Mind Where You Stand …

and close your mouth while you’re looking up.

Bendigo was a boom town in the gold rush days developing rapidly and rather splendidly after 1850. It is the fourth largest town in Victoria with a population of more than 95,000 people. Last time I was there I arrived late in the afternoon with the intention of some night-time photography (see The Bright Lights of Bendigo). As I scouted around I was surprised to find a colony of Grey-headed Flying Foxes in Rosalind Park in the city centre. I made a mental note to return and get some photographs.

Bats are the only mammals capable of sustained flight. They are a very successful group with more than 12,000 species forming the order Chiroptera (from the Greek χείρ – cheir, hand and πτερόν – pteron, wing). They are the second largest order (behind the Rodentia).

They can be divided into two groups. The microbats are typically insectivorous and use echolocation. They have a near universal distribution being found on all continents except Antarctica. Flying Foxes and their allies are large and restricted to the warm parts of the world. They don’t use echolocation. Their diet consists of succulent fruit, nectar and pollen. The fruit is crushed in the mouth, the juice swallowed and the pulp rejected.

The taxonomy has, of course, been much disputed. That Flying Foxes and microbats have different origins and developed flight independently was once a popular theory. The evidence now seems to support evolution from a single ancestral population that had taken to the air in pursuit of insects.

Flight has the great advantage of mobility at the expense of high energy requirements. Bats solved the problem of flight differently than birds making them even more maneuverable in the air and far less capable on the ground.The wing has a leading edge from the shoulder to the hand and then extends as a membrane that extends to the hind leg and may include the tail. The hind leg has also assumed the duty of hanging the animal from a perch.

Because their hindleg is somewhat tethered bats as a rule cannot take of from the ground (Vampires and the New Zealand Short-tailed Bat may be the exception). However they climb quite nimbly, head first, and once a few feet off the ground can take off losing a little height initially.

Australia has four species of Flying Fox and four more close allies. They are restricted to the northern and eastern forests. The Grey-headed Flying Fox Pteropus poliocephalus is the largest of them (typically 600 – 800 grams but a few as much as a kilogram) and the only one to form permanent colonies in Victoria.

They choose humid shady places for their communal daytime roost and fly out as much as 50km at night to feed. Presumably they have been summer visitors to Victoria for centuries. Europeans have planted ornamental figs and orchards of fruit trees that have induced them to stay. From 1986 there has been a permanent colony in the Botanical Gardens in Melbourne and since then a few colonies have formed at other sites. The Bendigo colony began in 2010 where there are about 2000 bats in summer with about 200 staying over winter.