The tammar wallaby (Notamacropus eugenii), also known as the dama wallaby or darma wallaby, is a small macropod native to South and Western Australia. Though its geographical range has been severely reduced since European colonisation, the tammar wallaby remains common within its reduced range and is listed as "Least Concern" by the International Union for Conservation of Nature (IUCN). It has been introduced to New Zealand and reintroduced to some areas of Australia where it had been previously extirpated. Skull variations differentiate between tammar wallabies from Western Australia, Kangaroo Island, and mainland South Australia, making them distinct population groups. The tammar wallaby is among the smallest of the wallabies in the genus Notamacropus. Its coat colour is largely grey. The tammar wallaby has several notable adaptations, including the ability to retain energy while hopping, colour vision, and the ability to drink seawater. A nocturnal species, it spends the nighttime in grassland habitat and the daytime in shrubland. It is also very gregarious and has a seasonal, promiscuous mating pattern. A female tammar wallaby can nurse a joey in her pouch while keeping an embryo in her uterus. The tammar wallaby is a model species for research on marsupials, and on mammals in general. Its genome was sequenced in 2011.
Taxonomy and classification The tammar wallaby was seen in the Houtman Abrolhos off Western Australia by survivors of the 1629 Batavia shipwreck, and recorded by François Pelsaert in his 1629 Ongeluckige Voyagie. It was first described in 1817 by the French naturalist Anselme Gaëtan Desmarest, who gave it the name eugenii based on a specimen found on an island then known as Ile Eugene in the Nuyts Archipelago off South Australia, which is now known as St. Peter Island. The island's French name was given in honour of Eugene Hamelin, caption of the ship Naturaliste; whose name is now the specific name of the tammar wallaby. The common name of the animal is derived from the thickets of the shrub locally known as tamma (Allocasuarina campestris) that sheltered it in Western Australia. It is also known as the dama wallaby or darma wallaby. The tammar wallaby is traditionally classified together with the kangaroos, wallaroos and several other species of wallaby in the genus Macropus, and in the subgenus Notamacropus with the other brush wallabies, all of which have a facial stripe. However, some authors have proposed elevating the three subgenera of Macropus, Macropus (sensu stricto), Osphranter, and Notamacropus into distinct genera, making the tammar's specific name Notamacropus eugenii. This has been supported by genetic studies. Fossil evidence of the tammar wallaby exists from the Late Pleistocene Era – remains were found in the Naracoorte Caves. The mainland and island-dwelling tammar wallabies split from each other 7,000–15,000 years ago, while the South Australian and Western Australian animals diverged around 50,000 years ago. The extirpated tammar wallabies on Flinders Island were greyer in colour with thinner skulls than present-day Kangaroo Island tammars, which are in turn larger than the East and West Wallabi Islands animals. The island tammar wallabies were once thought to be a separate species from the mainland population. A 1991 examination of tammar wallaby skulls from different parts of the species' range found that the populations can be divided into three distinct groups: one group consisting of the populations from mainland Western Australia, East and West Wallabi Islands, Garden Island and Middle Island; a second group consisting of the populations from Flinders Island, 19th-century mainland Southern Australia and New Zealand; and a third group consisting of the population from Kangaroo Island. The Western Australia Department of Environment and Conservation listed these populations as the subspecies Macropus eugenii derbianus, M. e. eugenii and M. e. decres, respectively. A 2017 study found many genetic differences between tammars from Western and South Australia and comparably little between the Kangaroo island and introduced New Zealand tammars. The researchers proposed dividing the species into two subspecies; the subspecific name eugenii for South Australian tammars and derbianus for those from Western Australia.
Characteristics and adaptations One of the smallest wallaby species, the tammar wallaby features a proportionally small head with large ears, and an elongated tail, with a thick base. It has dark greyish upperparts with a paler underside and rufous-coloured sides and limbs. The tammar wallaby exhibits great sexual dimorphism, males reaching 9.1 kg (20 lb) in weight compared to 6.9 kg (15 lb) for females. Males are 59 to 68 cm (23–27 in) long while females are 52 to 63 cm (20–25 in), while both sexes stand 45 cm (18 in) tall. The tail has a length of 34 to 45 cm (13–18 in) for males and 33 to 44 cm (13–17 in) for females.
Locomotion
As with most macropods, the tammar wallaby moves around by hopping. This species typically leaps 0.8 to 2.4 m (2.6–7.9 ft) with 3.5 landings per second. Proximal muscles at the knee and hip joints provide the power for each leap, which shifts to the ankle muscles as the animal pushes off. As it lands, the energy of the jump is converted into strain energy made when its leg tendons are stretched. As it leaps back off the ground, the tammar wallaby can recover much of this energy for reuse through elastic recoil. When on the move, animal's respiration is tied to its hopping cycle, inhaling when leaping and exhaling when landing. As it moves faster, its heart rate increases nearly twice as much as its hopping frequency. The amount of energy stored in the tendons increases with the animal's speed and the weight of the load it is carrying. This is particularly helpful for mothers carrying young, and explains why tammar wallabies can increase their hopping speed without using more energy. The tammar wallaby shares this characteristic with other macropods that move on flat terrain, like the red kangaroo. By comparison, rock-wallabies, such as the yellow-footed rock-wallaby, have traded efficient energy-saving for greater tendon strength: an adaption for rocky cliffs which allows them to leap higher and lowers the risk of their tendons breaking.
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