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.

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[3] 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.[8] 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.

Tammar wallabies lick their forearms and pant to keep cool in hot weather. They breathe more heavily and lose more water when the temperature is over 30 °C (86 °F). Tammar wallabies cannot survive in temperatures above 40 °C (104 °F) and must find cooler surroundings. To prevent dehydration, tammar wallabies urinate less and suck up water from the distal colon, which gives them relatively dry feces.  Being able to concentrate more urine in their kidneys allows them to survive on seawater.

The tammar wallaby is mostly nocturnal.

During the day, tammar wallabies stay close to scrub for shade and move out to more open grassland by nightfall.In winter their home ranges are about 16 ha (40 acres), but in the dry summers they range further afield to search for quality food, needing about 42 ha (100 acres) of space. Tammar wallaby home ranges overlap with those of conspecifics.  Like all macropods, the tammar wallaby is herbivorous. They are known to both graze and browse, but the latter is less effective, as they commonly drop leaves when chewing on them. When eating large leaves, tammar wallabies handle them with their fingers. Tammar wallabies consume several plant species such as heart-leaved poison (Gastrolobium bilobum), small-flowered wallaby grass (Austrodanthonia setacea), and marri (Corymbia calophylla). They survive on several islands that have no fresh water, subsisting on seawater.

Tammar wallabies are a social species.

Tammar wallabies gather into groups which lessens the chance of an individual being taken by a predator. As the group increases in size, tammar wallabies spend more time feeding, grooming, and interacting and less time being vigilant and moving around. They are also more likely to rest on their sides rather than in a more alert posture where their head is held up. Predators of the tammar wallaby include dingoes, feral cats, red foxes and wedge-tailed eagles. They may also have been preyed upon by the extinct thylacine. Tammar wallabies appear to respond more to the sight than the sound of predators. They can also use their acute sense of smell to detect a potential threat. When a predator is detected, a tammar wallaby will alert others by thumping its foot. When lost, young tammar wallabies are known to emit a distress call and adult females may respond with a similar call.

Use in science

Tammar wallabies are easy to keep in captivity.

The tammar wallaby is a model organism for studying marsupial biology, as well as mammal biology in general. It has been used in the fields of reproductive biology, immunology, metabolism, neurobiology and many others. Its "seasonal and lactational control of its reproduction" makes its reproduction particularly suited for study. Saunders and colleagues (2017) have suggested the bipedal tammar as a better model for research into human spinal cord injuries than quadrupedal rodents. Tammar wallabies are easy to keep in captivity as they are non-aggressive, can adjust to surgeries and reproduce easily, requiring just one male for five females. Tammar wallabies used for scientific study are generally housed in outdoor pens with enough water and shelter, instead of a laboratory.

The genomes of marsupials are of great interest to scientists studying comparative genomics, and the study of tammar wallabies has provided much information about the genetics of marsupials and mammals in general. Marsupials are at a convenient degree of evolutionary divergence from humans; mice are too close and have not developed many different functions, while birds are genetically too remote. Key immune genes from the tammar wallaby were highlighted and studied in 2009.

In 2011, the tammar would become the second marsupial to have its full genome sequenced after the grey short-tailed opossum. The researchers found "innovation in reproductive and lactational genes, rapid evolution of germ cell genes, and incomplete, locus-specific X inactivation". The researchers also found new HOX genes that control gene expression, as well as new microRNAs. Genes for producing milk were shown to be novel while gonad genes appeared to be more conserved. Prior to the full genome sequencing of marsupials, the identification and characterization of important immunological components were limited in most marsupial species. The current sequencing and annotation of whole marsupial genomes have been useful for the further understanding of marsupial immune systems by simplifying the characterization of immune molecules in marsupials, and has aided in biomedical research. A 2017 molecular study of the tammar and the mink found the potential involvement of EGF, FOXO, CDKN1A in controlling mammalian embryonic diapause. IL-10 and IL-10Δ3 are conserved in the tammar showing their immune system can respond to pathogens similarly to other eutherian mammals using these same immune components.

A compound in the milk of the tammar wallaby called AGG01 has the potential to be a new and effective antibiotic. AGG01 is a protein, and in laboratory tests has proven to be far more powerful than penicillin. It kills many types pathogenic bacteria (both Gram-positive and Gram-negative) and at least one fungus. Subsequent analysis of the genome has led to the finding of several cathelicidin peptides, which could also be used as antibiotics. The foregut of the tammar wallaby contains species of bacteria belonging to the phyla Bacillota, Bacteroidota and Pseudomonadota. New species have been discovered: WG–1 of Pseudomonadota and TWA4 of Bacillota. These bacteria produce less methane than others and do not require CO2 to survive. This has important environmental implications, as this information could be used to reduce carbon production in livestock.

Kangaroo Island Tammar Wallaby (Notamacropus eugenii eugenii) Hanson Bay Kangaroo Island, South Australia

Tammar Wallaby (Notamacropus eugenii derbianus) Dryandra, Western Australia