Tammar wallaby

Appearance

The tammar wallaby is the smallest wallaby species, featuring a small head and large ears with a long tail, thick at the base. In colour, 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 and maximum recorded weight in females is 6.9 kg . The body length is 59–68 cm in males and 52–63 cm in females. Both males and females are about 45 cm in height. The tails of males range from 34–45 cm and those of females from 33–44 cm .

Naming

The tammar wallabies on Flinders Island were distinguished from Kangaroo Island tammars by their greyer coats and thinner heads.:333 The East and West Wallabi Islands tammars were distinguished from the latter by their smaller size. Island tammars were once thought to be one species.:333

A 1991 examination of the 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.


As such, three subspecies of tammar wallaby are classified:
⤷  ''M. e. derbianus''
⤷  ''M. e. decres''
⤷  ''M. e. eugenii'' .

Distribution

Since European occupation, tammar wallaby populations on both mainland Australia and some islands have been greatly reduced or even eradicated. The mainland population of tammars have been descripted as "very plentiful in many parts of the south-west, but rapidly disappearing in the cultivated districts, especially towards the northern end of its range." Clearings made for wheat and sheep caused the population to decline further.:332 Farming activities led to the extinction of the tammar on Flinders Island and St. Peter's Island. Tammars in the Eyre Peninsula and around Adelaide were decimated by battues protecting crops and pastures. As a result, the tammar became extinct in the areas around Adelaide by the 1920s and in the Eyre Peninsula around the 1970s.:332-33

However, tammars from these areas were introduced to Kawau Island in New Zealand over 150 years ago by former South Australian Governor George Grey. Since their introduction to New Zealand, tammars have flourished and their over-grazing has damaged indigenous plants. Biologists have used sodium fluoroacetate to control their populations. In 1985, tammars were introduced to the North Island of the Houtman Abrolhos and have made similar impacts on native vegetation. Their numbers have grown up to 450 individauls, but culling efforts appear to have reduced their numbers to 25 individuals by 2008. In 2003, the Monarto Zoo temporarily housed 85 tammars from New Zealand before they were reintroduced 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.

The tammar wallaby is listed under Least Concern by the IUCN, due to "its wide distribution, presumed large population, occurrence in a number of protected areas, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category".

Status

Since European occupation, tammar wallaby populations on both mainland Australia and some islands have been greatly reduced or even eradicated. The mainland population of tammars have been descripted as "very plentiful in many parts of the south-west, but rapidly disappearing in the cultivated districts, especially towards the northern end of its range." Clearings made for wheat and sheep caused the population to decline further.:332 Farming activities led to the extinction of the tammar on Flinders Island and St. Peter's Island. Tammars in the Eyre Peninsula and around Adelaide were decimated by battues protecting crops and pastures. As a result, the tammar became extinct in the areas around Adelaide by the 1920s and in the Eyre Peninsula around the 1970s.:332-33

However, tammars from these areas were introduced to Kawau Island in New Zealand over 150 years ago by former South Australian Governor George Grey. Since their introduction to New Zealand, tammars have flourished and their over-grazing has damaged indigenous plants. Biologists have used sodium fluoroacetate to control their populations. In 1985, tammars were introduced to the North Island of the Houtman Abrolhos and have made similar impacts on native vegetation. Their numbers have grown up to 450 individauls, but culling efforts appear to have reduced their numbers to 25 individuals by 2008. In 2003, the Monarto Zoo temporarily housed 85 tammars from New Zealand before they were reintroduced 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.

The tammar wallaby is listed under Least Concern by the IUCN, due to "its wide distribution, presumed large population, occurrence in a number of protected areas, and because it is unlikely to be declining at nearly the rate required to qualify for listing in a threatened category".

Habitat

On Kangaroo Island, tammar wallabies can be found under divaricating bushes. They are mosly nocturnal and send much of the time foraging.:335 They commonly feed on acacia seeds. Other species consumed include heart-leaved poison , small-flowered wallaby grass , and marri .

Tammars live in summer home ranges of 42 ha and winter home ranges of 16 ha ; the ranges overlap with those of conspecifics. During the day, tammars avoid the sun by resting under scrub, and move out to grassland by nightfall. Then the grass dries off in summer, tammar will look for better food and move over long distances. They are primarily grazers and have "a high digesta throughput". When grazing, a tammar moves its lower jaw from side to side to grind its food. It appears that the digestion particles in the animal's foregut "expend relatively greater masticatory effort". In addition, "secondary" fermentation may occur the hind gut. Compared to browsing macropods around the same sizes, tammars have a longer colon and shorter small intestine.

The tammar rests in two different positions: firstly, the "sitting tail forward" position, where the hind legs are outstreached with tail brought forward inbetween, the body prone and the head above ground; secondly the "lying" position, where animal lays on its side with the head touching the ground. The former is of long duration, and done mostly during the day, while the latter is more brief and done mostly at night. Tammars are known to live in stable groups. Gathering in groups 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. It may also have been preyed upon by the now extinct thylacine. Tammars appear to respond more to the sights than the sounds of predators. When a predator is detected, a tammar will alert conspecifics 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.

Tammars lick their forearms and pant to keep cool in hot winter. They breathe more heavily and lose more water when the temperature is over 30 degrees Celsius. Tammars can't survive in temperatures above 40 degrees Celsius and must get away from the heat. To prevent themselves from dehydrating, tammars urinate less and reabsorb water from the distal colon, which gives them relatively dry feces.:335 Tammars live on several islands that have no fresh water and must subsist on seawater or the moisture in plants.:335 Their ability to concentrate urine allows them to survive drinking seawater.

Reproduction

The tammar wallaby has a promiscuous mating system. It is a seasonal breeder and births largely occur during late January and early February.:77 After giving birth, females enter estrous and mating ends within four hours. When the breeding season arrives, the male's prostate and bulbourethral gland enlarge and its peripheral testosterone is more concentrated. However, there does not appear to be any seasonal difference in the weight of the testes. Around two weeks before the first birth, the males will begin sniffing the uro-gential openings and pouches of the females to determine their reproductive status.:78 Females allow males to mate with them soon after giving birth. However, a male that attempts to mate with an estrous female may face aggression from other males, which can delay ejaculations. A male can achieve reproductive success by mate-guarding.:83 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 have been observed to pursue a single female.

The female tammar conceives a few hours after giving birth and suckles her young in her pouch for the next seven months. Tammars undergo embryonic diapause. For the first five months, the dormant embryo in the uterus can't develop while the young or joey is in the pouch.:338 However, after the antipodean winter solstice in June, the embryo's development does not depend on the absence of the joey and will remain dormant in the uterus until after the summer solstice in December; months after the joey leaves the pouch.:338 Gestation in the tammar lasts 26.5 days. At this time, the female's four mammary glands begin to lactate. The newborn joey climbs into the pouch and suckles the teat of one mammary gland and the lactation of the other glands decline. 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 at less regular intervals. The joey begins to leave the pouch and eat grass by 200 days. It suckles more forcefully but still less regularly. The joey leaves the pouch permanently after 250 days and is fully weaned at around 300–350 days.

Evolution

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 It is likely that tammars originated in South Australia and developed a resistance to sodium fluoroacetate when they reached Western Australia. It takes more than 5 mg of poison to kill a mainland Western tammar, while tammars on the East and West Wallabi Islands and Garden Island succome to a dose of less than 2 mg . Further east, tammars are much more vulnerable to the poison, as tammars on Kangaroo Island can be killed by a dose of less than 0.2 mg . Tammars from two ends of the species' range, Garden Island and Kangaroo Island, differ in serum proteins, iron-building transferrin protein and red cell antigens.:333On Kangaroo Island, tammar wallabies can be found under divaricating bushes. They are mosly nocturnal and send much of the time foraging.:335 They commonly feed on acacia seeds. Other species consumed include heart-leaved poison , small-flowered wallaby grass , and marri .

Tammars live in summer home ranges of 42 ha and winter home ranges of 16 ha ; the ranges overlap with those of conspecifics. During the day, tammars avoid the sun by resting under scrub, and move out to grassland by nightfall. Then the grass dries off in summer, tammar will look for better food and move over long distances. They are primarily grazers and have "a high digesta throughput". When grazing, a tammar moves its lower jaw from side to side to grind its food. It appears that the digestion particles in the animal's foregut "expend relatively greater masticatory effort". In addition, "secondary" fermentation may occur the hind gut. Compared to browsing macropods around the same sizes, tammars have a longer colon and shorter small intestine.

The tammar rests in two different positions: firstly, the "sitting tail forward" position, where the hind legs are outstreached with tail brought forward inbetween, the body prone and the head above ground; secondly the "lying" position, where animal lays on its side with the head touching the ground. The former is of long duration, and done mostly during the day, while the latter is more brief and done mostly at night. Tammars are known to live in stable groups. Gathering in groups 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. It may also have been preyed upon by the now extinct thylacine. Tammars appear to respond more to the sights than the sounds of predators. When a predator is detected, a tammar will alert conspecifics 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.

Tammars lick their forearms and pant to keep cool in hot winter. They breathe more heavily and lose more water when the temperature is over 30 degrees Celsius. Tammars can't survive in temperatures above 40 degrees Celsius and must get away from the heat. To prevent themselves from dehydrating, tammars urinate less and reabsorb water from the distal colon, which gives them relatively dry feces.:335 Tammars live on several islands that have no fresh water and must subsist on seawater or the moisture in plants.:335 Their ability to concentrate urine allows them to survive drinking seawater.