Tammar wallabies are found in Australia, New Zealand, and various islands off the western and southern coast of Australia. (Grzimek, 1990; Nowak, 1991)
Biogeographic Regions: australian (Native )
Significant sexual dimorphism exists between the males and the females of this species, with males growing to be larger. The maximum recorded weight in males is 9.1 kg, while in females it is 6.9 kg. The body length is 59 to 68 cm in males and 52 to 63 cm in females. Both males and females are about 45 cm in height. The tails of males range from 38 to 45 cm and that of females from 33 to 44 cm.
Males have considerably larger forelimbs and wider claws than the females. Macropus eugenii is the smallest species of wallaby. It has a small head and large ears; the tail is long and thick at the base. The hind legs are larger than the forelimbs and specialized for leaping. This species has a gray to yellow belly and red legs. Like all marsupials, the female of this species has a pouch in the skin of the abdomen in which she nurses her young.
Range mass: 4 to 9.1 kg.
Range length: 52 to 68 cm.
Sexual Dimorphism: male larger
Other Physical Features: endothermic ; bilateral symmetry
Average basal metabolic rate: 7.78 W.
These wallabies live in areas of dense vegetation with low trees and bushes, in thickets and around the outskirts of forests.
Terrestrial Biomes: desert or dune ; savanna or grassland ; scrub forest
Habitat and Ecology
Macropus eugenii is an herbivore that specializes on grass. Members of the family Macropodidae have the characteristic ability to move the lower jaw forward and backward, maximizing the shredding effect.
To obtain food, M. eugenii grazes, moving on all four limbs.
Primary Diet: herbivore (Folivore )
Vertebrate Associates on Kangaroo Island, Australia
The most notable mammal present is the endemic Kangaroo Island Kangaroo (Macropus fuliginosus fuliginosus), the icon for whom the island was named upon European discovery in 1802. A smaller marsupial present on the island is the Tammar Wallaby (Macropus eugenii). An endemic dasyurid is the Critically Endangered Kangaroo Island Dunnart (Sminthopsis aitkeni), which is found only in the west of the island in Eucalyptus remota/E. cosmophylla open low mallee, E. baxteri low woodland or E. baxteri/E. remota low open woodland. The Common Brush-tailed Possum (Trichosurus vulpecula) is a widespread folivore native to Australia.
Monotremes are also represented on the island. There is also an introduced population of the Duck-billed Platypus (Ornithorhynchus anatinus) in the western part of the island in Flinders Chase National Park. The Short-beaked Echidna (Tachyglossus aculeatus) is also found moderately widespread on Kangaroo Island.
Chiroptera species on Kangaroo Island include the Yellow-bellied Pouched Bat (Saccolaimus flaviventris), which species is rather widespread in Australia and also occurs in Papua New Guinea. Australia's largest molossid, the White-striped Free-tail Bat (Tadarida australis) is found on Kangaroo Island. Another bat found on the island is the Southern Forest Bat (Eptesicus regulus), a species endemic to southern Australia (including Tasmania).
Several anuran species are found on Kangaroo island: Brown Tree Frog (Litoria ewingii), Spotted Marsh Frog (Limnodynastes tasmaniensis), Painted Spadefoot Frog (Neobatrachus pictus), Brown Toadlet (Pseudophryne bibroni) and Brown Froglet (Crinia signifera).
The Heath Monitor (Varanus rosenbergi ) is a lizard that grows up to a metre in length, preying on smaller reptiles, juvenile birds and eggs; it is frequently observed on warmer days basking in the sunlight or scavenging on roadkill. The Black Tiger Snake (Notechis ater) is found on Kangaroo Island. Another reptile particularly associated with this locale is the Kangaroo Island Copperhead (Austrelaps labialis).
The Glossy Black Cockatoo (Calyptorhynchus lathami) is found on the island, especially in the western part, where its preferred food, fruit of the Drooping Sheoak, is abundant. The Kangaroo Island Emu (Dromaius baudinianus) became extinct during the 1820s from over-hunting and habitat destruction due to burning.
Marine mammals that are observed on the island include the Australian Sea Lion (Neophoca cinerea) and New Zealand Fur Seal (Arctocephalus forsteri), each species of which is native to Kangaroo Island, and abundant at Admiral's Arch as well as at Seal Bay.
Kangaroo Island is not so adversely impacted by alien species grazers as parts of the mainland. No rabbit species are present on the island, and introduced (but escaped) Domestic Goats (Capra hircus) and pigs (Sus scrofa) have generated only minor issues. However, a Koala (Phascolarctos cinereus) population introduced to the island in the 1920s has caused significant damage to certain woodland communities, especially to Manna Gum trees.
- C.Michael Hogan. 2013. Kangaroo Island. Encyclopedia of Earth, National Council for Science and the Environment, Washington DC ed. M.McGinley
Life History and Behavior
Perception Channels: tactile ; chemical
Status: captivity: 9.8 years.
Status: wild: 14.0 years.
Lifespan, longevity, and ageing
The gestation period of Macropus eugenii lasts 25 to 28 days. Young are born at a rudimentary stage of development. After birth, the joey remains in the pouch for 8 to 9 months until it is physically fully developed. Weaning occurs at about 10 to 11 months. Macropus eugenii has only one offspring per birth; the newborn weighs less than 1 gram. The young reaches sexual maturity at 9 months if it is a female, and 2 years if its a male.
The members of this family have a unique reproductive pattern called embryonic diapause. This phenomenon is also known as "delayed birth" because embryonic development is temporarily posponed until the proper conditions are available. A female that is nursing a joey in her pouch may also have a dormant embryo in its uterus. Then, when the joey stops nursing, the embryo resume its development.
Uterine gestation is very brief, and much of the development of the embryo takes place in the pouch outside of the uterus. The pouch contains the nipples.
The birthing process of Macropus eugenii starts with the newborn leaving the cloaca and freeing itself from the fetal membranes. Instinctively, led by sense of smell and gravity, it makes its way to the pouch. Once in the pouch, the newborn attaches its mouth to a single teat, from which the newborn gets milk high in fat and nutrients.
Male M. eugenii have a long duration of spermatogenesis and a long period of sperm transit in comparison with other mammals. These characteristics lend this species to studies of sperm production.
Average number of offspring: 1.
Range gestation period: 25 to 28 days.
Range weaning age: 10 to 11 months.
Average age at sexual or reproductive maturity (female): 9 months.
Average age at sexual or reproductive maturity (male): 2 years.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous ; embryonic diapause
Average birth mass: 0.429 g.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 730 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 274 days.
Evolution and Systematics
The tendons of tammar wallaby legs use energy efficiently by taking advantage of elastic energy storage.
"Moderate to large macropodids can increase their speed while hopping with little or no increase in energy expenditure. This has been interpreted by some workers as resulting from elastic energy savings in their hindlimb tendons. For this to occur, the muscle fibers must transmit force to their tendons with little or no length change. To test whether this is the case, we made in vivo measurements of muscle fiber length change and tendon force in the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies Macropus eugenii as they hopped at different speeds on a treadmill. Muscle fiber length changes were less than +/-0.5 mm in the plantaris and +/-2.2 mm in the lateral gastrocnemius, representing less than 2 % of total fiber length in the plantaris and less than 6 % in the lateral gastrocnemius, with respect to resting length. The length changes of the plantaris fibers suggest that this occurred by means of elastic extension of attached cross-bridges. Much of the length change in the lateral gastrocnemius fibers occurred at low force early in the stance phase, with generally isometric behavior at higher forces. Fiber length changes did not vary significantly with increased hopping speed in either muscle (P>0.05), despite a 1. 6-fold increase in muscle-tendon force between speeds of 2.5 and 6.0 m s-1. Length changes of the PL fibers were only 7+/-4 % and of the LG fibers 34+/-12 % (mean +/- S.D., N=170) of the stretch calculated for their tendons, resulting in little net work by either muscle (plantaris 0.01+/-0.03 J; gastrocnemius -0.04+/-0.30 J; mean +/- s.d. ). In contrast, elastic strain energy stored in the tendons increased with increasing speed and averaged 20-fold greater than the shortening work performed by the two muscles. These results show that an increasing amount of strain energy stored within the hindlimb tendons is usefully recovered at faster steady hopping speeds, without being dissipated by increased stretch of the muscles' fibers. This finding supports the view that tendon elastic saving of energy is an important mechanism by which this species is able to hop at faster speeds with little or no increase in metabolic energy expenditure." (Biewener 1998:1681)
Learn more about this functional adaptation.
- Alexander, RM. 1984. Elastic energy stores in running vertebrates. American Zoologist. 24(1): 85-94.
- Biewener, AA; Baudinette, RV. 1995. In vivo muscle energy storage during steady-speed hopping of tammar wallabies (Macropus eugenii). Journal of Experimental Biology. 198: 1829-1841.
- Biewener, AA; Konieczynski, DD; Baudinette, RV. 1998. In vivo muscle force-length behavior during steady speed hopping in tammar wallabies. Journal of Experimental Biology. 201: 1681-1694.
- Baudinette, RV; Biewener, AA. 1998. Young wallabies get a free ride. Nature. 395: 653-654.
- Dawson, TJ; Taylor, CR. 1973. Energetic cost of locomotion in kangaroos. Nature. 246: 313-314.
- Pabst, DA. 1996. Springs in swimming animals. American Zoologist. 36: 723-735.
- Lehmann JF; Price R; Boswell-Bessette S; Dralle A; Questad K; De Lateur BJ. 1993. Comprehensive analysis of energy storing prosthetic feet: Flex foot and Seattle foot versus standard SACH foot. 74: 1225-1231.
The milk of the tammar wallaby protects newborn wallabies from bacteria and fungi via the antimicrobial AGG01 molecule.
"A newborn wallaby is a tiny, bean-shaped creature, barely more than a fetus. It lacks a developed immune system, relying on compounds in its mother's milk to protect it against pathogens. Now a unique antimicrobial has been discovered in wallaby milk that could be used in hospitals to fight deadly antibiotic-resistant bacteria.
"When born, with a heart but no lungs, tammar wallabies (Macropus eugenii) crawl into their mother's pouch, where they latch on to milk-bearing teats. 'A huge amount of development happens in the pouch and during that time they just rely on milk,' says Ben Cocks of the Victoria Department of Primary Industries in Melbourne, Australia.
"Cocks has found that the mother's milk contains a molecule that is 100 times more effective against Gram-negative bacteria such as E. coli than the most potent form of penicillin. The molecule, called AGG01, also kills four types of Gram-positive bacteria and one type of fungus. The work was presented at the US Biotechnology Industry Organization 2006 meeting in Chicago [April 2006].
"AGG01 was probably lost from placental mammals, whose young have their own immune systems, when they split from marsupials." (New Scientist 2006:16)
Learn more about this functional adaptation.
- New Scientist. 2006. Fighting superbugs with milk. New Scientist [Internet], Accessed 4/20/2006.
Molecular Biology and Genetics
Statistics of barcoding coverage: Macropus eugenii
Public Records: 0
Specimens with Barcodes: 4
Species With Barcodes: 1
Humans have introduced tammar wallabies to islands previously uninhabited by this species. They have also played a part in the alteration of the habitat of M. eugenii. Domestic livestock have reduced the natural grassland vegetation, rendering it inappropriate for occupation by tammars.
Tamar wallabies continue to be shot for commercial purposes or pest control. The use and demand of kangaroo skins for leather products is high, although this species is not singled out for this purpose.
The habitat of M. eugenii may also be threatened by the introduction of new species. Rabbits were first introduced to Australia by European settlers and wreaked havoc ever since. Rabbit populations often reach astounding densities and their consumption of vegetation causes massive destruction to the grasslands. Since their first introduction, rabbits have posed a threat to native fauna, including kangaroos and wallabies.
With increased awareness and publicity, these animals should be protected to a greater degree.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
IUCN Red List Assessment
Red List Category
Red List Criteria
There are no current major threats to Macropus eugenii. Predation by foxes is a threat in parts of its range, and fox control is thought essential for survival on the mainland (A. Burbidge pers. comm.). Inappropriate fire regimes may also be a threat in places. On Kangaroo Island, it is considered to be an agricultural pest.
Relevance to Humans and Ecosystems
Kangaroos and wallabies damage cereal crops, eat livestock food, drink stock water and destroy fences. The magnitude of their role as agricultural pests was well documented in the early 1980's. In 1983 to 1984, the loss of sheep food due to kangaroo and wallaby consumption led to an opportunity cost that accounted for 51 percent of total agriculural losses. (Australian National Parks and Wildlife Service: Kangaroos; Counting the Cost.)
Negative Impacts: crop pest
Macropus eugenii is a very important animal in scientific research. As mentioned earlier, the species is used in studies of human reproduction and sperm production in mammals. Also, according to Russell Jones, M. eugenii is a model animal for studies of the transport of androgens (hormones that stimulate the development of male sex characteristics) to the accessory organs of reproduction. These studies may have profound effects on the field of human developmental biology.
These animals used to be hunted for meat and leather.
Positive Impacts: food ; research and education
The tammar wallaby (Macropus 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 remains common within its reduced range and it is listed as of 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 differences distinguish tammars from Western Australia, Kangaroo Island and mainland South Australia, making them distinct populations groups or possibly different subspecies.
Around the size of a rabbit, the tammar is among the smallest of the wallabies. Its coat colour is largely grey. The tammar 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 nighttime in grassland habitat and daytime in shrub. It is also very gregarious and has a seasonal, promiscuous mating pattern. A female tammar can nurse a joey in her pouch while keeping an embryo in her uterus. The tammar is a model species for research on marsupials, and on mammals in general. It is one of many organisms to have had its genome sequenced.
- 1 Taxonomy and classification
- 2 Population dynamics and conservation
- 3 Appearance and physiology
- 4 Ecology and life history
- 5 Use in science
- 6 References
- 7 External links
Taxonomy and classification
|Cladogram showing the genetic relationship between the Tammar wallaby (M. eugenii) and several other species in the Macropodidae family.|
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.:53 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;:333 whose name is now the specific name of the tammar. 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. The tammar is classified together with the kangaroos, wallaroos and several species of wallaby in the genus Macropus, and in the subgenus Notomacropus with the other wallabies, all of which have a facial stripe.
Fossil evidence of the tammar wallaby exists from the late Pleistocene era—remains were found in the Naracoorte Caves. The mainland and island dwelling tammars split from each other 7,000–15,000 years ago,:332 while the South Australian and Western Australian animals diverged around 50,000 years ago. The tammar wallabies on Flinders Island had greyer coats and thinner heads than the Kangaroo Island tammars, which are larger than the East and West Wallabi Islands animals. The island tammars were once thought to be a separate species from the mainland population.:333 A 1991 examination of tammar skulls from different parts of the species' range, found that populations can be divided into three distinct groups; one group made of populations from mainland Western Australia, East and West Wallabi Islands, Garden Island and Middle Island; a second group comprising populations from Flinders Island, 19th century mainland Southern Australia and New Zealand; and a third group consisting solely of the Kangaroo Island population. The Western Australia Department of Environment and Conservation listed these populations as subspecies; M. e. derbianus, M. e. eugenii and M. e. decres respectively.
Population dynamics and conservation
The tammar wallaby is listed as of Least Concern by the IUCN, due to its abundance and presumably stable population. 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 tammars in Western Australia was described as numerous in much of the south-west, but declining in the cultivated areas, particularly to the north. Clearings made for wheat and sheep caused the population to decline further.:332 From the 19th century, tammars in the Eyre Peninsula and around Adelaide were decimated by mobs of hunters organised to protect crops and pastures. As a result, they were extinct in the areas around Adelaide by the 1920s, and in the Eyre Peninsula around the 1970s.:332–33 Tammars from Flinders Island and St Peter Island were eradicated in a similar manner.:333
Tammars from these areas were introduced to Kawau Island in New Zealand by colonial administrator Sir George Grey in 1870. 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 due to its possible effect on organisms not targeted, including humans. Cyanide pellets have been used as an alternative. In 1985, tammars 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.:82–83 In 2003, the Monarto Zoo temporarily housed 85 tammars from New Zealand awaiting reintroduction to the Yorke Peninsula in Innes National Park. Four releases have been made, and a stable wild population of 100–120 animals now exists. Tammars have also been successfully translocated to other areas, such as Nambung National Park and Avon Valley National Park.
Resistance to sodium fluoroacetate
Different tammar populations have varying levels of resistance to sodium fluoroacetate. Mainland Western tammars appear to be the most resistant, while those on Kangaroo Island are much more vulnerable. Tammars from New Zealand probably have a similar resistance level to the latter as the poison has been successfully used to control their populations.:334 Tammars from East and West Wallabi Islands and Garden Island, which do not have plants containing sodium fluoroacetate, are less resistant than mainland Western tammars but are more resistant than those from Kangaroo Island. This suggests that tammars originated in South Australia and developed a resistance to sodium fluoroacetate when they reached Western Australia, where the poison is found in plants.:334
Appearance and physiology
One of the smallest wallaby species, 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 9.1 kg (20 lb) and maximum recorded weight in females is 6.9 kg (15 lb). The body length is 59–68 cm (23–27 in) in males and 52–63 cm (20–25 in) in females. Both males and females are about 45 cm (18 in) in height. The tails of males range from 34–45 cm (13–18 in) and those of females from 33–44 cm (13–17 in).
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 0.8–2.4 m (2.5–8 ft). 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 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 tammars can increase their hopping speed without using more energy. The tammar 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 as it allows them to leap higher and lowers the risk of their tendons rupturing.
The tammar has 324° peripheral vision and 50° binocular vision.:312 It can distinguish black/white gratings of different widths and in different light conditions better than most other small mammals, such as rabbits. It is nevertheless not as good as a cat or a human. Tammars 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 higher wavelengths in 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 20 nm (2.0×10−8 m) apart. The pinna (ear) of the tammar is mobile, allowing it to track sounds from different parts of its surroundings without moving its head. A tammar can point its pinna at a sound source and increase its eardrum's sound pressure by 25–30 dB at 5 kHz. When the pinna moves away from the sound source, the animal's hearing level quickly drops. When born, a tammar's sense of smell is already developed; this allows the newborn to find its mother's pouch by the scent.
Thermoregulation and water turnover
Tammars 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). Tammars can't survive in temperatures above 40 °C (104 °F) and must get away from the heat. To prevent dehydration, tammars 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.
In late 1998, 120–130 tammar wallabies died suddenly in research facilities and zoos in New South Wales and Queensland, perishing less than twelve hours after exhibiting the first symptoms, with most exhibiting no symptoms at all. Post mortem examination revealed haemorrhage of muscle, 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.
Ecology and life history
Mostly nocturnal, tammar wallabies spend much of their time foraging.:335 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 home ranges overlap with those of conspecifics.
During the day, tammars stay close to scrub for shade and move out to more open grassland by nightfall.:335 Like all macropods, the tammar 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, tammars handle them with their forelimbs.:116 This species spends more time chewing its food than other similar sized macropods, which likely aids digestion.:115–16 Tammars commonly feed on acacia seeds. Other species consumed include heart-leaved poison (Gastrolobium bilobum), small-flowered wallaby grass (Austrodanthonia setacea), and marri (Corymbia calophylla). Tammars survive on several islands that have no fresh water, subsisting on seawater and the moisture in plants.:335
The tammar rests in two positions: a "sitting tail forward" position, in which the hind legs are outstreached 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.:217–19 Tammars 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, tammars spend more time foraging, grooming and interacting and less time being vigilant and moving around. Predators of the tammar include dingos, feral cats, red foxes and wedge-tailed eagles. They may also have been preyed upon by the extinct thylacine. Tammars appear to respond more to the sight than the sound of predators. They can also use their acute sense of smell to detect a predator. When a predator is detected, a tammar will alert others by thumping its foot. When lost, young tammars 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.:77 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 uro-genital openings and pouches of the females to determine their reproductive status.:78 After giving birth, females enter estrous 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.:83 Several males may pursue a single female. The tammar wallaby has been observed to engage in alloparental care, in which an adult may adopt another's young.
The female tammar can conceive shortly after giving birth.:335 Tammars 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 in the end of December and the female gives birth around one month later. After birth the newborn young climbs unaided by its mother from the birth canal to the pouch.
When it reaches the pouch, the underdeveloped joey suckles the teat of one of the four mammary glands while the others recede. The joey remains attached to the teat for 100–125 days, after which it ceases its attachment but remains in the pouch and continues to suckle, but more intermittently. The joey begins to leave the pouch and eat grass at around 200 days when it is more developed. It still suckles, more forcefully but less regularly. By 250 days, the joey no longer needs the pouch, and it is fully weaned at around 300–350 days. Male tammars may live for around 11 years, while females live for 14 years.
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. Tammars 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. Tammars 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 tammars 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, and the full genome was sequenced in 2011. Sequencing of the tammar genome 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 micro RNAs. The tammar genome appears to have more rearrangements than those of both the human and the gray short-tailed opossum, another sequenced marsupial.
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 100 times more effective than penicillin. It has killed over 99% of the pathogenic bacteria, (both Gram-positive and Gram-negative), that it was incubated with, including Salmonella, Proteus vulgaris and Staphylococcus aureus. It also killed 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 Firmicutes, Bacteroidetes and Proteobacteria. Within the phylum Proteobacteria, species of the Succinivibrionaceae family are the most abundant and a new species named WG–1 was discovered. WG–1 is a capnophilic bacterium. This has important environmental implications as the bacteria produces less methane than others and does not require CO2 to survive. Research suggests that this information could be used to reduce carbon production in livestock.
- Morris, K.; Friend, T.; Burbidge, A; van Weenen, J. (2008). Macropus eugenii. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 28 December 2008. Database entry includes justification for why this species is of least concern.
- Bulazel, K. V.; Ferreri, G. C.; Eldridge, M. D.; O'Neill, R. J. (2007). "Species-specific shifts in centromere sequence composition are coincident with breakpoint reuse in karyotypically divergent lineages". Genome Biology 8 (8): R170. doi:10.1186/gb-2007-8-8-r170. PMC 2375000. PMID 17708770.
- Pearson, M. (2005). Great Southern Land: The maritime exploration of Terra Australis. Department of the Environment and Heritage, Government of Australia. ISBN 0-642-55185-5. Retrieved 21 December 2007.
- Tyndale-Biscoe, Hugh (2005). Life of Marsupials. CSIRO Publishing. ISBN 0-643-06257-2.
- "Tammar Wallaby". Western Australia Department of Environment and Conservation. Retrieved 12 June 2011.
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