15.12.04
Habitat and Distribution
The leadbeater’s possum is the only species of its genus found in the world and is only found in Victoria State, Australia. It is believed that it once had a wide range, however when it was discovered in 1867, it was already considered a rare species. After the disastrous forest fires of 1939, it was regarded as extinct, never to be seen on the face of earth again. However, in 1961, a small colony of leadbeater’s possums was discovered. It’s range is confined to an area of 3500 sq km near the western limits of Victoria Central Highlands, but in this area there is only 1700 sq km of Montane ash forests and 6.7% of that is suitable for the habitat it requires. The population density of this endangered creature is 1.5 to 3 individuals per hectare.
The leadbeater’s possum lives in a territorial monogamous environment where the female is prone to be the more socially aggressive half than the male. A monogamous lifestyle involves prolonged association and essentially exclusive mating between male and female. They are territorial because the monogamous pair shares a common territory. The monogamy the leadbeater’s possum exercises is also permanent because the pair remains together for like unless failed breeding attempts becomes routine. Though leadbeater’s possums are usually monogamous, there are still some colonies where it is polyandrous, meaning that there is more than one male with one female, but never more than one female because they are more aggressive and will fight to get rid of the competition. The main female defends their exclusive territory of 1 to 3 hectares. Colonies usually consist of up to 12 possums and engage in mutual grooming. One possum recognizes the other of its colony by smell. The male to female ratio in an average colony is 3 to 1.
There are requirements that must be fulfilled in order for a leadbeater’s possum to survive in the wild. Large old hollow trees for nesting and shelter are essential. They prefer short fat trees with numerous holes and a large quantity of dense surrounding understorey vegetation containing silver of mountain hickory wattle acacia. These requirements can be satisfied in the medium to high altitude sclerophyll forests in the Australia. There are moist, tall, open forests that are dominated by mountain ash, along with alpine oak and shining gum. The mountain ash exceeds 100 m in height which makes it the tallest flowering plant in the world. Sclerophyll forests are very wet; annually, the area receives over 2000 mm of rain and snow, making it unlikely to face water shortage.
Because of its nocturnal nature, all members of the colony huddle in the centre of large nests that are 25 or more cm in diameter make from Eucalyptus regnans bark. The nest is accessible through the three to five cm entrance hole. The nest sites serve important functions. It is an insulated retreat that reduces daily energy demands of resting possums when temperatures fall below 26 degrees Celsius. It is the centre of social activity, close to the centre of group’s defended territory. Nests are also insulated and protected retreats where the young can be left in at night up to several weeks to accommodate the adults’ evening feeding. It has also been observed that only females with a nest rear offspring. Nesting requirements are only met by mature trees and the regrowth around the nest is only for alimentary use.
The leadbeater’s possum is the only species of its genus found in the world and is only found in Victoria State, Australia. It is believed that it once had a wide range, however when it was discovered in 1867, it was already considered a rare species. After the disastrous forest fires of 1939, it was regarded as extinct, never to be seen on the face of earth again. However, in 1961, a small colony of leadbeater’s possums was discovered. It’s range is confined to an area of 3500 sq km near the western limits of Victoria Central Highlands, but in this area there is only 1700 sq km of Montane ash forests and 6.7% of that is suitable for the habitat it requires. The population density of this endangered creature is 1.5 to 3 individuals per hectare.
The leadbeater’s possum lives in a territorial monogamous environment where the female is prone to be the more socially aggressive half than the male. A monogamous lifestyle involves prolonged association and essentially exclusive mating between male and female. They are territorial because the monogamous pair shares a common territory. The monogamy the leadbeater’s possum exercises is also permanent because the pair remains together for like unless failed breeding attempts becomes routine. Though leadbeater’s possums are usually monogamous, there are still some colonies where it is polyandrous, meaning that there is more than one male with one female, but never more than one female because they are more aggressive and will fight to get rid of the competition. The main female defends their exclusive territory of 1 to 3 hectares. Colonies usually consist of up to 12 possums and engage in mutual grooming. One possum recognizes the other of its colony by smell. The male to female ratio in an average colony is 3 to 1.
There are requirements that must be fulfilled in order for a leadbeater’s possum to survive in the wild. Large old hollow trees for nesting and shelter are essential. They prefer short fat trees with numerous holes and a large quantity of dense surrounding understorey vegetation containing silver of mountain hickory wattle acacia. These requirements can be satisfied in the medium to high altitude sclerophyll forests in the Australia. There are moist, tall, open forests that are dominated by mountain ash, along with alpine oak and shining gum. The mountain ash exceeds 100 m in height which makes it the tallest flowering plant in the world. Sclerophyll forests are very wet; annually, the area receives over 2000 mm of rain and snow, making it unlikely to face water shortage.
Because of its nocturnal nature, all members of the colony huddle in the centre of large nests that are 25 or more cm in diameter make from Eucalyptus regnans bark. The nest is accessible through the three to five cm entrance hole. The nest sites serve important functions. It is an insulated retreat that reduces daily energy demands of resting possums when temperatures fall below 26 degrees Celsius. It is the centre of social activity, close to the centre of group’s defended territory. Nests are also insulated and protected retreats where the young can be left in at night up to several weeks to accommodate the adults’ evening feeding. It has also been observed that only females with a nest rear offspring. Nesting requirements are only met by mature trees and the regrowth around the nest is only for alimentary use.
well... now instead of quotes, this site is for convenience sake while i do my bio project in various places :D haha... and so it begins. voici mon projet biologie sur le LEADBEATER'S POSSUM!
Factors affecting population
The environment in which a species dwells makes an impact on the lifestyle of that species. According to evolutionary theory, a species adapts to its environment and surroundings to sustain life. The leadbeater’s possum has adapted to its environment very well, however human influences are causing the population of the leadbeater’s possum to decrease rapidly. However there are many other non-human factors that aid and destroy the population. These factors have either positive effects or negative effects that shape the distribution of the species. Some factors affecting the population of the leadbeater’s possum are food, nest sites, predation, reproduction, and dispersal rates.
A need that all living things need to survive is food. Without it, a species survival is zero percent. Different animals have adapted to different appetites according to their surroundings. Leadbeater’s possum enjoy devouring small arthropods, plants and insect exudates. As their habitat is high in tall, large, hollow Eucalyptus Regnans, their cuisine consists of foodstuff found in and on trees.
Arthropods are common food for the small leadbeater’s possum. Some types that the possum prefers are tree crickets, beetles, moths and spiders. This food source is very reliable and is abundant in all areas of the forest. The relationship between the leadbeater’s possum and the arthropods is mostly non-interactive, meaning that the possum’s harvesting pressure has no effect on the rate of renewal of the resource (Groves, 1982). However, sometimes it is interactive; the harvesting pressure has effect on the rate of renewal. Both of these circumstances depend on environmental factors such as climate and other factors. Arthropods are a temporally non-renewable resource because they are only available seasonally. Once they are harvested from a specific area, they are not available until the next breeding season the next year. Though, in the present, the arthropods in the leadbeater’s possum’s area are abundant, the consummation of these arthropods and the total population size may cause a reduction in population densities in subsequent years. Nonetheless, at the point in time, arthropods are very dependable sources of nutrition and energy for the leadbeater’s possum.
Another source of nutrition in the leadbeater’s possum’s diet is found in and on trees in the area. Gum exudates and insect exudates are favourable to the small creatures. The exudates form on trunks and braches of trees at sites of insects or mechanical damage. The leadbeater’s possum make characteristic cuts into acacia branches to induce the flow of gum. The most favourable are the Acacia Dealbata the Acacia Obliquinervia because of its abundance. They are widespread in sclerophyll forests, road edges and gullies and formed in spring, summer and autumn. In order to microbially degrade the gum, the possum has adapted and has alimentary specialization such as an enlarged caecum. Insect exudates are licked from trunks and braches of Eucalyptus Regnans. A common type of insect exudates is honeydew, a sweet secretion produced by naked lerp insects that live beneath bark on upper branches. Exudates are abundant; however Acacia trees are short-lived, shade intolerant, depend on soil disturbances such as forest fires to promote regeneration and occur at low density in mature Eucalyptus Regnans forests where insect exudates are found and where these marsupials thrive.
Leadbeater’s possums live in mature, hollow Eucalyptus Regnans that are preferably 200 years old. However, not all hollow trees are suitable. These trees need to be dry, well ventilated, and small entrance diameters to exclude larger hollow-dwelling vertebrates (3-5 cm diameter). The trees do not grow under normal conditions, but they depend on previous fire history. Mild fires help regeneration without killing the overstorey trees while severe fires can destroy all the living ash trees and make them into dead “stags”. An extremely severe fire occurred on ‘Black Friday’ in 1939. Almost 70% of the area was burnt and 60% of the ash forests were destroyed. Not only did animals lose their habitat, 70 people also lost their lives. After the fire, the forests were extensively logged for the next 20 years, causing an even greater decrease in possum population. The “stags” left over provide ready-to-use nest hollows until regrowth forests are ready for colonization; however, this number is declining due to the rapid deterioration of E. Regnans. Mountain ash is a soft hardwood that rots away rapidly and has a short standing-life after death making them unsuitable and unreliable for the leadbeater’s possum. As the stags’ numbers decline, so will the leadbeater’s possum habitat. It is estimated that there will be a severe reduction after the next 60 years until regrowth of new, sturdy, reliable overstorey trees is fully grown in about 120 years. The decreasing numbers of nest sites contribute to the rapid decrease of the leadbeater’s possum’s population and increase the chances of extinction.
Competition for habitat and food is generally frequent in animal behaviour. Usually, this affects the population growth of a species. The leadbeater’s possum and the Sugar Glider both have identical food resources and the distribution of these similar species is alike. Where they occur sympatrically in the ash forests in Cambarville, Lake Mountain and Tooloongi State forest, they must compete for nests and food. However, it is observed that there is no direct aggression between the two, but sugar gliders can glide from tree to tree making them more adaptable to mature forests, giving them more chances at food, allowing them to colonize an area more rapidly and excluding the other species through superior local knowledge. The gliding ability of the sugar glider helps it adapt to the environment more readily decreasing the chance of endangerment. However, the leadbeater’s possum can only jump and run from tree to tree so it is restricted to densely packed forests which are only found in certain regions. Competition is a factor that is causing the population to decline.
Predation is commonly a major factor affecting the population of an animal; however, for the leadbeater’s possum, predators do not play a large role in its decreasing numbers. There have only been records of juvenile leadbeater’s possum tails found in owl faecal matter. The most likely predators are the Boobook and Sooty owls. Only juveniles are found to be eaten because adult Leadbeater’s possums have been observed to attack and chase away the owls. The speed and agility and relatively dense habitat of these small creatures, adults are unlikely to fall prey on most other animals in the forest.
A factor that is aiding in the increase of population of the leadbeater’s possum is reproduction and dispersal. One hundred percent of these vivacious adult marsupials can breed from April-June and October-December. On average, they can give up to 12 births per litter and up to 3 litters in less than 12 months. The body size of the female is proportional to the litter size and the number of young per year. If the possum has access to excess resources, it has a high capacity to increase. However due to the diminishing nesting sites, resources are limited. Leadbeater’s possums generally have a relatively high dispersal rate. Females disperse at 10 months to colonize other areas while males disperse at 15 months. This allows the young to start new colonies to multiply their numbers. If the dispersal distance is higher, the predicted risk of extinction is lower, but there are not enough trees suitable for colonization causing them to all stay in the same area making the population of these possums localized and at risk.
Factors affecting population
The environment in which a species dwells makes an impact on the lifestyle of that species. According to evolutionary theory, a species adapts to its environment and surroundings to sustain life. The leadbeater’s possum has adapted to its environment very well, however human influences are causing the population of the leadbeater’s possum to decrease rapidly. However there are many other non-human factors that aid and destroy the population. These factors have either positive effects or negative effects that shape the distribution of the species. Some factors affecting the population of the leadbeater’s possum are food, nest sites, predation, reproduction, and dispersal rates.
A need that all living things need to survive is food. Without it, a species survival is zero percent. Different animals have adapted to different appetites according to their surroundings. Leadbeater’s possum enjoy devouring small arthropods, plants and insect exudates. As their habitat is high in tall, large, hollow Eucalyptus Regnans, their cuisine consists of foodstuff found in and on trees.
Arthropods are common food for the small leadbeater’s possum. Some types that the possum prefers are tree crickets, beetles, moths and spiders. This food source is very reliable and is abundant in all areas of the forest. The relationship between the leadbeater’s possum and the arthropods is mostly non-interactive, meaning that the possum’s harvesting pressure has no effect on the rate of renewal of the resource (Groves, 1982). However, sometimes it is interactive; the harvesting pressure has effect on the rate of renewal. Both of these circumstances depend on environmental factors such as climate and other factors. Arthropods are a temporally non-renewable resource because they are only available seasonally. Once they are harvested from a specific area, they are not available until the next breeding season the next year. Though, in the present, the arthropods in the leadbeater’s possum’s area are abundant, the consummation of these arthropods and the total population size may cause a reduction in population densities in subsequent years. Nonetheless, at the point in time, arthropods are very dependable sources of nutrition and energy for the leadbeater’s possum.
Another source of nutrition in the leadbeater’s possum’s diet is found in and on trees in the area. Gum exudates and insect exudates are favourable to the small creatures. The exudates form on trunks and braches of trees at sites of insects or mechanical damage. The leadbeater’s possum make characteristic cuts into acacia branches to induce the flow of gum. The most favourable are the Acacia Dealbata the Acacia Obliquinervia because of its abundance. They are widespread in sclerophyll forests, road edges and gullies and formed in spring, summer and autumn. In order to microbially degrade the gum, the possum has adapted and has alimentary specialization such as an enlarged caecum. Insect exudates are licked from trunks and braches of Eucalyptus Regnans. A common type of insect exudates is honeydew, a sweet secretion produced by naked lerp insects that live beneath bark on upper branches. Exudates are abundant; however Acacia trees are short-lived, shade intolerant, depend on soil disturbances such as forest fires to promote regeneration and occur at low density in mature Eucalyptus Regnans forests where insect exudates are found and where these marsupials thrive.
Leadbeater’s possums live in mature, hollow Eucalyptus Regnans that are preferably 200 years old. However, not all hollow trees are suitable. These trees need to be dry, well ventilated, and small entrance diameters to exclude larger hollow-dwelling vertebrates (3-5 cm diameter). The trees do not grow under normal conditions, but they depend on previous fire history. Mild fires help regeneration without killing the overstorey trees while severe fires can destroy all the living ash trees and make them into dead “stags”. An extremely severe fire occurred on ‘Black Friday’ in 1939. Almost 70% of the area was burnt and 60% of the ash forests were destroyed. Not only did animals lose their habitat, 70 people also lost their lives. After the fire, the forests were extensively logged for the next 20 years, causing an even greater decrease in possum population. The “stags” left over provide ready-to-use nest hollows until regrowth forests are ready for colonization; however, this number is declining due to the rapid deterioration of E. Regnans. Mountain ash is a soft hardwood that rots away rapidly and has a short standing-life after death making them unsuitable and unreliable for the leadbeater’s possum. As the stags’ numbers decline, so will the leadbeater’s possum habitat. It is estimated that there will be a severe reduction after the next 60 years until regrowth of new, sturdy, reliable overstorey trees is fully grown in about 120 years. The decreasing numbers of nest sites contribute to the rapid decrease of the leadbeater’s possum’s population and increase the chances of extinction.
Competition for habitat and food is generally frequent in animal behaviour. Usually, this affects the population growth of a species. The leadbeater’s possum and the Sugar Glider both have identical food resources and the distribution of these similar species is alike. Where they occur sympatrically in the ash forests in Cambarville, Lake Mountain and Tooloongi State forest, they must compete for nests and food. However, it is observed that there is no direct aggression between the two, but sugar gliders can glide from tree to tree making them more adaptable to mature forests, giving them more chances at food, allowing them to colonize an area more rapidly and excluding the other species through superior local knowledge. The gliding ability of the sugar glider helps it adapt to the environment more readily decreasing the chance of endangerment. However, the leadbeater’s possum can only jump and run from tree to tree so it is restricted to densely packed forests which are only found in certain regions. Competition is a factor that is causing the population to decline.
Predation is commonly a major factor affecting the population of an animal; however, for the leadbeater’s possum, predators do not play a large role in its decreasing numbers. There have only been records of juvenile leadbeater’s possum tails found in owl faecal matter. The most likely predators are the Boobook and Sooty owls. Only juveniles are found to be eaten because adult Leadbeater’s possums have been observed to attack and chase away the owls. The speed and agility and relatively dense habitat of these small creatures, adults are unlikely to fall prey on most other animals in the forest.
A factor that is aiding in the increase of population of the leadbeater’s possum is reproduction and dispersal. One hundred percent of these vivacious adult marsupials can breed from April-June and October-December. On average, they can give up to 12 births per litter and up to 3 litters in less than 12 months. The body size of the female is proportional to the litter size and the number of young per year. If the possum has access to excess resources, it has a high capacity to increase. However due to the diminishing nesting sites, resources are limited. Leadbeater’s possums generally have a relatively high dispersal rate. Females disperse at 10 months to colonize other areas while males disperse at 15 months. This allows the young to start new colonies to multiply their numbers. If the dispersal distance is higher, the predicted risk of extinction is lower, but there are not enough trees suitable for colonization causing them to all stay in the same area making the population of these possums localized and at risk.
Leadbeater’s Possum (Gymnobelideus leadbeateri)
General Information
- small omnivorous arboreal marsupial (petaurid)
o young born blind and naked, early development in mother’s pouch
- status: endangered
- head and body length: 150-170 mm
- tail length: 145-180
- weight: 100-135g (in spring), 110-166g (in autumn)
- grey to greyish-brown above, paler below
- prominent dark mid-dorsal stripe
- similar to Sugar Glider (Petaurus breviceps): no gliding membrane and club-shaped tail (broader near the top than base)
- nocturnal
- short retractable claws and striated foot pads
o enables them to ascend and descend smooth trunks of E. regnans
o move at considerable speed in the canopy of regenerating E. regnans, A. dealbata at height of 15-30 m above ground
o can jump about 1.6 m from a solid base
- official animal of Victoria State, Australia
- diet:
o consists of arthropods (tree crickets, beetles, moths, spiders), plant (nectar, acacia gum, eucalypt sap, manna), insect exudates
o Common gum exudates: Acacia dealbata, A. obliquinervia
§ Formed on trunks and branches of trees at sites of insects or mechanical damage
§ Possums make characteristic cuts into acacia branches to induce flow of gum
§ Gum formed during spring, summer and autumn, most in summer
§ To be microbially degraded, leadbeater’s possum must have alimentary specialization such as enlarged caecum
o Lick exudates from trunks and branches of E. regnans
§ Feed on honeydew (a sweet secretion produced by naked lerp insects that live beneath bark on the upper branches
o Ingest 1.5-6.0 g of arthropods/day, only 10% of daily energy requirement
- Litter size: 1.6 (12)
- Annual Fecundity: 3.2
- Months of births: April-June, October-December
- Adult breeding/year (%): 100
- Age at weaning: 3 months
- Mortality of dependent young (%): 0-100
- Age at dispersal: 11-26 months (male), 7-14 months (female)
- Age of female at birth of first litter: 12 months
- Exercises monogamy: prolonged association and essentially exclusive mating between male and female
o Territorial monogamy: monogamous pair shares common territory
o Permanent monogamy: pairs remain together for life, unless failed breeding attempts
o Sometimes polyandrous: more than one male with one female
- Females prone to be more aggressive socially than males
o Defend exclusive territory of 1-3 hectares
- Colony up to 12 possums
- Members of colony engage in mutual grooming
- Recognize each other by smell
- Male: female ratio: 3:1
- Probability of death:
o Newborn: 0
o Juvenile: 0.3
o Adult: 0.3
Habitat and Distribution
- found in Victoria state, Australia
o once wide range
o rare when discovered in 1867
o regarded as extinct because of forest fires in 1939
o presumed extinct until1961, small colony rediscovered
o confined to area of 3500 sq km near the western limits of Victoria Central Highlands
§ only 1700 sq km of Montane ash forest
§ suitable habitat only 6.7%
o population density of 1.5-3 individuals/hectare
- large old hollow trees for nesting and shelter are essential
- prefer short, fat trees with numerous holes and large quantity of dense surrounding vegetation
- harvests dispersed food supply
- run and jump to move from tree to tree
- favour structurally dense regrowth, understory vegetation containing silver or mountain hickory wattle acacia
- restricted to medium to high altitude wet sclerophyll forests
o moist tall open forest dominated by mountain ash (mountain ash, alpine ask, shining gum)
§ mountain ash exceeds 100 m in height, tallest flowering plant in the world
o forests very wet; over 2000 mm of rain and snow
§ unlikely to face water shortage because predominantly nocturnal activity pattern and humid shelters during the day
- nest sites:
o during daylight, all members of colony huddle in centre of large nests (25+ cm diameter made from Eucalyptus regnans bark
o nest accessible through narrow (3.5-5 cm) entrance hole
o serves important functions
§ insulated retreat that reduces daily energy demands of resting possums, when temperature falls below 26 degrees Celsius
§ centre of social activity, close to centre of group’s defended territory
§ insulated and protected retreat where young can be left in at night up to several weeks
§ only females with a nest rear offspring
o nesting requirements only met by mature trees, regrowth only for food
Factors affecting Population
- only member of Gymnobelideus
- wild populations confined to Victoria; survival completely dependent on conservation measures taken in Victoria
- predicted massive decline until 2075
- nest trees decaying
- possums do not prefer mature trees they are approximately 200 years old
- estimate 92% population decrease
- Food
o Eat gums of Acacia
§ Widespread in sclerophyll forests, road edges and gullies
§ However, short-lived, shade intolerant, depend on soil disturbances, medium to high-intensity fire to promote regeneration
§ Forest fires of 1939 helped A. dealbata to regenerate, however short-lived and occur at low density in mature E. regnans forests
o Arthropods
§ Relationship is non-interactive (harvesting pressure has no feedback effect upon rate of renewal of resource) and interactive (harvesting pressure has effect on renewal
§ Rate of renewal dependent on climate and other factors
§ Arthropods temporally non-renewable resource
· Available seasonally; once harvested from an area, not again available until breeding season
· Consummation vs. total population size
o Reduction in population densities in subsequent years
§ Feed on trees that are close together; restricted; cannot glide, only jump and run
§ Need regrowth forests or mature forests with shrub or regrowth understorey
§ E. regnans forests, canopy becomes more open, which may increase harvesting cost to prohibitive levels
o Competition
§ Food resources identical to Sugar Glider
§ Distribution of both species similar
· Must compete where they occur sympatrically
o Ash forests in Cambarville, Lake Mountain
o Tooloongi State Forest
§ No direct aggression, but sugar gliders can glide from tree to tree to make them more adaptable to mature forests, more chances at food, can colonize area more rapidly, and exclude the other species through superior local knowledge and efficient use of resources
- Nest sites
o Mature trees must be over 100 years of age, preferably 200
o Not all hollow trees are suitable
§ Need to be dry, well ventilated, small entrance diameters to exclude larger hollow-dwelling vertebrates
· 3-5 cm in diameter
o availability of trees depend on previous fire history
§ mild fires help regeneration without killing overstorey trees
§ severe fires can destroy all the living ash trees and make them into dead “stags”
· The fire in 1939 – ‘Black Friday’
o 70% of area burnt
o 70 people lost lives
o destroyed 60% of the state’s ash forests
o forests extensively logged for next 20 years
· They provide ready to use nest hollows until regrowth forests are ready for colonization, however this number is declining
§ Mountain ash is a soft hardwood that rots rapidly and has a short standing-life after death
· Unsuitable for possums; unreliable
· Stags will decline rapidly and so will the Leadbeater’s possum’s habitat
o Severe reduction after the next 60 years until regrowth of new overstorey trees in 120 years
o
- Predation
o Not a big impact
o Boobook owls and Sooty owls might feed on juvenile leadbeater’s possums
§ Tail found in owl faecal matter
§ Adult Leadbeater’s possums observed to attack and chase away owls
· Because of speed and agility and relatively dense habitat, adults unlikely to fall prey
- Reproduction
o Can produce in winter and spring
o Average 12 births/litter, up to 3 litters in less than 12 months
o Body size proportional to litter size and number of young/year
o If there are excess resources, the possum has a high capacity to increase
- Dispersal
o Relatively high dispersal rate
§ Females disperse at 10 months while males disperse in 15 months
o Females sent off to colonize other areas
§ Not enough trees suitable for colonization
§ All stay in same area
o Rate of spread away from fire refuges inhibited by rate by which the possums can find and excavate tree hollows that meet their specific requirements
Human Control efforts
- Land Conservation Council of Victoria made 4 major land-use recommendations:
o Parks
§ Conservation, recreation, education
§ Leadbeater’s possum not found in reserves where wildlife conservation is principal objective
§ Located in areas where Leadbeater’s possum cannot use as a long term habitat
· Lack of Acacia understorey and large Eucalyptus overstorey
§ If used to support possum population, most be managed with fire, logging and soil disturbance to maintain a suitable habitat
§ 27% of state forests excluded from timber harvesting by prescription
· reserved forests in Yarra ranges National Park, placed at core of species distribution
o 3 large water catchments
o extensive areas of old growth and mixed-age forest
o has medium and long-term resources of hollow trees
o Water Catchment
§ Possums found in water catchment areas controlled by Melbourne and Metropolitan Board of Works
§ No human interaction so create “wilderness”
§ No fires, dense forests of large overstorey trees, but no regrowth understorey for food
· Can be made suitable by burning, logging and ploughing
§
o Hardwood Production
§ Area of mature ash remaining in hardwood production areas: 1500 ha
· Small patch treated by ploughing and planting to promote understorey growth
· Other areas too open to support the possum
§ Silvicultural methods: cutting intensity, number of retained trees in a coupe, coupe size, coupe rotation time, size, shape and pattern of unlogged reserves
§ Area zoned for both hardwood production and wildlife conservation
§ Appropriate amounts of logging should be made sure to ensure the possum’s survival
§ Hollow trees are avoided and protected in order to ensure a habitat for the Leadbeater’s possum
o Wildlife conservation
§ Creation of artificial nest sites
· In an area with large favourable overstorey Eucalyptus trees
· Manually burned Acacia regrowth
· Excavation for leadbeater’s possum
§ Minimal human interaction, but protected
Possible human action
- monitor recovery program
- apply conservation strategies in each of the 21 Leadbeater’s possum management units
- assess habitat and range
o zone areas where possums are found
- implement population monitoring
General Information
- small omnivorous arboreal marsupial (petaurid)
o young born blind and naked, early development in mother’s pouch
- status: endangered
- head and body length: 150-170 mm
- tail length: 145-180
- weight: 100-135g (in spring), 110-166g (in autumn)
- grey to greyish-brown above, paler below
- prominent dark mid-dorsal stripe
- similar to Sugar Glider (Petaurus breviceps): no gliding membrane and club-shaped tail (broader near the top than base)
- nocturnal
- short retractable claws and striated foot pads
o enables them to ascend and descend smooth trunks of E. regnans
o move at considerable speed in the canopy of regenerating E. regnans, A. dealbata at height of 15-30 m above ground
o can jump about 1.6 m from a solid base
- official animal of Victoria State, Australia
- diet:
o consists of arthropods (tree crickets, beetles, moths, spiders), plant (nectar, acacia gum, eucalypt sap, manna), insect exudates
o Common gum exudates: Acacia dealbata, A. obliquinervia
§ Formed on trunks and branches of trees at sites of insects or mechanical damage
§ Possums make characteristic cuts into acacia branches to induce flow of gum
§ Gum formed during spring, summer and autumn, most in summer
§ To be microbially degraded, leadbeater’s possum must have alimentary specialization such as enlarged caecum
o Lick exudates from trunks and branches of E. regnans
§ Feed on honeydew (a sweet secretion produced by naked lerp insects that live beneath bark on the upper branches
o Ingest 1.5-6.0 g of arthropods/day, only 10% of daily energy requirement
- Litter size: 1.6 (12)
- Annual Fecundity: 3.2
- Months of births: April-June, October-December
- Adult breeding/year (%): 100
- Age at weaning: 3 months
- Mortality of dependent young (%): 0-100
- Age at dispersal: 11-26 months (male), 7-14 months (female)
- Age of female at birth of first litter: 12 months
- Exercises monogamy: prolonged association and essentially exclusive mating between male and female
o Territorial monogamy: monogamous pair shares common territory
o Permanent monogamy: pairs remain together for life, unless failed breeding attempts
o Sometimes polyandrous: more than one male with one female
- Females prone to be more aggressive socially than males
o Defend exclusive territory of 1-3 hectares
- Colony up to 12 possums
- Members of colony engage in mutual grooming
- Recognize each other by smell
- Male: female ratio: 3:1
- Probability of death:
o Newborn: 0
o Juvenile: 0.3
o Adult: 0.3
Habitat and Distribution
- found in Victoria state, Australia
o once wide range
o rare when discovered in 1867
o regarded as extinct because of forest fires in 1939
o presumed extinct until1961, small colony rediscovered
o confined to area of 3500 sq km near the western limits of Victoria Central Highlands
§ only 1700 sq km of Montane ash forest
§ suitable habitat only 6.7%
o population density of 1.5-3 individuals/hectare
- large old hollow trees for nesting and shelter are essential
- prefer short, fat trees with numerous holes and large quantity of dense surrounding vegetation
- harvests dispersed food supply
- run and jump to move from tree to tree
- favour structurally dense regrowth, understory vegetation containing silver or mountain hickory wattle acacia
- restricted to medium to high altitude wet sclerophyll forests
o moist tall open forest dominated by mountain ash (mountain ash, alpine ask, shining gum)
§ mountain ash exceeds 100 m in height, tallest flowering plant in the world
o forests very wet; over 2000 mm of rain and snow
§ unlikely to face water shortage because predominantly nocturnal activity pattern and humid shelters during the day
- nest sites:
o during daylight, all members of colony huddle in centre of large nests (25+ cm diameter made from Eucalyptus regnans bark
o nest accessible through narrow (3.5-5 cm) entrance hole
o serves important functions
§ insulated retreat that reduces daily energy demands of resting possums, when temperature falls below 26 degrees Celsius
§ centre of social activity, close to centre of group’s defended territory
§ insulated and protected retreat where young can be left in at night up to several weeks
§ only females with a nest rear offspring
o nesting requirements only met by mature trees, regrowth only for food
Factors affecting Population
- only member of Gymnobelideus
- wild populations confined to Victoria; survival completely dependent on conservation measures taken in Victoria
- predicted massive decline until 2075
- nest trees decaying
- possums do not prefer mature trees they are approximately 200 years old
- estimate 92% population decrease
- Food
o Eat gums of Acacia
§ Widespread in sclerophyll forests, road edges and gullies
§ However, short-lived, shade intolerant, depend on soil disturbances, medium to high-intensity fire to promote regeneration
§ Forest fires of 1939 helped A. dealbata to regenerate, however short-lived and occur at low density in mature E. regnans forests
o Arthropods
§ Relationship is non-interactive (harvesting pressure has no feedback effect upon rate of renewal of resource) and interactive (harvesting pressure has effect on renewal
§ Rate of renewal dependent on climate and other factors
§ Arthropods temporally non-renewable resource
· Available seasonally; once harvested from an area, not again available until breeding season
· Consummation vs. total population size
o Reduction in population densities in subsequent years
§ Feed on trees that are close together; restricted; cannot glide, only jump and run
§ Need regrowth forests or mature forests with shrub or regrowth understorey
§ E. regnans forests, canopy becomes more open, which may increase harvesting cost to prohibitive levels
o Competition
§ Food resources identical to Sugar Glider
§ Distribution of both species similar
· Must compete where they occur sympatrically
o Ash forests in Cambarville, Lake Mountain
o Tooloongi State Forest
§ No direct aggression, but sugar gliders can glide from tree to tree to make them more adaptable to mature forests, more chances at food, can colonize area more rapidly, and exclude the other species through superior local knowledge and efficient use of resources
- Nest sites
o Mature trees must be over 100 years of age, preferably 200
o Not all hollow trees are suitable
§ Need to be dry, well ventilated, small entrance diameters to exclude larger hollow-dwelling vertebrates
· 3-5 cm in diameter
o availability of trees depend on previous fire history
§ mild fires help regeneration without killing overstorey trees
§ severe fires can destroy all the living ash trees and make them into dead “stags”
· The fire in 1939 – ‘Black Friday’
o 70% of area burnt
o 70 people lost lives
o destroyed 60% of the state’s ash forests
o forests extensively logged for next 20 years
· They provide ready to use nest hollows until regrowth forests are ready for colonization, however this number is declining
§ Mountain ash is a soft hardwood that rots rapidly and has a short standing-life after death
· Unsuitable for possums; unreliable
· Stags will decline rapidly and so will the Leadbeater’s possum’s habitat
o Severe reduction after the next 60 years until regrowth of new overstorey trees in 120 years
o
- Predation
o Not a big impact
o Boobook owls and Sooty owls might feed on juvenile leadbeater’s possums
§ Tail found in owl faecal matter
§ Adult Leadbeater’s possums observed to attack and chase away owls
· Because of speed and agility and relatively dense habitat, adults unlikely to fall prey
- Reproduction
o Can produce in winter and spring
o Average 12 births/litter, up to 3 litters in less than 12 months
o Body size proportional to litter size and number of young/year
o If there are excess resources, the possum has a high capacity to increase
- Dispersal
o Relatively high dispersal rate
§ Females disperse at 10 months while males disperse in 15 months
o Females sent off to colonize other areas
§ Not enough trees suitable for colonization
§ All stay in same area
o Rate of spread away from fire refuges inhibited by rate by which the possums can find and excavate tree hollows that meet their specific requirements
Human Control efforts
- Land Conservation Council of Victoria made 4 major land-use recommendations:
o Parks
§ Conservation, recreation, education
§ Leadbeater’s possum not found in reserves where wildlife conservation is principal objective
§ Located in areas where Leadbeater’s possum cannot use as a long term habitat
· Lack of Acacia understorey and large Eucalyptus overstorey
§ If used to support possum population, most be managed with fire, logging and soil disturbance to maintain a suitable habitat
§ 27% of state forests excluded from timber harvesting by prescription
· reserved forests in Yarra ranges National Park, placed at core of species distribution
o 3 large water catchments
o extensive areas of old growth and mixed-age forest
o has medium and long-term resources of hollow trees
o Water Catchment
§ Possums found in water catchment areas controlled by Melbourne and Metropolitan Board of Works
§ No human interaction so create “wilderness”
§ No fires, dense forests of large overstorey trees, but no regrowth understorey for food
· Can be made suitable by burning, logging and ploughing
§
o Hardwood Production
§ Area of mature ash remaining in hardwood production areas: 1500 ha
· Small patch treated by ploughing and planting to promote understorey growth
· Other areas too open to support the possum
§ Silvicultural methods: cutting intensity, number of retained trees in a coupe, coupe size, coupe rotation time, size, shape and pattern of unlogged reserves
§ Area zoned for both hardwood production and wildlife conservation
§ Appropriate amounts of logging should be made sure to ensure the possum’s survival
§ Hollow trees are avoided and protected in order to ensure a habitat for the Leadbeater’s possum
o Wildlife conservation
§ Creation of artificial nest sites
· In an area with large favourable overstorey Eucalyptus trees
· Manually burned Acacia regrowth
· Excavation for leadbeater’s possum
§ Minimal human interaction, but protected
Possible human action
- monitor recovery program
- apply conservation strategies in each of the 21 Leadbeater’s possum management units
- assess habitat and range
o zone areas where possums are found
- implement population monitoring
