Zorro volador de cabeza gris, Royal Botanic Gardens, Sydney. Foto: Mireia Querol Rovira.

What is a bat for?

Bats are the only mammals that can fly actively . They represent 22% of all mammal species and are distributed across all continents except Antarctica. However, they are unknown animals and big prejudices about them exist. Learn more about these fascinating animals, discover their ecological importance and why its conservation is vital.

WHAT ARE NOT BATS?

THEY ARE NOT FLYING RATS

Despite its appearance, bats are not rodents like rats, but belong to the order Chiroptera, with two sub-orders and about 1,240 species:

  • Megachiroptera (flying foxes): they have a face like a fox and only one species (Rousettus aegyptiacus) has the ability of echolocation   (knowledge of the environment due to ultrasonic sounds). The biggest one is the giant golden-crowned flying fox (Acerodon jubatus) , with a wingspan of 1.5 m.
  • Microchiroptera: they are smaller and  they all use echolocation. The smallest one (Craseonycteris thonglongyai) measures up to 3.3 cm. It holds the record for world’s smallest mammal.
Megachiroptera, macrochiroptera, comparison
Megachiroptera (left) and microchiroptera (right). Notice the difference in development of the ears and eyes. Source

THEY ARE NOT BLIND

Although sometimes their eyes are small they are fully functional. Nevertheless, hearing and smell are more important than sight, especially in Microchiroptera.

Artibeus gnomus, Dermanura gnoma, murciélago frutero enano
Gnome fruit-eating bat (Dermanura gnoma). The nose leaf and tragus help the bat to echolocate. Photo: Carlos Boada

Echolocation is the ability to know the environment (and especially, locate prey) that some animals have, like some bats and some cetaceans, through the emission of ultrasounds and echo reception. The sonar of ships and submarines is based on echolocation.

Bats produce ultrasonic sounds (“clicks“) of between 14,000 and 100,000 Hz in the larynx. They are emitted through the nose or mouth and directed by the nose leaf (if it exists). When the sound  is reflected from an object, the echo returns and it is captured by the ears of the bat. The time it takes to receive the echo gives to the bat information on the size and location of what’s on its way. As it approaches the prey, the frequency of clicks increases, to have greater accuracy.

Some species of bats use very specific frequencies ranges, which can be used in research for the identification of these species. Unfortunately many species overlap same frequency ranges, so identification is not always possible. Keep in mind that investigate bats is not as easy as visual observation of other animals. Ultrasonic recorders are used  (bat detectors)  and then ultrasonic sounds are converted into audible frequencies for humans. In Wildlife  Sound you  can hear some of those signals.

echolocation echolocation, dolphins, bat, cetacean
Comparison between the echolocation of a bat and a dolphin. Infographic by Antonio Lara. Source

THE ARE NOT VAMPIRES

Among more than one thousand existing species, only three feed on blood and live in central and South America: the common vampire (Desmodus rotundus), the hairy-legged vampire bat (Diphylla ecaudata) and the white-winged vampire bat (Diaemus youngi).

Desmodus rotundus feeding on a cow. Vampires don’t suck the blood, they lick it. Source

Other species eat fruitinsects, fish, frogs and nectar. Despite this, bats still inspire fear because of the nocturnal habits of some of them and myths and legends, but they are not aggressive animals. Therefore, the probability of transmission of diseases such as rabies by bats is very low. Within its population, has an incidence of only 0.5-1%.

 Bat fishing. Photo: Christian Ziegler
Bat fishing. Photo: Christian Ziegler

WHY ARE BATS SO IMPORTANT?

THEY ARE BIG BUG CONSUMERS

A city bat can devour in one night 60% of their body weight in prey. In New Mexico there is a colony eating on a night the equivalent of 25 elephants weight in mosquitoes. This makes them great potential pest controllers, helping to reduce the use of pesticides on crops.

Bat orejón eating an insect. Photo: unknown
Bat eating an insect. Photo: unknown

They also play a role in disease control, as many diseases are transmitted by the mosquitoes they eat, like the Zika virus, transmitted by the mosquito Aedes aegypti . For these reasons many Spanish communities, such as Madrid, Catalunya or Navarra are installing bat boxes to favor bat populations and  its reproduction.

Safe haven in an urban garden of Barcelona. Source
Bat box in a urban garden in Barcelona. Source

THEY ARE POLLINATORS AND SEED DISPERSERS

Some bats play a crucial role in the pollination of more than 500 species of plants and seed dispersal. Many plant species rely exclusively on these animals to reproduce. Without them, they would become extinct. The best known case is the flower of agave, the plant from which tequila is obtained. Only it is pollinated by the bat Leptonycteris curasoae and patterns of blooming agave are related to the patterns migration of this species in Mexico.

Bat megueyero lower (Leptonycteris yerbabuenae) feeding on flower Nector Agave.Foto: Barry Mansell
Leptonycteris yerbabuenae feeding on an Agave flower. Photo: Barry Mansell

Some coevolution cases are surprising, as the bat with the longest tongue (150% of the length of its body). It is also the mammal with the longest tongue in the world. It is the tube-lipped nectar bat (Anoura fistulata) and is the only pollinating a plant called Centropogon nigricans, despite the existence of other bat species in the same habitat of the plant.

 tube-lipped nectar bat, bat, bat
The tube-lipped nectar bat and its long tongue. Photo: Nathan Muchhala

The seed dispersers play a key role in the regeneration of forests, helping plants to colonize new territories in fragmented habitats or after natural disasters. It is estimated they  disperse from 1 to 8 times more seeds than birds in tropical regions.

THEIR IMMUNE SYSTEM IS UNIQUE

Bats are the natural host of many species of virus. They can carry up to 100 diseases at once, but they don’t usually become ill. How do they do It?

We only activate the immune system in response to infection but bat’s immune system is always in function. This allows them to be immune to serious diseases such as ebola, rabies, Hendra virus, SARS (severe acute respiratory syndrome) and MERS (Middle East Respiratory Syndrome). Investigating the functioning of their immune system, we could find the key to control or eradicate these diseases in people.

Vector species of ebola virus. Source

There are other medicine research based on bats, as the study of an enzyme of the saliva of vampire bats (Desmodus rotundus). It is studied as a safe and effective alternative in the treatment of stroke.

 Desmodus rotundus. Photo:
Desmodus rotundus. Photo: Michael & Patricia Fogden

THEY ARE GOOD BIOINDICATORS

Many bat species are sensitive to habitat degradation. Thus, studying changes in bat populations, we can have a knowledge about the state of the ecosystem. If you want to know more about what a bioindicator is check this post of Irene about water bioindicators.

TEHY ARE ECOSYSTEM REGULATORS

Due to its high mobility and activity, bats in tropical regions participate in the heterogeneous distribution of energy and nutrients and distribution of plants. They are also prey to numerous animals such as reptiles, birds and other mammals.

Bats also create niches where other animals can live. For example, the guano (excrement) of the species living in caves provide organic matter for the development of invertebrate communities.

THEY ARE BENEFICIAL ECONOMICALLY

As we have seen, bats disperse seeds and pollinate many plants. At least 163 of them have an economic interest. In addition, bat guano can be used as fertilizer.

Its role in insect pests and diseases controllers also brings economic benefits effect in agriculture, health, tourism…

CONSERVATION

Finally, we’ve seen that bats are key to ecosystems and their disappearance leads to serious consequences for the other species. However, they face the following threats:

3 pensaments a “What is a bat for?”

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