Boodie

Taxobox
name = BoodieMSW3 Groves | pages = 57]
fossil_range=Late Oligocene - Recent
status = NT
status_system = iucn3.1
trend = increasing
regnum = Animalia
phylum = Chordata
classis = Mammalia
infraclassis = Marsupialia
ordo = Diprotodontia
familia = Potoroidae
genus = "Bettongia"
species = "B. lesueur"
binomial = "Bettongia lesueur"
binomial_authority = (Quoy & Gaimard, 1824)

The Boodie ("Bettongia lesueur"), also known as the Burrowing Bettong, is a small marsupial related to the kangaroo. It is a fascinating example of the effects of introduced animals on Australian fauna and ecosystems. Once the most common macropodiform mammal on the whole continent, the Boodie now only lives on off-lying islands and in a newly introduced population on the mainland at Shark Bay.cite journal | author = Sander, U., Short, J., & Turner, B. | year = 1997 | title = Social organisation and warren use of the burrowing bettong "Bettongia lesueur" (Macropodoidea: Potoroidae) | journal = Wildlife Research | volume = 24 | pages = 143–157 | doi = 10.1071/WR96021] This animal, first collected during an 1817 French expedition of the west coast, was named after Charles Lesueur, an artist and naturalist who accompanied a previous French expedition. "B. lesueur" is known by many common names, including the Tungoo, Lesueur’s Rat-kangaroo, and the Short-nosed Rat-kangaroo.cite web | url = http://www.wildliferesearchmanagement.com.au/bettong.htm | title = The burrowing bettong ("Bettongia lesueur") | date = 2005-09-25 | accessdate = 2006-12-08 | work = [http://www.wildliferesearchmanagement.com.au/overview.htm Heirisson Prong Threatened Species Project] ]

Taxonomy

The Boodie belongs to the family Potoroidae, which includes the rat-kangaroos, potoroos, and other bettongs. Four species make up the genus "Bettongia". Also, three subspecies of the Boodie exist: "Bettongia lesueur graii", the extinct mainland subspecies; "Bettongia lesueur nova", an undescribed species on Barrow and Brodie Island; and "Bettongia lesueur lesueur".cite web | author = Massicot, P. | date = 2006-06-02 | url = http://www.animalinfo.org/species/bettlesu.htm | title = Burrowing Bettong | work = [http://www.animalinfo.org/index Animal Info] | accessdate = 2006-12-08]

Paleontology

In the late Oligocene, fossils of paleopotoroines and potoroines (potoroid ancestors) appear. During the Oligocene, ice buildup on Antarctica resulted in less rainfall on Australia. Rainforests declined, replaced by more arid-tolerant leathery leaf woodlands and reed swamps. This climate shift may have favored a radiation of terrestrial marsupials, including potoroid ancestors. [cite journal | author = Burk, A. & Springer, M.S. | year = 2000 | title = Intergeneric relationships among Macropodoidea (Metatheria:Diprotodontia) and the chronicle of kangaroo evolution | journal = Journal of Mammalian Evolution | volume = 7 | issue = 4 | pages = 214–237 | doi = 10.1023/A:1009488431055] Fossils of the Potoroidae family appear from the mid-Miocene to Recent sediments.cite book | author = Seebeck, J.H. and Rose, R.W. | year = 1989 | chapter = Potoroidae | chapterurl = http://www.deh.gov.au/biodiversity/abrs/publications/fauna-of-australia/pubs/volume1b/30-ind.pdf | title = Fauna of Australia. Vol 1B Mammalia | editor = eds. D.W. Walton and B.J. Richardson | publisher = Australian Government Publishing Service] Subfossil records of the burrowing bettong have been found in West Victoria, western New South Wales, and South Australia. [http://www.naturebase.net/component/option,com_docman/task,doc_details/Itemid,1288/gid,122/ Burrowing bettong (boodie)] . "Nature Base Fauna Species Profiles".]

Morphology

The Boodie is a small, rat-like marsupial with short, rounded ears and a lightly-haired, thick tail. This animal has a pointed rostrum and beady black eyes, hind limbs longer than the forelimbs and large hind feet. This bettong is yellow-gray above and light gray below. Its short, dense fur feels soft and woolly. The animal bears a faint hip stripe and a distinctive white tail tip. This tail is weakly prehensile and used to carry nest material. [http://www.arkive.org/species/GES/mammals/Bettongia_lesueur/more_info.html Burrowing bettong ("Bettongia lesueur)] . (2006). "ARKive".] About the size of a wild rabbit, this little marsupial weighs an average of 1.5 kg. Head and body length is an average of 40 cm. Little to no sexual dimorphism seems to exist. However, morphology varies among subspecies and between islands.cite journal | author = Short, J. & Turner, B. | year = 1999 | title = Ecology of burrowing bettongs, "Bettongia lesueur" (Marsupialia: Potoroidae), on Dorre and Bernier Islands, Western Australia | journal = Wildlife Research | volume = 26 | pages = 651–669 | doi = 10.1071/WR98039] In general, a potoroid skull can be separated from a macropodid skull by the presence of well-developed upper canines and large plagiaulacoid (bladelike) premolars. Also unlike macropodids, the squamosal bone widely contacts the frontal. "B. lesueur" skulls are short and broad with large palatal vacuities, inflated auditory bullae, and short, broad nasals. The mandible is relatively short and deep compared to other relatives. The dental formula for all the modern potoroines is I 3/1 C 1/0 PM 1/1 M 4/4. Molars are bunodont and quadrate, and the premolars have 9-11 fine, vertical ridges. Young bettongs have two molars which are replaced by one adult premolar; this event is a good indication of maturity. The post-cranial skeleton of all potoroids has 7 cervical, 13 thoracic, 6 lumbar, 2 sacral, and 22 caudal vertebrae, with 13 pairs of ribs.

Reproduction and development

If conditions are good, the Boodie seems to mate throughout the year, probably utilizing a polygynous mating system. Males do not seem to have dominance hierarchies; rather, they defend females against other males. Some females seem to establish associations with other females; whether these contribute to increased reproductive success is unknown. Gestation lasts 21 days, with only one young per litter. Like other marsupial newborns, the newborn is altricial. About four months elapse until weaning. After young leave the pouch, they take 6-7 months to sexually mature. Females mate the day after giving birth, and the fertilized egg arrests development until the young is weaned. This is an example of facultative embryonic diapause. In captivity, females are able to bear three young per year.

Ecology

The Boodie once lived in a range of dry subtropical and tropical habitats, from open eucalyptus and acacia woodlands to arid spinifex grasslands. In its current range on the islands, it seems to prefer open "Triodia" (spinifex) and dune habitats, but will burrow anywhere except places with rocky substrate. The burrowing bettong eats a variety of food, such as seeds, fruits, flowers, tubers, roots, succulent leaves, grasses, fungi, termites, and marine refuse. It will also raid vegetable gardens. Current populations fluctuate, building up during the years with average or good rainfall and crashing during drought years. These marsupials are known to live at least three years in the wild.

After colonization of Australia, predators were mainly the introduced Red Fox and cats. Some natural predators on the islands include the Wedge-tailed Eagle and sea eagles; on Barrow Island, monitor lizards appear to be a significant predator. Before its extinction on the mainland, the Boodie served a very important function in the Australian grassland ecosystem. As it foraged, it mixed organic matter into the soil, spreading fungi and seeds. This mixing also increased water absorption into the soil and reduced the combustible material under trees, decreasing the likelihood of fire. These actions helped maintain the balance of trees, shrubs, and grasses. The loss of small, ground foraging animals after European settlement contributed to widespread soil deterioration.cite journal | author = Martin, G. | year = 2003 | title = The roll of small ground-foraging mammals in topsoil health and biodiversity: Implications to management and restoration | journal = Ecological Management & Restoration | volume = 4 | issue = 2 | pages = 114–119 | doi = 10.1046/j.1442-8903.2003.00145.x] Also, "B. lesueur" may have helped to thin woody weeds on rangeland by browsing shrubs growing after fires.cite journal | author = Sarre, A. | year = 1999 | url = http://www.publish.csiro.au/?act=view_file&file_id=EC100p44.pdf | title = Slow change on the range | journal = Ecos | issue = 100 | pages = 44 | doi= 10.1071/EC100p44]

Behavior and physiological attributes

"B. lesueur" is very vocal, communicating through grunts, hisses, and squeals. It shelters in underground burrows, the only macropodiform to do so. Burrows vary from simple tunnels to complex networks with multiple entrances and deep, interconnecting tunnels. These elaborate burrows, or warrens, have been seen having from 4 to 94 entrances. Warrens are communal, housing an average of 20-40 bettongs. Bettongs appear to switch warrens from time to time, though each has one or two preferred warrens. During the day in the warrens, they form groups of one male and one or many females; males never share warrens with other males. Some of the female-female groups seem to be mother-daughter associations. However, individuals seem to forage alone, showing none of the day-range group associations.

The Boodie is nocturnal, sheltering during the day in burrows and foraging widely at night for food. Locomotion is mainly with the hind legs. The forelimbs are used for support when the Boodie is stationary. This bettong exhibits a slow gait and fast gait. The fast gait (or bipedal hop) is characteristic of the macropodiforms and uses only the hind limbs, with the forelimbs held close to the body and tail acting as a counter-balance. The slow gait (or quadrupedal crawl) is used during foraging and other unstressed times. Nighttime movement is usually fairly limited, averaging less than 200 m. However, researchers have measured this marsupial traveling 2.2 km searching for food. One individual tracked on Barrow Island traveled 5 km. "B. lesueur" uses scent to locate food, which it digs up with the claws on its strong forelimbs. The Boodie will even climb into low shrubs to find food. Demonstrating little interspecific interactions, bettongs are apparently undisturbed by run-ins with other non-predators.

Bettong digestive systems are characterized by a very large sacciform forestomach, a tubiform forestomach with limited sacculation, and a small hind stomach. The hind gut has a well-developed, simple cecum. Like many macropodiforms, bettongs have foregut fermentation. Daily water intake is only about 3% of its body weight. "B. lesueur" seems to have renal adaptations to conserve water, which is important in its arid and semi-arid habitats.

Conservation

As with any extinction, the causes of the Boodie's demise on mainland Australia are many and interrelated. Researchers have proposed many possible causes of decline, which began once Australia was colonized. Nineteenth century colonists killed Boodies, considering them a destructive garden pest. As ranches spread over the grasslands, livestock grazing reduced vegetation cover, shrinking the rat-kangaroo's habitat. Also, introduced species such as foxes, cats, and rabbits took a severe toll on the Boodie, especially on islands. Rabbits competed with them for food and shelter, and the foxes and cats became their major predators. Finally, the Aboriginals maintained certain fire regimes, and when these ceased, the habitat probably changed. By the 1960s, all the Boodies on the mainland were extinct.

Once present in all mainland states except Queensland, the Boodie survives in three remnant populations on small offshore islands. These islands include Bernier, Dorre and Faure Islands in Shark Bay and Barrow Island off the northwest coast of Western Australia. This marsupial is listed on the 2006 IUCN Red List as Vulnerable due to acute restriction of its area of occupancy to less than 100 km². Even with increased conservation efforts, the Red List describes the current population trend as deteriorating.IUCN2006 | assessors = Australasian Marsupial & Monotreme Specialist Group | year = 1996 | id = 2783 |title = Bettongia lesueur | downloaded=2006-10-15]

Recently, conservationists introduced this marsupial in several new places. In 1992, conservationists transferred bettongs from Dorre Island to Heirisson Prong, a peninsula that juts into Shark Bay. Heirisson Prong is a fox- and cat-free area, maintained by a predator-proof fence and a 20 km buffer zone. The geography of the peninsula limits recolonization by foxes and cats. In 1999, ten individuals were transferred to Roxby Downs Arid Recovery Project in South Australia, and in 2002, seventeen bettongs went to Faure Island in an attempt to restock natural fauna. Hopefully, this second chance for the burrowing bettong will be successful and serve as a model for reintroduction of other nearly extinct and endangered mammals.

References

Tim Flannery (2007). Chasing Kangaroos: A Continent, a Scientist, and a Search for the World's Most Extraordinary Creature, ISBN 978-0802118523

External links

* [http://animaldiversity.ummz.umich.edu/site/topics/mammal_anatomy/tooth_diversity.html Types of teeth - Animal Diversity Web]
* [http://www.wtamu.edu/~rmatlack/Mammalogy/lab1.htm Skull terminology mammalogy lab for Texas A&M]
* [http://www.aridrecovery.org.au Arid Recovery]