During the summer a bat colony is usually a lively affair, with a great cacophony of sounds as juveniles call and adults vie for spots on the branches or search for their youngsters. On a very hot day, however, the colonies become unusually quiet and the only sounds are those of flapping wings, as individuals try to cool themselves.
Research has shown that once the temperature gets to 35C, bats start changing their behaviour in order to try and maintain as steady a body temperature as possible (thermo-regulation). This behaviour can include clustering or clumping, panting, licking wrists and wing membranes to try and cool via evaporation, and descending to lower levels of vegetation or to the ground.
And though it was believed for many years that bats drank directly from the river, wildlife photographer Vivien Jones learned by watching that they instead skim the water to soak their belly fur (pictured) which they later lick while resting on a tree branch.
Two species of this important pollinator, in particular, suffer from heat stress: the grey-headed flying fox (Pteropus poliocephalus) and the black flying fox (P. alecto). Sadly, it was reported that more than 45,000 flying foxes died in South East Queensland in one day in February 2014 during a heat wave.
Our grey-headed flying-fox population, once estimated in the millions, is now said to consist of only between 300,000 and 400,000 individuals, with the species listed nationally as Vulnerable.
As the temperatures soar this summer, why not take to the breezes on the Brisbane River for a Batty Boat Cruise on Sunday 26 February or 12 March? Watch these charismatic creatures fly out from their camps as the sun goes down and perhaps even see them skimming the surface of the water in search of a much-needed drink.
by Jenny Thynne.