Wednesday, May 04, 2011

The Predatory Behaviour of the Thylacine

The predatory behaviour of the thylacine: Tasmanian tiger or marsupial wolf?. 2011. B. Figueirido and C. Janis. Biology Letters

Jimmy Olsen © DC Comics
Its head and body looked like a dog, yet its striped coat was cat-like. It carried its young in a pouch, like a kangaroo. No wonder the thylacine — the enigmatic, iconic creature of Australia and Tasmania — was the object of so much confusion, alternately called the "marsupial wolf" and the "Tasmanian tiger."

So what was it? By studying bones of thylacines and 31 other mammals, researchers at Brown University have the answer: The thylacine was a Tasmanian tiger — more cat than dog, although clearly a marsupial. The researchers have also shown that the extinct thylacine was a solitary, ambush-style predator. That hunting approach separates thylacines from wolves and other large canid, or dog-like, species that hunt in packs and generally pursue their quarry over some distance.

Image: Carl Buell
For millions of years, Thylacinus cynocephalus roamed mainland Australia. Its numbers declined as humans settled throughout the continent, beginning some 40,000 years ago, and the dingo, a small, dog-like creature, was introduced, about 4,000 years ago. Thylacines' last remaining outpost was in dingo-free Tasmania, but a concerted eradication effort wiped out the species. The last known thylacine, said to be named "Benjamin," died at a zoo in Hobart in 1936.

Examining the bones, they found that the thylacine's humerus was oval and elongated at the end closest to the elbow, implying that the animal's forearm bones, the radius and ulna, were separate. That means the Tasmanian tiger would have been able to rotate its arm so that the palm faced upwards, like a cat. The distal humerus on dog-like animals, such as dingoes and wolves, is "more squared-up and shorter," Janis said. This indicates the radius and ulna were closer together in these species, reflecting that these animals' hands are more fixed in the palm-down position.

In terms of hunting, the increased arm and hand movement would have given the thylacine a greater capability of subduing its quarry after a surprise attack. Since dingoes and other dog-like creatures have less latitude in arm-hand movement, that helps explain why these animals hunt by pursuit and in packs, rather than in an ambush setting, the researchers note. link