Continental-scale shift in foraging habitat use by a highly nomadic species following Australia’s Black Summer megafires

Extreme ecological disturbances, such as floods, droughts, heatwaves, and
wildfires, have increased in frequency and intensity under anthropogenic
climate change, and this is projected to continue in the coming decades.
The responses of nomadic species to these events are largely unknown. The
Australian 2019/2020 ‘Black Summer’ megafires burnt a substantial
proportion of the range of the highly nomadic grey-headed flying-fox
(Pteropus poliocephalus). Here, we examine the foraging habitat
utilisation of P. poliocephalus in response to this extreme disturbance
event by comparing continental-scale telemetry datasets of pre- and
post-fire foraging locations from large samples of flying-foxes tracked
before (2012-17) and after (2022-24) the 2019/20 megafires. We performed a
spatial overlay analysis of foraging locations with static maps of the
burnt area and foraging habitat characterised by resource quality
(productivity-reliability scores) and coverage (fractional cover). Tracked
flying-foxes preferentially visited higher-quality foraging habitats that
were generally of higher coverage; yet these habitats were
disproportionately burnt by the megafires, despite their already limited
areal availability. Subsequent to the megafires, we observed a
population-level redistribution of foraging visits to unburnt,
lower-quality, lower-coverage foraging habitats, including those in inland
areas rarely visited previously. The extreme mobility of P. poliocephalus
enhances its resilience to the impacts of widespread habitat disturbance
caused by megafires, but the observed shift in foraging habitat
utilisation to more marginal foraging habitat suggests an overall negative
impact of the disturbance on the population. It is unclear whether these
marginal habitats provided sufficient resources to support the population
following the megafires. Incorporating dynamic environmental data,
alongside population monitoring data, is needed to provide a more precise
assessment of the impacts of widespread ecological disturbances on P.
poliocephalus and other highly nomadic species to inform specific
interventions needed to enhance the resilience of these species in a
changing climate.