Suchergebnisse

The roosting and foraging ecology of the golden-tipped bat (Kerivoula papuensis) was studied by radio-tracking on the south coast of New South Wales. Despite a previous scarcity of records, 16 bats were harp-trapped during spring and summer, of which 11 were radio-tracked. Roost types (n = 33 roosts over 48 roost days) were the suspended nests of yellow-throated scrubwrens (Sericornis citreogularis) (50%), nests of brown gerygone (Gerygone mouki) (27%), beneath hanging moss on tree trunks (21%) and in foliage (2%). All roosts were located in rainforest and close to creek lines (mean = 6 m). Yellow-throated scrubwren nests were more common in rainforest on small, first- and second-order streams (4.6 nests km–1 – 5.2 km searched) than on larger, third-order streams (1.1 nests km–1 – 2.7 km searched). Colonies were small (<10 bats) and usually comprised a mix of sexes. Maternity roosts in summer were located in both yellow-throated scrubwren nests (n = 8) and brown gerygone nests (n = 3). Foraging bats were recorded flying a maximum of 2.1 km and were regularly recorded (43% of monitored time) on upper slopes away from rainforest. Plots (5 × 5 m) were used to compare prey densities (small web-building spiders) between rainforest and sclerophyll forest and different topographies (creeks, riparian vegetation and upper slopes). Although spider numbers were patchy, upper-slope sclerophyll forest supported the greatest number of spiders, the number being significantly greater in upper-sclerophyll forest than in sclerophyll creeks and rainforest on upper slopes. A forward step-wise multiple regression showed that spider numbers per plot were positively related to the density of understorey stems. Management implications from this research are that riparian rainforest provides the key roosting habitat for K. papuensis. Recent management prescriptions in New South Wales' forests available for logging have correctly targeted the protection of this environment. However, the extent of foraging in sclerophyll forest on upper slopes was previously unknown. Attention needs to be given to management actions that maintain a mosaic of dense patches of understorey on upper slopes, where the numbers of web-building spiders are high. Further research is required to determine the effectiveness of using buffered protection zones within logged areas for K. papuensis.

Context
Environmental benefits of timber plantations have been a major selling point for land use change from previously cleared farmland, but data concerning the response of biodiversity are scarce.


Aims
We investigated the use of young (4–11 years old) timber plantations by bats in comparison with other vegetation classes in a highly cleared and productive agricultural landscape in north-west New South Wales (NSW), Australia.


Methods
Initially, we recorded activity in paddocks before plantation establishment, and then four to six years after establishment. We compared activity within young eucalypt plantations with surrounding paddocks and remnant woodland. We also radio-tracked four different bat species to investigate how roosting and foraging was apportioned into different habitats.


Key results
The ultrasonic survey of bats found that the young plantations were typically used by 7–8 species and activity averaged 87 passes per night. Activity within plantations was similar to treeless paddocks, and approximately six times less than in small remnants. The very high activity levels and feeding buzzes in small remnants was significantly related to rich, basalt soil (which was used as a proxy for invertebrate biomass) on agricultural plains. Total activity and species richness was correlated positively with the number of remnant trees on the site, but neither plantation area nor shape influenced bat activity. Plantations were not used preferentially by radio-tracked bats at night compared with their availability in the local landscape (13–14% bat use, 17% available). No bat roosts were located within the plantations. Most bat roosts were in tree hollows, which were absent in the plantations. Decorticating bark was abundant in eucalypt plantations, but only Nyctophilus geoffroyi was observed beneath bark and only in remnant trees outside of plantations.


Conclusions
Young eucalypt plantations have limited value for bats, and this is comparable to previous studies on more environmentally focussed plantings.


Implications
The value of plantations for bats would be improved by retaining remnant trees, both in the surrounding landscape and within plantations. We also recommend varying tree densities to increase the diversity of animal species using plantations.

Context
Studies of habitat suitability in disturbed landscapes based on species traits can improve predictions about how alternative management strategies are likely to affect threatened species.

Aims
We studied the south-eastern long-eared bat (Nyctophilus corbeni), which represents a group of bats prone to extinction due to attributes that adapt it to flight within cluttered forest vegetation, typically making them forest-dependent. To support decisions about management of the species in timber production forests, we investigated roost selection and characterised diet in a mosaic of disturbance histories in the Pilliga forests of north-western New South Wales.

Methods
We caught 54 N. corbeni, radio-tracked 39 individuals and located 41 unique maternity roost trees. Attributes of roost trees were compared with the local neighbourhood and the landscape mosaic of habitat types and logging treatments (recently logged, recently thinned and old regrowth). Preliminary observations were collected on foraging movements. Diet was characterised for maternity and non-maternity seasons using faecal DNA techniques.

Key Results
Small maternity colonies (<10 bats) were found in hollows and fissures often in exposed locations of trees with a small diameter (means range 23–39 cm) that were usually dead (82.5% of roosts). Buloke Allocasuarina luehmannii was most commonly used for roosting (49%), yet has been overlooked previously as a source of hollows for fauna. Landscape-scale habitat use was subtle: bats avoided roosting in commercially thinned stands and selected old regrowth. Logged and mechanically thinned stands were used in proportion to availability. Nyctophilus corbeni consumed a diverse range of prey in spring (November) and autumn (March), dominated by moths.

Conclusions
Areas of high stem density, especially those containing dead trees, provide key roosting habitat for N. corbeni and this is likely to be a significant factor explaining the species rarity.

Implications
Roosting ecology as well as foraging ecology contributes to a species' sensitivity to disturbance consistent with trait-based predictions. Heterogeneity in the landscape should be maintained when the habitat of N. corbeni is manipulated (e.g. thinned) by retaining a diversity of stem densities, including dense patches (especially with dead A. luehmannii).

Context Selective logging of native forests creates a mosaic of disturbance histories; however, little is known about how different taxa respond to such a mosaic. Aims We followed adaptive-management principles to test logging and burning impacts on eastern pygmy possums, Cercartetus nanus (Geoffroy and Desmarest, 1817), by undertaking a large-scale field experiment that coincided with harvesting. We predicted that home range would increase after logging because of a reduction in resources (food and/or dens) and because hollows suitable for denning would decrease, resulting in greater use of unlogged patches and alternate dens. Methods We radio-tracked C. nanus in a before-and-after logging experiment to investigate home range, habitat selection and den use. We tracked 50 possums, some individuals for a maximum of 8 months, within control, recently logged and regrowth (5 years since logging) sites. Key results Home ranges were variable (0.04–19.5 ha), with males having significantly larger home ranges. We were unable to detect a difference in home-range size between controls and the first year after logging and burning, or regrowth 5 years after logging. Home ranges comprised a mosaic of disturbed and undisturbed areas, and possums did not avoid logged habitat in their home ranges, indicating that logging did not significantly influence habitat selection. We suggest that possums were not sensitive to selective logging and burning because nectar-producing plants are adapted to fire disturbance and because a variety of den sites were used, most commonly in tree hollows and fallen logs, which were commonly left as logging residue. Indeed, possums frequently denned in logged patches, both recently after logging (63% of dens) and in regrowth 5 years after logging (76% of dens). Counts of fallen hollow logs at each site indicated that their density was not reduced by logging, with regrowth sites having the greatest abundance of logs (260 ha–1). Conclusions The mosaic of disturbance created by selective logging operations did not negatively affect home range or den selection of C. nanus. Implications Ecologically sustainable logging practices that include a range of mitigation measures to protect biodiversity can be compatible with the management of threatened species. Assessment of the effectiveness of these methods often will rely on scientific research.