A few years ago a family of Common Fruit Bats (Cynopterus brachyotis) consisting of an alpha male and his harem of females roosted in my porch LINK. But then the mess they left on the floor below left me with no choice but to discourage their presence.
The colony has now gone and in its place are groups that arrive at two different times, to rest for a few hours after a heavy meal. I have managed to partially discourage them, especially the early morning group LINK but not those that arrive in the late evening LINK.
In late June 2014 Andrew Scott (above), who was assigned by Channel New Asia to produce some documentaries on Singapore’s wildlife, came to film the remnants of the bat colony roosting in my porch. There were many bats arriving to check out the roosting site between 1930-2030 hours but less than a handful actually roosted on the roof – even when all devices to discourage their roosting were off.
We agreed to discontinue actively discouraging their roosting for the time being, hoping to encourage more bats to return, thus making the filming more exciting.
But then II found that switching on the two spotlights (rather than switching them off) during the late evenings encouraged more bats to roost (see video above). Why this is so remains a mystery.
In fact with the spotlights on they remained roosting up till 0100 hours – when I turned off the light to go to bed. There were then about 20 bats. But once the lights went off, the bats immediately dispersed. During evenings when the lights were on, fewer bats came and left much earlier.
The edited video clip above shows the bats dispersing from their roosting site between 2110h on 9th August and 0020h on 10th August 2014. During this period a few bats flew in as if to disturb the roost, sometimes making contact with one of the roosting bats, then flying out. At other times one or two roosting bats would disengage from the wooden strip to fly around before returning to roost. Such activities are signs that the colony is about to disperse. It only takes a loud noise or even the switching off of the spotlights to trigger the dispersal of the entire colony.
Obviously there is much we do not know about the behaviour of the Common Fruit Bats.