Testing the microclimatic effects of sprinklers aimed at mitigating heat stress in flying-fox roosts

Extreme heat events are a serious concern for the conservation management of wildlife. In flying-foxes (Pteropus spp.), exposure to air temperatures (Ta) > 42° C can result in mass mortality, sometimes at catastrophic scales. To mitigate the worst of the impacts on flying-foxes, sprinklers are increasingly being deployed in roosts to cool flying-fox roosting habitat and/or the flying-foxes directly. However, while anecdotal reports suggest positive outcomes from these interventions, the effects of sprinklers on microclimatic conditions and flying-fox thermoregulatory responses have not been studied empirically. We aimed to test experimentally the impacts of sprinklers on microclimatic conditions of a flying-fox roost and so provide a much-needed evidence base for flying-fox heat stress mitigation.
We used an automated split-system sprinkler setup in the understory of a permanently occupied grey-headed flying-fox (P. poliocephalus) roost site in Campbelltown, NSW. Sprinklers were deployed within two 500m2 areas of the roost vegetation (site A and B) and were programmed to operate for 30 minutes in an alternating sequence so that site A operated on day 1, site B on day 2 and so on. High-resolution weather data were systematically collected at sprinkler and control areas throughout the roost across a range of daily meteorological conditions between the austral summers of 2020-21 and 2023-24, including during an extreme heat event that resulted in mortality of flying-foxes across the region.
This dataset contains 3 files: two .csv files that include the data from a) weather stations, and b) data logger arrays, and one .txt file that explains the variables in each of the csv files.

The “weatherstations_dataframe.csv” file represents the data collected using Davis Pro 2 weather stations that were installed at the two sprinkler sites (Site A and Site B) and a control site that was not subject to the sprinklers (Control).

The “array_dataframe.csv” file represents the data collected using data loggers deployed at ten locations within the vegetation occupied by flying-foxes. This was used to investigate the spatiotemporal effects of the sprinklers. At each of the ten locations, data loggers were installed at four vertical heights (0, 1.5, 3 and 6 m), for a total of n = 40 data loggers. In the summers of 2020-21, 2021-22, 2022-23, iButtons were used (DS1923, Dallas Semiconductor, Dallas, TX, USA) and in 2023-24 Kestrel Drops (D2) were used (Kestrel, AU). iButtons (Ta resolution: 0.5° C; RH: 0.06%) and Kestrel D2 Drops (Ta resolution: 0.1° C; RH: 0.1%; dewpoint = 0.1° C) were calibrated in an incubator at four temperature points (15, 25, 35 and 45° C) against a standardised high precision digital thermometer (Platinum Ultra-Accurate Digital Thermometer, Model 6413CC, Traceable, Texas, USA). A linear regression was fitted to explain measured temperature as a function of logger temperature, and the intercept and slope of this equation was used to adjust the data for each logger. Calibrated Kestrel Drop and iButton data collected in the lab were compared using a paired Wilcoxon signed rank test, and we found no significant difference between data loggers for air temperature (W = 8383, P = 0.138) or dewpoint (W = 10772, P = 0.123).

极端高温事件是野生动物保护管理中备受关注的严重问题。在狐蝠（flying-foxes，Pteropus spp.）中，暴露于超过42°C的空气温度（Ta）会导致大规模死亡，有时甚至达到灾难性规模。为减轻对狐蝠的最严重影响，越来越多的栖息地开始部署洒水装置，以冷却狐蝠栖息环境和/或直接为狐蝠降温。然而，尽管轶事报告显示这些干预措施具有积极效果，但洒水装置对微气候条件和狐蝠体温调节反应的影响尚未经过实证研究。我们旨在通过实验测试洒水装置对狐蝠栖息地微气候条件的影响，从而为狐蝠热应激缓解提供亟需的实证依据。

我们在新南威尔士州坎贝尔敦一处永久被灰头狐蝠（P. poliocephalus）占据的栖息地下层，使用了自动化分体式洒水装置系统。洒水装置部署在栖息地植被中的两个500平方米区域（A站点和B站点），并按交替序列运行30分钟：A站点在第1天运行，B站点在第2天运行，依此类推。在2020-2021至2023-2024年的南半球夏季期间，我们在整个栖息地的洒水装置区域和对照区域系统收集了高分辨率气象数据，覆盖多种日常气象条件，包括导致该地区狐蝠死亡的极端高温事件期间的数据。

该数据集包含3个文件：两个.csv文件（分别对应a）气象站数据和b）数据记录仪阵列数据），以及一个.txt文件（用于说明每个csv文件中的变量）。

“weatherstations_dataframe.csv”文件包含使用Davis Pro 2气象站收集的数据，这些气象站安装在两个洒水装置站点（A站点和B站点）以及未部署洒水装置的对照站点（Control）。

“array_dataframe.csv”文件包含使用数据记录仪（data loggers）收集的数据，这些记录仪部署在狐蝠占据的植被区域内的10个位置。这用于研究洒水装置的时空效应。在每个位置，数据记录仪安装在4个垂直高度（0、1.5、3和6米），共40台数据记录仪。2020-2021、2021-2022、2022-2023年夏季使用iButtons记录仪（DS1923，Dallas Semiconductor，美国得克萨斯州达拉斯），2023-2024年使用Kestrel Drops记录仪（D2，Kestrel，澳大利亚）。iButtons（空气温度分辨率：0.5°C；相对湿度：0.06%）和Kestrel D2 Drops（空气温度分辨率：0.1°C；相对湿度：0.1%；露点：0.1°C）在培养箱（incubator）中通过四个温度点（15、25、35和45°C）进行校准，校准参照标准化高精度数字温度计（Platinum Ultra-Accurate Digital Thermometer，型号6413CC，Traceable，美国得克萨斯州）。通过线性回归拟合，将测量温度解释为记录仪温度的函数，并使用该方程的截距和斜率对每个记录仪的数据进行校正。实验室中收集的校准后Kestrel Drop和iButton数据通过配对Wilcoxon符号秩检验（paired Wilcoxon signed rank test）进行比较，结果显示两种记录仪在空气温度（W=8383，P=0.138）或露点（W=10772，P=0.123）方面无显著差异。