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  • Session 3

    Biodiversity of the Grassy Landscape

  • Keywords: bats, remnant vegetation, nature conservation

    Bats—a prominent component of the mammal fauna

    There are 90 taxa of bats currently known from Australia, which together make up more than 25% of the native mammal fauna (Duncan et al. 1999). These species belong to seven families: the Pteropodidae (flying-foxes, fruit-bats and blossom- bats), Megadermatidae (Ghost Bat), Rhinolophidae (horseshoe bats), Hipposideridae (leaf-nosed bats), Emballonuridae (sheathtail bats), Molossidae (freetail bats) and Vespertilionidae (vespertilionid bats). Bats occur in substantial numbers throughout

    all environments in Australia, from the tropics to the arid deserts, and in most areas constitute a large part of the local mammalian fauna. They are important contributors to a range of ecosystem processes, including seed dispersal, pollination, and predation of invertebrates.

    However, other than the flying foxes, which are large and visible in their diurnal roost sites, most species of bats are poorly known and rarely encountered. This is particularly true in temperate environments of southern Australia, where the dominant group of bats are the vespertilionids. These species are all small (4-25 g body weight), nocturnal in activity, and roost during the day in locations seldom seen by most people. They have two main habitat requirements: suitable areas in

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    Bats in rural landscapes: a significant but largely unknown faunal component

    L. F. Lumsden1 and A. F. Bennett1, 2

    1 Arthur Rylah Institute for Environmental Research, Department of Natural Resources and Environment, 123 Brown St, Heidelberg VIC 3084

    [email protected] 2 School of Ecology and Environment, Deakin University – Rusden Campus

    662 Blackburn Rd., Clayton VIC 3168 [email protected]

    The Northern Plains of Victoria, like other agricultural regions of southern Australia, has experienced extensive loss and fragmentation of its native woodlands. Thirteen species of insectivorous bats occur in

    the area. All are dependent on remnant native vegetation for roosting and foraging. To investigate how these species are distributed throughout the landscape, we sampled 195 sites in remnants of varying size and form. Bats were widespread throughout all remnant types, with at least some activity at every site. In addition to the larger blocks, foraging occurred around individual trees in paddocks, but not in open farmland devoid

    of trees. Two species were studied intensively to investigate how they used the fragmented landscape. Gould’s Wattled Bats (Chalinolobus gouldii) roosted predominantly in very large live trees in Barmah State Forest, an extensive floodplain woodland, while foraging up to 11 km away in remnants in farmland. There were

    differences in the behaviour of males and females of the Lesser Long-eared Bat (Nyctophilus geoffroyi). Most males roosted and foraged in relatively small woodland areas in farmland. In contrast, females moved considerably further with most roosting in Barmah S.F. and foraging up to 12 km distant in

    farmland remnants. Different types of roost were selected by males and females, and during the breeding and non-breeding seasons. Insectivorous bats can consume up to half their body weight in invertebrates in a night and some species feed extensively on agricultural pests. They therefore play an important role

    in maintaining the health of the rural landscape.

  • which to forage for invertebrates; and roost sites (mostly in tree hollows) for diurnal shelter and seasonal reproduction.

    The extensive loss and fragmentation of the natural environment in agricultural regions of southern Australia has been well-documented, and the negative effects on many groups of animals are becoming increasingly evident (e.g. Loyn 1987; Saunders 1989; Bennett 1990; Barrett et al. 1994). As most species of wildlife cannot survive in cleared farmland, conservation in such regions depends upon the ability of the fauna to use the remaining natural vegetation. Several recent studies (e.g. Lumsden et al. 1994; Law et al. 1999) suggest that insectivorous bats have a relatively high capacity to persist in heavily disturbed rural environments, at least in comparison with other faunal groups such as terrestrial mammals and woodland birds that have shown marked decline and local extinctions (e.g. Robinson & Traill 1996). There is no evidence that any species of bats have become extinct in south-eastern Australia, although the lack of historic data limits detailed assessment. In this paper, we discuss the status of bats in one such rural environment in south-eastern Australia and summarise aspects of the roosting and foraging ecology of two species amongst remaining woodland vegetation in the area. This information is used to identify a number of important issues in the conservation of remnant vegetation.

    Ecology of bats in the Northern Plains of Victoria—a case study

    The Northern Plains is a natural physiographic region in northern Victoria that extends from the inland side of the Great Dividing Range to the Murray River (Fig. 1), forming the Victorian Riverina bioregion (Thackway & Cresswell 1995). It encompasses an area of approximately 22,000 km2 (about 10% of Victoria) and consists of gently sloping floodplains that rarely exceed 150 m elevation. Natural vegetation in this region mainly comprises grassy woodlands dominated by Grey Box (Eucalyptus microcarpa), Yellow Box (E. melliodora), or Black Box (E. largiflorens) on the drier plains; and River Red Gum (E. camaldulensis) along streams and across floodplains (Bennett et al. 1998). Most (>90%) land in the Northern Plains is privately owned and has been extensively cleared for agriculture. Only 1.8% of private land retains tree cover, and this occurs primarily as linear strips along streams, or as small remnants and scattered trees within farm paddocks (Bennett et al. 1998). Larger tracts of forest and woodland are located on public land, mainly along the major river systems, such as the Murray, Goulburn and Ovens Rivers. The total extent of tree cover in the region, including these large blocks, is only 6.2% (Bennett & Ford 1997).

    Balancing Conservation and Production in Grassy Landscapes | Bats in rural landscapes

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    Figure 1. The Northern Plains region of Victoria with areas of remnant woodland shown as shaded.

  • Survey of insectivorous bats

    As part of a broader research project investigating the distribution and conservation of wildlife within rural environments, we undertook a study of the bat fauna of the Northern Plains (Lumsden et al. 1995). Bats were surveyed at 195 sites located across the region, selected to represent different types of remnant woodland vegetation. These included

    large (> 200 ha) and several size-classes of smaller blocks (5-200 ha), roadside vegetation, streamside vegetation and scattered trees in paddocks. To investigate the dependence of the bats on remnant woodland, sites were also established in open farm paddocks devoid of trees.

    The occurrence and abundance of bats at survey sites were assessed using two techniques (Lumsden et al. 1995). First, harp traps were set at sites for two consecutive nights to catch bats while they were foraging or commuting from roost sites to foraging areas. This technique allows positive identification of species, plus the collection of information on the age, sex and reproductive status of individuals. Second, ultrasonic detectors, which record the high frequency echolocation calls that bats use for navigation and prey location, were also set at each site. Data from these detectors provides an indication of comparative levels of activity by bats.

    More than 1500 individuals of 13 species of insectivorous bats were caught during this study (Table 1). Together, these species comprise 45% of the extant mammalian fauna of the region. The most common species were Gould’s Wattled Bat (Chalinolobus gouldii), Chocolate Wattled Bat (C. morio), Lesser Long-eared Bat (Nyctophilus geoffroyi) and Little Forest Bat (Vespadelus vulturnus), which together accounted for 60% of captures. Most species were widespread across the region, but two were rare and restricted in distribution. The Southern Myotis (Myotis macropus) was limited

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    Figure 2. The mean number (± SE) of bat passes recorded by ultrasonic detectors set in remnant vegetation of different forms and sizes in the Northern Plains, Victoria. The number of sites surveyed were: large blocks (>200 ha) n=38, smaller blocks (

  • to areas of permanent water where it forages for aquatic insects and small fish. The Greater Long-eared Bat (Nyctophilus timoriensis) is a rare species in Victoria, the individual caught in this study was only the fourth record for the state (Lumsden 1994).

    Bats were widespread throughout all types of remnant woodland vegetation. They were trapped at 78% of sites where traps were employed, and their echolocation calls were recorded by ultrasonic detectors at 100% of the survey sites. Using the latter technique, the highest levels of activity were recorded in streamside vegetation and smaller blocks (< 200 ha) of remnant vegetation within farmland (Fig. 2). Activity levels of bats in roadside vegetation and scattered trees in paddocks were similar to those recorded in the larger blocks of forest. The number of bats and the range of species using isolated trees in paddocks was surprisingly high (Fig