The predatory behaviour of the thylacine: Tasmanian tiger or marsupial wolf?

Abstract

The extinct thylacine (Thylacinus cynocephalus) and the extant grey wolf (Canis lupus) are textbook examples of convergence between marsupials and placentals. Craniodental studies confirm the thylacine's carnivorous diet, but little attention has been paid to its postcranial skeleton, which would confirm or refute rare eyewitness reports of a more ambushing predatory mode than the pack-hunting pursuit mode of wolves and other large canids. Here we show that thylacines had the elbow morphology typical of an ambush predator, and propose that the 'Tasmanian tiger' vernacular name might be more apt than the 'marsupial wolf '. The 'niche overlap hypothesis' with dingoes (Canis lupus dingo) as a main cause of thylacine extinction in mainland Australia is discussed in the light of this new information.

Habitat changes and changing predatory habits in North American fossil canids

“…2a; Supplementary Table 1). Furthermore, changes in elbow-joint shape captured by each axis show the morphological adaptations for different types of predatory behaviour: ambush predators retain the generalized mammalian condition of relatively wide joints with high supinatory abilities, enabling grappling with the prey; pursuit predators have narrow and 'box-like' elbows with limbs locked into a more prone position; and the elbow-joint morphology of pounce-pursuit predators is somewhat intermediate, but with some unique features 22 (Fig. 2b,c).…”

“…It should be noted that, to a certain extent, among cursorial predators, pounce-pursuit versus pursuit behaviour is related to body size (but see ref. 22): smaller carnivores (420 kg) are pounce-pursuit predators and larger ones are pursuers, but some large pounce-pursuit predators exist (for example, dingoes and the striped and brown hyenas).…”

“…The elbow-joint shape in the 139 specimens (92 living specimens distributed among the families Felidae, Hyaenidae, Viverridae, Mustelidae and Canidae of the order Carnivora (Table 1) and 47 fossil specimens of the family Canidae including representatives of the three subfamilies, Hesperocyoninaew, Borophaginaew and Caninae [17][18][19] (Table 3) was recovered by digitizing six landmarks in 2D on the anterior surface of the humerus distal epiphysis [20][21][22] from high-resolution digital images (Fig. 1a).…”

“…1a), ranging from the Oligocene (B37 Myr ago) to the end of the Pleistocene (B0.01 Myr ago), in comparison with a large sample of modern carnivores of known predatory behaviour. We analyse the shape of the elbow-joint because it is an established morphological indicator of locomotor/predatory behaviour in living carnivores [20][21][22] , as it reflects the relative range of forearm motion (Fig. 1b).…”

“…1b). Whereas ambush predators need to retain supinatory ability (that is, rotation of the manus to palm-upwards position) to grapple with prey, both pursuit (long-distance running 23 ) and pounce-pursuit (short-distance sprinting 23 ) carnivores have forelimbs with the manus more locked into a prone position, and limb movement more restricted to the parasagittal plane 21,22 .…”