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| Queen of the night, Epiphyllum oxypetalum, bat-pollinated cactus of the American tropics, now grown all over the world. Fitbit mini for scale. Flowers can be 12" long and 12" across |
Most of the world's 1,400 species of bats eat insects, and some of them eat fruit, but two families, one in the Old World (flying foxes and their relatives, Pteropodidae) and one in the New World (American leaf-nosed bats, Phyllostomidae) are specialized nectar-feeders and so, pollinators. These include 68 and 45 species respectively, large and small bats of many different habitats. In addition, bats of more than a dozen other species take nectar opportunistically--in addition to eating insects or fruit--and so also pollinate.
Bat pollination is an important fact of life in most of the tropics, but because bats fly at night, are fast and nearly silent, and don't come very far north or south of the tropics, they are not well-known to most temperate-zone people. I don't have any photos of bats pollinating. Here are links to a couple of good videos: Tuttle https://www.youtube.com/shorts/MQIpHnoZFms (in the video the bats are visiting saguaro and banana flowers, among others) and of pollinating bats that migrate into the US Southwest https://www.youtube.com/watch?v=g3O-Muyirwc
Specialized bats are excellent pollinators because their fur holds lots of pollen and they will fly long distances foraging for nectar. They are particularly valuable as pollinators for plants in harsh habitats, such as tropical mountains, where it is a little too cold for good insect pollination.
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| saguaro cactus, Carnegiea gigantea. The flowers open and release pollen at night. Flowers face up so bats can easily stick their faces into the flowers, drinking nectar and getting pollen all over their faces. |
Balanced against bat efficiency is that bats need bigger nectar rewards than insects, easily-accessible flowers, and a warm or at least mild climate all year. For bats to specialize on floral nectars, the region has to have plants with nectar for bats that are in flower all year round. Tropical rainforests and low to moderate elevations on tropical mountains fit this. In addition, some nectar-feeding bats are migratory, so bat-pollinated plants, such as columnar cacti, can be found in areas without year round flowering, the bats flying in to feed on flowers for only part of the year.
Bats fly at night, so the flowers of bat-pollinated plants reflect that. They tend to be drab-colored: cream colored or greenish or white. The flowers open after dark and frequently have a strong, fruity odor. Bat-specialist flowers produce lots of pollen which brushes off onto the bat.
Bat-pollinated flowers also tend to be large.
Bats fly well but certainly can't reach a flower deep inside the foliage, so bat-flowers are held up above the leaves or dangle down from a branch below the leaves, so the bats can easily fly to it. In some species bat-pollinated flowers grow on branches and trunks, again, away from the leaves that make flying difficult. Flowers that stick out also help the bat watch for predators such as snakes.
Angle's trumpet, Brugmansia species, is a bat-polinated plant of the mountains of the American tropics. The flowers were originally white or cream-colored but more intense shades have been cultivated. It is extinct in the wild. The scent, released after dark by the flowers, is very strong, too intense to be pleasant for some people.
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| angel's trumpet, Brugmansia Imagine the bats flying in to reach into the flowers |
Specialized bats in the New World tropics hover to visit flowers; Old World bats and nonspecialized bats land and perch before drinking nectar. In all cases bats forage quickly, spending only a few seconds on each flower.
Commercial bananas are generally propagated by cloning (rooting a shoot of an established plant), but in southeast Asia where they are native, wild bananas are pollinated by bats. The actual flowers are in a row (orangy) on the upper edge of the big pink bud. Note the long stem that pushes this flower stalk out into space.
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| banana plant with flowers The flowers are orangy. |
Bat pollination is hard to study; just to watch it you need telescopic binoculars with night vision. We know a lot but lots of questions remain. Some of the bat-pollinated plants are iconic, the saguaro cactus for example. Others are economically important: the agave that produces tequilla (Agave tequilana), dragon fruit (Selenicereus undatus, a cactus), durian (Durio zibethinus), mangoes (Mangifera indica) and less well known fruits. Overall, plants in 66 different families, from species of morning glories (Ipomoea example) to mallows (for example kapok Ceiba pentandra) to leguminous trees and vines (Bauhinia example) to Australian Banksia species (example) are pollinated primarily by bats.
As you might expect, bat-pollination is considered at risk in the future, due to changes in land use, the requirements of bats for nest sites usually in caves, and predicted shifts in the climate that will disrupt the availability of their food.
Look at the big pale flowers of bat-pollinated plants. View videos of bats pollinating. If the opportunity presents itself, watch bats visiting flowers--so fast, so graceful, and performing an essential service for the plant.
Comments and corrections welcome.
References
Fleming, T. H., C. Geiselman and W. J. Kress. 2009. The evolution of bat pollination: a phylogenetic perspective. Annals of Botany. 104: 1017-1043. online link This paper includes lists of bat-pollinated species. It was really fun googling the species and looking at the flowers.
Proctor, M., P. Yeo, and A. W. Lack. 1996. The Natural History of Pollination. Timber Press, Portland, OR. Has a summary of bat pollination. I checked it after writing this post and wow! they said the same things I did.
Ramírez-Fráncel, L. A., l. V. García-Herrera, S. Losada-Prado and 5 others. 2022. Bats and their vital ecosystem services: a global review. Integrative Zoology. 17:2-23. doi:10.1111/1749-4877.12552
More on bat pollination:
Candieas, M. A palm with a unique pollination syndrome. 2019. In Defense of Plants link
I gathered posts from this blog into books for those who don't read the internet or prefer books, for example:
Kathy Keeler. Curious Stories of Familiar Plants from Around the World available from Amazon link and from me
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