Bats Among Us

October Meeting

Our speaker was Diana Prada, a PhD student at Murdoch University, whose current research focuses on the population genomics of microbats and the viruses they carry. She has expertise in applying molecular tools to conservation projects.

Surprisingly, bats—which are the only nocturnal flying mammals—make up 20 per cent of the terrestrial biodiversity. Australia has approximately 79 species. They give birth to one pup a year (and occasionally twins), and the newborns are about 30 per cent of the mother’s weight. Female bats carry the pup under their arm, where the teat is located. Once the baby bat is a little bit older, it is left in a maternity roost where they stay until they can fly on their own, at two or three months of age. Since bats are very long-lived, they are a model organism to study ageing, which may have implications for human health and longevity.

Broadly, bats can be divided into non-echolocating and echolocating bats. The main representatives of the former are fruit bats or ‘flying foxes’. There are four species of such bats in mainland Australia, ranging across the north and east coasts. Other examples are the Tube-nosed Bat whose appearance earns it the nickname of ‘Shrek Bat’, and the Blossom Bat, which includes nectar and pollen in its diet. Fruit bats do not use echo-location but have good senses of sight and smell. The echolocating group includes Horseshoe Bats, Leaf-nosed Bats and Ghost Bats, which have intricately shaped noses to help with echo-location. The microbats—containing the majority of species—use echo-location for navigation and predation of insects, but also have a good sense of smell, and contrary to the ‘blind as a bat’ myth, have good eyesight as well.

Bats’ skeletons are adapted for flight and also to enable them to hang upside-down. The wrist and fingers are highly modified, and the thumb can be used for climbing trees. Wing morphology varies between species, allowing some species to fly fast above the tree canopy and others—with broader wings—to have low speed manoeuvrability, searching for prey under the canopy. In this way, two or more species of bat can effectively share the same habitat. Microbats use their wing and tail membranes to scoop up prey in flight.

Diana outlined her own research on viruses in insectivorous bats in the South-West Botanical Province of WA. They are difficult to study because our local bats generally live not in huge cave colonies, but in small groups in tree hollows. There is a question about why they can carry lots of viruses without it affecting their health, whether viral expression varies with stress levels of the host, and the possible implications in human health. Diana’s research involves using genetics to study connectivity between different populations as the impact of habitat fragmentation on the dispersal capacity of microbats is unclear. Habitat loss is a threat to the survival of all types of bats, and insectivorous bats need old-growth forests or woodlands with plenty of tree hollows for roosting.

Right: Western False Pippistrelle (Falistrellus mackenziei), unique to Jarrah & Marri forest

White-striped Bat (Austronomus australis)
Harp Trap to capture microbats.JPG

Catching bats for sampling is mostly done by means of ‘harp’ traps (left). These consist of a series of vertical fishing lines on a frame over a ‘capture bank’ with a plastic flap over the top of it to prevent captured bats from escaping. The traps are placed near water in summer, remaining for two or three nights and checked every night. Alternatively, mist nets can be placed near water bodies and bats need to be extracted from the nets carefully and rapidly. Traps can also be placed among flowering trees, where insects would be abundant. Sampling involves a mouth swab, measurements of size and weight, a tissue sample for genetics and DNA analysis, and a blood sample for evidence of previous exposure to viruses.

Diana recommended the book Australian Bats by Sue Churchill, and the Australasian Bat Society website, and said that the best time and place to look for bats is at dusk, near water. She recommended Dryandra Woodland as a good locality for bat-watching. She said that bat boxes need to be maintained and monitored because they may host bees or wasps, and they might shift the proportion of bat species in the area. If a sick or injured bat is found, it is best to avoid touching it (due to possible Lyssa virus), and to contact Kanyana Wildlife Rescue on 9291 3900, or Wildcare Helpline (Parks and Wildlife) on 9474 9055.

Mike Gregson