Tasmanian Wolves (Thylacinidae)

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Tasmanian wolves

(Thylacinidae)

Class Mammalia

Order Dasyuromorphia

Family Thylacinidae

Thumbnail description
Medium-to-large carnivore, characterized by a long, narrow snout, sloping hindquarters that taper to a long, semi-rigid tail, with broad back stripes from shoulders to tail base

Size
4.9–6.4 ft (1.5–2 m); 33–77 lb (15–35 kg)

Number of genera, species
1 genus; 1 species

Habitat
Forest and woodlands

Conservation status
Extinct

Distribution
Island of Tasmania, Australia; subfossil on Australian continent

Evolution and systematics

At least 14 species of Tasmanian wolves from six genera are known from the fossil record, including Thylacinus, the last species (T. cynocephalus), which persisted until historical times. Thylacinids originated in the late Oligocene, reached their greatest diversity, with coexisting species, in the Miocene, and then declined steadily with only two species, including the giant T. potens, living in the Pleistocene. Thylacinids ranged in size from small carnivores (4.4–11 lb; 2–5 kg) to slightly larger than the thylacine (66 lb; 30 kg). Thylacinids are morphologically conservative among the Dasyuromorphia, including T. cynocephalus, which were little derived from the late Oligocene thylacinids, and are most closely related to the dasyurids, although they are convergent with the extinct South American marsupial borhyaenids.

The taxonomy for this species is Thylacinus cynocephalus (Harris, 1808), Tasmania, Australia.

Physical characteristics

Tasmanian wolves are superficially dog-shaped. They walk on four legs, although the legs are shorter than most canids. The head is doglike with a long, narrow snout, medium-sized (3 in; 80 mm) erect ears, and a strong jaw. The hindquarters slope and taper to a long, semi-rigid tail. The footpads extend to the heel and wrist joints. The recently extinct T. cynocephalus was sexually size dimorphic: females approximately 33 lb (15 kg), males up to 66 lb (30 kg). Body hair is short (to 0.6 in; 15 mm) and sandy brown in color, with 15–20 brown stripes across the back, extending from behind the shoulders to the base of the tail. The female

pouch opens slightly posteriorly and contains four teats. Males also have a small pouch-like depression around the scrotum. There are four upper and three lower incisor teeth, one set of canines, and three sets of premolars. Each of the four molars is similar in form, with major slicing (carnassial) and minor grinding surfaces.

Distribution

Records from diaries and bounty payments in the nineteenth century indicate a historic range that incorporated the entire island of Tasmania, although the wolves were very scarce in the southwest and western regions, except on the coastal strip. This distribution is similar to the current range of the Tasmanian devil (Sarcophilus laniarius) and correlates with mean annual rainfall and associated vegetation. The thylacine reached its highest population densities in the low-to-moderate rainfall zones of the north, center, and east of the state, and thylacines occurred at all altitudes. Thylacines have been extinct on the Australian continent for not less than 2,000 years; subfossil and prehistoric distribution was broad. There are fossil records from New Guinea.

Habitat

Historic reports indicate a broad range of reasonably open habitats: grassy woodlands, coastal and alpine scrub, and open forests. Thylacines seem to have avoided the dense, wet rain-forest of western and southwestern Tasmania. Their habitat preferences completely overlap with those of the devil and are consistent with the distribution of dense populations of prey. Tasmanian wolves are reported to have used dense vegetation and rocky outcrops during the day (probably for dens), hunting in adjacent open grassy woodlands and forests at night. The number of subfossil remains found in caves in Tasmania attest to the use of larger caves as lairs.

Behavior

Sightings of thylacines were usually of solitary animals. Occasional sightings of adult-sized animals together cannot be construed as evidence of pair-bonding, and there is no evidence to support territorial defense of home ranges. Tasmanian wolves were mostly nocturnal but were occasionally observed active during the day. Vocalizations included a coughing bark and a sigh emitted while hunting, and a warning hiss, a low growl, and an undulating screech that were thought to be antagonistic. These vocalizations are not dissimilar in structure to the vocal repertoire of the Tasmanian devil.

Feeding ecology and diet

Unfortunately, early research interest in the thylacine concerned classical anatomy and the species became extinct without any serious study of its ecology. What is known of diet, hunting, and killing behaviors has been gleaned from historical anecdotes or reconstructed from comparison of skeletal remains with its living relatives. Thylacines are reported to have taken a wide variety of prey, including wombats, macropods, possums, bandicoots, small mammals, and birds, suggesting they were generalist predators of prey between less than 2.2 lb (1 kg) and probably not much more than 66 lb (30 kg). Tasmanian wolves had a long, thin snout relative to all other mammalian carnivores, marsupial or placental, most like that of a fox. This translates to a relatively weak bite force at the canine teeth. Museum-collection skulls also have very low rates

of breakage of the canines. Combined with the dietary records, and in contrast to prey sizes taken by devils and the larger quolls (up to three times their body weight), this combination of features suggests that thylacines did not routinely kill very heavy-bodied prey or prey much larger than themselves (33–66 lb; 15–30 kg). While they are recorded killing kangaroos, it is unlikely that they regularly killed healthy large males (up to 155 lb; 70 kg) or the larger megafauna such as diprotodonts. A similar ovoid cross-sectional shape of the canine teeth to the living larger dasyurid carnivores suggests that thylacines probably killed their prey using a generalized crushing bite used in killing. Tasmanian wolves were probably not swift runners, which is indicated by comparison of their leg bone ratios with other marsupial and placental carnivores. Unlikely to be capable of sustained, fast pursuit, thylacines probably hunted using a combination of stealth, short pursuit, and ambush. Putting all of these pieces of information together, it is likely that the thylacine filled a niche more similar to a medium-sized canid such as a coyote than to a wolf.

Reproductive biology

Little is known of reproduction in the Tasmanian wolves and they were bred only once in captivity, although females with pouch young were trapped and kept in zoos. Breeding appears to have been timed, as with other dasyurid carnivores, so that young became independent in spring when food supply is maximal. Gestation was probably less than one month, pouch life thought to be around four months. Neither the period of maternal care, post-pouch-vacation, nor the mating system is known.

Conservation status

Thylacines are classified by IUCN criteria as Extinct. The story of the decline and extinction of the thylacine is a sad tale of a deliberate strategy of persecution and a convenient scapegoat. Eighteenth-century settlers, experiencing signifiant sheep losses, employed "tiger men" to destroy Tasmanian wolves on their properties and successfully lobbied the government to instigate a bounty. While there is no doubt that thylacines killed sheep, it is thought that poaching and feral dogs were responsible for the majority of missing and dead sheep. The intense pressure placed on populations (2,184 bounty payments in 22 years as well as unrecorded deaths) of this probably never-abundant top predator would have driven thylacines to very low densities. Thylacines suddenly became very scarce in the first decade

of the twentieth century, with bounty payments falling from 100 to 150 per year to none between 1905 and 1910, and populations never recovered. The bounty scheme was scrapped in 1912 and the species given official protection on July 14, 1936. The last confirmed living animal died in the Hobart Zoo on September 7, 1936, and the last confirmed killing of a wild Tasmanian wolf was in 1930. There have been and continue to be sightings that appear credible but no thylacine has turned up.

Significance to humans

Tasmanian wolves were deliberately killed and eaten by aboriginal peoples both on the Australian mainland and in Tasmania. Mainland aboriginal rock art depicts speared thylacines as well as females feeding young. Practices varied from tribe to tribe. George Augustus Robinson, an early colonist, recorded consumption of thylacines by some tribes, but others seemed to revere the species, building shelters to cover the body after skinning it and keeping the skull.

Resources

Books

Archer, M., T. Flannery, S. Hand, and J. Long. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Sydney: UNSW Press, 2002.

Dixon, J. M. "Thylacinidae." In Fauna of Australia, edited by D. W. Walton, and B. J. Richardson. Canberra: Australian Government Publishing Service, 1989.

Guiler, E., and P. Godard. Tasmanian Tiger, A Lesson to be Learnt. Perth, Western Australia: Abrolhos Publishing, 1998.

Guiler, E. R. Thylacine: The Tragedy of the Tasmanian Tiger. Melbourne: Oxford University Press, 1985.

Jones, M. E. "Predators, Pouches and Partitioning: Ecomorphology and Guild Structure of Marsupial and Placental Carnivores." In Predators with Pouches: The Biology of Carnivorous Marsupials, edited by M. E. Jones, C. R. Dickman, and M. Archer. Melbourne: CSIRO Books, 2003.

Krajewski, C., and M. Westerman. "Molecular Systematics of Dasyuromorphia." In Predators with Pouches: The Biology of Carnivorous Marsupials, edited by M. E. Jones, C. R. Dickman, and M. Archer. Melbourne: CSIRO Publishing, 2003.

Paddle, R. The Last Tasmanian Tiger. The History and Extinction of the Thylacine. Cambridge: Cambridge University Press, 2000.

Strahan, R. The Mammals of Australia. Sydney: Australian Museum Reed Books, 1995.

Wroe, S. "Australian Marsupial Carnivores: An Overview of Recent Advances in Palaeontology." In Predators with Pouches: The Biology of Carnivorous Marsupials, edited by M.E. Jones, C. R. Dickman, and M. Archer. Melbourne: CSIRO Publishing, 2003.

Periodicals

Jones, M. E., and D. M. Stoddart. "Reconstruction of the Predatory Behaviour of the Extinct Marsupial Thylacine." Journal of Zoology 246 (1998): 239–246.