Two of my banana plants (Musa ‘Cavendish’) were flowering on 2nd January 2015 (above). The inflorescence of the older plant had finished putting forth female flowers that were then developing into fruits. The inflorescence was in the process of exposing its first bunch of male flowers found towards the end, just above the inflorescence bud where only male flowers were left. This male bud would continue to produce male flowers for the next few weeks (below).
The younger plant had just extended its inflorescence and the oldest bract of the bud was in the process of being raised to expose the double rows of female flowers.
As I had already recorded the Cave Nectar Bats (Eonycteris spelaea) visiting these banana flowers LINK, I was curious to find out when and how often the bats would arrive to feed on the flower nectar.
The camera was thus set to video-record the two plants from 2130 hours on 2nd January to 0200 hours on 3rd January 2014. The video clips were examined and a consolidated clip was compiled as shown below.
The bats arrived mostly after 2130 hours. According to Benjamin Lee, who has been studying bats for the past few years, these Cave Nectar Bats leave their nearby roost about an hour or so before to forage.
Bats regularly flew past the two trees at about 20-30 minutes intervals. A few approached the banana flowers but failed to actually land on them. Only after 2230 hours did one landed on the flowers to feed on the nectar. And up till 0200 hours when observations ended, there were two other feedings.
Why only three instances of nectar feeding were recorded is a puzzle. Was it possible that most of the bats flying through were Common Fruit Bats (Cynopterus brachyotis), as suggested by Benjamin? Or was it because there was a spotlight on during the period that discouraged most, but not all Cave Nectar Bats from feeding?
Another interesting observation was that all three instances of feeding involved the older inflorescence bearing male flowers and not the younger with female flowers. This would suggest that male flowers produced more nectar (above) and the early blooming female flowers little or no nectar at all (below). I suspect that as the flowering moves from the tip of the flowering bud down, the amount of nectar increases, as earlier observations showed that these bats did visit female flowers.
Note that female flowers have abortive stamens and male flowers abortive ovary. And although nectar is produced to lure nectar-feeding animals to visit the flower, and in the process help in pollination, our cultivated bananas have evolved to become parthenocarpic, that is, the female flowers do not need to be pollinated to develop into fruits.
YC Wee & Benjamin Lee