least contributed their part if other factors were also involved, as is more than likely. It is as if scientists have simply assumed that the dingo's conservation status, in danger of extinction through hybridization with domestic dogs (Corbett, 2008), but more importantly were undoubtedly cosmopolitan in prehistoric times (Corbett, 1995b), means that they existed in the requisite density. In reality, distribution neither entails nor commonness nor rarity. A microendemic may be locally common, while a cosmopolitan species may be extremely rare.
New Guinea, Same Story?
The dingoes closest living relative is the New Guinea singing dog (NGSD). It is unsurprising that such a breed should exist since the dingo's ancestor was presumably brought from mainland Asia through New Guinea. However, unlike the dingo the status of the New Guinea singing dog in the wild is not well understood. It appears to be extremely rare, having been photographed only several times. At least once it has been claimed to have been rediscovered in the wild. Such claims are rather overstated as the New Guinea highlands and adjacent territories are not well surveyed. It is well known that there is a small captive population with limited genetic diversity, which owes its existence to Sir Edward Hallstrom, then president of the Taronga Park Zoo. Indeed famed Australian zoologist Ellis Le Geyt Troughton named the "species" after him: Canis hallstromi (Troughton, 1957).
The first discovery of thylacine remains from New Guinea was a part mandible excavated by Susan Bulmer in April 1960 (van Deusen, 1963), later found to be of early Holocene age (Sutton et al., 2009). Further remains, albeit far more ancient of almost certainly of a different species were reported by (Plane, 1976). More recent excavations at Nombe Rockshelter and other archaeological sites have yielded remains that are mid-Holocene in age, the youngest c.5,000 cal. BP (Mountain, 1991; but see Sutton et al., 2009). Like Tasmania, and unlike mainland Australia, New Guinea seems to have suffered far less from climatic changes at the time. Although famously the home of literally thousands of different languages, the human population was not cosmopolitan:
"At the time of European contact the population was concentrated along the coastal fringe with quite sparse and isolated groups in the rainforests and mountain slopes. Some areas, such as the Fojes Mountains, seemed to be totally without habitation." (Hope & Haberle, 2005:542)
Although unlike Tasmania, and like the mainland, it is evidently home to canids. Surprisingly, a 2016 study (Cairns & Wilton, 2016) found that Australian dingoes constitute two genetically distinct populations, with one being closer to the New Guinea singing dog than the other. This is made more surprising by the fact that the New Guinea singing dog is significantly smaller than either dingo population at the withers, which is reflected in their respective weight. This probably reflects an adaptation to their respective environments, hinting that New Guinea thylacines were even smaller than their mainland Australian coutnerparts, although New Guinea thylacines are so little studied that not even basic biometric data gathering appears to have taken place. The sheer paucity of the relevant data therefore means that a huge big question mark sits over the island. With simply nothing more to say at this point.
Like the broader debate over the extinction of Australia's Late Pleistocene megafauna, our understanding of the extinction of the thylacine on the mainland has evolved substantially over time. What was initially thought to be a relativey simple case of plain competition with a placental carnivore (what some would call "placental chauvinism"), has turned out to be a rather more complex affair. Our understanding of climatic changes which were taking place at the time of the thylacine's terminal decline has come leaps and bounds in the last decade or more. Which mirrors that taking place in the Americas (i.e. the Younger Dryas), and to a lesser extent Europe and Africa (e.g. Prado et al., 2015; Faith, 2014). As well as archeological evidence which suggests that human intensification could have been a significant factor in its demise.
Combined with new and more accurate dating techniques, which have helped overturn old extinction chronologies and tighten others, our picture of the Late Pleistocene-Holocene megafaunal extinctions are slowly coming together. The true cause of the thylacine's extinction on the mainland may never be fully known, however, the case is more than conjectural. We can point to explicit causes, dingo competition, climatic changes, human intensification, which may collectively have contributed to its demise. The debate is now over the relative importance of these with respect to each other. Some of which reappeared millennia later as Tasmania was visited by an even greater tragedy.
Appendix 1: A mounting myrmecophagous monotreme mystery
Museums are like glorified morgues. Thousands upon thousands of dead specimens sit lifeless in untold cabinets, cupboards and crates, most of which are in storage at any one time. After all proper preservation is key so that future generations can also enjoy the collections. Specimens of recently extinct species are especially hallowed, and understandably so since the loss of even a single one means that it literally cannot be replaced. Given all this, it is ironic then that museums are abuzz with activity; staff conduct research on the specimens and those on loan from other institutions, plan expeditions to acquire new specimens, seek funding to continue their many activities, and of course interact with the public in various ways. They are repositories of the natural world, amounting to our collective knowledge of the world around us. With so many specimens, many donated or bequeathed, it is hard to keep track of them all. Records today are invariably digitised, which means that you don't even have to leave your living room to go to the museum in a sense. Dead curators (not kept in museums!) would have relished the use of such technology.
There is of course something human in researching old handwritten records that does not tranfer to the digital dimension. Ink stains, different handwriting, indeed the evolution of handwriting, are all captured in dusty old books and ledgers recording the history of a museum from its humble (or not so humble) origins. While Charles Darwin died almost 140 years ago, it is perfectly possible to see specimens that he himself collected aboard the H.M.S. Beagle (1831-1836). Or to see the giant moa that famed Victorian era anatomist Richard Owen was photographed next to, one of the few instances when he was exceeded10. Incidentally, Darwin's own records of the finches he collected in the Galápagos Islands were not good enough to trace each form to its native island, so that he had to rely upon his shipmates and their more careful records (Sulloway, 1982). Moreover, museums do not always know precisely what they have. New species aren't always discovered in the field, they can also sit unrecognised in old museum collections for decades before serendipity intervenes (e.g. Bauer & Russel, 1986; Eldridge et al., 2018).
Not all discoveries made in old museum collections are new species of course. When Kristofer Helgen stumbled across a specimen of Zaglossus bruijni stated as coming from Western Australia's Kimberley region, he recognised its importance as a major extension to the recent distirbution of a monotreme, those bizarre egg-laying mammals. The genus as a whole, which also contains the extremely rare Z. attenboroughi (named after famed naturalist Sir David Attenborough), has been thought to have been historically confined to New Guinea. Such a discovery would not be unprecedented as several other species have been discovered to range over both New Guinea and Queensland's Cape York Peninsula in recent decades. However, with no other recent record of the species in Australia, one might think it more likely that there has simply been an accident whereupon the specimen has ended up with a label attached to it that doesn't belong.
Helgen and his co-authors, however, disagree. They use several lines of evidence to argue that in fact Zaglossus was a native of Australia into the recent past, and indeed may still exist. Their case in many ways mirrors that of Paddle, especially the cross-cultural aspect. There is no doubt that the species existed here in Western Australian in the past, as evidenced by fossils. However, rock art images are notoriously difficult to identify with living or recent species, since that presupposes an intent by the artist to document accurately what exists. Aboriginal art includes many depictions that everyone agrees do no represent real biological entities, and so it is somewhat arbitrary to point out morphologically ambiguous art and assign it taxonomically to a species. Contra (Helgen et al., 2012) there are no uncontroversial records of any Australian megafaunal rock art depictions (Bednarik, 2013; Lewis, 2017). If we accept that the rock art depicts an echidna it is far more likely to represent Tachyglossus aculeatus than Zaglossus bruijnii (see below).
More pertinent are the claimed aboriginal memories of two distinct species of echidna. In general native people are extremely good at distinguishing between species, which lends credence to their memories. Moreover their remote locations mean that they are often better placed to provide science with knowledge of animals than scientists are. Especially rare, extirpated or extinct taxa (e.g. Burbidge & Fuller, 1979; Burbidge et al., 1988; Tunbridge, 1991). However, methodology and interpretation are everything. And it seems that (Helgen et al., 2012) have fallen into the trap of desiring aboriginal corroboration a bit too much. After all, without it a label mix up is almost certain. After reading their paper, Andrew Burbidge made extensive inquiries with the Nykina-Mangala and Wunambal people on whose land the echidna was supposedly collected, and has found that both groups only recognise one kind of echidna (Burbidge, 2017). The couple of reports of Zaglossus knowledge by aboriginals cited by (Helgen et al., 2012) are thus anomalous.
The biggest problem, however, is that even if we accept for the sake of the argument that two species of echidna existed in Australia until at least 1901, it should still be here. And yet no other specimens have come to light either before or since, despite numerous surveys and expeditions (see Burbidge, 2017) and a $43k four-year grant. Burbidge (Ibid.) thus concludes that the "simplest and most plausible explanation" is that a label mix up occured sometime between the specimen leaving Perth and arriving in Tring (the location of Lord Walter Rothschild's collection). This is a far simpler explanation than that a species of echidna has largely gone unnoticed by both aboriginal people and science. Incidentally, Burbidge (Ibid.) recounts an instance of a Wunambal man, Geoffrey Mangolamara, telling he and colleague Phillip Fuller of the thylacine: "this was volunteered and not in response to a question from us – and he made it clear that it had not occurred in his country for many generations".
Appendix 2: An unfinished list of pre-1950 references to dingo extermination
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1 Although unrelated to the present article, I find it fascinating enough to mention that at least two breeds of dog from northern USA and southern Canada, the Salish Wool dog and the Plains-Indian dog, were both bred for their woolly coats. Their wool was literally used to make blankets, and their extinction was in part caused by the introduction of sheep.
2 There has also been a less covered discovery of a mummified thylacine head in Murra-El-Elevyn Cave, also on the Nullarbor Plain, that took place sometime in 1990. However, I lack further details.
3 R. J. W. Selleck has proposed that 'Cambrian' is the well known former museum director Frederick McCoy (Selleck, 2003:83).
4 This would seem to predate the earliest known transportation of live thylacines to the mainland from Tasmania. However, the animal needn't have been alive when it left Tasmania. Equally it might have died during the journey.
5 The fact that 'Dr.' Litchfield was a conman was brought to my attention by thylacine researchers Chela Tnyi (pseudonym) and Gareth Linnard, who each thoroughly researched his background.
6 It is certainly true that Holocene thylacines exhibited reduced genetic diversity (Menzies et al., 2012; White et al., 2018a). However we also have relatively little genetic diversity. Moreover, mutations would have accumulated over thousands of years, thus injecting new alleles into the mix.
7 For a review, see (Whelan, 2007).
8 Another possibility, too brief to discuss in any real detail, is that the arrival of the dingo introduced a parasite to the mainland which wiped out the thylacine (Freeland, 1993).
9 See her comments in (Judd & Steer, 2018).
10 He also came off second best against Gideon Mantell, who discovered the first dinosaur: Iguanodon, during their famous dinosaur dispute. Deborah Cadbury's book The Dinosaur Hunters (2000) gives an excellent extended account of the saga.
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