Burramys parvusmountain pygmy possum

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Geographic Range

The mountain pygmy possum, Burramys parvus, lives in the alps of Victoria and New South Wales, Australia. More specifically, it is found atop the Mount Bogong, Mount Loch and Mount Higginbotham mountain ranges of Victoria. In New South Wales, it is found predominantly in the mountain ranges of Kosciusko National Park, which include Mount Townsend, Mount Kosciusko, and Mount Blue Cow (Broome and Mansergh 1994). Burramys parvus ranges in elevation from 1400m to 2230m (Strahan 1995).

Habitat

Burramys parvus lives in a cold, wet climate. Snow is possible year round, but is most frequent between June and September. When snow is not blanketing the ground, rain and powerful winds are typical. The New South Wales and Victorian alps annual rainfall is greater than 1500mm. The altitude of the alps causes temperatures to be low, seldom exceeding 10 degrees celsius from May to September (Broome and Mansergh 1994). The habitat of this species can be described as a boulderfield. Recurrent wetting and freezing of water on the rock surfaceshas led to fragmentation of boulders. These fragments provide necessary protection from the harsh climatic conditions and alpine predators. Burramys parvus often has been found nesting among the crevices. Plants establish in shallow fragments, providing the mountain pygmy possum with plentiful resources (Strahan 1995). These plants are typically low shrubs with grasses intermixed (Strahan 1983).

Physical Description

Burramys parvus is a small, rodentlike marsupial. Both sexes are about 110mm in head and body length, with males being slightly longer and heavier than females. The tail of B. parvus is prehensile, ranging from 140mm in females to 148mm in males (Strahan 1983). The fur is fine, but dense. The dorsal side is grey, with a darker section at the back and head midline. The ventral surface is light cream, with males developing a bright fawn-orange in breeding season. The forepaws are dexterous, easily able to manipulate food, while on the hindfoot the hallux aids in climbing (Broome and Mansergh 1994).

  • Average mass
    45 g
    1.59 oz
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  • Average basal metabolic rate
    0.205 W
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Reproduction

Burramys parvus follows a low fecundity, high longevity life strategy. The mountain pygmy possum has a non-breeding season from January-April, when it gain sweight for the coming winter and the young disperse. The inactive season, from May-September, is hibernation season for B. parvus. From September through December, B. parvus is in an active season of breeding. B. parvus females are polyestrous but limited to one litter per year by the need to store fat reserves for hibernation. Without sufficient fat, the females die. In response to fat reserve limitations, B. parvus synchronizes its reproduction with spring, when nutrient rich Bogong moths are abundant. Breeding occurs annually for many consecutive years. Reproducing females have been found up to 12 years of age, which makes them one of the longest lived small terrestrial mammals.

Studies have successfully mapped out the reproductive timeline of the mountain pygmy possum (Mansergh and Scotts 1990). Mating occurs between late September and mid October. Female estrous lasts ~20 days. After fertilization, a gestation period of 13-16 days ensues, followed by birth in the last week of October of four altricial young (Mansergh and Scotts 1990). The young have well developed forelimbs and heads for traveling from the cloaca to the pouch. The female cleans a trail for the young to the pouch, where the young attach to a teat (Broome and Mansergh 1994). Frequently the female bear smore than four young, leading to more offspring than teats. Under these circumstances, the 'slowest' young will not have a teat when it arrives in the pouch, and will die. The lactation period lasts 30 days, with a subsequent nesting period of 30-35 days (Strahan 1995). The young are fully weaned and independent after 65 days. Young disperse between January and March (Lee and Cockburn 1985). At approximately 1 year of age, the young begin mating. Only 50% of the reproducing young will survive, due to the inability of younger B. parvus to maintain fat reserves for hibernation (Mansergh et al. 1990). By their second summer, young are fully capable of sustaining themselves for both activities (Strahan 1995).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    3.5
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  • Average gestation period
    15 days
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  • Average age at sexual or reproductive maturity (female)
    Sex: female
    320 days
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  • Average age at sexual or reproductive maturity (male)
    Sex: male
    320 days
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Lifespan/Longevity

Behavior

The mountain pygmy possum is a calm, social animal, rarely engaging in competition for space or food. Burramys parvus is secretive and nocturnal. During the day, it sleeps curled in a ball to retain heat. In captivity, its temprament is much the same. Mountain pygmy possums have been seen running over the backs of each other with little disturbance. They also seem to socially groom each other. Only when distressed does B. parvus make a low guttural vocalization (Broome and Mansergh 1994). Mating behavior of B. parvus is cued by several factors, including spring equinox, arrival of Bogong moths, male encroachment into natal areas, and disappearance of snow (Mansergh and Scotts 1990). The behavior of B. parvus has a characteristic pattern, with the male first pursuing a female and sniffing her anal region. If the female chooses to mate, she allows him to mount and clasp her flanks. Copulation lasts several minutes, after which the male leaves. The female may show extreme post-copulatory aggression towards the male if he chooses to stay in the vicinity after copulation (Broome and Mansergh 1994).

After birth and growth of young males, females are aggressive towards them and force them to leave the natal area. Older males leave first, followed by juvenile males and sometimes juvenile females. Over time, the sex ratio of a natal area becomes female biased (Strahan 1995). The sedentary females have a better resource pool than the dispersed males, leading to increased longevity of females (Mansergh and Scotts 1990). In fact, females are four to five times more likely to survive the winter than males (Menkhorst 1995). This type of social organization has been termed matriarchical resource defence polygyny (Mansergh and Scotts 1990).

Female's natal areas have communal nesting sites and overlapping home ranges. Older females tend to share their ranges with up to 10 younger females. It is likely that the younger females are genetic descendants of the older female. Only during nightly forages do the females leave the natal area. Since the natal area is in the higher elevations, where food is more abundant, these dispersals are relatively short distances (Broome and Mansergh 1994).

Males have less structured home ranges. When not invading the female's range to mate, the males are nomads, foraging during the evening over broad expanses of nutrient poor resources (Broome and Mansergh 1994). Their foraging distances can reach relatively long distances, decreasing their likelihood of survival due to predators and insufficient nutrients.

Communication and Perception

Food Habits

The mountain pygmy possum is best described as an omnivore-insectivore-granivore- frugivore. While eating habits of B. parvus are diverse, the diversity of prey is low, making B. parvus a specialized feeder, according to the season. During the 'active season' from October-April, B. parvus' diet contains high energy food. During this period, B. parvus is an omnivore and insectivore, feeding heavily upon the Bogong moth (Agrotis infusa), which migrates yearly to the Australian alps for breeding. The yearly migration of the moth provides a predictable, energy rich and abundant food supply for B. parvus. Studies conducted by Mansergh and associates (1990) reveal that the Bogong moth constitutes over 33% of the total 'active season' diet of B. parvus. A later study by Smith and associates (1992) reported that the moth may actually be the only dietary item during the reproductive season (October-December) of B. parvus. It has been found that females take a higher percentage of Bogong moths than males, due to the concurrent breeding season and additional nutritional supplements required to raise offspring (Smith and Broome 1992). Other insects, consumed in sparse quantities, are caterpillars, millipedes, beetles and spiders (Broome and Mansergh 1994). As the active season progresses, the abundance of Bogong moths decreases, leading to a dietary switch from moths to seeds and berries. The mountain pygmy possum prefers the seeds of habitat specific species such as Mountain Plum-pine, Rambling Bramble, and Snow Beard-heath, during the months of January-April (Broome and Mansergh 1994).

During the 'non-active', or hibernation season, B. parvus caches seeds and berries, which constitute over 75% of their diet from May-October (Broome and Mansergh 1994). The mountain pygmy possum is the only marsupial found to cache non-perishable food items (Menkhorst 1995).

Burramys parvus is well adapted to its specialized diet. The mountain pygmy possum has agile forelimbs that permit manipulation of seeds, berries and insects. The hard coats of seeds and insect exoskeletons are easily opened with a plagiaulacoid premolar. Burramys parvus uses its procumbent lower incisors to scoop out the interior of the seed or insect.

Economic Importance for Humans: Positive

Conservationists consider Burramys parvus economically important to research. The confined habitat and home ranges of B. parvus make it ideal for studies on wildlife managment, especially those with rapidly declining population. By establishing broad range methods to effectively treat animal populations, less monetary funds will be required for species specific method development.

Economic Importance for Humans: Negative

Ski industries sometimes feel their land acquistion opportunities are being thwarted by efforts aimed at conservation of B. parvus habitats. Recent conservation efforts (tunnel building) for B. parvus have been tolerated and accepted by established ski resorts. However, it has become increasingly difficult for new entrepeneurs in the industry to find unprotected portions of B. parvus habitat to develop.

Conservation Status

The Mountain Pygmy Possum lives in the Australian alps, where the ski industry has been growing since the mid 1950's. Leveling and grooming of land for ski trails has greatly affected the amount of available habitat for B. parvus. While B. parvus oftens makes its home in ski lodge foundations, the dispersal of males to and from the natal site has become increasingly difficult. Also problematic is the destruction of trees and shrubs, which B. parvus uses for food. Sufficient field data were collected in 1979 by Ken Norris, an Australian zoologist, and his associates to place a threatened label on B. parvus. A debate between tourism economists and wildlife conservationists soon developed (Broome and Mansergh 1994). Since these debates, measures have been taken to decrease the amount of habitat fragmentation and destruction by the ski industry. For the B. parvus habitats in established ski resorts, underground tunnels with simulated B. parvus habitat substrate have been constructed to aid in dispersal between intact habitat and ski resort habitat (Mansergh and Scotts 1992). These tunnels have become respected at the ski resorts by tourists and government officials alike. Future management plans to save B. parvus include protecting undestroyed lands and buffer lands surrounding the ski areas, continuing to devise tunneling systems for already affected B. parvus populations, monitoring effects of snow grooming on B. parvus habitats and populations, and making the public more aware of the vulnerability of this animal (Broome and Mansergh 1994).

The present habitat of B. parvus is less than 10 square kilometers. The present population of B. parvus is no more than 2600 adults (Strahan 1995).

Other Comments

The mountain pygmy possum was discovered as a fossil by Robert Broome in 1894. He named the species Burramys parvus, meaning small rock mouse, although it is not a mouse at all (Broome and Mansergh 1994). Dentition studies revealed a plagiaulacoid premolar, like that characteristic of the family Potoroidae. From this observation, it was questioned whether the pygmy possum was actually a tiny kangaroo (Ride 1970). For seventy years, B. parvus was considered a fossil, until again found in a Victorian alps ski lodge in 1966 by accident (Ride 1970). Another interesting aspect of B. parvus life history is hibernation. Burramys parvus hibernates in the cold alps winter. It puts on large amounts of fat, which serves as energy during the reduced metabolic and body temperature state of torpor. During torpor, B. parvus rolls itself into a ball and tucks its tail around the body. Although energetically costly to rewarm the body, B. parvus occasionally arises during hibernation to feed on the seeds cached in its burrow (Broome and Mansergh 1994). The hibernation period lasts for 6 months, from February through July.

Contributors

Jamie Bender (author), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

bilateral symmetry

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.

chemical

uses smells or other chemicals to communicate

endothermic

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.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

References

Broome, L. and Mansergh, I. 1994. The Mountain Pygmy Possum of the Australian Alps. New South Wales University Press, New South Wales.

Lee, A. and Cockburn, A. 1985. Evolutionary Ecology of Marsupials. Cambridge University Press, Melbourne.

Mansergh, I., Baxter, B., Scotts, D., Brady T., and Jolley, D. 1990. Diet of the Mountain Pygmy Possum, Burramys parvus, and other small mammals in the alpine environment at Mt. Higginbotham, Victoria. Australian Mammalogy 13:167-177.

Mansergh, I. and Scotts, D. 1992. Habitat continuity and social organization of the Mountain Pygmy Possum restored by tunnel. Journal of Wildlife Management 53: 701-707.

Mansergh, I. and Scotts, D. 1990. Aspects of the life history and breeding biology of the Mountain Pygmy-Possum, Burramys parvus, in alpine Victoria. Australian Mammalogy 13:179-191.

Menkhorst, P.W. 1995. Mammals of Victoria: distribution, ecology, and conservation. Oxford University Press, Melbourne.

Ride, R.D.L. 1970. A Guide to the Native Mammals of Australia. Oxford University Press, Melbourne. Smith, A.P. and Broome, L. 1992. The effects of season, sex and habitat on the diet of the Mountain Pygmy Possum. Wildlife Research 19:755-58.

Strahan, R. 1983. The Australian Museum complete book of Australian Mammals: the National Photographic Index of Australian Wildlife. Angus and Robertson, London.

Strahan, R. 1995. Mammals of Australia. Reed Books, Chatswood, New South Wales.

Wilson and Reeder. 1997. http://nmnhwww.si.edu/gopher-menus/MammalSpeciesoftheWorld.html.