Skulls show lone wolf is more of a jackal
Convergent evolution and a broad carnivorous diet are what led the warrah, or Falkland Islands wolf (Dusicyon australis), to resemble a jackal, Museum scientists have found.
The team compared the shape of the now-extinct warrah's skull to skulls from 24 other wild canids (members of the wider dog family), including grey wolves (Canis lupus) and foxes (genus Vulpes).
They found that the warrah's skull was most like those species with broad carnivorous diets, such as jackals, despite the two being only distantly related.
This suggests that its appearance may have developed due to convergent evolution - as the only land mammal on the Falkland Islands, the warrah, like the jackals it resembles, took on the role of a generalist carnivore, able to both hunt and scavenge.
Both the warrah and jackals have wide, elongated muzzles, narrow cheekbones and thick lower jaws - all typical features of medium-sized, opportunistic predators.
'The skulls show that D. australis likely had a similar diet to modern jackals,' explains Roberto Portela Miguez, Senior Curator of the Museum's mammal collection and one of the study's co-authors.
'It may even have been able to bring down large prey, such as the sheep that were brought to the islands by settlers.
'While this opportunistic approach to feeding was an advantage at first, in the end it may have contributed to the Falkland Islands wolf's downfall - by making it public enemy number one among the settlers whose sheep it killed.'
Despite its alternative name, the warrah is not actually a true wolf, but is more closely related to the fox-like canids of mainland South America.
Yet in many ways, the species is more similar in appearance to bigger dogs, such as wolves - which led Darwin to describe the warrah as a 'wolf-like fox' when he encountered it in 1833. His was one of the only scientific observations of the warrah before it was hunted to extinction just over 40 years later.
For many years, this appearance caused difficulties for scientists attempting to classify the warrah, but an understanding of the groups' diets may help to explain many of the differences.
Compared with the strong-jawed warrah, the skulls of its mainland South American relatives more closely resemble those of 'hypocarnivores' - carnivorous species, such as foxes, that eat few vertebrates and get only a small portion of their daily calorie requirement from meat.
These animals have narrow muzzles and less powerful jaws than either opportunistic predators, such as the jackal, or 'hypercarnivores', like wolves and big cats.
In contrast, the warrah lived in a region with many marine mammals and nesting birds, so could sustain a more carnivorous diet than its closest relatives.
'Across these canid species, we can see how their ecological niches - their habitats and diets - helped to drive the evolution of their skulls,' says Portela Miguez.
'Its isolation on the Falkland Islands allowed D. australis to evolve completely independently, and in vastly different conditions, to its mainland relatives.
'This range of habitats means that South America has the world's richest variety of canid species - but, as the loss of the warrah shows, this diversity is under threat from human-driven extinction.'