Plans by Cairns City Council to move on a spectacled flying fox camp in the area has thrust the species into the spotlight again. Do dispersal techniques work, and why should we take an interest in the fate of this often maligned animals? Sarah Jacob finds out more from CSIRO’s Senior Principal Research Scientist Dr David Westcott.
What is the ecological importance of the spectacled flying fox? Why should people care about what happens to them?
Flying foxes have been in Australia for millions of years. They are an integral part of the ecosystem, and they move very long distances and because they fly, they’re not really subject to a lot of the constraints that other animals are subject to. That fact makes them very important in terms of ecosystem services they provide, moving seed but particularly pollen through the landscape. In the case of the spectacled flying foxes, it’s a species that is restricted to rainforest, it’s a habitat specialist and it links the Australian rainforests with the rainforests of south-east Asia.
You coauthored a study published in Nature that indicated that this species has declined by around 75% over the past 15 years – what are the main contributors to that decline?
That’s a pretty major decline for any species and allowed it to be listed as Endangered, and it’s pretty close to Critically Endangered. In the long term, there has been loss of habitat – and when I say a long timeframe I mean the timeframe of European settlement. In that timeframe, we have cleared a quarter to a third of its habitat. That was the initial cause of the decline. But in the timeframe that we looked at for that study, the drivers of decline… what we think is going on is environmental disturbances – cyclones in particular. Since 2006 we’ve had a couple of very large cyclones and a number of smaller cyclones, and they were sufficient to strip flowers and fruit off the canopy. So we think they reduced the amount of foraging resources for the flying foxes. At the same time there was a period of clearing out on the western margin and that probably didn’t help.
If they are a rainforest species, why do they come so close to human settlements?
Humans and flying foxes choose the same parts of the landscape to live in, but they do it for different reasons. Flying foxes tend to forage in fertile parts of the landscape. Humans choose fertile landscapes for farming and so on. Flying foxes like to be near water. Humans like to be near water. They like cool shady forest, we like cool shady parks. We choose similar places and in a lot of instances, they flying foxes are there first. We then build our towns, our parks and gardens, and we create perfect flying fox habitat. In some places like Cairns, we came to the flying foxes, they didn’t come to us.
You’ve said that you don’t think attempts to move the Cairns camp will work. Why does dispersal tend to be ineffective in moving camps?
All the evidence tells us that flying foxes have extraordinarily good memories and they move very large distances. They’re changing camps all the time, so an individual that is in the Cairns camp tonight may be in the Tablelands tomorrow night and it might be up in the Daintree next week. It’s very likely that most of the animals in the population know about the Cairns camp and so when you try and push a couple of thousand animals out of one spot, there’s still the rest of the population that know about the camp but don’t know they’re not supposed to be going there. So they’ll keep coming back in. It takes a very long time to get rid of that population’s memory. I am in favour of dispersals if they’re done appropriately and the appropriate commitment is made. That means a long-term investment, and dispersals are really expensive when you do them properly. That means that communities really have to sit down and think hard about all their options.
What does an inappropriate dispersal look like?
They can actually look exactly the same, but they’re just done at the wrong time. For instance, when there are babies in the camp. There is a period where the young are not on the mother, they’re too heavy for her to carry, so they stay in the camp, but they’re not big enough to fly by themselves. If you do a dispersal at that time, then you’re going to have an impact on the animals.
A lot of people dislike or are afraid of flying foxes – and in particular there is a perception that they are diseased. How much risk is there in living near a camp – is this fear overblown or is it justified?
I think it is overblown. You need to take risk assessment approach. Do flying foxes carry diseases that are severe and significant? Yes. What are the chances of getting one of those diseases? Very, very low. There are a range of behaviours that we can adopt to reduce that chance even further. We need to make sure that we don’t handle flying foxes. If we have horses, we need to make sure they don’t feed or drink under trees where we know flying foxes forage. We have lived in close contact with them for hundreds of years now and we’ve only just found out about these diseases they carry. We lived in circumstances in the past where it would have been much more likely that we’d get these diseases. Today, our lifestyles really don’t put us in contact with them, even when there’s a camp in an urban area. We don’t need to be afraid of flying foxes.
Is cohabitation between humans and flying foxes possible?
There are towns where people accept flying foxes even when they’re inconvenient. There’s a town near me where around 200,000 flying foxes basically smothered the town. People weren’t happy about it, but their view was that they would be there for a few weeks and then they’ll be gone, and they were. There are other towns where there are small camps, and people don’t mind them at all. So it’s partly a matter of attitude. People need to understand the nature of the problem and the reasons why camps are hard to move on. It’s not good enough to just say “We don’t like these flying foxes, let’s get rid of them.” There’s a lot of different options that communities can adopt between doing absolutely nothing about it, and moving them on.
Photo: Brian Gratwicke
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