Effects of site, time, weather and light on urban bat activity and richness: considerations for survey effort
Annette T. Scanlon A and Sophie Petit A BA Sustainable Environments Research Group, School of Natural and Built Environments, University of South Australia, Mawson Lakes, SA 5095, Australia.
B Corresponding author. Email: sophie.petit@unisa.edu.au
Wildlife Research 35(8) 821-834 https://doi.org/10.1071/WR08035
Submitted: 29 February 2008 Accepted: 20 August 2008 Published: 16 December 2008
Abstract
To maximise bat retention in urban environments, efficient bat monitoring is needed, but the factors that influence survey results for urban bats are unclear. We used echolocation call detectors (n = 378 detector-nights from November 2005 to October 2006) to assess bat activity among different sites in the Adelaide City parklands, temporal variations in activity (hourly, nightly, monthly), and responses to weather and light (artificial and moon). Bat species did not occur evenly in urban conditions; dark parks were more important for bat diversity and activity (six species groups in the darkest park) than were artificially lit parkland areas (three species groups in the flood-lit park). Gould’s wattled bat (Chalinolobus gouldii) and Mormopterus species 4 (94% of calls) were advantaged in urban parklands, being the only species recorded when lights were on at sports parks, whereas five species groups occurred when the lights were off. Minimal bat activity was recorded in the first 2 h after civil twilight, suggesting that bats may roost outside the city and commute nightly into parklands. Bat activity increased with temperature, with a burst in activity occurring after 7°C. Rainfall (>1 mm/24 h) and moon illumination at midnight did not influence activity. Urban environments should provide diversity to attract a diverse assemblage of bat species. Activity fluctuated among sites, nights, and across the year, indicating that large sample sizes over long periods of time are required to monitor and survey bats reliably with detectors.
Acknowledgements
We thank G. Bottroff, A. Dickens, A. Egan, T. Erickson, M. Gemmell, C. Havelberg, D. Hunt, M. Jervois, R. Hutchinson, D. Kristensen, S. Lattanzio, L. Lauder, M. Lewicki, A. Pestell, P. Roetman, K. Scanlon, F. Scanlon, J. Tomlinson, A. Walker, J. Walterfang, H. Waudby and M. Wright for their technical and field support. We are grateful to T. Reardon for his help and advice and to thesis reviewers J. Gibbs and C. Pavey, as well as M. Brigham, M. Pennay, A. Taylor and anonymous reviewers for commenting on the manuscript. Thanks to Z. Drechsler, P. Baldacchino, B. Castellucci, P. Keane and the Adelaide City Council as well as G. Johnston and the Royal Zoological Gardens of South Australia, A. Rossis at Rymil Park café, and the Wilderness School and the Adelaide West Terrace cemetery staff for facilitating access to the study sites. We acknowledge the Australian Bureau of Meteorology for temperature, cloud and rain data, Geoscience Australia for civil twilight data, and BioCity for the loan of a bat detector. This study was funded by the Field Naturalists’ Society of South Australia’s Lirabenda Fund, the Nature Conservation Society of South Australia’s Conservation Biology Grant, the University of South Australia’s Summer Scholarship program, and the Honours Program in Applied Science (Biodiversity, Environmental and Park Management) of the School of Natural and Built Environments.
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