It can be beautiful to look out the window at night and see flying foxes making their way across the dark sky. Sure, it's a wonderful sight, even somewhat majestic, but only because you're watching from a distance. It's far less wonderful when a colony of flying foxes decide to make their home in the trees on your property, with all the noise and mess that this entails. You don't want to hurt the poor creatures, but is there a way to politely (yet firmly) discourage them from staying?
Their Primary Roost
The flying foxes will have chosen a specific tree (or trees) to roost in during daylight hours. You need to make these trees less appealing, while still retaining the tree. This can be achieved by removing key branches, which in turn discourages the bats from returning. Given the size and weight of these branches (along with the potential for damage and injury during the removal process), it's generally unwise to do the job yourself. Contact a professional arborist for removal, and remember that the job will need to be done at night while the bats are away feeding, which is another reason why you shouldn't do it yourself.
While You Wait
In the short-term, while waiting for your trees to be pruned, you need to protect any property immediately under the roosting tree. Bat droppings (guano) are high in uric acid and so can be extremely corrosive. Although rich in nitrogen, and therefore an excellent fertiliser, guano and your property don't mix. Remove any outdoor furniture from around a tree where bats are roosting. Anything that cannot be moved (such as a built-in BBQ) should be protected with a durable plastic tarpaulin. Promptly remove any guano that happens to be deposited on your outdoor possessions.
Remove Food Sources
If you have a number of fruit trees on your property, these might have been what attracted the flying foxes in the first place, even if these trees are not the primary roosting ground. You should place a protective net over these trees in order to prevent the bats from accessing them. The gaps in the mesh must be less than 30mm so that flying foxes cannot get through, along with other considerations to preserve the wellbeing of the local wildlife, while still offering adequate protection for the tree.
Sure, flying foxes look beautiful (and even a little eerie) when they're in flight, but you probably don't want that flight to end on your property. Sometimes a bit of discouragement is necessary.