The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation

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The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation
    Greer, A. 2018. The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation. Version: 1 October 2019. 1 The Tasmanian Devil Biology, Facial Tumour Disease and Conservation Allen Greer Visit:  “  At the present time the future of the Tasmanian Devil looks good .... The only danger would seem to be a return of the disease which has devastated the population several times in the past  ”  (Guiler, 1992) “ Wholly protected, common and secure, at present  ” (Moo ney, 1992) “  Barring further epidemics … its status appears to be secure ” (Jones, 1995)   “ The devil is not threatened  …”  (Jones and Rose, 1996) “… secure in Tasmania .  Lower risk  –   least concern ” (Jones et al ., 2003a: table 1) Introduction For many years, the public attitude towards most Australian animals was one of indifference at best and hostility at worst. In the past, fish were mainly “good to eat;” frogs “ slimy ;” reptiles weird , sinister or dangerous; small and some medium-sized  birds attracti ve, “useful” or “good to eat,” but many medium-sized to large birds pests or vermin, as were most mammals. And while many of these attitudes are still  prevalent, there is an increasing appreciation of animals either for what they “ do for us ”  or, even more encouragingly, just as interesting creatures in their own right; indeed, beings with which we share both an evolutionary past and an uncertain future, and without which we would be truly alone in the universe. Just how much attitudes have changed can be judged by contrasting attitudes in the 1950s and 1960s with those of today regarding animals such as sharks, kangaroos, whales and dingoes. No species has benefited from this makeover as much as the Tasmanian Devil, a small dog-sized carnivorous mammal now living only on the island state of Tasmania. The Devil was almost universally loathed up until the 1960s  but is now one of the few species for which the overused word “ iconic ’ is truly appropriate, not only in its home state of Tasmania but also in Australia generally (Darby 2003a). In May 2015, it was named Tasmania’s official animal emblem (ABC  News, 30 May 2015; Tasmanian Government media release, 31 May 2015). But with the timing of a romantic tragedy, humankind’s  recent reconciliation with the Devil has been tempered by a severe population decline with the threat of extinction, due to a rare transmissible tumour, Devil Facial Tumour Disease, sweeping through the  population.    Greer, A. 2018. The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation. Version: 1 October 2019. 2 As a result of the renewed interest in the Devil both in its own right and because of its disfiguring and lethal tumour, research on the animal’s biology has proliferated and a multi-faceted conservation effort put in place. But to date, no one has tried to bring all this information together and provide a concise overview of all aspects of the species ’  biology, its strange disease and current conservation. Such an overview might be especially interesting to those who take an interest in or have responsibility for the Devil but lack the background or the time to access and assimilate the relevant scientific and associated literature. The primary purpose of this book is to provide such an overview. The high public interest in the Devil’s plight has also meant that people working on the Devils biology, disease and conservation have provided a vast amount of information to the public. This on-going flow of information provides an unusual opportunity to see how science operates on a near daily basis. A second purpose of this book, therefore, is to look at the sometimes “all too human” aspect of science  on display in the effort to save the Devil. In this regard, the last two sections of this book (Devil Facial Tumour Disease and Conservation) are a small contribution to the history of science in Australia and can be read profitably along with essays on the Wollemi Pine (Greer, 2007) and cloning the Thylacine (Greer, 2009). Biology How the Devil Got its Names The only written record of how the Devil got its common English name comes from Gou ld (1863) who said that its “black colouring and unsightly appearance” led to the name Devil or Native Devil. Indeed, early settlers with a Christian background may have found many of the Devil’s features suggestive of an alliance with the Devil. Devils are largely black and mostly nocturnal and when annoyed, they scream and their ears turn red. Furthermore, what more appropriate place to find the Devil’s home th an the “other side of the world?”  A t the time of first European settlement in Tasmania, the Devil’s common name was “Native Devil” (Harris, 1808 ; Waterhouse, 1846; Gunn, 1852). At that time, it was unknown if the species occurred on the mainland as well as Tasmania. But when it  became clear the Devil did not occur on the mainland, the common name “ Tasmanian Devil ”  came into usage. In the mid-1850s, the Devil was also occasionally referred to as the “Tasmanian Land Devil (Howitt, 1855). As a logical corollary to the species ’  common name, the Devils’ young became known   as “imps.”  Nowadays, they are also called “joeys” and   “pups.”  Although the co mmon name “Devil” stuck, a mamma logist working in the British Museum was scathing about the propensity of British colonists to give inappropriate names to local animals. “The Ursine Da syure [his preferred common name] is called  by the colonists “The Devil,” or “Native Devil;” I see no necessity for adopting such  barbarous names, nor do I think it desirable to adopt other names given by our colonists, when they convey an erroneous impression of the nature of the animals which have received them (Waterhouse, 1846).”      Greer, A. 2018. The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation. Version: 1 October 2019. 3 A number of scientific names have been applied to the Devil. The species was first formally described and named for science in 1808 by George Harris, the Deputy Surveyor General for the new colony of Van Diemen’s Land. He named his new species  Didelphis   ursina , as “many of their actions, as well as their gait, str  ikingly resembled those of the bear (Harris, 1808). ”  From his description, Harris was obviously impressed with the species’ large mouth, diverse array of teeth, and array of muzzle bristles. He noted correctly that males are larger than females and have a  pendulous scrotum carried in a pouch, and that females have a pouch and give birth to small, naked and blind young which adhere firmly to the teats with their mouths. Fig. 1. The first European image of the Tasmanian Devil (in Harris, 1808) He also noted that the species burrows; preys on small vertebrates; uses the front feet to convey food to the mouth, and is querulous, with females dominant. There are only two errors in Harris’ observations. He miscounted the number of  premolars and molars (“grinders”) as four and five in each the upper and lower jaw, respectively, instead of six and six (below). He also observed that the tail was “ slightly prehensile ”  (repeated in Geoffroy Saint-Hilaire, 1810 and Boitard, 1841: “prenant”)  for which there have been no further observations, although there is a  photo of a young animal with its tail curled around a fern stem (Sanderson et al ., 1979: fig 1). And in an observation that would prove to be important in determining post-European changes in population size, he noted that the first settlers of Hobart Town found the species to be “very common . ”  Interestingly, the specimen(s) that Harris used to describe his new species are now lost. He notes that the specimen he illustrated was to be sent to Sir Joseph Banks in England, but it “died before the vessel left New South Wales (Harris, 1808).”   After reading Harris’ paper, the French zoologist Étienne Geoffroy Saint-Hilaire realised that the Devil was not particularly closely related to American marsupials, as was implied by the generic name  Didelphis , but instead was most closely allied to    Greer, A. 2018. The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation. Version: 1 October 2019. 4 other Australian marsupials. Consequently, he placed Harris’ species in the existing Australian genus  Dasyurus . Thus, it was realised relatively quickly after the Devil  became known scientifically that its relationships lay with  Dasyurus . This generic name was also used by the Dutch zoologist Coenraad Jacob Temminck in 1827 and the Tasmanian botanist Ronald Campbell Gunn in 1838 and again in 1852, and somewhat oddly, even by the Victorian comparative anatomist William Colin Mackenzie as late as 1921. In 1837, however, the French zoologist Frédéric Cuvier thought the Devil differed enough from  Dasyurus  to warrant its own generic name and proposed Sarcophilus . This name is derived from two Greek words, one for “lover” (  philus ) and the other for “meat” ( sarco ). Cuvier had no first-hand knowledge of the species’ habits but interpreted them from Harris’ srcinal description and its dentition. Hence, the De vil’s scientific name became Sarcophilus ursinus . A few years later, in 1841, John Edward Gray (1841) of the British Museum, in what was perhaps a bit of cross channel rivalry, proposed, without explanation, a new generic name for the species,  Diabolicus . Under current rules of zoological nomenclature, however, whimsical name changes such as this have no validity. In this same year, 1841, the French naturalist Pierre Boitard proposed, again without explanation, another completely new name, Ursinus harrisii . The new generic name was perhaps Boitard’s own attempt to impose his nomenclatural will, but it was doomed to fail for the same reason s Gray’s name did. But the new species name was   perhaps proposed in recognition that this p art of the Devil’s name was “unavailable , ”  due to its application eight years earlier to the Common Wombat,  Didelphis   ursina  (now Vombatus ursinus ). Parenthetically, there is some justice in this, as the wombat is surely more “bear  - like” (ursine) than the Devil. Boitard’s new species name  harrisii  graciously recognised the srcinal describer of the species. Much later, the British zoologist Oldfield Thomas thought he was the first to realise that the second part of the name Sarcophilus ursinus  was unavailable for the Devil and proposed his own substitute name, Sacrophilus   satanicus  (Thomas, 1903). Nine years later, however, he realised his mistake and acknowledged Boitard’s much earlier substitute name (Thomas, 1912). Finally, in 1987 the Swedish palaeontologist Lars Werdelin, while working briefly in Australia, proposed a subspecies name for the recently extinct Devils in western Victoria, dixonae , after Joan Dixon, the then curator of mammals at the then National Museum of Victoria (now the Museum of Victoria). He gave some dental measurements to justify the taxonomic recognition of this population, but he did not compare them statistically with the Tasmanian population. This name has never been used in any context. There is one other twist in the history of the Devil ’s scientific name, but it is  discussed under the section on “ Distribution. ”   Phylogenetic Relationships    Greer, A. 2018. The Tasmanian Devil. Biology, Facial Tumour Disease and Conservation. Version: 1 October 2019. 5 All living mammals are members of a single lineage that evolved sometime in the early Jurassic. This lineage split into the monotremes or prototherians (egg laying mammals) and the therians (live-bearing mammals), and the therians then split into the metatherians (marsupials) and eutherians (placentals). Mammals appear to have evolved about 220 Ma (Meredith et al ., 2011: table S6). The prototherians and then the metatherians and eutherians all evolved within a very short period, sometime  between 190 and 160 Ma (Phillips et al ., 2009; Luo et al ., 2011). Australia is the only continent with all three major groups of living mammals. The metatherians appear to have first evolved in the great northern landmass, Eurasia and then extended into the great southern landmass, Gondwana. They went extinct in the North American part of Eurasia about 15 to 20 Ma but persisted in Gondwana. Relationships within the metatherians are not completely resolved, but one of the most consistently supported subgroups is the Australidelphia (Szalay, 1982; Kirsch et al ., 1991; Springer et al ., 1998; Horowitz and Sánchez-Villagra, 2003; Asher et al ., 2004). The living members of this group are all Australasian except for one South American species,  Dromiciops gliroides , the only living species of the Microbiotheriidae. The australidelphians evolved in Gondwana about 70 to 65 Ma (Meredith et al ., 2011: table S6; Mitchell et al ., 2014: fig. 1; Weisbecker and Beck, 2015: fig. 2). Early work considered the South American species to be nested within the Australasian species (Kirsch et al ., 1991; Springer et al ., 1998; Horowitz and Sánchez-Villagra, 2003; Asher et al ., 2004; Cardillo et al ., 2004). More recent work, however, suggested the South American species is the sister group to the Australasian species, called the Eomarsupialia (Amrine-Madsen et al ., 2003; Phillips et al ., 2006; Meredith et al ., 2008; Springer et al ., 2009; Nilsson et al ., 2010; Meredith et al ., 2011). The most parsimonious interpretation of the latter relationship is that the eomarsupialians entered the Australasian section of Gondwana to the exclusion of all other marsupial lineages. (Szalay, 1982). The eomarsupialians evolved into four major groups 67-64 Ma: the kangaroos and their relatives (diprotodontians); the marsupial moles (notoryctemorphians); the  possums and their relatives (peramelemorphians), and the quolls and their relatives (dasyuromorphians) (Meredith et al ., 2008; Mitchell et al ., 2014). The Tasmanian Devil is in the last group. The four groups appear to have evolved within a very short  period, perhaps as little as three million years (Gallus et al ., 2015b). The relationships among these four groups are uncertain, possibly partly due to the very short period in which they evolved, some 3 million years (Gallus et al ., 2015b). The highly specialised notoryctemorphians (two burrowing, blind mole-like species)  being especially difficult to place (Nilsson et al ., 2010; Gallus et al ., 2015b). Indeed, some researchers have opined that the relationships of the four groups may never be resolved as a neat dichotomously branching tree (Gallus et al ., 2015b).
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