Common ringtail (Image: James Turner)
Hot Topic

The impacts of heatwaves on Australia’s wildlife

Tuesday, 8 December 2020  | 

Author: James Turner (Charles Sturt University), jaturner@csu.edu.au

Heatwaves are predicted to increase in frequency, duration and intensity in Australia [5]. Although brief, they cause mass wildlife die-offs and long-lasting ecological changes, such as reduced body condition of populations [4, 6, 8]. During heatwaves, air temperatures rise above normal maxima for several days, placing many species at risk of heat stress [10, 18]. Individuals at geographic range edges may be under considerable threat, because these areas often have climates at the limit of a species’ heat tolerance [7].

Research shows mammals and birds adjust their behaviour and physiology to avoid overheating. They move into shaded, cooler areas; reduce activity; change posture; or forego eating to avoid increased body temperature during digestion [1, 2]. Additionally, animals radiate heat through skin regions with many blood vessels, such as ears; sweat or spread saliva on the skin to aid evaporative cooling; pant; or allow body temperature to increase with air temperature [7, 8, 9]. When air temperature exceeds body temperature, birds and mammals can only cool themselves using evaporative water loss, which puts them at risk of dehydration and hyperthermia [13, 18]. During extreme heatwave temperatures these adaptations may not be enough, resulting in death [15, 19].

In recent summers, mass mortality has become more common [8, 19]. Bats are the most conspicuous victims—one third of the world’s spectacled flying-fox population died during one heatwave in November 2018. Heatwaves have also killed possums, koalas, three other flying-fox species, fish and at least 30 bird species. Currently, only emergency solutions for reducing impacts exist, such as providing animals with water, food or shelter [12, 14]. While these may be successful in the short-term, their usefulness relies on ongoing funding and infrastructure support. To best identify which species are at risk, and where animals can survive future temperature extremes, we need to combine physiological and behavioural data with climate predictions to find potential areas of suitable habitat [3, 10, 11].

A downloadable pdf on this Hot Topic can be found here.

Supporting Research

Title
Aims
[1] Beale, P.K., Marsh, K.J., Foley, W.J., and Moore, B.D. (2018). A hot lunch for herbivores: physiological effects of elevated temperatures on mammalian feeding ecology. Biological Reviews 93, 674-692.
A review of the literature describing the influence of herbivorous diets on mammal thermoregulation and the potential implications of increasing ambient temperatures associated with climate change.
[3] Briscoe, N.J., Kearney, M.R., Taylor, C.A., and Wintle, B.A. (2016). Unpacking the mechanisms captured by a correlative species distribution model to improve predictions of climate refugia. Global Change Biology 22, 2425-2439.
To improve predictions of climate refugia by develop a fine-scale model predicting koala distribution under various climate change scenarios using behavioural, morphological and physiological data.
[2] Briscoe, N.J., Handasyde, K.A., Griffiths, S.R., Porter, W.P., Krockenberger A., and Kearney M.R. (2014). Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals. Biology Letters 10, 20140235.
To describe koala tree-hugging behaviour during high ambient temperature and model the effects of this on the costs of evaporative cooling.
[4] Conradie, S.R., Woodborne, S.M., Cunningham, S.J. and McKechnie, A.E. (2019), Chronic, sublethal effects of high temperatures will cause severe declines in southern African arid-zone birds during the 21st century. Proceedings of the National Academy of Sciences 116, 14065-14070.
To assess the relative roles of lethal and sublethal high ambient temperature exposure in the decline of bird communities in a southern African desert.
[5] Gardner, J.L., Amano, T., Sutherland, W.J., Clayton, M., and Peters, A. (2016). Individual and demographic consequences of reduced body condition following repeated exposure to high temperatures. Ecology 97, 786-795.
To test whether exposure to high ambient temperature affects the body condition, fitness and survival of white-plumed honeyeaters using a 26-year dataset.
[6] Krockenberger, A.K., Edwards, W. and Kanowski, J. (2012). The limit to the distribution of a rainforest marsupial folivore is consistent with the thermal intolerance hypothesis. Oecologia 168, 889-899.
To determine whether the thermal physiology of green ringtail possums limits their distribution.
[7] McKechnie, A.E., and Wolf B.O. (2010). Climate change increases the likelihood of catastrophic avian mortality events during extreme heat waves. Biology Letters 6, 253-256.
To predict the current and future effects of extreme high ambient temperature during heatwaves on the water requirements and survival times of birds.
[8] McKechnie, A.E., and Wolf B.O. (2019). The physiology of heat tolerance in small endotherms. Physiology 34, 302-313.
A review of the literature on small mammal and bird heat tolerance and physiological mechanisms used to cope with high ambient temperature.
[9] McKechnie, A.E., Hockey, P.A.R., and Wolf B.O. (2012). Feeling the heat: Australian landbirds and climate change. Emu 112, i-vii.
A review of the literature on the effects of heatwaves on Australia's avifauna.
[10] Meade, J., VanDerWal, J., Storlie, C., Williams, S., Gourret, A., Krockenberger, A., and Welbergen, J.A. (2018) Substantial reduction in thermo-suitable microhabitat for a rainforest marsupial under climate change. Biology Letters 14, 20180189.
To predict the effect of increasing ambient temperature associated with climate change on the green ringtail possum, via estimations of available suitable habitat under four greenhouse gas emission scenarios, using a model informed by thermal physiological data.
[11] Meehl, G.A., and Tebaldi, C. (2004). More intense, more frequent and longer lasting heat waves in the 21st century. Science 305, 994-997.
To model current and future heatwave dynamics of Europe and North America
[12] Mella, V.S.A., McArthur C., Krockenberger M.B., Frend, R. and Crowther M.S. (2019). Needing a drink: Rainfall and temperature drive the use of free water by a threatened arboreal folivore. PLoS ONE 14, e0216964.
To test artificial water stations as a potential tool for mitigating the effects of hot, dry weather on koalas.
[13] Mitchell, D., Snelling, E.P., Hetem, R.S., Maloney, S.K., Strauss, W.M., and Fuller, A. (2018). Revisiting concepts of thermal physiology: Predicting responses of mammals to climate change. Journal of Animal Ecology 87, 956-973.
A literature review on how misconceptions about heat transfer and thermoregulation can influence the accuracy of models aiming to predict the affect of climate change on large mammals.
[14] Mo, M., and Roache, M. (online early). A review of intervention methods used to reduce flying-fox mortalities in heat stress events. Australian Mammalogy.
A literature review on intervention methods used in an attempt to help flying-foxes during heatwaves.
[15] Ratnayake, H.U., Kearney, M.R., Govekar, P., Karoly, D., and Welbergen, J.A. (2019). Forecasting wildlife die-offs from extreme heat events. Animal Conservation 22, 386-395.
To develop an improved model for predicting the occurence flying-fox mortality events.
[16] Riddell, E.A., Iknayan, K.J., Wolf, B.O., Sinervo, B. and Beissinger, S.R. (2019). Cooling requirements fueled the collapse of a desert bird community from climate change. Proceedings of the National Academy of Sciences 116, 21609-21615.
To determine whether a 50-species bird community collapse caused by climate change was driven by water required for evaporative cooling at high ambient temperature.
[17] Sergio, F., Blas, J. and Hiraldo, F. (2017) Animal responses to natural disturbance and climate extremes: a review. Global and Planetary Change 161, 28-40.
A literature review on how increases in natural disturbances caused by climate change and human activities are likely to affect animal behaviour, life history traits, morphology, physiology and genetic structure.
[18] Turner, J.M. (2020) Facultative hyperthermia during a heatwave delays injurious dehydration of an arboreal marsupial. Journal of Experimental Biology 223, jeb219378.
To examine the physiological responses of the common ringtail possums to heatwave exposure.
[19] Welbergen, J.A., Klose, S.M., Markus, N., and Eby, P. (2008). Climate change and the effects of temperature extremes on Australian flying-foxes. Proceedings of the Royal Society B 275, 419-425.
To describe the contribution of heatwaves to mortality events recorded for Australian flying-fox species.