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Bats: Natural Pesticide and Protector of Ecosystem Rather Than Blood-sucking Vampires

In an effort to clear names for the long demonized bats and highlight their great contributions to the world’s ecosystem, United Nations Environment Programme declared 2011-2012 Year of the Bat. This year, Bat Association of Taiwan, one of the United Nations Year of the Bat campaign’s partner organizations in Asia, will join with Taipei Zoo and Endemic Species Research Institute, Executive Yuan to organize a series of celebrations and academic conferences for Year of the Bat. Additionally, Bat Association of Taiwan will build up bat houses in junior high schools and elementary schools around Taiwan and make teaching materials to educate students about bat conservation.

Chung-Hsin Wu, chairman of Bat Association of Taiwan, also a professor of Life Science at National Taiwan Normal University (NTNU), has been studying bats’ echolocation system for more than 10 years. While studying master program of biology at NTNU, Professor Wu researched how the feline brain controls breathing and heart rate. While he was pursuing his doctorate in neurology at the University of Missouri in the United States, Professor Wu shifted his studies to the bat. He jokingly said: “I started out with C for Cat, and now I have moved up to the B's instead."

Bat species comprise one-fourth of the approximately 5,000 mammals in the world. Bats also account for more than 40% of Taiwan’s mammals, which makes Taiwan the most densely bat-inhabited place on earth. Bats are dark-colored and are not pleasing-looking animals, and a lot of people fear bats because of unfounded stories. As a matter of fact, most species of bats prey insects and are not blood-sucking creatures. Some species of bats make great contributions to ecosystem by helping spread plant seeds and pollen.

However, bats are often misunderstood because they are only active at night, making it difficult for humans to observe and understand them. Humans often, intentionally or otherwise, harm bats or destroy bats’ habitats, posing significant threats to bats’ survival worldwide.

Taiwan’s diverse natural environment and rich bat biodiversity

 

According to Professor Wu, there are over 1,000 species of bats globally. Taiwan is located between subtropical and tropical region. Frequently changing climate and ample precipitation help create Taiwan’s diverse natural environment, which is ideal for many species of bats to inhabit. Taiwan is home to more than 30 species of bats, among which are mostly endemic species. Taiwan ranks No. 1 in bat population density and boasts rich biodiversity.  

Bats can be discovered from plains to 3,000 meters of altitude. Formosan flying foxes perch on trees. Watase’s bats hang under plant leafs. Chestnut bats flock together at palm plants. Myotis flavus stay under house beams while Formosan tube-nosed bats can be found in shrubs, dead wood and tree fern. Japanese house bats live in roof gaps. Horikawa's brown bats inhabit tunnels, and Formosan leaf-nosed bats reside in caves.

 

A species of small-sized bat was found in Hsinchu last July. Experts discovered that the bats were frosted bats that used to inhabit only boreal forests and temperate forests. Frosted bats have back fur that is purely white during springs, summers and autumns. Frosted bats were seen in Dongshi Forest Park in Taichung in 1952 and had since not been spotted for more than 50 years, so the reappearing of them was exhilarating to Taiwan’s bat scientists.

 

Gravity assists bats’ flight; different species of bats differ greatly in sizes

Bats are often seen hanging with an upside-down position in caves or under roofs as most of bats’ natural enemies are unable to climb onto roofs. Another reason for the rather unique resting position is that once letting off grasp from the upside-down position, bats can launch into flight with the assistance of gravity.

 

Bats are the only mammals that can fly. Different species of bats are significantly different in sizes. Bats’ weight ranges from 2 gs to 1,000 gs. Wing spans range from 3 centimeters to 200 centimeters. Formosan broad-muzzled bats, the lightest bats in Taiwan, weigh only 3.5 gs. Formosan flying foxes, the most heavy and biggest species of bats in Taiwan, weigh 500 gs.

The fur colors of Taiwan bats are mostly between dark brown and gray brown. But Myotis flavus have golden-colored fur that resembles fur coats worn by elegant ladies. Formosan flying foxes have a ring of fur around their shoulder and neck that has a color that lies between milky white and golden color, much like a beautiful scarf.
 
Bats: natural pesticide, essential for ecosystem and human economies

 

Bats are generally known as blood-sucking creatures. In fact, among the 1,000-plus bat species worldwide, only 3 bat species feed on blood. More than four-fifth of bat species are primarily insect-eaters. Researchers found that a single insect-eating bat can consume approximately 3,000 insects in one night, many of which are agricultural pests. Bats are nature’s “natural pesticide”, which is essential for pests control. Bats are, therefore, vital for ecosystem and human economies.

Aside from pests control, bats offer other ecological services such as helping spread plant seeds and protecting forests. Over 100 fruit trees rely on bats to spread seeds and pollen. Bats also help preserve temperate forests and tropical forests and assist them grow. Health of forests is closely linked to well-being of bats.

 

Although most bat species primarily feed on insects, there are bat species in Taiwan that eat fruits. For example, Formosan flying foxes and Greater short-nosed fruit bats found in Kinmen both feed on Moraceae Ficus fruits. Fruit-eating bats mainly rely on vision and sharp noses to look for fruits.

 

Are there bats that live on blood in Taiwan? Blood-sucking bats are all located in Central and South America. There are no blood-sucking bats in Taiwan. Blood-sucking bats lap up blood from a wound they make on a host’s skin with their bladelike incisor teeth. Such bats’ saliva contains anticoagulants that inhibit blood clotting, enabling them to extract blood without difficulty. The so-called blood-sucking bats actually do not suck blood out of their hosts, so their victims are seldom severely harmed.

Bats that feed on blood are smart enough to look for old wounds that they made on hosts they fed upon. That way, bats only have to remove dried blood scabs to restart blood flow. In addition, blood-sucking bats exhibit a special food-sharing behavior. Fully-fed bats that have returned to caves would throw up some blood to other hungry bats to save them from dying. 

 

Bats’ strategic reproduction: delayed fertilization

Female bats in Taiwan generally have one pregnancy in one year. Each pregnancy delivers one or two young bats. Young bats are mostly born in summer, during which temperatures and food availability are higher. Female young bats become reproductive in the autumn of the year it is born. After mating, most bats enter into hibernation. In order to coincide the timing of birth of young with summer seasons, bats use a variety of strategies to delay fertilization.  

 

For instance, in southern Taiwan, female Japanese house bats can store sperm in reproductive tract and delay sperm exposure to eggs until next spring. Some species of female bats can even go into hibernation when the fetus is in early stage of development and delay the development until next year. Other species exhibit delayed implantation. All the biological adaptation and strategies are intended to control timing of birth so that young bats can be born in summer when the weather is warm and food sources are many.

Some male bats leave caves they hibernate to seek other shelters after young bats are born. For example, only male bats can be found in the Bat Pavilion of Fukuyama City Zoological Park. Professor Wu points out that male bats leaving their families “are not being irresponsible but are leaving the best habitat for female bats and newborn bats”.  

 

Global warming endangers bats’ survival; 2011 Year of the Bat campaign calls for bat conservation action

Bats have been in existence since the ages of dinosaurs. Many of animals that lived back then have long gone, but tenacious bats have survived tens of millions of years of evolutionary process and all kinds of disasters. Bats are now the second largest group of mammals after rodents. Bats’ special flying skill and echolocation ability increase their chances of catching prey, securing them with enough food sources.

 

Nonetheless, under the impact of global warming, seasons have become less distinctive. Some bats mistake that winters have vanished while some other bats cannot find places for hibernation. Bats’ growing and reproduction patterns have been affected as a result, which lead to infertility of female bats and growing disruption for young bats. Worse yet, people who mistake bats for evil creatures would destroy bats’ habitats, causing drastic reduction of bat population. Many valuable bat species have become extinct, leaving behind the saddening sight of empty bat caves.  

While Western cultures associate bats with evil vampires, bats are considered symbols of blessing in Taiwan. For instance, Chinese architectures have many totem designs that feature bats. Totems with different numbers of bats on them refer to different auspicious word phrases like “five forthcoming blessings”, “four heavenly fortunes”, and “blessed with both wealth and good luck”. United Nations Environment Programme declared 2011-2012 Year of the Bat in an attempt to make people know more about bats and to call for countries around the world to join hands in protecting bats, so that bats can continue to fly at night skies. 
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