November 5, 2009

Bats Are Not The Bad Guys

Hendra has given bats a bad name. Understandable given Hendra virus has killed people and horses, and scientists have discovered that Hendra virus is carried by bats. But it's not all the bats' fault.

"Flying-foxes or fruit bats are large, very mobile animals that can fly long distances, possibly 100s of kilometers overnight. They are also very social animals, and roost during the day in large communal groups. We are very aware of them because they are so visible at dawn and dusk when we see them leaving or returning to their roosts" says Billie Roberts, an expert in flying-fox ecology and behavior.

"Because flying-foxes roost and feed within urban and coastal landscapes people have the impression there are more flying-foxes than ever, when in fact some species are actually undergoing dramatic decreases in numbers because of habitat loss and shooting of flying-foxes to protect crops."

We've long had a mixed relationship with bats. These species are important to Australian forests because they are the major pollinators and seed dispersers of the forests, and tourist operators regarded them as a key ecotourism species. In urban areas, though, local governments are interested in the impact of flying fox camps on residential areas, because people are disturbed by the bats' noise and smell. Farmers are concerned about fruit damage and loss. And now health departments and horse owners are worried about Hendra virus.

But some of the negative outcomes we blame on bats are of our own making.

"As urban development sprawls the flowering eucalypt trees that flying foxes should be feeding on are being chopped down. As a result, hungry flying foxes have to travel more to search for food, and sometimes they find an orchard with ripe fruit as a substitute to their natural food."

"We should think of flying foxes as the canary in the coalmine; they are messengers of what we're doing to our environment. We shouldn't be shooting the messengers but regarding them as important indicators of the health of our environment."

Scientists are starting to think that the recent appearance of Hendra virus is a symptom of bats showing stress as a result to changes we've made to the environment.

"The actual virus is uncommon in flying-foxes and does not appear to cause them any problems. All indications are that Hendra virus spills over from bats to horses and then from horses to humans "“ there are no known cases of people contracting Hendra virus from flying-foxes" says Dr Stephen Prowse, CEO with the Australian Biosecurity CRC.

Despite recent annual outbreaks, Hendra infection is rare in horses and people. Hendra virus does not appear to be highly infectious and does not spread easily; however when it does the consequences can be devastating.

"More research is required to get a better understanding of how the virus persists in bats and spreads to horses, and for the development of vaccines and treatments. However, the public should not be unduly concerned about fruit bats but treat them as they would any other wild animal and enjoy having them in our urban environment. We need to better learn to live with bats."

So, if you find a sick or injured bat don't try to pick it up, but call the RSPCA or the bat rescue helpline on 0488 228 134. Horse owners need to try to minimize the likelihood of contact between fruit bats and horses. And horse owners and veterinarians need to improve their biosecurity and infection control practices.

In this way we can better manage and reduce the risks of Hendra virus outbreaks and allow bats, horses and people to safely share our environment.


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