Using weather radar to monitor the number, timing and directions of flying-foxes emerging from their roosts

Jessica Meade,David A Westcott,Phillip M Stepanian,Rodney Van Der Ree,Justin A Welbergen

doi:10.1038/s41598-019-46549-2

Abstract

Knowledge of species’ population trends is crucial when planning for conservation and management; however, this information can be difficult to obtain for extremely mobile species such as flying-foxes (Pteropus spp.; Chiroptera, Pteropodidae). In mainland Australia, flying-foxes are of particular management concern due their involvement in human-wildlife conflict, and their role as vectors of zoonotic diseases; and two species, the grey-headed flying-fox (Pteropus poliocephalus) and the spectacled flying-fox (P. conspicillatus), are currently threatened with extinction. Here we demonstrate that archival weather radar data over a period of ten years can be used to monitor a large colony of grey-headed flying-foxes near Melbourne. We show that radar estimates of colony size closely match those derived from traditional counting methods. Moreover, we show that radar data can be used to determine the timing and departure direction of flying-foxes emerging from the roost. Finally, we show that radar observations of flying-foxes can be used to identify signals of important ecological events, such as mass flowering and extreme heat events, and can inform human activities, e.g. the safe operation of airports and windfarms. As such, radar represents an extremely promising tool for the conservation and management of vulnerable flying-fox populations and for managing human interactions with these ecologically-important mammals.

Highlights

Monitoring population trends is a fundamental component of species conservation and management, and is of growing importance as human impacts increase the necessity for conservation management of wild populations[1]
In this paper we use the Yarra Bend colony of grey-headed flying-foxes near Melbourne as a case study demonstrating the potential use of archival weather radar data to monitor flying-fox population dynamics
Our analyses demonstrate that radar data can reliably be used to assess flying-fox colony size, as well as the timing and departure directions of emerging individuals

Summary

Introduction

Monitoring population trends is a fundamental component of species conservation and management, and is of growing importance as human impacts increase the necessity for conservation management of wild populations[1]. In 2013 the National Flying-Fox Monitoring Program was implemented by Australia’s national science agency (CSIRO) with support from state and local governments, with the aim of counting the flying-foxes in all known daytime roosts of P. poliocephalus and P. conspicillatus across the species’ ranges once per quarter[23] This program, like other flying-fox monitoring programs (e.g. https://megabatcount.wordpress.com), involves traditional methods of counting animals in colonies via fly-out and static (or walk-through) counts[1,24]. In this paper we use the Yarra Bend colony of grey-headed flying-foxes near Melbourne as a case study demonstrating the potential use of archival weather radar data to monitor flying-fox population dynamics. This colony is ideal for this purpose as it has been monitored at fortnightly to monthly intervals via traditional counting methods since 200324 These data can be used to estimate local flying-fox abundance, can inform local airports in relation to the risk of flying-fox strike, and generates exciting new opportunities for investigating the drivers of flying-fox movements and population redistribution at a landscape scale

Methods

Results

Conclusion