Why bats matter
Bats play an important role in many environments around the world. Some plants depend partly or wholly on bats to pollinate their flowers or spread their seeds, while other bats also help control pests by eating insects. In the UK, some bats are ‘indicator species’, because changes to these bat populations can indicate changes in aspects of biodiversity. Bats might suffer when there are problems with insect populations (because our bats feed on insects) or when habitats are destroyed or poorly managed (for example, some bats only live in large woodlands). Read about bats and biodiversity.
Many people are unaware that over 500 plant species rely on bats to pollinate their flowers, including species of mango, banana, cocoa, durian, guava and agave (used to make tequila). So, next time you eat some chocolate, say thanks to the bats! The pollination of plants by bats is called chiropterophily.
Plants pollinated by bats often have pale nocturnal flowers (in contrast, bees are mostly attracted to bright, daytime flowers). These flowers are often large and bell shaped, and some bats have evolved specifically to reach the nectar at the bottom of them. The tube-lipped nectar bat of Ecuador and the banana bat that lives only on the Pacific coast of Mexico both have extraordinarily long tongues for this exact reason. The tube-lipped nectar bat’s tongue is more than one and a half times the length of its body!
While these plants rely on bats to pollinate their flowers, bats also rely on the fruit and flowers of these plants to survive. Disturbing this intricate system can have severe consequences. For example, in Mexico, the lesser long-nosed bat that is partly responsible for the pollination of agave plants, used to make mescal and tequila. However, in the majority of tequila production, farmers harvest the plant before it puts out its flowers, meaning it has to reproduce through cloning. This is bad for bats, as they feed on the flowers as well as pollinating them. It’s also bad for the agave crops, as they lack diversity – all tequila plants in one farming area have been traced to less than a handful of clones. Disease has recently killed off more than a third of the agave plants in some areas, something that might have been avoided by allowing more agave plants to flower and reproduce through pollination. Read more on our blog.
While some people think bats are pests, some bats are actually pest controllers eating thousands of insects every night. UK bats won’t bite you or suck your blood – but they will help clear the air of bloodsucking mosquitoes!
All bats in the UK are insectivores – they only eat insects. Insect-eating bats are great for keeping bugs away from crops, as well as the places where the bats roost. The Brazilian free-tailed bat has been recognised as an important “pest management service” in cotton farming. Because bats eat so many insects in some regions, they can also reduce the need for pesticide sprays.
While bats can provide a valuable service for agriculture, some agricultural practices can have a detrimental impact on bats. Increased use of pesticides may mean that bats go hungry from the lack of insect prey. The destruction of hedgerows and woods in farmland is also concerning, as bats rely on these features for roosting, hunting and getting around.
Like birds, some bats play a critical role in spreading the seeds of trees and other plants. Some tropical fruit bats carry seeds inside them as they digest the fruit, then excrete the seeds far away from the original tree. These seeds drop to the ground in their own ready-made fertiliser, which helps them germinate and grow. Because bats help pollinate and disperse seeds, they can even play an important part in helping regrowth after forest clearance.
Even small bats can have an important part to play in seed dispersal, as recent research on neotropical bats in Central and South American forests suggests. These forests have been cleared and fragmented, while hunting and habitat loss has wiped out some populations of large bodied animals like deer and macaws. It had been thought that without these animals, many large-seeded plants would have no way of dispersing their seeds. However, researchers looked at seed dispersal both at random through the forest and underneath the tents of tentmaker bats. These studies have shown that the number of large seeds under the tents is higher than would occur at random, so tentmaker bats might be playing a crucial role in the dispersal of up to 44-65 large seeded plant species throughout the forest.