Needing a drink: Rainfall and temperature drive the use of free water by a threatened arboreal folivore

Abstract

Arboreal folivores are particularly vulnerable to the impacts of extreme climate change-driven heatwaves and droughts as they rely on leaf moisture to maintain hydration. During these increasingly frequent and intense weather events, leaf water content may not be enough to meet their moisture requirements, potentially leading to large-scale mortality due to dehydration. Water supplementation could be critical for the conservation of these animals. We tested artificial water stations for a threatened arboreal folivore, the koala ( Phascolarctos cinereus ), as a potential mitigation measure during hot and dry weather in New South Wales, Australia. We provided ground and tree drinkers to koalas and investigated changes in use with season, environmental conditions and foliar moisture. Our study provides first evidence of the regular use of free water by koalas. Koalas used supplemented water extensively throughout the year, even during cooler months. Time spent drinking varied with season and depended on days since last rain and temperature. The more days without rain, the more time koalas spent drinking. When temperature was high, visits to water stations were more frequent, indicating that in hot weather koalas need regular access to free water. Our results suggest that future changes in rainfall regimes and temperature in Australia have the potential to critically affect koala populations. Our conclusions can be applied to many other arboreal folivorous mammals worldwide which rely on leaves for their nutritional and water requirements. Artificial water stations may facilitate the resilience of vulnerable arboreal folivores during heat and drought events and may help mitigate the effects of climate change.

Facultative hyperthermia during a heatwave delays injurious dehydration of an arboreal marsupial

“…process these compounds decreases with increasing T a (Beale et al, 2018;Moore et al, 2015). Given that 55% of a ringtail possum's water intake comes from leaves (Munks, 1991), these toxins are likely to constrain rehydration and survival with projected global warming in general, and during heatwaves in particular (Mella et al, 2019;Moore et al, 2015). Possums can avoid consuming leaves at high T a , but reduced foraging will lead to decreased body condition and dehydration (Conradie et al, 2019;Mella et al, 2019), and may impact the growth of young (Cunningham et al, 2013).…”

“…Given that 55% of a ringtail possum's water intake comes from leaves (Munks, 1991), these toxins are likely to constrain rehydration and survival with projected global warming in general, and during heatwaves in particular (Mella et al, 2019;Moore et al, 2015). Possums can avoid consuming leaves at high T a , but reduced foraging will lead to decreased body condition and dehydration (Conradie et al, 2019;Mella et al, 2019), and may impact the growth of young (Cunningham et al, 2013). Provision of free water to offset reduced intake of leaf water has been trialled for the arboreal and folivorous koala Phascolarctos cinereus, which increased use of supplemented water at high T a (Mella et al, 2019), but such strategies are still impractical beyond a local scale.…”

“…Possums can avoid consuming leaves at high T a , but reduced foraging will lead to decreased body condition and dehydration (Conradie et al, 2019;Mella et al, 2019), and may impact the growth of young (Cunningham et al, 2013). Provision of free water to offset reduced intake of leaf water has been trialled for the arboreal and folivorous koala Phascolarctos cinereus, which increased use of supplemented water at high T a (Mella et al, 2019), but such strategies are still impractical beyond a local scale. It has been suggested that water loss would become physiologically limiting when green ringtail possums Pseudochirops archeri are exposed to T a >30°C for >5 h per day during heatwaves of 4-6 days, the effect of which would be exacerbated with climate change (Krockenberger et al, 2012;Meade et al, 2018).…”

Habitat fragmentation affects movement and space use of a specialist folivore, the koala

“…Koalas receive most of their moisture intake from their diet (Munks, Corkrey & Foley, 1996). But they may drink from pools of water during increased periods of drought, and drink more from water stations with higher ambient temperatures and the more days since it last rained (Mella et al ., 2019). Previous research found that captive koalas selected leaves that contained at least 55% leaf moisture (Hume & Esson, 1993).…”

Fires in Nature: A Review of the Challenges for Wild Animals

“…Feeding and water areas, easily arranged along the natural transects [259], can supply many different species [260]. Particularly, water should also be supplemented on the way to the rescue centre.…”