DOI: 10.26183/k853-p165
title: Testing the microclimatic effects of sprinklers aimed at mitigating heat stress in flying-fox roosts

description: 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).