Bat Facts and Fictions

Fiction: Bats are blind

All of our UK bat species have excellent vision that allows them to see in dim light conditions. This is useful during dusk when bats are emerging from their roosts for the evening. Many bats can also see in the UV range. Their excellent hearing is well known, and many people believe that this occurred to compensate for complete blindness, hence the expression “blind as a bat”. Despite evolving sophisticated echolocation strategies for navigating at night, relatively few bats globally have sacrificed vision in any form. This shows that vision is a vital sense that benefits the bat in different ways to echolocation [1].

Fiction: All bats drink blood

Not all bats drink blood! Bats worldwide are varied in their diet. Some bats eat nectar from flowers, others eat insects but only the three species of vampire bats (Desmodontinae) drink blood.  All of the bats in the UK are insectivorous so we are in no danger from blood-sucking bats. Sanguivory (blood-drinking) is very rare in animals as nutritionally it is a very poor diet to have. Blood is high in protein, which is very energy-intensive to break down, along with iron but it lacks many essential vitamins and lipids needed for a balanced diet.  While there is very little competition for blood as a food source, vampire bats open themselves up to blood-borne diseases such as HIV and Ebola. Vampire bats evolved specific genomes along with a specialised gut biota in order to tolerate the nutritional imbalances that a blood diet represents [2].

Lesser horseshoe bats (Rhinolophus hipposideros)
Image Credit: Jessica Jil (CC BY-SA 2.0)

Fiction: Bats cause coronavirus

The recent COVID-19 pandemic is caused by a coronavirus called SARS-CoV-2 [3]. The virus causes an acute respiratory response that can range from a mild cold to a severe life-threatening illness. None of our UK bats have been found to have SARS-CoV-2 or any coronavirus that are harmful to humans. A single species of bat in China (Rhinolophus affinis) was found to have a similar strain of coronavirus, but studies suggest an intermediate species may have been involved in the transfer to humans [4]. We cannot catch COVID-19 from bats. The evolution of the virus into a zoonotic disease has been linked to the habitat destruction and wildlife market trade. This increases the exposure of humans to animal diseases and increases the chance of the viruses mutating to infect a human host. For more information, please visit the Bat Conservation Trust COVID-19 Q&A [5].

Fact: Bats pollinate agave and help make tequila

In many tropical regions, bats are important pollinators. Nectivorous bats such as the Mexican long-tongued bat (Choeronycteris mexicana) have an incredible ability to hover while they press their faces into flowers to eat the nectar produced there. In doing so, they get covered in downy pollen which they transfer between flowers as they forage. Frequent beneficiaries of bat-powered pollination are Agave plants, including Agave tequilana which provides the base ingredient for tequila [6]! Many tropical fruits are also pollinated by bats such as mangos, bananas and guava [7].

Just for fun: Here is a recipe for a tasty Chilli Lime Mango Margarita by the Minimalist Baker [8]!

Mexican Long-tongued Bat (Choeronycteris mexicana)
Image Credit: USFWS (public domain)

Fact: Bats provide pest control

Insectivorous bats like our 18 UK species provide an essential ecosystem service to humans as they remove insects that may otherwise become crop pests. This directly impacts food security of staple foods such as rice in Thailand [11]. Bat’s are also vital protectors or luxury items such as coffee and olives [12, 13]. Another example from abroad that may interest chocolate lovers is that bats eat a pest called the cacao pod borer Conopomorpha cramerella, the larvae of which eat into cacao pods and disrupt the development of the beans [9]. Bats are therefore fundamental for increasing cacao yield and protecting our chocolate supply [10]!

Cacao (Theobroma cacao) pods
Image credit: Luis Ovalles (CC BY-SA 3.0)

Fact: Bats are vital bioindicators

Bioindicators are species that can be surveyed to assess the environmental health of an area. Bats fit neatly as bioindicators in the UK because they are high on the food chain, and therefore connected to insect abundance, while also being tightly linked with plants through pest control, pollination and seed dispersal [14]. They are also vulnerable to land-use changes, habitat fragmentation and high-intensity agricultural systems [15]. The presence and absence of bats can be very telling about human impacts on wild spaces and the environmental quality of an area. Knowledge of bat distribution is essential for informing conservation work as it demonstrates the effect human changes have on the natural world.

References

[1] Bruno F. Simões, Nicole Foley, Graham Hudges, Huabin Zhao, Shuyi Zhang, Stephen Rossiter and Emma C. Teeling (2019). Blind as a bat? Opsin phylogenetics illuminates the evolution of colour vision in bats. Molecular Biology and Evolution 36(1): 54-68. DOI:10.1093/molbev/msy192.
[2] Zepeda Mendoza, M.L., Xiong, Z., Escalera-Zamudio, M. et al. Hologenomic adaptations underlying the evolution of sanguivory in the common vampire bat. Nat Ecol Evol 2, 659–668 (2018). https://doi.org/10.1038/s41559-018-0476-8
[3] Wu et al (2020) A new coronavirus associated with human respiratory disease in China. Nature 579, 265-269
[4] Andersen et al (2020) The proximal origin of SARS-CoV-2. Nature Medicine 26, 450–452
[5] https://www.bats.org.uk/about-bats/bats-and-disease/covid-19-and-bats
[6] Flores-Torres, A., & Galindo-Escamilla, A. (2017). Pollination biology of Agave horrida (Agavaceae) in the Chichinautzin mountain range, in Central Mexico”. Botanical Sciences, 95(3), 423-431. https://doi.org/10.17129/botsci.1022
[7] https://www.bats.org.uk/about-bats/why-bats-matter/bats-as-pollinators
[8] https://minimalistbaker.com/chili-lime-mango-margaritas/
[9] https://www.cabi.org/isc/datasheet/7017
[10] Maas,Clough and Tscharntke (2013) Bats and birds increase crop yield in tropical agroforestry landscapes Ecology Letters, (2013) 16: 1480–1487 doi: 10.1111/ele.12194
[11] Wanger et al (2014) Bat pest control contributes to food security in Thailand. Biological Conservation Volume 171, March 2014, Pages 220-223 https://doi.org/10.1016/j.biocon.2014.01.030
[12] Costa et al (2020) Structural simplification compromises the potential of common insectivorous bats to provide biocontrol services against the major olive pest Prays oleae. Agriculture, Ecosystems and Environment Volume 287, 1 January 2020, 106708 https://doi.org/10.1016/j.agee.2019.106708
[13] Librán-Embid, Coster & Metzger (2017) Effects of bird and bat exclusion on coffee pest control at multiple spatial scales. Landscape Ecol (2017) 32:1907–1920 DOI 10.1007/s10980-017-0555-2
[14] Russo & Jones (2015) Editorial – Bats as bioindicators: an introduction Mammalian Biology 80 (2015) 157–158 https://doi.org/10.1016/j.mambio.2015.03.005
[15] Park (2015) Mitigating the impacts of agriculture on biodiversity: bats and their potential role as bioindicators. Mammalian Biology Volume 80, Issue 3, May 2015, Pages 191-204 https://doi.org/10.1016/j.mambio.2014.10.004

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