Designing surveys for microchiropteran bats in complex forest landscapes—a pilot study from south-east Australia

Abstract

Most of Australia's forest-dwelling microchiropteran bats are reliant on hollows in trees for shelter and breeding. These bats typically comprise a significant proportion (at times over 40%) of the mammalian fauna of a forest region. Because of past and current impacts of timber harvesting and other human activities on native forest ecosystems, insectivorous bats may be threatened by the loss of habitat, hollow-bearing trees and food sources that provide essential life requirements. Unfortunately, reliable assessment of the conservation status of most species remains problematic because of a lack of basic data on distribution, abundance and autecology. Here, we outline an approach for designing regional surveys of microchiropteran bats based on the use of sophisticated, geographic information system techniques. The forests of south-east New South Wales are used as a case study. We also assess the duration of trapping on the detection of bats and compare the efficacy of harp traps and ultrasonic detectors in censusing forest bats. A gradsect or gradient-oriented transect approach was employed in the design of the regional survey. We characterised regional variation in climate, forest vegetation, and terrain as a basis for sampling. The assessment of bat sampling methods was restricted to three areas (South Brooman/Shallow Creek, Quart Pot/Buckenbowra, and Badja State Forest) with specific climate attributes within unlogged portions of one of the common forest types (Dry Forest dominant over Moist Forest) in the region. A total of 13 species of insectivorous, forest-dwelling bats was detected with the use of harp traps. Three of these species, the Golden-tipped Bat ( Kerivoula papuensis), Eastern False Pipistrelle ( Falsistrellus tasmaniensis) and the Eastern Little Freetail-bat ( Mormopterus norfolkensis) are listed as vulnerable and rare on Schedule 12 of the N.S.W. National Parks and Wildlife Act 1974. One further species, the White-striped Mastiff bat ( Tadarida australis) was detected only by the use of ultrasonic equipment. Our data indicate that two to three nights trapping per area may be adequate to estimate species presence but this must be qualified with regard to weather. Variation in the trapping of bats between sites within an area indicated that improved sampling may be achieved by using more traps per night rather than extending the duration of trapping.