Comparison of home range size, habitat use and the influence of resource variations between two species of greater gliders (Petauroides minor and Petauroides volans).

Knowledge of the spatial requirements of a species is fundamental to understanding its environmental requirements. However, this can be challenging as the size of a species' home range can be influenced by ecological factors such as diet and size-dependent metabolic demands, as well as factors related to the quality of their habitat such as the density and distribution of resources needed for food and shelter. Until recently, the genus Petauroides was thought to include only a single species with a widespread distribution across eastern Australia. However, a recent study has provided genetic and morphological evidence supporting Petauroides minor as a distinct northern species. Previous studies have focused on the ecology of P. volans, but there has been inadequate research on P. minor. Data on home range and habitat use were obtained for both species using a combination of techniques including GPS collar locations, radiotelemetry, and spotlighting and comparisons were made using consistent methodology. Home range sizes of P. minor (4.79 ha ± 0.97 s.d., KUD .95) were significantly larger than those of P. volans (2.0 ha ± 0.42 s.d., KUD .95). There were no significant differences between male and female home range sizes in either species. Both species showed site-specific preferences for tree species and for larger diameter trees for both forage and shelter. Tree size and biomass/ha were significantly greater in the P. volans study sites than the P. minor study sites and there was a negative correlation between home range size and eucalypt biomass. Larger home range size is likely driven by the substantial differences in biomass between northern (tropical) and southern (temperate) eucalypt-dominated habitats affecting the quality and quantity of resources for food and shelter. Understanding landscape use and habitat requirements within each species of Petauroides can provide important information regarding limiting factors and in directing conservation and management planning.

Elevation, disturbance, and forest type drive the occurrence of a specialist arboreal folivore.

Quantifying the factors associated with the presence and abundance of species is critical for conservation. Here, we quantify the factors associated with the occurrence of the Southern Greater Glider in the forests of the Central Highlands of Victoria, south-eastern Australia. We gathered counts of animals along transects and constructed models of the probability of absence, and then the abundance if animals were present (conditional abundance), based on species' associations with forest type, forest age, the abundance of denning sites in large old hollow-bearing trees, climatic conditions, and vegetation density. We found evidence of forest type effects, with animals being extremely uncommon in Alpine Ash and Shining Gum forest. In Mountain Ash forest, we found a negative relationship between the abundance of hollow-bearing trees and the probability of Southern Greater Glider absence. We also found a forest age effect, with the Southern Greater Glider completely absent from the youngest sites that were subject to a high-severity, stand-replacing wildfire in 2009. The best fitting conditional abundance model for the Southern Greater Glider included a strong positive effect of elevation; the species was more abundant in Mountain Ash forests at higher elevations. Our study highlights the importance of sites with large old hollow-bearing trees for the Southern Greater Glider, although such trees are in rapid decline in Mountain Ash forests. The influence of elevation on conditional abundance suggests that areas at higher elevations will be increasingly important for the conservation of the species, except where Mountain Ash forest is replaced by different tree species that may be unsuitable for the Southern Greater Glider.

Food intake: an overlooked driver of climate change casualties?

Reduced voluntary food intake is a common response of endotherms to warmer temperatures. However, the implications of this are rarely considered for wild animals exposed to higher temperatures caused by climate change. We provide a conceptual model to demonstrate the potential consequences of elevated temperatures on food intake and survival.

Genetic evidence supports three previously described species of greater glider, Petauroides volans, P. minor, and P. armillatus.

The identification and classification of species are essential for effective conservation management. This year, Australia experienced a bushfire season of unprecedented severity, resulting in widespread habitat loss and mortality. As a result, there has been an increased focus on understanding genetic diversity and structure across the range of individual species to protect resilience in the face of climate change. The greater glider (Petauroides volans) is a large, gliding eucalypt folivore. This nocturnal arboreal marsupial has a wide distribution across eastern Australia and is considered the sole extant member of the genus Petauroides. Differences in morphology have led to suggestions that the one accepted species is actually three. This would have substantial impacts on conservation management, particularly given a recent history of declining populations, coupled with extensive wildfires. Until now, genetic evidence to support multiple species has been lacking. For the first time, we used DArT sequencing on greater glider tissue samples from multiple regions and found evidence of three operational taxonomic units (OTUs) representing northern, central and southern groups. The three OTUs were also supported by our morphological data. These findings have important implications for greater glider management and highlight the role of genetics in helping to assess conservation status.

The distribution and abundance of an unusual resource for koalas (Phascolarctos cinereus) in a sodium-poor environment.

Environmentally available sodium tends to decrease with increasing elevation, and sodium resources in these sodium-poor environments are critical for the survival of herbivores. Eucalypt leaves in the subalpine Monaro region of NSW, Australia contain much less sodium than eucalypt leaves at lower elevations, and subalpine koalas obtain this much needed resource by eating the bark from some Eucalyptus mannifera trees. To better understand the availability of salty-barked trees, we searched for evidence of koala bark chewing at 100 randomly generated locations in the region. We found 318 E. mannifera trees with koala chew marks. We also analysed sodium concentrations in the bark of three unchewed E. mannifera trees from each site to determine whether there were trees with high bark sodium content that had not yet been utilized by koalas. Although 90% of unchewed trees had sodium concentrations less than 225.4 mg.kg-1 DM, some unchewed trees contained high sodium concentrations (up to 1213.1 mg.kg-1 DM). From the random survey, we can extrapolate that 11% of trees in this area have bark sodium above 300 mg.kg-1 DM, which is based on the concentration of bark sodium observed in at least moderately chewed trees. We would expect to find 0.24 of these trees per 200 m2, or 720,000 salty-barked trees in the 30 km by 20 km study area. Bark chewing by koalas is widespread in the area, and trees with salty bark are more common than initially thought. We discuss correlations with the occurrence of salty-barked trees and other landscape attributes; however, questions remain about why some E. mannifera trees have much more bark sodium than others. Studies such as this one should be expanded to identify sodium resources and their availability for other herbivorous species, since many are predicted to move to higher elevations in response to climate change.

Occurrence and distribution of unsubstituted B-ring flavanones in Eucalyptus foliage.

A group of plant specialised metabolites (PSMs) collectively known as unsubstituted B-ring flavanones (UBFs) have previously been found in the foliage of some species from the genus Eucalyptus L'Hér. (Myrtaceae), specifically from the subgenus Eucalyptus (monocalypts). Captive feeding studies using artificial diets suggest that these compounds may potentially influence the feeding preferences of marsupial folivores, such as koalas. Understanding natural variation in the composition and concentration of UBFs in eucalypt foliage is a first step to deciding whether, through their effects on herbivory, they might have broader effects on ecosystem dynamics. We used ESI-LCMS/MS and HPLC to characterise and quantify UBFs in 351 individual trees from 25 monocalypt species. We found large variation in the total UBF concentration both between and within species. For example, the mean concentration of UBFs in Eucalyptus muelleriana was 0.2 mg g-1 dry wt, whereas it was 105.7 mg g-1 dry wt, with a range of 78.2-141.3 mg g-1 dry wt, in Eucalyptus mediocris. Different eucalypt species contained different subsets of ten UBFs, and three species showed potential chemotypic variation between individuals within species. Our results suggest that UBFs naturally vary between monocalypt species and individuals at concentrations that could realistically be expected to affect the feeding dynamics of marsupial eucalypt folivores. UBFs could be measured relatively rapidly and cheaply in future studies using near-infrared reflectance (NIR) spectroscopy, as we were able to successfully predict the total UBF concentration of samples from their NIR spectra, with an r2 value of 0.98 and a standard error of prediction (SEP) of 6.07. This work further solidifies NIR spectroscopy as a powerful tool enabling ecologists to analyse the chemical composition of large numbers of samples.

Foliage chemistry influences tree choice and landscape use of a gliding marsupial folivore.

The chemical quality of forage may determine landscape use and habitat quality for some herbivorous species. However, studies that investigate the relationship between foliar chemistry and foraging choices in wild vertebrates are rare. Petauroides volans (the greater glider) is unique among Australian marsupial folivores because it glides. It also frequently consumes foliage from both major Eucalyptus subgenera, Eucalyptus (common name "monocalypt") and Symphyomyrtus (common name "symphyomyrtle"), which differ markedly in their foliar chemistry. Such differences are thought to be a product of co-evolution that also led to guild-specific plant secondary metabolite (PSM) specialization among other marsupial eucalypt folivores. To explore whether foliar chemistry influences tree use, we analyzed foliage from eucalypt trees in which we observed P. volans during a radio tracking study and from eucalypt trees in which animals were never observed. We used a combination of chemical assays and near infrared spectrophotometry (NIRS) to determine concentrations of nitrogen (N), in vitro available nitrogen (AvailN), and in vitro digestible dry matter (DDM) from foliage sampled from the monocalypt and symphyomyrtle species, and total formylated phloroglucinol compounds (FPCs) and sideroxylonals (a class of FPCs) from the symphyomyrtle species (FPCs do not occur in monocalypts). Tree size and spatially-dependent, intraspecific variations in sideroxylonals and DDM concentrations in the symphyomyrtle foliage and of N, AvailN, and DDM in the monocalypt species were important indicators of tree use and habitat suitability for P. volans. The results i) demonstrate that guild-specific PSMs do not always lead to guild-specific foraging; ii) provide a compelling co-evolutionary case for the development of gliding in P. volans; and iii) have implications for the management and conservation of this and other folivorous species.