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Forearms point to Tasmanian tiger as a solitary hunter

By Martin Leggett - 03 May 2011 23:0:0 GMT
Forearms point to Tasmanian tiger as a solitary hunter

'Dem dry bones' are telling an intriguing tale on the extinct Tasmanian tiger - known to science as the thylacine. They are helping to bring to life its style of hunting, and so help to answer an age-old question; was this marsupial predator more like a cat or a dog?

The latest paper on these fascinating Australian animals, published in today's Biology Letters looked to the forearm bones of Thylacinus cynocephalus, to try and work out its strategy for bagging prey. And it appears that its arms were best adapted to the lone ambush technique of many big cats - rather than the pack-hunting tactics of wolves and dogs.

Thylacines were just one of a number of distinctly Australian marsupial adaptations, filling the role of top predator across the continent - that is until the introduction of dingos by man, which seemed to tip them towards extinction.

They looked like wolves, but were striped like tigers, and continued to hold out in the southern island of Tasmania until the last century. An effort to eradicate what was, at that time, seen to be a pest, killed the last 'Tasmanian tigers' in 1936.

Because of the lack of behavioral studies before their untimely extinction, quite how these predators operated in their natural environment has been something of a mystery. But this new study has found the key to that - in the arrangement of the ulna and radius bones of the thylacine's forearm. By making a comparison between the forearm bones of the thylacine and 31 other mammals, a match was found. And these 'marsupial wolves' were really more akin to tigers than wolves.

For big-cat ambushers, such as tigers and pumas, being able to grasp and handle their prey with a dexterous elbow joint is important. Their prey is grappled in a surprise attack - and still able to strongly resist, and so escape. That makes flexibility in the prey-predator struggle vital.

Such a hunting-style means bones that the ulna and radius are separate, allowing the paw to be rotated 180 degrees. Wolves and other pack hunters, by contrast, rely on speed to exhaust and run down their prey. That requires a squarer and shorter humerus, and closely a paired ulna and radius, with a paw that is much less flexible.

This study shows that thylacine's bones were a good match for the tigers - meaning they probably hunted alone and ambushed their prey. One of the paper's co-author's, Christine Janis, from Brown University, said ''It's a very subtle thing, you never would think that the shape of just one bone would mean so much.'' The paper does raise the question as to why the appearance of the dingo had such a negative effect on the 'Tasmanian tigers'.

Scientists had speculated that the dingo, a smaller wolf-like animal, filled the ecological niche of the thylacine - and so out-competed it there. But this study suggests that the pack-hunting dingo was not a carbon-copy of the thylacine. ''I don't think there's anything like it around today,'' said Janis. ''It was sort of like a cat-like fox.''

Photograph by E.J. Keller, from the Smithsonian Institution archives.