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    Despite the relationship between the Tasmanian devil and the thylacine, the devil is taxonomically closer to the other members of the Dasyuridae family, the quolls and the tiny mice-like marsupials—dibblers, antechinuses, kowaris, mulgaras, kalutas, phascogales, planigales, ningauis, dunnarts and kultarrs. (The more distantly related numbats, bandicoots, bilbies and the marsupial mole make up the rest of Australia’s sub-order of carnivorous marsupials.)
    Quolls are well covered with spotted fur, have long tails, pointed facial features and sharp teeth. Two of the four species are found in Tasmania, the abundant eastern quoll ( Dasyurus vivevrinus , once called the native cat) and the larger, less common spotted-tailed quoll ( D. maculatus , tiger cat), which weighs up to 7 kilograms. Both species were once common across the mainland, but the eastern quoll is extinct there now and its larger cousin reduced to rump populations. Quolls are excellent hunters and prey on many invertebrates, reptiles, rodents, possums and small macropods. They climb very well, and birds and sugar gliders are included in their prey. But carrion also forms an important part of the diet, while rubbish-dump scavenging, poultry raiding, corbey grubs and fruit all add to an impressively varied diet.
    The great mammalogist John Eisenberg visited Tasmania in 1990 on sabbatical. He had recently published The Mammalian Radiations , the most comprehensive summary of mammal evolution to date. Earlier in his career he had published studies of the behaviour of Tasmanian devils, and while in Tasmania he discussed with zoologists the concept of the carnivore guild and its functioning as a unit. His seminal thoughts and discussions contributed to the work and management directions which followed.
    In his book (subtitled An Analysis of Trends in Evolution, Adaptation and Behaviour ) Eisenberg first conceptualised the importance of studying a marsupial carnivore guild rather than individuals in isolation. 15 Menna Jones’ resulting guild-structure findings derive from dentition studies carried out in the field and on skulls held in Australian collections. She showed that the relationship between devils and quolls evolved as one of direct competition. She sought to determine the role of such competition in structuring body size, habitat usage and diet. In general, species will space out in a habitat according to their own size and the size of their prey. It is called equal spacing.
    A major finding was that, for this to be achieved, ‘the spotted-tailed quoll had to redefine itself in an evolutionary sense’. 16 And it happened quickly: Jones puts the evolutionary timescale of this at as little as 100 to 200 generations, a generation being two years. While devils and the small eastern quoll are sufficiently different in size as to have minimal dietary overlap, the larger spotted-tailed quoll is in the middle, and therefore in competition with both. Jones believes that this may explain why it is the rarest of the three. How did she arrive at these conclusions?

    The spotted-tailed quoll competes with the devil for both live prey and carrion.Devils are frequently blamed for raiding poultry yards, when quolls are the more likely culprit. The spotted-tailed quoll, once commonly known as the tiger cat, is extinct across most of mainland Australia and no longer common in Tasmania.
(Courtesy Dave Watts)
    Skulls and skeletal material held in collections across Australia were measured. Particular attention was paid to dentition, with arrays of data compiled to create an index of tooth strength, as opposed to mere changes in tooth size over time. As well, the size and therefore strength of the temporalis muscles, the jaw-closing muscles, were measured by dimensions taken off the skulls. Tooth strength and jaw strength determine the size of prey a particular species can take. Analysis of the data indicated ‘intense competition in Tasmania . . .