On the back of our "under-appreciated pollinators" blog and with spooky season in full swing, we're taking the time to elaborate a bit more on one of our favourite pollinators: bats! Pollination by bats, which actually has its own name - chiropterophily - is vital for plants like mango, banana, and even agave! In this post, we'll talk a bit more about bats, their role in pollination globally, as well as the conservation concern for bats generally and in The Land Between specifically. Keep reading!
What is pollination? A recap.
Pollination is the movement of a pollen grain from the anther of a flower to the stigma. This can occur through self-pollination, wind or water, and pollinators. Pollinators provide this service and allow for plant reproduction through the movement of pollen from one plant to another. This results in a plant’s ability to produce fruit and seeds that ultimately feed the world.
Pollinators are animals whose food sources include nectar or pollen, and who carry pollen sacs from plant to plant as they feed. Most of us correlate pollination with a variety of bees and insects since they are the most effective and well-known pollinators, but there are many other animals that contribute to plant pollination.
Over 500 flowering plant species are pollinated by bats around the world. Without bat pollination, we wouldn’t have some types of bananas, cacti, peaches and blue agave (which can sweeten our teas and make tequila!)
What do bats feed on?
Most bat species are insectivorous, but there are two families of tropical bats that have flower-visiting species, with some being nectarivorous bats (those who eat nectar or pollen). Pollination by bats is beneficial for many plants, as bats are able to carry larger pollen loads and travel longer distances. The downside, however, is that plants need to provide enough nectar to draw bats in, which comes at a greater cost to the plant. This extra energy demand is compensated for by gaining a greater pollen distribution. This complex bat-plant relationship has allowed for the adaptation of ‘bat flowers’ and ‘bat fruits’, which are plants that are reliant on bat pollination for pollen dispersal. Conversely, bat pollinators have adapted common morphological features for optimal feeding that include smaller and fewer teeth, long snouts, and a long bristly tongue.
Bat Fun Fact: The Tube-lipped Nectar Bat (Anoura fistulata) of Ecuador has the longest tongue-to-body ratio in mammals. Its tongue can extend 1.5x its body length!
Nectar-feeding bats are found in every continent with subtropical and tropical regions. The two families of flower-visiting bats are often referred to as Old World fruit bats and New World fruit bats. Like their name suggests, New World bats are present in the Americas while Old World bats, who likely originated in Australasia, have dispersed across Africa, Europe, and Asia.
Old world bats, new world bats
Other than differences in distribution, Old World and New World bats have a few morphological differences that affect the way they interact with flowers. For instance, New World fruit bats have longer tongues and are smaller, being less than half the size of their Old World fruit bats. Another difference is the ability to echolocate. Unlike New World bats, Old World fruit bats do not use echolocation for communication, orientation or foraging. Instead, they must land on flowers before feeding. As a result, New World bat-flowers are smaller than their Old World counterparts and have flower parts that reflect sound to help bats echolocate flowers at night.
A talking plant and echolocation
As you may know, bats use echolocation to navigate their surroundings as well as to socialize and even find food! Echolocation makes use of sound waves to do this. Bats will make high-pitched noises from their mouth and nose to create sound waves, which bounce off of objects that can then be detected.
One plant, The Black Hamburger Bean Flower in Central America (pictured right), is actually able to communicate with echolocating bats. This flower is able to tell bats how much nectar it has by increasing the angle of reflectance to echolocating bats. A flower can provide 5 times more nectar if the bat visits at the right time. The association of these echoes with the nectar output entices the bats to seek out flowers with the same features. Once the bat has landed, one of the petals will burst and the plant will release most of its pollen onto the bat’s back. This interaction allows for a bat to receive a substantial amount of nectar, but not without getting a full load of pollen, resulting in a mutually beneficial interaction.
All about bat pollination
Since bats are active during the night, bats choose plants with nocturnal anthesis (plants with flowers that open at night), light colouration, and that emit a musty, often rotten-like smell. These flowers are often dangly (flagelliflory) or found on branches or tree trunks (cauliflory), are large-sized, bell-shaped and produce an abundance of pollen or nectar at night.
Most nectarivorous bats are solitary eaters that travel far to feed and transfer the pollen that unintentionally sticks to their fur from flower to flower. Some of the longest travel distances are 88km for Pteropus genus bats. They are also able to cross a variety of terrains, both continuous and fragmented areas, giving them a crucial role in maintaining gene flow in remote plant populations. Overall, bats are able to carry larger loads of pollen for longer distances than other pollinators, making them the most efficient for the job!
Just as flowers have different strategies for pollination, plants often have different methods of scattering seeds. This is where fructivorous bats come in. These bats eat the fruits of the plant; however, the seeds are undigested and are secreted in locations far from the parent plant. The important role bats play as seed dispersers are emphasized as they often reach areas that other seed dispersers (ex. birds) avoid in fear of predators.
Species at risk
Unfortunately, there are many threats that put pollinating bats in jeopardy. Globally they are threatened by habitat loss and overhunting; approximately 37% of pteropodidae were classified as threatened in 2020 by the IUCN.There are local successes, however, like the Lesser Long-nosed Bat (Leptonycteris curasoae yerbabuenae) which was delisted by the US Fish and Wildlife Service in 2018 due to species recovery.
Of Ontario’s 8 bat species, 4 are currently listed as Endangered (Eastern Small-footed Myotis, Little Brown Myotis, Northern Myotis, and Tri-coloured Bat). The leading cause of bat population decline in Ontario is a disease called White-nose Syndrome. This disease is caused by a fungus introduced from Europe that disrupts bats’ ability to hibernate; exposure to this fungus for a minimum of two years has reportedly reduced bat populations by 99%.
Bats in Canada
Although bats in Canada are insectivorous and don’t directly act as pollinators, they serve a great and complementary purpose in our ecosystem related to food production. In Canada, bats control insect populations, protecting our crops (and us!) from undesirable infestations. Not only that, but if a bat does come into contact with pollen, it will unknowingly act as a pollinator and assist with this role.
If you are curious to learn more about bats in The Land Between, you can read more on our website, where we also have resources (like blueprints for TLB Bat Boxes!) to help our native bat species.
Sources
Aziz, S. A., McConkey, K. R., Tanalgo, K., Sritongchuay, T., Low, M. R., Yong, J. Y., ... & Racey, P. A. (2021). The critical importance of Old World fruit bats for healthy ecosystems and economies. Frontiers in Ecology and Evolution, 9, 181.
Becker, N. I., Rothenwoehrer, C., & Tschapka, M. (2010). Dynamic feeding habits: efficiency of frugivory in a nectarivorous bat. Canadian journal of zoology, 88(8), 764-773.
Kevan, P. G., & Viana, B. F. (2003). The global decline of pollination services. Biodiversity, 4(4), 3-8.
Fleming, T. H., Geiselman, C., & Kress, W. J. (2009). The evolution of bat pollination: a phylogenetic perspective. Annals of botany, 104(6), 1017-1043.
Muchhala, N., & Thomson, J. D. (2010). Fur versus feathers: pollen delivery by bats and hummingbirds and consequences for pollen production. The American Naturalist, 175(6), 717-726.
von Helversen, D., & von Helversen, O. (1999). Acoustic guide in bat-pollinated flower. Nature, 398(6730), 759-760.
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