Petaurus Norfolcensis Research Articles

Gliding performance and its relevance to gap crossing by the squirrel glider (Petaurus norfolcensis)

Gliding mammals occur worldwide and many are subject to increasing levels of habitat fragmentation. Knowledge of their ability to cross tree-gaps by gliding is quite poor. We describe aspects of the gliding performance of the squirrel glider (Petaurus norfolcensis) based on recorded parameters of 85 glides of 73 individuals. Animals launched from a horizontal position ~1.7 m below the top of a tree and 2.3 m out from the main trunk. All but one glide was to the trunk of a tree, landing 5.7 m above the ground. Animals glided a mean of 21.5 ± 0.9 m (range 9–47 m) in a horizontal plane, with no significant difference between the sexes. Horizontal glide distance appears to reflect tree spacing where individuals were released. The mean glide angle was 28.5 ± 0.8°, with no significant difference between the sexes. We predict that trees beside roads that create a tree-gap of 20 m (two-lane road) or 43 m (four-lane road) will need to be a least 13 m and 25 m tall, respectively, to enable animals to safely glide across a road. Where trees are absent, 12-m-high wooden poles could be installed, requiring some in the median strip of four-lane roads.

Diet of the squirrel glider in a fragmented landscape near Mackay, central Queensland

We investigated the diet of the squirrel glider (Petaurus norfolcensis) from within a highly fragmented landscape in the northern (tropical) part of its geographic range where information was absent. We analysed 86 faecal samples of 53 gliders from 11 locations and obtained 97 observations of 10 gliders feeding at two locations. Pollen of Eucalyptus/Corymbia was present in 70% and Melaleuca in 20% of faecal samples. Indicators of sap feeding were present in 44% of samples and seeds were present in 14% of samples. Invertebrates, mostly moth larvae, were present in 54% of samples. Observations of gliders feeding revealed that the main food types were invertebrates (36% of observations), nectar and pollen (27% of observations) and sap (26% of observations) of five tree species. Differences in the use of the major food types revealed by the two methods of diet analysis partly reflect site-based differences. Qualitatively, the diet was similar to that described in southern Australia, with confirmation that sap may be important at some locations. Our results reveal the contribution that different tree species make to the diet, which should be used to guide habitat restoration for the squirrel glider in this fragmented landscape.

Vocal behaviour of the squirrel glider (Petaurus norfolcensis)

We describe the vocal behaviour of the squirrel glider (Petaurus norfolcensis) from 465 h of observation across five sites in north-east New South Wales and south-east Queensland. A monosyllabic or polysyllabic nasal grunt was the most frequent call (56% of 208 calls); it ranged from single calls to sequences of up to 20-min duration (mean 2.1 min ± 0.6, s.e.) and was heard on 34% of nights (n = 83) at two sites. The rate of the nasal grunt showed a positive relationship with population density at one site. The nasal grunt was typically made when conspecifics were near the caller, but responses were infrequent (7% of observations). Call playback produced no discernable change in call response. The nasal grunt appears to regulate individual spacing by facilitating mutual avoidance, a function hypothesised to be an evolutionary precursor to the use of calls in territorial defence. Threatening calls were the next most common vocalisation (17% of calls) and were accompanied by scuffles and/or chases. They were also used when gliders were preyed upon and during animal handling. The calling behaviour of the squirrel glider confirms the importance of vocal communication among petaurid gliders.

Can wooden poles be used to reconnect habitat for a gliding mammal?

This study describes the first attempt in the world to use timber poles to provide habitat connectivity for a gliding mammal. The Australian squirrel glider Petaurus norfolcensis is a small tree-dependent gliding marsupial whose habitat is characterized by ongoing fragmentation. We installed five 12 m-high poles across a 70 m gap that had existed between two woodland remnants for over 45 years. Our aims were to determine whether animals were able to use the poles for gliding and to travel between the remnants. We released 22 animals onto the poles at night. All animals readily climbed and glided from the poles. Five individuals successfully glided pole-to-pole on initial release. Squirrel gliders were captured in both remnants only after pole erection and two were trapped on poles. One radio-collared individual was observed gliding pole-to-pole to reach the non-home remnant where it foraged on two separate nights. Petaurus hair was detected on several poles by hair-sampling devices in four separate periods up to 12 months after radio-tracking and trapping had ceased. Our observations suggest that wooden poles may assist gliding mammals to traverse open areas between habitat patches and have the potential to be used as a rapid technique to reconnect severed habitat.

The characteristics of den trees used by the squirrel glider (Petaurus norfolcensis) in temperate Australian woodlands

Being able to recognise critical habitat features such as nesting and denning sites is essential for wildlife conservation. It is particularly true for the den trees of species threatened by habitat loss, such as the squirrel glider (Petaurus norfolcensis). Measurements of 146 den trees of the squirrel glider were made in fragmented woodlands of the South-west Slopes of New South Wales and data compared with random trees to quantify the key characteristics of den sites. The likelihood of use as a den tree increased with increasing numbers of visible tree hollows and tree size. Dieback was also a positive indicator of den use. However, when visible hollows within a tree are abundant, dieback-free trees were preferred. Measures of den tree context such as basal area, the number of neighbouring large trees and distance to the next nearest tree, were also found to be important determinants of the likelihood of usage. The above variables were combined into a multiple regression model. The squirrel glider favoured particular Eucalyptus species and some broader eucalypt groups. We believe such variations were most likely due to interspecific differences in hollow development and dieback among the various groups, rather than bark type, a factor previously cited as an important determinant of den tree usage. The ‘best’ model had high negative predictive power, suggesting it would be useful for identifying (1) trees that could be felled without a loss of this critical habitat resource (e.g. at development sites) and (2) areas unsuitable for potential squirrel glider relocation or habitat enhancement. Squirrel gliders show preference for a combination of tree and tree context features in selecting den trees. Understanding these features will help managers enhance and protect denning resources for this species.

The characteristics of squirrel glider (Petaurus norfolcensis) den trees in subtropical Australia

Effective management of tree-hollow-dependent wildlife requires a sound knowledge of the characteristics of the trees used for shelter or breeding. We used radio-tracking to identify the den trees of squirrel gliders (Petaurus norfolcensis) in south-east Queensland (Qld) and north-east New South Wales (NSW). Squirrel gliders used dead trees as well as 13 species of living tree for dens across the two locations. Dead trees accounted for a large percentage of dens (54% of 48 dens in Qld, and 50% of 18 dens in NSW) despite comprising only 3–10% of the forest (trees >20 cm diameter at breast height (dbh)) at each location. This preference is largely due to dead trees being more likely to contain hollows, accounting for 26–44% of available hollow-bearing trees. Mean den tree size (dbh) was 48.9 ± 2.4 cm in Qld and 62.8 ± 5.6 cm in NSW. Den entrance height averaged 6.8 ± 1.2 m in Qld and 11.9 ± 1.3 m in NSW. Fissures in the trunk and holes in branches were the most common of six hollow types used. At one location branch end hollows were ignored relative to their availability. Den entrances varied in size (2.5–12 cm wide) but most were ≤5 cm in diameter. Entrance size of hollows appears to be the hollow attribute of most importance to squirrel gliders. Monitoring of these den trees over several years revealed the collapse of three dead den trees at each location, which is equivalent to an annual loss of 3% of den trees. Further research is needed to determine whether this will lead to a future shortage of den trees.

Locomotor performance in the squirrel glider, Petaurus norfolcensis, and the sugar glider, Petaurus breviceps.

We evaluated gliding, climbing, and running performance by Petaurus norfolcensis in southern Queensland, Australia and by a laboratory colony of P. breviceps. The data were used to test the hypothesis that gliding locomotion is energetically less expensive than quadrupedal transport, and is thus a reasonable explanation for the evolution of gliding. Gliding locomotion is less expensive than quadrupedal transport only when P. norfolcensis is able to climb to a launch point rapidly. We found no conditions in which gliding was less expensive than quadrupedal transport for P. breviceps. We compare these results with published data on North American flying squirrels, and argue that gliding locomotion in mammals may be a solution to foraging optimisation problems such as decreasing travel time between patchy food resources and increasing foraging velocity.

Home Range of the Australian Squirrel Glider, Petaurus norfolcensis (Diprotodontia)

Knowledge of the home range of threatened species is basic to their management and conservation. We describe the home range of the squirrel glider (Petaurus norfolcensis), a threatened marsupial, in the central part of its geographic range in eastern Australia. Thirteen individuals belonging to 6 monogamous social groups were radiotracked for 2–9 months. The adaptive kernel (AK95%) estimate reached an asymptote at approximately 30 locations, giving a mean area of 6.2 ha 6 0.6 SE for the 9 gliders with .30 locations. The AK50% averaged 0.9 6 0.2 ha, indicating that small core parts of the home range were used intensively. Home ranges of group members (AK95%) showed a high degree of overlap (77%) and when combined averaged 6.7 6 1.0 ha. They overlapped substantially (50%) with adjacent glider groups but core areas (AK50%) within them overlapped by only 12%. Two of 5 available habitats were well represented in all group home ranges. Habitat dominated by coast banksia (Banksia integrifolia), a key winter nectar food resource, was overrepresented compared to its availability. Conservation measures for this species involving habitat retention or restoration must be informed by recognition of what comprises a preferred local habitat and its distribution.

Time-budget and feeding behaviour of the squirrel glider (Petaurus norfolcensis) in remnant linear habitat

The squirrel glider (Petaurus norfolcensis) occurs in forests and woodlands in eastern Australia. In Victoria it is now largely restricted to small, fragmented areas and is considered endangered. In this study, the time-budget, feeding behaviour and related habitat use of the squirrel glider were investigated in a linear remnant of roadside vegetation near Euroa, Victoria. Timed observations of three males and three females, fitted with radio-collars, were made in each of four seasons. Gliders were observed for a total of 53.2 h, during which they devoted 72% of time to foraging activities. Grooming accounted for 16% of observation time. Exudates associated with homopterous insects were the primary food items consumed throughout the year. Arthropods, nectar and pollen, and Acacia gum formed the remainder of the diet. The proportion of time devoted to harvesting these food items showed marked seasonal variation. The primary dependence on homopterous insect exudates in this study area contrasts with other investigations at sites of greater floristic diversity where nectar and pollen were the most important dietary resources. This highlights the need to obtain ecological information from the range of habitats occupied by a species. Large trees are a vital habitat component of remnant linear vegetation in this study area, providing gliders with critical foraging resources. Retention of such trees is essential for the longevity of glider populations.

Do feathertail gliders show a preference for nest box design?

Although nest boxes have considerable application in the research and management of hollow-using arboreal marsupials, few studies have assessed whether species show a preference for particular nest box designs. This study aimed to determine whether the feathertail glider (Acrobates pygmaeus) showed a preference when offered four different designs, each of which had been used in earlier studies. We established one of each design in 45 plots across five locations, spanning north-east New South Wales and south-east Queensland. Feathertail gliders used 34 nest boxes at four locations but avoided a medium-sized rear-entry box with a 45-mm-diameter entrance. No clear preference was shown for three designs with narrow (≤25 mm) entrances. Feathertail gliders used 15 small rear-entry boxes, 10 large slit-entrance boxes and 9 wedge-shaped bat boxes. A slight preference was shown by breeding groups to occur in the non-wedge boxes compared with the wedge boxes. Squirrel gliders (Petaurus norfolcensis) used 51% of medium rear-entry boxes at four locations. This may account for the avoidance of this box design by feathertail gliders at these locations. Breeding and prolonged use of nest boxes by resident feathertail gliders and squirrel gliders at two locations in eucalypt plantations suggest that nest boxes can support local populations of arboreal marsupials where tree hollows are absent or scarce.

A new trap design for capturing squirrel gliders and sugar gliders.

A trap constructed from 90 mm PVC stormwater pipe and attached to the trunk of trees was more effective for trapping sugar gliders (Petaurus breviceps) and squirrel gliders (P. norfolcensis).

Road upgrade in Victoria a filter to the movement of the endangered Squirrel glider (Petaurus norfolcensis): Results of a pilot study

Road upgrade in Victoria a filter to the movement of the endangered Squirrel glider (<i>Petaurus norfolcensis</i>): Results of a pilot study

Faecal steroid analysis and urinary cytology of the squirrel glider (Petaurus norfolcensis)

Non-invasive techniques were used to investigate the reproductive biology of captive squirrel gliders (Petaurus norfolcensis) for 3 months during the breeding season. The squirrel glider is a medium-sized marsupial glider of eastern Australia and is currently listed as a threatened species as a result of habitat destruction and fragmentation. Urinary cytology was used to determine the timing of oestrus, and the presence of sperm confirmed mating. Progesterone and oestradiol-17β were identified in faecal samples via thin-layer chromatography, and were used to characterise the reproductive cycle. Reproductive activity was observed in three of four females, with births occurring during June and July. A preoestrus increase in faecal oestradiol-17β was detected in a single female, whilst significant increases occurred post partum (±2 days) in two of four females, suggesting that the squirrel glider may undergo a postpartum oestrus. Faecal progesterone profiles showed low concentrations before oestrus and significantly elevated concentrations after oestrus, which were maintained throughout pregnancy. Parturition coincided with a decrease in progesterone concentrations (±1 day). This study successfully used non-invasive monitoring of urinary cytology and faecal steroids to define luteal and gestational length as 16–17 days, a previously unpublished detail.

Using ecological studies to understand the conservation needs of the squirrel glider in Brisbane?s urban forest-remnants.

This paper provides an overview of our current ecological research on squirrel gliders (Petaurus norfolcensis) living in forest-remnants within an urban matrix in south-east Queensland. We have conducted population censuses and behavioural observations primarily in one 60-ha remnant. The number of tagged gliders (minimum number known alive) in this remnant varied from 75 in 2002 when flowering trees were abundant, to 33 the following year when flowering was poor. Poor flowering led to a delay in breeding and a decline in the probability of glider survival. Feeding observations on gliders in the year of abundant flowering revealed that almost 50% of the diet was comprised of nectar and pollen derived from 10 tree species. A more detailed focus on flowering and its influence on population dynamics at several sites would be of considerable value in understanding the population ecology of this species. We assessed the viability of the subpopulations of P. norfolcensis distributed across the various remnants to allow identification of management actions that may improve viability. Viability analyses under various scenarios suggest that our focal metapopulation will have a high likelihood of extinction within the next 100 years. Predictions of population viability are sensitive to changes in life history parameter estimates. Thus, current field-work has been directed by the need for more precise empirical values. The remnants containing our metapopulation need to be functionally linked to larger nearby remnants to enable glider dispersal among sites. We need a better understanding of glider dispersal behaviour and how permeable the urban matrix might be for P. norfolcensis. Arterial roads and freeways sever connections between many remnants, requiring novel approaches to corridor provision. Future research should examine how habitat quality of the remnants changes over time due to tree die-back and wind-throw. We are investigating the potential role of nest boxes to facilitate glider dispersal and to supplement the availability of den trees. The findings of our studies should contribute to a greater understanding of the general conservation requirements of P. norfolcensis.

An extension to the known distribution of the squirrel glider Petaurus norfolcensis in Australia.

In South Australia the squirrel glider (Petaurus norfolcensis) was only known from one museum specimen from Bordertown collected in 1939. During a genetic study of Petaurus breviceps, using nucleotide sequence variation in mitochondrial DNA, two additional museum specimens collected near Bordertown, were identified as P. norfolcensis and recent field investigations in the area provided two additional specimens. The nearest locality for P. norfolcensis is the eastern side of the Grampians, several hundred kilometers east.

Longevity in wild populations of the squirrel glider Petaurus norfolcensis.

Petaurus norfolcensis were trapped between December 1996 and April 2005 at 3 sites in south-eastern Australia. In 2005 nine individuals marked in previous years were captured. Age estimates at first capture were based on body mass, tooth wear and pouch condition. Most recaptured individual were propertly assigned to the correct age category (&gt;3 years), but the age of 2 were underestimated. This indicates uncertainty in using physical characteristics, chiefly wear of upper incisors, to estimate age in P. norfolcensis.One individual captured in 2005 was over 7 years 9 months old. This compares to captive P. breviceps and P. australis records of 9 years and 16 years respectively.

Fauna habitat modelling and mapping: A review and case study in the Lower Hunter Central Coast region of NSW

Abstract Habitat models are now broadly used in conservation planning on public lands. If implemented correctly, habitat modelling is a transparent and repeatable technique for describing and mapping biodiversity values, and its application in peri‐urban and agricultural landscape planning is likely to expand rapidly. Conservation planning in such landscapes must be robust to the scrutiny that arises when biodiversity constraints are placed on developers and private landholders. A standardized modelling and model evaluation method based on widely accepted techniques will improve the robustness of conservation plans. We review current habitat modelling and model evaluation methods and provide a habitat modelling case study in the New South Wales central coast region that we hope will serve as a methodological template for conservation planners. We make recommendations on modelling methods that are appropriate when presence‐absence and presence‐only survey data are available and provide methodological details and a website with data and training material for modellers. Our aim is to provide practical guidelines that preserve methodological rigour and result in defendable habitat models and maps. The case study was undertaken in a rapidly developing area with substantial biodiversity values under urbanization pressure. Habitat maps for seven priority fauna species were developed using logistic regression models of species‐habitat relationships and a bootstrapping methodology was used to evaluate model predictions. The modelled species were the koala, tiger quoll, squirrel glider, yellow‐bellied glider, masked owl, powerful owl and sooty owl. Models ranked sites adequately in terms of habitat suitability and provided predictions of sufficient reliability for the purpose of identifying preliminary conservation priority areas. However, they are subject to multiple uncertainties and should not be viewed as a completely accurate representation of the distribution of species habitat. We recommend the use of model prediction in an adaptive framework whereby models are iteratively updated and refined as new data become available.

Feeding behaviour of the squirrel glider in remnant habitat in Brisbane.

The diet of the squirrel glider (Petaurus norfolcensis) was studied in a 45 ha forest remnant within an urban area close to Brisbane in south-east Queensland. Qualitative observations of feeding behaviour were conducted during each of 10 months between May 2002 and April 2003, on over 27 P. norfolcensis from at least 10 social groups. Four different feeding behaviours were recorded from 750 observations. Feeding from flowers accounted for 48% of the diet. Nectar and pollen were derived from 10 overstorey tree species, though forest red gum (Eucalyptus tereticornis) dominated because of its high abundance and protracted flowering period. Honeydew and lerp feeding accounted for 15% and 2% of all observations, respectively. Searching for arthropods accounted for 35% overall and occurred in 20 different tree species, where a range of substrates was used. Brushbox (Lophostemon confertus) was the most important; it was used in all seasons and accounted for 49% of these observations. These results contrast with assessment of the diet of P. norfolcensis at other sites where a greater range of broad food types was used. This may reflect the disturbed quality of the habitat at our site. However, these observations confirm the importance of eucalypt nectar in the diet of this species.

Avian psychology and communication.

The evolution of animal communication is a complex issue and one that attracts much research and debate. 'Receiver psychology' has been highlighted as a potential selective force, and we review how avian psychological processes and biases can influence the evolution and design of signals as well as the progress that has been made in testing these ideas in behavioural studies. Interestingly, although birds are a focal group for experimental psychologists and behavioural ecologists alike, the integration of theoretical ideas from psychology into studies of communication has been relatively slow. However, recent operant experiments are starting to address how birds perceive and respond to complex natural signals in an attempt to answer evolutionary problems in communication. This review outlines how a psychological approach to understanding communication is useful, and we hope that it stimulates further research addressing the role of psychological mechanisms in signal evolution.

How effective is spotlighting for detecting the squirrel glider?

Recent studies have questioned the reliability of spotlighting to detect certain species of arboreal marsupial or to provide an index of population size. This study assesses the reliability of transect spotlighting to detect the squirrel glider (Petaurus norfolcensis) by comparison with grid trapping. Trapping was conducted for 3–4 nights, approximately every second month during 2001. Spotlighting was conducted monthly along four transects through the grid. The two techniques combined showed that at least 7–11 gliders were present during most of 2001 in the spotlit area. Trapping detected 1–4 individuals per census within this area. Only one was detected during 4 of 6 census periods. Spotlighting detected 2–4 individuals during 9 of 12 census periods. We estimate that spotlighting surveys detected an average of 25% of the squirrel gliders present; trapping surveys detected an average of 21% of gliders. We conclude that spotlighting under suitable conditions by experienced personnel was equally effective as trapping in detecting and providing a population index of squirrel gliders at our site. The generality of this finding must be tested at other sites. A review of published studies involving transect spotlighting of arboreal marsupials found that most incorporated repeat traverses of transects to improve detection, and standardised abundance or density for comparing site categories. Thus, the conclusions of these studies should not be affected by recognition that spotlighting detects only a proportion of the actual population size of a given species. We recommend further studies to assess detection of arboreal marsupials by spotlighting surveys.