Above: Photo by Joe Navin. Flickr (CC BY-NC-SA 2.0 with minor changes).
Flying-foxes are essential to many Australian ecosystems. They have a unique role in exchanging pollen across large distances and also help disperse large-fruited plant species, particularly rainforest plants.
Flying-foxes are highly mobile – some have been recorded travelling 500 km within 48 hrs (Roberts, et.al., 2012). It was initially thought that flying-foxes would be able to adapt to the projected average increases in temperature associated with climate change by simply moving to more comfortable environs. In fact recent research suggests the reverse may well be the case due to the increased number of catastrophic events, such as heat waves.
In 2008, following an extreme heat event in NSW, Dr Justin Welbergen conducted research looking at the impact of 19 similar events across Australia between 1994 and 2008. The result? More than 30,000 dead flying-foxes due to extreme heat events.
Closer to home, the 4 January 2014 extreme heat event in South East Queensland (SEQ) caused the largest single loss of flying-foxes on record, with more than 45,500 estimated dead. Three species of ying-fox were a ected (Black, Grey- headed and Little Red Flying-foxes). Similar to the impact of heat waves on humans, the groups of ying-foxes most impacted were the young, the old, and pregnant or lactating females. More recently, the 16 November 2014 extreme heat event caused more flying-fox mortalities in parts of SEQ and northern NSW.
Last January, Black Flying-foxes were the hardest hit, representing 96% of the dead and more than 50% mortality in SEQ camps. This may be because Black Flying-foxes appear to be expanding their range southwards and thus are becoming exposed to temperature extremes not experienced in tropical areas of Australia. A similar impact is likely on the less abundant, threatened, Grey-headed Flying- fox, which was once an occasional visitor to Melbourne, but now has a permanent population there.
Whilst the impact on ying-fox distribution and abundance, and consequent impacts on the plant species and ecosystems they interact with, is unknown, a number of facts and trends give cause for concern:
- Climate change projections indicate extreme heat events are likely to become more common. Dr Welbergen’s investigations found that Grey-headed Flying-foxes today are three times more likely to experience temperatures over 42°C than in the 1970s.
- Flying-foxes have a low reproduction rate, the loss of significant numbers of mature females in the January 2014 heat event will slow population recovery.
- The disparate impact across the three species may affect inter-species relationships and distribution.
- The impact of extreme heat events on flying-foxes is conspicuous due to their gregarious nature, however, the impact on other wildlife, particularly solitary and cryptic species, e.g. Koalas, is less obvious.
For more information on how to help injured or stressed bats visit www.bats.org. au or call the 24 hr Bat Rescue Hotline on 0488 228 134.
How do flying-foxes cool down?
Flying-foxes have four strategies for thermoregulation – fanning, clumping, licking and panting. These are applied in this order and reflect the level of heat stress being felt. Panting is the last resort strategy
as it, along with licking, lead to dehydration. When temperatures reach 42°C and above, these strategies start to fail and animals suffer heat stroke and imminent death.
Stressed flying-foxes should not be handled except by trained handlers or wildlife carers due to human health risks associated with being bitten or scratched. Whilst awaiting expert help, heat-stressed animals can be assisted by wetting them directly with a hose or other water source. Do not mist animals, this increases ambient humidity and reduces the ability of flying-foxes to thermoregulate.
References
Roberts BJ, Catterall CP, Eby P and Kanowski J (2012) Long-Distance and Frequent Movements of the Flying-Fox Pteropus poliocephalus: Implications for Management. PLoS ONE 7(8): e42532.
Welbergen JA, Klose SM, Markus N and Eby P (2008) Climate change and the e ects of temperature extremes on Australian flying-foxes. Proceedings of the Royal Society London B: 275, 419–425.
http://theconversation.com/killer-climate- tens-of-thousands-of- flying-foxes-dead- in-a-day-23227
Article by Liz Gould Biodiversity Conservation Manager SEQ Catchments