Tammar wallabies are found in Australia, New Zealand, and various islands off the western and southern coast of Australia. (Grzimek, 1990; Nowak, 1991)
These wallabies live in areas of dense vegetation with low trees and bushes, in thickets and around the outskirts of forests.
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.
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.
Macropus eugenii are a very social species. These wallabies socialize, feed, and mate in groups with a hierarchial dominance structure. These groupings are called "mobs". Higher ranking individuals are usually males. Dominance is determined through aggressive encounters, and the victor is the highest ranking individual. Males wrestle with one another until one proves he is the strongest male. The strongest male then has a high chance of mating with females and, ultimately, reproducing.
An individual's position in the hierarchy is generally based on size, which in turn is correlated with fighting ability. Individual with a greater height and more muscular forelimbs have a significant advantage over rivals while fighting.
Variation in the appearance of structures related to size and strength plays a significant role in the "displaying" ritual shown by one male to another. "Displaying" is a series of postures or actions performed by an individual to impress and intimidate a rival during aggressive confrontation. In M. eugenii, displaying includes several actions: the maintenance of an upright posture, the expansion of the chest, and the flexing of the forearms to showcase arm length and muscularity.
Display behavior is also used as a part of a courting ritual. A male trys to impress a female with his strength and superior physical structure, showing her his dominance and rank.
The style of fighting of all macropodids consists of the use of the limbs to grab and hold an opponent around the head, neck or shoulders. Also, all macropodids use their hindlimbs to kick forward, in the meantime using their tails for balance and support.
Mobs have a territory that may extend to 100 hectares. This territory may be partly shared with other mobs in the peripheral areas. Mobs are comprised of all ages and sexes and usually have up to 50 members.
Macropus eugenii is primarily nocturnal.
Tamar wallabies have two natural enemies: dingos and birds of prey. Dingos catch and hunt kangaroos. Tamar wallabies demonstrate an anti-predator behavior that entails the same hind leg kicking mentioned earlier. When attacked by a dingo, a tamar wallaby is often trapped with its back up against a tree. It then attempts to strike the dingo with its forepaws, and finally thrusts its hindlimbs forward, aiming for the attacker's belly. The force of the hindlimbs or gashes made by a wallaby's sharp claws can seriously injure a dingo.
A mob's home range may be up to 100 ha in size.
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.
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.
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.)
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.
The controversy regarding the human consumption of kangaroo meat has resurfaced. Decades ago, many animal activist groups helped reduce the consumption of kangaroo meat and passed a ban on the sale of kangaroo meat as human food. The sale of kangaroo meat for human consumption is banned in every state of Australia except South Australia. Professor Gordon Grigg of the University of Sidney supports the establishment of kangaroo farms to harvest meat for human consumption in order to protect the Australian countryside. Grigg proposes a switch from sheep farming to kangaroo farming, claiming kangaroos cause less damage to Australia's rangelands. The stress caused by sheep and cattle's hard hooves and overgrazing strips Australian land of vegetation, leaving it dry and unproductive. Grigg sees kangaroo farming as a way to prevent further destruction of the rangelands because of kangaroo's soft feet and slightly more conservative grazing methods (Grigg reports that kangaroos only eat the tops of grasses enabling further growth and recovery).
Advocates of this plan point out that kangaroo meat is nutritious and considerably lower in fat than the cattle or sheep meat. Thus, this proposed change in diet can have health benefits for humans.
Although it may not be the case for the larger members of the family, kangaroo meat harvesting is a minor threat for tammar wallbies. Macropus eugenii, the smallest of the wallabies, is unlikely to be targeted for its meat as long as larger kangaroos are available.
Nancy Shefferly (editor), Animal Diversity Web.
Annette M. Labiano-Abello (author), University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
At about the time a female gives birth (e.g. in most kangaroo species), she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or embryonic diapause. The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
union of egg and spermatozoan
an animal that mainly eats leaves.
A substance that provides both nutrients and energy to a living thing.
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
specialized for leaping or bounding locomotion; jumps or hops.
scrub forests develop in areas that experience dry seasons.
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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