Video conf. notes 11 Feb 2016 - Threatened possums & gliders
SWIFFT video conference notes are a summary of the video conference and not intended to be a definitive record of presentations made and issues discussed.
This video conference was supported through resources and technology provided by the Department of Environment, Land, Water and Planning, Victoria. SWIFFT wishes to thank speakers for their time and delivery of presentations.
The first video conference for 2016 had a theme on Victoria's Threatened Possums and Gliders.
A total of 85 participants were connected across 16 locations; Ararat, Ballarat, Bairnsdale, Benalla, Bendigo, Colac, Geelong, Hamilton, Heywood, Heidelberg (Arthur Rylah Institute), Knoxfield, Melbourne (Nicholson Street), Orbost, Traralgon, Warrnambool and Wodonga.
- KEY POINTS SUMMARY Quick take home messages from this video conference or read through the speaker summaries.
- Introduction to threatened possums & gliders in Victoria
- Leadbeater's Possum research
- Squirrel Glider research
List of groups/organisations in attendance;
Educational: Deakin University
Local Government: Baw Baw Shire, Nillumbik Shire,
Field Naturalist Clubs: Ballarat, Geelong, Hamilton and Portland.
Community Conservation Groups: Karra Karra CMN, Winda-Mara Aboriginal Corporation, Victorian Volcanic Plains Biosphere Network, Ararat Landcare, Bellarine Landcare, Green Hill Lake Dev.Board., Friends of Eastern Otways, Wombat Forestcare, Ballarat Environment Network and Meredith landholder.
Conservation Organisations: Trust for Nature,Parks Victoria, Vic Forests, Department of Environment, Land, Water and Planning (DEWLP) staff across 15 locations, inc. Nicholson Street Melbourne, Knoxfield and Arthur Rylah Institute, Heidelberg.
Industry: Bendigo Wildlife Shelter
Introduction to threatened possums & gliders in Victoria - Peter Menkhorst, Arthur Rylah Institute, Department of Environment, Land, Water & Planning.
Possums and gliders fall into six families in the Order Diprotodontia which is comprised mainly of Kangaroos, Wallabies, Wombat and Koala. Five of the six families are found in Victoria. Peter pointed out that gliders are not a homogenous group, in fact the gliding capacity has evolved independently in three of the six families.
Victoria contains a very diverse fauna of possums and gliders with 14 species. The only region of Australia matching that is the wet tropics of northern Queensland.
Possums and gliders of Victoria
- Mountain Brushtail Possum
- Common Brushtail Possum
- Mountain Pygmy-possum (Critically endangered)
- Western Pygmy-possum (Near threatened)
- Little Pygmy-possum (Near threatened)
- Eastern Pygmy-possum (Near threatened)
- Leadbeater's Possum (Endangered)
- Yellow-bellied Glider
- Sugar Glider
- Squirrel Glider (Endangered)
- Common Ringtail Possum
- Southern Greater Glider (vulnerable)
- Feathertail Glider (broad-toed)
- Feathertail Glider (narrow- toed)
Peter pointed out that 'Near threatened' refers to species which are not threatened but species which we need to watch.
The family Petauridae comprises the wrist-winged gliders but the Leadbeater's Possum does not have gliding capacity.
Apart from the Eastern Pygmy-possum the other species of Pygmy-possum are partly terrestrial. Not all possums are arboreal.
Peter spoke about the situation where all Victorian fauna has suffered due to drought conditions over the last 15 years or so and apart from some of the high priority species we have little knowledge of the status of wildlife in Victoria due to limited research. This makes it difficult to determine population trends, particularly for pygmy-possums and gliders.
Synopsis of Victoria's Threatened possums and gliders
(modified from presentation)
Possums & gliders listed in the Advisory List of Threatened Vertebrate Fauna in Victoria 2013
Distribution maps from the Victorian Biodiversity Atlas
Mountain Pygmy-possum Burramys parvus
The Mountain Pygmy-possum is found in the Kosciusko region of NSW and the Mt Hotham High Plains of Victoria and a small population at Mt Buller. This species is actively managed but still faces threats from ski developments, foxes and cats. There is a recovery team undertaking active management including genetic rescue involving translocation of some males from the larger Mt Hotham population to Mt Buller with the aim of improving genetic diversity. Recods shown near Snowy River are old sub-fossil records.
Leadbeater's Possum Gymnobelideus leadbeateri
Leadbeater's Possum is confined to the Central Highlands of Victoria. There are sub-fossil records near the Snowy River and historical records in North East Victoria and the Westernport area where Leadbeater's Possum became extinct in 19th Century. (More about this species in the main presentation).
Squirrel Glider Petaurus norfolcensis
The Squirrel Glider is mainly found in the Murray Valley Plains. Scattered populations are also found in western Victoria including the northern Grampians, Stawell and Deep Lead area, although the population status in these areas is unknown and requires survey, particularly in light of the prolonged drought conditions in the area.
Southern Greater Glider Petauroides volans
The Southern Greater Glider is widespread in the eastern half of Victoria, west to around the Daylesford, Wombat Forest area. It is found across most of Gippsland and the North East Forests but there has been a significant decline in the Central Highlands which requires more investigation.
Eastern Pygmy-possum Cercartetus nanus
The Eastern Pygmy-possum is widespread but only abundant in the coastal areas of East Gippsland which contain Coast Banksia. The Eastern Pygmy-possum has had a significant decline in the Box-Ironbark Forests and may no longer be present. Populations are thought to be fairly stable in the Eastern Highlands, Otways, Lower Glenelg and Grampians.
Little Pygmy-possum Cercartetus lepidus
The Little Pygmy-possum is widespread in the Big Desert and parts of the Sunset Country. There are a few records from the Little Desert area. The status of this species is not well known and requires more survey as it is difficult to ascertain estimates on a species which has shifting home ranges influenced by habitat changes, particularly related to fire.
Western Pygmy-possum Cercartetus concinnus minor
The Western Pygmy-possum is more widespread than the Little Pygmy-possum being found in a wider range of habitats but it's population status is not well understood.
Key points from questions
- It is difficult to identify the two species of Feathertail Glider from remote camera images.
- All Mountain Brushtail Possums in Victoria are now considered to be Trichosurus cunninghamii More details
Targeted surveys to increase protection for Leadbeater’s Possum - Jenny Nelson, Arthur Rylah Institute, Department of Environment, Land,Water and Planning.
Jenny acknowledged the eight member team involved in this large and intense project.
Leadbeater's Possum image from Jenny Nelson's presentation.
About the Leadbeater's Possum
Leadbeater's Possum is a small non-gliding arboreal mammal with a body length of about 160 mm, weighing about 120-160 grams.
After 52 years without a sighting it was considered extinct until it was rediscovered near Marysville in 1961. It is the only mammal which occurs only in Victoria and is Victoria's faunal emblem.
- Listed under the Victoria Flora & Fauna Guarantee Act 1988.
- Considered endangered under the Victorian Threatened fauna Advisory List.
- Listed as Critically Endangered under the federal Environment Protection Biodiversity Conservation Act 1999.
- A recovery plan was first published in 1998 and is currently being revised. See Draft Recovery Plan 2016
Leadbeater's Possum is confined to a specific area of about 70 km x 80 km in Victoria's Central Highlands.
Most populations of Leadbeater's Possum occur in tall wet mountain forests (Montane Ash Forests) between 500 to 1200 m altitude. The main overstory species include Mountain Ash, Alpine Ash and Shining Gum which collectively makes up about 96% of the possums habitat. Leadbeater's Possum is also found on adjoining sub-alpine woodland at about 1300m altitude dominated by Snow Gum.
Montane Ash Forests with a dense understorey are a typical feature of Leadbeater's habitat.
Jenny said all of the primary habitat type (about 8,000 Ha) is within forests at Mt Bullfight, Lake Mountain and the Baw Baw plateau. There is also a small isolated population occurring in Lowland Floodplain Woodland dominated by Mountain Swamp Gum at Yellingbo Conservation Area.
Jenny spoke about a common feature in all three habitat types, all being dominated by smooth barked eucalypts that have long strips of shedding bark. This type of bark provides habitat for the possums food resources such as tree crickets, beetles and moths. The bark is also a major resource used to build nests in tree hollows.
Hollow bearing trees
Leadbeater's Possums live in colonies of 3 to 12 animals, they use large hollows around 30 cm in diameter mainly found in dead trees to nest and shelter during in daylight. Jenny said the Ash forests hollows don't form until trees are about 120 years of age but the type of hollows used by Leadbeater's are typically in trees that are 190 - 220 years old.
Each colony uses several nest trees within their exclusive territory of 1-3 ha which is actively defended from neighbouring colonies.
Structurally dense interlocking canopy
Leadbeater's Possum is not a gliding possum therefore their movement is restricted to running along branches and jumping from tree to tree. Forests with a dense understorey are a typical feature of Leadbeater's habitat, wattles comprise important understory for movement and feeding.
Jenny said all sites where Leadbeater's Possum occur are characterised by a cold wet climate with low summer temperatures and high summer rainfall.
The Leadbeater's Possum is particularly vulnerable to disturbances, especially in relation to the long time it takes for suitable hollows to form.
Fire: Over the last Century there has been a bushfire in the Central Highlands about once every 10 years with large hot bushfires being damaging.
Timber harvesting: about 30% of Leadbeater's Possum potential habitat range is available for harvesting.
Climate change: Altered climatic conditions, i.e. a warmer, drier climate is likely to be detrimental to the Leadbeater's Possum and also increase the risk of more frequent and sever bushfires.
Habitat decline: There has been a noticeable decline in the number of dead standing trees from the 1939 bushfires which have been providing dens for the Leadbeater's Possum. As the old trees decay they are prone to falling over.
Population fragmentation: Timber harvesting and bushfires can fragment populations.
2009 Black Saturday bushfires: Jenny said this was a significant fire for Leadbeater's Possum as 34% of its potential habitat was burnt within its range and a third of the population lost.
To-date no Leadbeater's Possums have been detected in the burnt areas despite a number of surveys in long term monitoring sites where this species was previously recorded.
Hatched area indicates burnt area. Jenny pointed out that the fire has caused further fragmentation of remaining habitat and colonies.
Leadbeater’s Possum Advisory Group ‘LPAG’
This group was established to develop recommendations to support recovery of Leadbeater's Possum whilst maintaining a viable timber industry. Thirteen recommendations were made and accepted and $11 million allocated for implementation.
Key recommendations for conservation of Leadbeater's Possum
Provide protection for known colonies by establishing 200 m radius timber exclusion zones round new and existing colonies from records within the last 15 years and new verified records.
Undertake surveys to locate new colonies for protection over 5 years which has since been fast tracked to 3 years to provide information to the Timber Industry Taskforce.
Targeted surveys in high probability areas
A model has been developed to predict strongholds post 2009 fire.
Red areas are high probability areas where there is a > 65% likelihood of possums occurring. These areas include the Baw Baw plateau and southern slopes, Toorngo plateau south of the Upper Yarra Catchment, State Forest in the vicinity of Powelltown, southern parts of the Yarra Ranges National Park and parts of Toolangi State Forest.
The survey team is targeting specific areas based on the probability model within areas identified as >65% probability of occupancy. Areas where there are likely to be clusters of records and known areas of high density records are also targeted.
To-date the occupancy model has been very effective in identifying areas where Leadbeater's are most likely to be found with 44% of surveyed sites containing Leadbeater's Possums but this in part due to the targeting of areas where possums were most likely to occur.
Surveys were also conducted on 42 coupes on the 2013-2016 Timber Release Plan with 15 Leadbeater's detected.
There is a current moratorium on timber harvesting in areas where surveys are being conducted.
Remote camera traps are extensively used. They are positioned in areas where there is well connected vegetation and where Leadbeater’s Possums are most likely to be moving. Reconyx survey cameras are placed between 3 – 36 m above ground depending on the forest type and connectivity. Bait stations are located about 2-3 metres away on an opposite branch facing the camera. Two cameras were set per site about 100 m apart and left for 2 to 4 weeks.
Images of Leadbeater's Possum. Over 180,000 images were taken during the 5,400 camera trap nights.
Analysis of data found that most detections were only on 1 of the 2 cameras per site which raises the question regarding the need to increase survey effort to increase delectability.
Assessment of the forest habitat is carried out to improve the existing habitat model and the understanding of habitat requirements, particularly as the forest is changing. Measured habitat attributes correlated with presence/abundance of Leadbeater’s Possum
- Dominant eucalypt species
- Density and form of hollow-bearing trees
- Basal area of wattle
- Extent of connectivity
Results from first year surveys (2014 -15)
The highest % of camera detections occurred in the 1978 - 2000 logging regrowth but this could be due to where the possums are foraging but not nesting.
113 sites were surveyed over five areas of the Leadbeater’s range. Leadbeater’s Possums were detected at 50 of the sites. This has enabled the creation of 50 new timber harvesting exclusion zones totalling 630 ha.
The detection of 15 records from proposed coupes highlights importance of pre-harvest surveys to protect resident colonies.
Above, example of Leadbeater's Possum sites and 200 m radius timber harvest exclusion zones, including clusters of zones at the Toorongo Plateau/Noojee. The eight sites clustered to the right of the map now form a 100 ha exclusion zone which also abuts a special protection zone thus providing greater habitat security.
2015 - 2016 survey plan
The team is aiming to survey 180 sites, again using the occupancy model as a guide but also building on existing records to identify potential clusters. Surveys will include the Rubicon, Big River, Thomson, Latrobe and Yarra State Forests to fill in gaps regarding where Leadbeater's could occur.
The team will use 3 traps per site instead of 2 traps to increase survey efficiency.
Habitat assessments will be completed with a full analysis of survey and habitat data for a major review of progress by the end of 2016.
Jenny made a particular thanks to the team involved in the project.
More information: Leadbeater's Possum web site & Interactive map
Key points from questions
Areas burnt in 2009 were mostly 1939 regrowth, these trees were probably not old enough to provide large enough den hollows. A small area of 'old growth' forest in the O'Shannassy catchment was also burnt and it is expected these dead 'old growth' trees will provide ideal denning habitat.
Survey kits are available from ARI for community groups to undertake surveys.
The survey team used a number of different models of the Reconyx survey cameras and did not find any significant difference between their effectiveness but it was stressed that high quality cameras must be used with sensitive settings.
Hollow supplementation is being trialled by ARI in conjunction with Vic Forests to increases denning habitat.
All survey records are placed on the Victorian Biodiversity Atlas.
Research to inform management and restoration works for squirrel gliders - Kylie Soanes Australian Research Centre for Urban Ecology
Kylie spoke about the process of planning research which can be used to guide and evaluate management actions. In this case 'evaluating the success of wildlife crossing structures on the Hume Freeway'.
Squirrel Gliders are sensitive to population fragmentation. The average gliding distance is 30 - 40m and gaps in the tree canopy greater than 50 m poses a difficulty for Squirrel Gilders to move through the landscape.
Improving habitat connectivity and providing corridors is a focus of Squirrel Glider management but linear infrastructure such as roads, rail and powerlines can have significant impacts on the movement of Squirrel Gliders.
Squirrel Gliders require large old trees which provided the necessary hollows for shelter and nesting. Unfortunately across much of its range the large old trees are confined to roadsides which means many populations of Squirrel Gliders are dependent on roadsides for their survival.
In some areas of Victoria Squirrel Gliders are almost exclusively confined to remnant roadside vegetation.
Roadside ecology involves trying to understand the movement of species from one side of the road to the other for food, shelter resources and gene flow, the ecological impacts of roads on wildlife and how it can be best managed.
In 2004/05 a group of researchers from Monash University, Melbourne University and VicRoads started to look at the impacts of the Hume Highway on Squirrel Glider connectivity and possible management measures. Methods to assist movement across the highway included the use of canopy bridges and glider poles as well as measuring the role of vegetation in centre median strips.
A before after controlled impact experiment was carried out in 2005 to 2007 on different crossing sites as well as a control site away from the highway with a 10 m gap between either side of the road. In 2007 five crossing structures were installed along the Hume, these were monitored between 2008 to 2012.
Evaluating Hume crossing structures
Kylie spoke about defining what the project was trying to achieve, which included;
Functional connectivity across the road
Improvements in ecological function where structures installed
Comparisons with sites that had no structures
Restoration to ‘non-impacted’ levels
A key question to be answered; Do crossing structure have to be provided to allow Gliders to cross the road?
Radio tracking studies
Before and after radio tracking was carried out on a local narrow road, vegetated median, where there was no crossing structure and where a crossing structure was installed. The study was repeated 4 years after the crossing structures were installed.
Results indicate the crossing structures have performed very well, in fact just as well as sites where remnant trees remained in the median strip. Sites where no structures were installed remained a barrier to movement.
If there is no vegetated median and no crossing structure the highway becomes a barrier to movement.
Monitoring cameras were installed on the crossing structures in 2007 & 2009 to improve detection of species movement, microchip scanners were included in the design to detect animals which had been microchiped either side of the highway, thus enabling the study of individual gliders.
Kylie said they have monitored thousands of crossings since the cameras were installed.
Kylie explained that measuring gene flow is a good means of assessing functional connectivity as it shows not only did an animal cross the road but how it integrated in with the population through reproduction.
The study involved DNA sampling of gliders either side of the road before and after the crossing structure and comparing results. It was found that with no crossing structure there was a strong genetic difference either side of the road but four years after the crossing structure was installed there was very little genetic difference which meant the populations were no longer isolated.
Combining genetic data with, microchip data and camera images Kylie said the team was able to gain an insight down to individual Squirrel Gliders, reproductive success and family structure.
Over the 7 years since crossing structures were installed there has been a measurable improvement in connectivity across wide roads and no negative consequences detected, however connectivity is not restored to 'non impacted levels'.
Kylie spoke about the need to evaluate how different crossing structure compare and to determine how many structures are needed. She also spoke about answering the question about crossing rates and the reasons why some structures are used more than others.
Kylie explained there are possibilities to use crossing structure techniques in other situations where habitat gaps are created by linear infrastructure or even across bare paddocks to connect habitats.
Kylie thought we still need to determine if roadside populations are viable in the long term even where crossings are provided and look at ways of managing roadsides so they provide valuable habitat for arboreal wildlife.
Kylie's web site: Life on the verge
Key points from questions
The issue of fox predation at the base of the structures was raised but this issue is minimised because there are a number of feeder lines connected from the structure into nearby trees. This reduces the need for animals to cross the ground on foot.
Increased predation by owls could be a problem in some landscapes but structures can be designed with shelter areas. Observations indicate animals can seek shelter under the rope bridge when being swooped by an owl.
Ascertaining the level of road kill is helpful in understanding the need for crossing structures but measuring road kill for Squirrel Gliders it is very difficult. The study found the survival rate of Squirrel Gliders was the same at the crossing sites as they were at the control sites.
There did not seem to be any detectable negative interaction between different species using the rope bridge at the same time.
Funding for new crossing structures can sometimes be factored into new road or upgraded road projects where they are large enough to have an impact on threatened species. There is no program at present to retrofit existing roads in Victoria.
General discussion key points
We should be looking at ways of incorporating federal programs on indigenous training with surveys on possums & gliders. There are opportunities for increased monitoring, installation and monitoring of nest box hollows etc. This is currently being considered for the Leadbeater's program which is a high profile species.
The building of adequately funded indigenous partnerships involved in monitoring and management should be applied to a range of other lower profile possums & gliders.
The creamed honey bait for Leadbeater's was fitted into plumbing fittings with mesh either end but contained in the fitting so as to ensure the camera could get a good image of the animal.
There should be more consideration and effort directed to retaining large trees in median strips and along roadsides.
Crossing structures are sometimes factored into the design of new infrastructure projects e.g. wide powerline or pipeline easements but rarely on existing infrastructure.
|Victoria contains a very diverse fauna of possums and gliders with 14 species, 7 of which are on Victoria's Threatened Fauna Advisory List.|
|Apart from some of the high priority species we have little knowledge of the status of possums & gliders in Victoria due to limited research.|
|Leadbeater's possum was considered extinct until it was rediscovered near Marysville in 1961. It is the only mammal which occurs only in Victoria and is Victoria's faunal emblem.|
|In 2009, 34% of Leadbeater's potential habitat was burnt within its range and a third of the population lost.|
In 2015, 50 new Leadbeater's timber harvesting exclusion zones were established totalling 630 ha.
Installation of crossing structures has resulted in a measurable improvement in Squirel Glider connectivity across wide roads with no negative consequences detected.
See notes from other SWIFFT video conferences