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Tree hollows are an important landscape resource used by fauna for shelter, nesting, and predator avoidance. In fire-prone landscapes, wildfire and climate may impact hollow dynamics; however, assessments of their concurrent impacts are rare. We conducted a field survey at 80 sites in the Sydney Basin bioregion (Australia) to understand how fire frequency, fire severity, mean annual temperature, and mean annual precipitation concurrently impacted the site-density of small- (<5 cm entry width), medium- (5–10 cm entry width) and large-size (>10 cm entry width) tree hollows and tree basal scars (which mediate hollow formation via invertebrate access to heartwood), when tree-size and dead/live status were considered. A unimodal relationship occurred between medium- and large-sized hollow densities and fire frequency and severity, respectively, with hollow densities greatest at intermediate frequencies/severities. Increases of 1.82, 1.43, and 1.17 hollows per site were observed between the 1 (reference) and 2, 2 and 3, and 3 and >3 fire frequency categories. Increases of 1.26, 1.75 and 0.75 hollows per site were observed between the low (reference) and moderate, moderate and high, and high and very high fire severity categories. Fire severity was also positively associated with basal scar density, with increases of 2.52, 8.15, and 8.47 trees per site between the low (reference) and moderate, moderate and high, and high and very high categories. A weak positive and stronger negative association was observed between mean annual temperature and small-sized hollow and basal scar density, respectively. Dead and medium-sized tree density was positively associated with medium-sized hollow and basal scar tree density, respectively. Collectively, our results suggest that wildfires, and in some cases climate, have diverse and size-specific impacts on tree hollow and basal scar density. Our results imply that fire regimes that allow for moderately severe wildfire will promote larger-sized tree hollows, which are a limiting resource for many fauna species. [ABSTRACT FROM AUTHOR]

Redressing the paucity of tree hollows is essential for conservation of hollow‐dependent fauna in many landscapes around the world. We describe a method of accelerating availability of natural hollows in regenerating landscapes by mechanically creating entrances in tree stems that have existing voids or internal decay but have not yet developed entrances. We trialed this method in woodland and forest of south‐eastern Australia in 39 stems in the closely related tree genera Eucalyptus and Angophora. Exploratory drilling of 10‐mm diameter holes was used to detect the presence of internal decay or voids. We then drilled 40‐, 65‐, or 90‐mm diameter entrance holes, depending on the size of the potential cavity, 2.4–4.8 m above ground level. Camera traps showed that drilled entrances were investigated or used within hours of creation. A diverse suite of invertebrates, reptiles, mammals, and birds were recorded entering or leaving entrances, including threatened species. All 39 holes were used by animals with up to six vertebrate taxa using some entrances. Two bird species excavated material from within cavities, and three species of marsupial were recorded taking nesting material into the cavities. This trial provides evidence that adding entrances to currently inaccessible internal cavities in trees has potential to accelerate development of habitat for hollow‐dependent fauna, particularly in regenerating vegetation. [ABSTRACT FROM AUTHOR]

Cryptococcosis is a fungal infection caused by members of the Cryptococcus gattii and C. neoformans species complexes. The C. gattii species complex has a strong environmental association with eucalypt hollows (particularly Eucalyptus camaldulensis), which may present a source of infection. It remains unclear whether a specific mycobiome is required to support its environmental survival and growth. Conventional detection of environmental Cryptococcus spp. involves culture on differential media, such as Guizotia abyssinica seed agar. Next‐generation sequencing (NGS)‐based culture‐independent identification aids in contextualising these species in the environmental mycobiome. Samples from 23 Australian tree hollows were subjected to both culture‐ and amplicon‐based metagenomic analysis to characterize the mycobiome and assess relationships between Cryptococcus spp. and other fungal taxa. The most abundant genera detected were Coniochaeta, Aspergillus, and Penicillium, all being commonly isolated from decaying wood. There was no correlation between the presence of Cryptococcus spp. in a tree hollow and the presence of any other fungal genus. Some differences in the abundance of numerous taxa were noted in a differential heat tree comparing samples with or without Cryptococcus‐NGS reads. The study expanded the known environmental niche of the C. gattii and C. neoformans species complexes in Australia with detections from a further five tree species. Discrepancies between the detection of Cryptococcus spp. using culture or NGS suggest that neither is superior per se and that, rather, these methodologies are complementary. The inherent biases of amplicon‐based metagenomics require cautious interpretation of data through consideration of its biological relevance. [ABSTRACT FROM AUTHOR]

• Red-tailed Black-Cockatoos select nest hollows primarily at the hollow and landscape scales. • Cockatoos prefer hollows that are deep and have wide floors. • They prefer hollows located close to ephemeral and permanent drink sites. • Hollow availability for cockatoos is constrained both by suitable hollows and their proximity to water. • The number of suitable hollows is likely to decline in the future due to declining rainfall in the region. Conserving wide-ranging species is challenging and requires an understanding of resource selection at multiple spatial scales, including how functional resources interact. Understanding this interaction is likely to be particularly important if resources are rare, such as tree hollows, or likely to change into the future under climate change, such as water availability and distribution. We examined nest selection by Karak (Calyptorhynchus banksii naso), a threatened obligate tree hollow nester endemic to south-western Australia, globally one of the regions most affected by climate change. We aimed to identify factors influencing nest hollow selection at multiple spatial scales including interactions between functional resources. We found that nest selection occurred primarily at the hollow scale, with deeper, higher hollows selected, and at the landscape scale, with hollows closer to ephemeral and permanent drink sites selected. The preference for specific types of hollows indicated that suitable hollows are likely to be scarce in the landscape and that management prescriptions need to be developed to maintain the supply of suitable hollows. Maintenance of drink sites in an area experiencing significant declines in rainfall will require more novel management prescriptions, which could potentially include the provision of artificial drink sites. Overall, our study demonstrated the importance of understanding interactions between functional resources at large spatial scales for the effective conservation of wide-ranging species. [ABSTRACT FROM AUTHOR]

Tree cavities are an important shelter site for a variety of vertebrate species, including birds, reptiles and mammals. Studies indicate that in most taxa favoured tree hollows are those in larger trees and higher from the ground, generally thought to be related to decreased predation risk and a more optimal thermal environment. However, neither of these ideas has been tested definitively. Here, we investigate the microclimate of daytime den sites in tree hollows of common brushtail possums in tropical northern Australia. We compare tree and hollow characteristics of dens known to be used by possums, and those not known to be used, to determine whether possums choose trees with microhabitats with a more favourable daytime microclimate. Possums chose to den in tree hollows which were on average 1.6 °C cooler during the day, and were more buffered from temperature extremes, than other potential den locations. Important factors explaining daytime temperatures between hollows included height of the hollow, entrance width and tree diameter. Tropical arboreal marsupials have been identified as being particularly vulnerable to climate change and there are calls to identify and preserve natural refuges, such as tree hollows, which could buffer them from extreme temperatures. Our results highlight the value of older, larger hollow-bearing trees as refuges from extreme temperature, the importance of which may become critical for some temperature-sensitive species under the combined effects of continuing habitat loss and climate change. [ABSTRACT FROM AUTHOR]

• Tree hollows carved by chainsaws have potential to restore degraded forest habitat. • Two mammal species were detected more often in carved hollows than in nest boxes. • Tree species differed in their response to carved hollows and inserted faceplates. • Some tree species had relatively rapid growth of bark over faceplates. • Further study of changes in carved hollow condition is required. Constructing hollows or cavities in trees with chainsaws is an emerging approach to manage hollow-dependent species in hollow depleted landscapes. Small-scale experiments are required to refine this approach before implementing on a broad scale. We addressed two questions: i) are chainsaw hollows used by the regionally threatened brush-tailed phascogale (Phascogale tapoatafa) and the non-threatened sugar glider (Petaurus notatus) , ii) do chainsaw hollows retain their integrity over time. We paired 45 chainsaw hollows with nest boxes of equivalent internal dimensions in southeastern Australia and inspected these on 20 occasions over 2.5 years. Camera traps revealed phascogales visited some cavities within hours of installation and monthly inspections revealed rapid uptake of these hollows by both target species. Overall, phascogales and sugar gliders used 32% and 84% of the chainsaw hollows respectively, and 21% and 82% of the nest boxes. We used multi-method occupancy to compare detection within the two types of cavities. Detection models that included cavity type had more support than those without. Detection of both species was substantially higher in the chainsaw hollows compared to the nest boxes. Over the 2.5-year monitoring period the faceplates of some chainsaw hollows showed signs of deformity. Callous regrowth over the faceplate was pronounced on some trees suggesting the need for periodic maintenance. Our study confirms the potential of chainsaw hollows to restore habitat for hollow-dependent mammals but highlights periodic maintenance is likely to be a feature of this approach as it is with nest boxes. [ABSTRACT FROM AUTHOR]