Gray Headed Flying Fox, Getting a Grip, Victoria, Australia

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The grey-headed flying fox (Pteropus poliocephalus) is the largest of three megabat species, all of the genus Pteropus, that are native to Australia. The wingspan of adults is up to 1 meter (3 ft 3 in) with weights up to 1 kg (2.2 pounds). The combined length of the head and body is from 230 to 290 mm (9.1 to 11.4 inches). The grey-headed flying fox has a lifespan of up to 23 years in captivity and a shorter lifespan in the wild.

The population of these mammals has been in steep decline in recent years. Thousands died en masse, decimating some camps, during recent and unprecedented heat waves in Victoria. Global warming, habitat loss, and lack of food due to urbanization are their primary threats. The grey-headed flying fox is now a prominent federal conservation problem across Australia. Early in the last century these bats were considered abundant, with numbers estimated in the many millions. In recent years evidence has been accumulating that the species is in serious decline. An estimate for the species in 2019 put the number at 586,000 and the national population may have declined by over 30% between 1989 and 1999 alone.

Bats do not have hollow bones like birds. They have evolved to save weight by making their back leg bones shorter and thinner. As a result bats can no longer stand on their back legs because the pressure is too much for their small bones. Unlike birds they cannot launch their bodies into the air from the ground but they can easily launch themselves into flight by letting go of their perch. Hanging upside down creates a state of stable equilibrium which takes less energy to maintain than the unstable equilibrium of perching upright.

I captured this photograph on a clear autumn morning when the bats were sunning themselves after a cold night. They flap their wings in hot weather, using blood pumped through the patagium (part of the wing) to lower their body temperature. A colony of these bats is surprisingly noisy during the daytime, making a cacophony of complex sounds and often fighting among themselves. Typically some bats are awake and aware of their surroundings while a few fly from tree to tree and others sleep with their faces shielded from light by their wings. I was fortunately able to isolate one awake animal against the blue sky from among the multitude. At around dusk, grey-headed flying foxes leave the roost and travel up to 50 km (31 miles) to feed on pollen, nectar and fruit. They consume the fruit, flowers, and pollens of around 187 plant species.

You can see other photographs of these unique creatures here and here.