A comparison of the effectiveness of bat detectors and harp traps for surveying bats in an urban landscape

Obtaining adequate information for informed conservation-management decisions requires effective and cost efficient survey techniques. We compared the effectiveness of bat detectors and harp traps for surveying bat assemblages within an urban landscape in Brisbane, Australia, with respect to number and composition of species. Nine sites within each of three habitat types (remnant bushland, parkland, and low-density residential - a total of 27 sites) were sampled twice each. The bat detectors recorded 3628 calls, from which 13 taxa were identified. The harp traps captured 17 individuals, from which five taxa were identified. All species captured by harp trap were also detected by bat detector, with the possible exception of N. bifax. Bat detectors recorded significantly more species per site than were captured by harp traps, both overall and within each of the three habitat types. And although a considerable amount of time and expense was required to identify the recorded echolocation calls to species, bat detectors were also the most cost-efficient sampling method. These results collectively show that bat detectors were the most effective and cost-efficient method for surveying the bat assemblage in this urban landscape.