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Hamilton City long-tailed bat survey: Annual monitoring report, 2022
Abstract
Deforestation, urbanisation and the introduction of mammalian predators has resulted in a significant decline of New Zealand’s long-tailed bat (Chalinolobus tuberculatus or pekapeka-tou-roa), which is currently classified as threatened, nationally critical. Hamilton City is one of three urban areas with confirmed long-tailed bat populations. Since 2016, annual city-wide surveys have been conducted by Project Echo, a multi-agency advocacy group for Hamilton City bats. The purpose of the annual surveys is to monitor for changes in bat activity and habitat use throughout Hamilton City, this report presents findings from the 2022 survey.
A total of 72 automatic bat monitors (ABMs) were deployed across 20 historically monitored sites and 52 spatially distributed sites, as specified by a Master Sample design. Acoustic bat monitors (Model AR4) were deployed for approximately 3 weeks, however, only 14 ABMs remained operational for the full 3-weeks, with 30 units failing to operate for more than 4 days. ABM failure was ascribed to the use of older rechargeable batteries. Despite this, a total of 6,734 bat passes were detected from 19 sites, compared to detections at 18 sites from 64 deployments in the 2021 city survey. Similar to previous years, most bat activity was recorded in the south of the city, in close association with the Waikato River and the Mangakotukutuku gully system. There were also six passes recorded in the central city (Site 67, Tristram Street) along with multiple detections in the Hillcrest, Fairfield and Melville residential areas. This data supports the continued use of the Master Sample survey design for the selection of survey sites. While it is advantageous to retain a proportion of previously monitored sites (~25%) for continuity of data, the Master Sample design has improved the proportion of habitats surveyed with greater coverage of residential areas and the inclusion of commercial and industrial areas which have rarely been surveyed.
The reduced number of operational ABM nights is likely to have substantially reduced the sensitivity of the survey to identify locations of low bat activity, as well as the magnitude of detections in high activity areas. Therefore, it is recommended that the data be treated with caution if making comparisons to previous or similar surveys. On-going annual city-wide bat surveys will help identify key habitat areas for conservation and enhancement, in addition to helping understand the effects of urban development and intensification. This is of particular importance given the ongoing and proposed future development in the south of the city, which raises concerns for the preservation of current bat habitats and their connectivity to the city.
Type
Report
Type of thesis
Series
Environmental Research Institute Reports
Citation
Date
2022
Publisher
Environmental Research Institute, The University of Waikato