Abstract
Understanding maternity roost requirements is fundamental to guide timber production forest management given such roosts are vital to sustain bat populations. We tracked lactating females of three tree cavity-roosting species: Gould's long-eared bat (Nyctophilus gouldi) (n = 7), eastern broad-nosed bat (Scotorepens orion) (n = 6) and little forest bat (Vespadelus vulturnus) (n = 25), over five weeks in young (predominately <5 years old) forest regenerating from heavy timber harvest in southeast Australia. We aimed to investigate interspecific maternity roost selection in a regenerating landscape and by doing so, increase our understanding of the three species’ roost ecology. Sixteen V. vulturnus, 15 N. gouldi and six S. orion unique maternity roost trees were located. Bats displayed a degree of maternity roost selection plasticity, however, interspecific differences were found. Nyctophilus gouldi roosted selectively in retained riparian buffers, in trees of high senescence and switched roosts every day. Vespadelus vulturnus roosted in logged areas and displayed high roost site fidelity, with one roost used for 33 consecutive days. Scotorepens orion selected large live trees of low senescence. The preliminary data for this species suggests that females roost most days in ‘primary’ roosts but display a roost switching behaviour conforming to the fission-fusion model. Dead trees were identified to be important for both N. gouldi and V. vulturnus. Historical and recent logging at our study area drastically reduced cavity-bearing tree density to 1.4 trees per hectare in the logging zones (outside of exclusion areas), potentially limiting local populations of tree cavity-roosting bats and other cavity-dependent wildlife. Our data demonstrate that forest management must consider a range of maternity roost requirements to accommodate differences among species and highlight the importance of exclusion areas for roost habitat. We propose that an expanded ‘retention forestry’ approach should be implemented in logged areas that includes in-perpetuity forest patch retention to increase habitat complexity and continuity.
Highlights
Given a large proportion of a bat’s life is spent in roosts, roost sites are fundamental for survival and the quality of available roosts have the potential to influence fitness of individuals [1,2,3,4]
16 maternity roost trees were located for V. vulturnus, 15 for N. gouldi and six for S. orion
Not all lactating females of a species that were caught at the same trap site and during the same tracking period congregated in the same maternity colony, i.e. of the 13 V. vulturnus tracked at “Site 1”, four separate maternity colonies were identified and at “Site 3”, the 12 V. vulturnus females tracked were from at least three different maternity colonies
Summary
Given a large proportion of a bat’s life is spent in roosts, roost sites are fundamental for survival and the quality of available roosts have the potential to influence fitness of individuals [1,2,3,4]. In disturbed landscapes, maternity roosts have the potential to be a limiting resource (e.g., [5,10,11,12]). Forest management practices differ vastly across the world [13,14] with unregulated timber harvesting being considered a major threat to bats worldwide, including timber extraction in old-growth forest, clear felling practices and some forms of selective logging [15]. In Australia, silvicultural practices range from clear-cut methods to less intensive group or selective tree harvesting [14]. Knowledge about the ecological implications of different silvicultural practices and mitigation measures is essential for the conservation of cavity-using wildlife including bats [13,14,16] so the need for adequate cavity-bearing tree retention in commercial forests is critical (e.g., [14,17,18,19])
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