Tammar wallaby
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 eradicated. 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 1628 "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 where it was found: an island he knew 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, commander 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 propose elevating the three  subgenera of "Macropus", "Macropus" (sensu stricto), "Osphranter", and "Notamacropus" into distinct genera, making the tammar's specific name "Notamacropus eugenii". Fossil evidence of the tammar wallaby exists from the Late Pleistocene Eraremains 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 had greyer coats and thinner heads 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 "M. e. derbianus", "M. e. eugenii" and "M. e. decres", respectively. A 2017 study found extensive genetic differentiation between tammars from Western and South Australia and little differentiation 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 in the genus "Notamacropus", the tammar wallaby features a small head and large ears with a long tail, thick at the base. It has dark grey-brown upperparts with  paler grey highlights, rufous on the sides of the body and limbs, particularly in males, and pale grey-buff underparts. The tammar wallaby exhibits significant sexual dimorphism, with the maximum recorded weight in males being and maximum recorded weight in females is . The body length is in males and in females. Both males and females are about in height. The tails of males range from and those of females from . Locomotion. As with most macropods, the tammar wallaby moves around by hopping. This species has a hopping frequency of 3.5 strides per second, with a stride length of . When hopping , proximal muscles at the knee and hip joints generate most of the power for each leap, which are delivered by multi-joint muscles at the ankle. 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 though elastic recoil. 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 plains-dwelling macropods, like the red kangaroo. By comparison, rock-wallabies, such as the yellow-footed rock-wallaby, have traded efficient energy-saving for greater tendon thickness: an adaption for steep rocky terrain which allows them to leap higher and lowers the risk of their tendons rupturing. Senses. The tammar wallaby has 324° peripheral vision and 50° binocular vision. It can distinguish black/white gratings of different widths and in different light conditions better than most other small  mammals, such as rabbits. Its vision is, nevertheless, not as good as that of a cat or human. Tammar wallabies appear to have some colour vision: its eyes have only blue sensitive and green sensitive photoreceptor cones, allowing it to see colour in the blue-green band of the colour spectrum, but not the longer wavelengths of the red-yellow band. Nevertheless, in the band where it can see colour, it can differentiate between two monochromatic colours with wavelengths as close as apart. The pinna (ear) of the tammar wallaby is mobile, allowing it to track sounds from different parts  of its surroundings without moving its head. A tammar wallaby can point its pinna at a sound source and increase its eardrum's sound pressure by 25–30 dB at 5kHz. When the pinna moves away from the sound source, the animal's hearing level quickly drops. When born, a tammar wallaby's sense of smell is already developed; this allows the newborn to find its mother's pouch by scent. Thermoregulation and water turnover. 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  . Tammar wallabies cannot survive in temperatures above and must find cooler surroundings. To prevent dehydration, tammar wallabies urinate less and reabsorb 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. Ecology and life history. Mostly nocturnal, tammar wallabies spend much of their time foraging. In winter their home ranges are about , but in the dry summers they range further afield to search for quality food, needing about of space. Tammar wallaby home ranges overlap with those of conspecifics. During the day, tammar  wallabies stay close to scrub for shade and move out to more open grassland by nightfall. 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 forelimbs. This species spends more time chewing its food than other similar sized macropods, which likely aids digestion. Tammar wallabies commonly feed on acacia seeds. Other species consumed include heart-leaved poison ("Gastrolobium bilobum"), small-flowered wallaby grass ("Austrodanthonia setacea"), and marri ("Corymbia  calophylla"). Tammar wallabies survive on several islands that have no fresh water, subsisting on seawater and the moisture in plants. The tammar wallaby rests in two positions: a "sitting tail forward" position, in which the hind legs are outstretched with tail brought forward in between, the body prone and the head above ground; and a "lying" position, in which the animal lies on its side with the head touching the ground. The former position is typically used during the day for long periods, and the latter position is used at night for brief periods. Tammar wallabies are known to live  in stable groups, which lessens the chance of an individual being taken by a predator. As the group increases in size, tammar wallabies spend more time foraging, grooming and interacting and less time being vigilant and moving around. 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 coarse screeching call and adult females may respond with a similar call. Breeding and development. The tammar wallaby has a promiscuous mating system. It is a seasonal breeder and births largely occur during late January and early February. During the breeding season, the male's prostate and bulbourethral gland enlarge. However, there does not appear to be any seasonal difference in the weight of the testes. Around two weeks before the first births, the males will begin sniffing the urogenital openings and pouches  of the females to determine their reproductive status. After giving birth, females enter estrus and allow males to mate with them. However, a male that attempts to mate with an estrous female may face aggression from other males. A male can achieve reproductive success by mate-guarding. During the estrous period, males establish a dominance hierarchy and the higher ranking males will try to prevent subordinates from mating with estrous females. Several males may pursue a single female. The female tammar wallaby can conceive shortly after giving birth. Tammar wallabies undergo embryonic diapause and the blastocyst remains dormant for nearly  a year. For the first half of the year, the presence of the joey in the pouch prevents the blastocyst from developing and experiments have shown that removing the joey within this first half will stimulate the blastocyst's development. However, after this, the blastocyst remains dormant even after the joey has left. It begins to develop by the summer solstice at the end of December and the female gives birth around one month later. A 2019 study found that birth ratios are biased towards males, due to greater Y chromosome sperm in males at the population level, while weaning  ratios are biased towards females. Tammar mothers may abandon male joeys and reactivate embryos in diapause to adjust the sex ratios of offspring born. The lactation period of the tammar is divided into phases 2A, 2B and 3 (pregnancy is labeled phase 1). Phase 2A encompasses the first 100–120 days after birth, and the underdeveloped young is fed diluted milk which is rich in carbohydrates and low in proteins and lipids. This allows for the rapid development of organs and systems including the respiratory system, lymphoid system and nervous system. During this phase, the young is continuously attached to the  teat. Phase 2B lasts for another 100 days; the young attaches and reattaches to the teat intermittently but remains in the pouch. The composition of the milk is similar, though the proteins change. During phase 3, the joey can leave the pouch and feed on plant material. The joey will return to the pouch to suckle, the mammary gland having enlarged and the milk having become richer in protein and lipids and poorer in carbohydrates to give the joey higher energy. During this time, the joey also experiences its most dramatic changes in morphology and growth and transitions from ectothermy  to endothermy. The joey no longer needs the pouch by 250 days and is fully weaned at 300–350 days. The tammar wallaby has been observed to engage in alloparental care, in which an adult may adopt another's young. Male tammar wallabies may live eleven years, females to age fourteen. Health. In one population of tammar wallabies, the tick species "Ixodes hirsti" was found to infest them during autumn and winter while those of the genus "Amblyomma" were more common in spring and summer. In late 1998 and again in early 1999, 120–230 tammar died suddenly in research facilities and  zoos in New South Wales and Queensland respectively, perishing less than 12 hours after exhibiting the first symptoms, with most exhibiting no symptoms at all. Post mortem examination revealed haemorrhage of the muscles, and abdominal and thoracic organs. The syndrome is known as tammar sudden death syndrome and the pathogen is an orbivirus of the family Reoviridae. It does not occur south of Sydney. Captive populations of tammar wallabies in New South Wales have subsequently suffered infections in summer months. No treatment has been attempted due to the rapid progression of the disease. Population dynamics and conservation. The tammar wallaby  is listed as Least Concern by the IUCN as of 2016, being particularly numerous on Kangaroo Island and on four islands in Western Australia. It has a maximum population of 50,000 mature individuals total. However, the fragmentation of its range has led to high amounts of inbreeding and morphological abnormalities in some populations. Since European occupation, tammar wallaby populations on both mainland Australia and some of the islands have been greatly reduced or even eradicated. In the early 20th century, the mainland population of tammar wallabies in Western Australia was described as numerous in much of the southwest, but declining  in the cultivated areas, particularly to the north. Clearings made for wheat and sheep caused the population to decline further. From the 19th century, tammar wallabies in the Eyre Peninsula and around Adelaide were decimated by mobs of hunters organised to protect crops and pastures. As a result, they were extirpated in the areas around Adelaide by the 1920s, and in the Eyre Peninsula around the 1970s. Tammars from Flinders Island and St Peter Island were eradicated in a similar manner. Tammar wallabies from these areas were introduced to Kawau Island in New Zealand by colonial administrator Sir George Grey  in 1870. They were introduced to the Rotorua area in the early 20th century. Since then, they have flourished to the point where their foraging has damaged indigenous plants. Pest control operators have used sodium fluoroacetate, a naturally occurring rodenticide, to control their populations, a practice which has been controversial because of its possible effect on organisms not targeted by the poison, including humans. Cyanide pellets have been used as an alternative. In 1985, tammar wallabies were introduced to the North Island of the Houtman Abrolhos and have made similar impacts on native vegetation. Their numbers grew to 450 individuals , but by 2008 culling efforts appeared to have reduced their numbers to 25 individuals. In 2003, the Monarto Zoo temporarily housed 85 tammar wallabies from New Zealand awaiting reintroduction to the Innes National Park on the Yorke Peninsula in South Australia. Four releases have been made, and the population increased to 100–120 animals by 2012. Tammar wallabies have also been successfully translocated to various areas in Western Australia. Tammar wallaby were reintroduced to Kalbarri National Park in 2010 though the project was not considered successful as the majority of radio-collared individuals died within a year. Resistance to sodium fluoroacetate . Different tammar wallaby populations have varying levels of resistance to sodium fluoroacetate. Mainland Western Australian tammar wallabies appear to be the most resistant, while those on Kangaroo Island are much more vulnerable. Tammar wallabies from New Zealand are also vulnerable, as poison has been successfully used to control their populations. Tammar wallabies from East and West Wallabi Islands and Garden Island, which do not have plants containing sodium fluoroacetate, are less resistant than mainland Western Australian tammar wallabies, but are more resistant than those from Kangaroo Island. This suggests that tammar wallabies originated in South Australia and developed a resistance  to sodium fluoroacetate when they reached Western Australia, where the poison is found in plants. Use in science. 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" make its reproduction particularly suited for study. Saunders and colleagues (2017) have suggested the bipedal tammar as a more appropriate model for research into human spinal cord injuries than quadrupedal rodents. Tammar wallabies are inexpensive to keep in captivity and  are easy to handle. They also breed well, especially if there is at least one male for five females. Tammar wallabies used for scientific study are generally housed in outdoor pens with access to water and shelter, which is closer to their natural habitat than 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 isolated and studied in 2009. The full genome was sequenced in 2011 and 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 novel microRNAs. The tammar wallaby genome appears to have more rearrangements than those of both the human and the gray short-tailed opossum, another sequenced marsupial.<ref name="Renfree/Papenfuss"></ref> A 2017 molecular study of the tammar and  the mink found the potential involvement of EGF, FOXO, CDKN1A in the molecular control of embryonic diapause in mammals. A compound in the milk of the tammar wallaby called AGG01 has the potential to be a new and powerful antibiotic. AGG01 is a protein, and in laboratory tests has proven to be a hundred times more effective than penicillin. It kills over 99% of the pathogenic bacteria (both Gram-positive and Gram-negative) it is incubated with, including "Salmonella", "Proteus vulgaris" and "Staphylococcus aureus" (It also kills one species of fungus). Subsequent analysis of the genome has led to the  discovery 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 CO to survive. This has important environmental implications, as this information could be used to reduce carbon production in livestock. External links.