GOT International

THE UNLOVABLES

The Mountain Long-Eared Bat, wings tucked in like folding umbrellas–picture by Dr. CARLES FLAQUER (biologist & Coordinator of the Area of Investigation of Chiropteras at the Natural Science Museu of Granollers)

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OME of nature’s creatures are simply incapable of inspiring love or affection, and high on that list must come the bats. Yet that didn’t put a damper on the 2011 European Bat Night celebrated in Catalonia  last week. The event, held in 42 townships to draw public awareness to our menaced bat populations, attracted several thousand ecologically interested people, families, and children, a turnout just large enough to raise the spirits of anxious Bat Night organisers.

In the tiny town of Riells de Fai alone, some 150 people, mainly children, turned up to get an insight into the bizarre world of bats at an evening jointly hosted by the Town Hall, the Natural Science Museum of county-capital Granollers, and GOT. And what they learnt during an hour-long talk by museum director Toni Arrizabalaga, not just fascinated them, but got one and all raring to go on the programmed bat-hunt that followed.

Museum director Toni Arrizabalada, sporting a LED headlamp and flashing a Heterodyne Pettersson D240x  bat detector to record and replay bat calls and cries, leads the pack on a Bat Night field expedition through the narrow streets and surrounding woods of Riells del Fai. 

For the uninitiated, which includes most of us, a bat is a strange creature that looks like a mouse with wings,  flies around only at night, sleeps hanging upside down, and conjures up images of blood-sucking vampires. Toni Arrizabalaga did a great job setting the records straight, and went behind the scenes to reveal that bats have a complex lifestyle, a rich social life and a sixth sense that is almost beyond human comprehension.

First and foremost, he stated, bats are mammals,  meaning  that the females give birth to their young, which are then weaned on mother’s milk. In fact, of the world’s 4,800 species of mammals, an astonishing 1,100  are bat species!  And they vary in size from tiny creatures no bigger than butterflies, to huge animals with wingspans of almost two metres. A little-known fact is that bats, whose forelimbs are webbed and developed as wings, are the only mammals which can actually fly like birds. Depending on the species, bats by and large feed on either insects or fruits, but some species live on nectar, others on frogs, a few on  fish, still others  on small mammals and birds, and one particular species, aptly called the Vampire Bats, feed entirely  on blood – the only mammals that do so. The 30 species of bats found in Catalonia, though,  are all  insect eaters, called insectivores. Fruit Bats, called frugivores, among them the flying foxes, live exclusively  in tropical regions, while Vampire Bats are found only in South America.  

Bats are indispensable to the ecosystem. In particular, Insect-eaters, which make up 75 per cent of the world’s bat population, are primary predators of the vast swarms of mosquitoes, flies and other insects that emerge at night, especially those that plague forests and farms, causing millions of euros in crop losses annually. Each bat can gobble up an average of 600 insects a night, almost a third of its weight. That’s equivalent to a man weighing  60 kg swallowing  20 kg of meat everyday. The frugivores, which make up most of the rest of the bat species, also perform vital ecological roles such as pollinating flowers and dispersing fruit seeds. In fact, many tropical plant species depend entirely on bats for the distribution of their seeds.

BLIND AS A BAT?

This popular expression notwithstanding, all bats can see, some  very well indeed. The problem is that we humans hardly ever see them, let alone hear them. At twilight time we may be lucky enough to see a few feeding on insects, but as darkness falls we usually don't even know they are there. Bats however have no problem with darkness, even total darkness – they “see” with sound, using what is called echolocation, a system by which they give out high-pitched calls and then instantaneously interpret the echoes to locate, identify and capture the tiniest insect. Echolocation turns them into excellent aerial navigators. Unlike birds, bats  never fly into glass panes or get entangled  in your hair. 

                   Pinpointing a prey with echolocation—ultrasonic squeaks  out, echos in.

                         Picture courtesy of the Granollers Natural Science Museum

The human ear, however, can’t detect most bat calls. Children hear sound up to about 20 kHz (20,000 Hz or cycles per second), but most adults are unable to hear anything above 16 kHz. Bats emit calls at typically 2, 3 or even 4 times higher pitch than we can hear. Sounds beyond human hearing are called ultrasonic. Not all bat species operate at ultrasonic levels. Some like the  Molossidae or Free-Tailed bat species echolocate at as low as 9-15 kHz, and can be quite audible to us.

       So: hearing range for humans. Ultraso: ultrasonic (high-pitched) sound inaudible to the human ear.

         Picture courtesy of  the Granollers Natural  Science Museum.

    Resting comfortably on the tip of a finger, Catalonia’s smallest bat, the Common Pipistrelle– Picture by Carles Flaquer.

Compared to the fruit bats, which are the veritable giants of the bat world, insect-eating bats are relatively small. The smallest found in Catalonia is the Soprano Pipistrelle (Pipistrellus pygmaeus), a 3.5cm long pygmy  with a wingspan of 19cm and covered in brown fur. Sopranos echolocate at 55 kHz, and are common in wetland, woodland and farmland but also found in towns, where they roost in lofts and buildings.  The largest insectivore found here is the Greater Noctule bat (Nyctalus lasiopterus), one of the rarest European bat, with a body length of about 16cm and  wingspan of up to 46 cm. It also happens to be one of the few bat species that feed on little birds, preying extensively on night-migrating songbirds on the wing. It has an echolocation frequency of above 20 kHz -- beyond the hearing range of birds.

     The Greater Horseshoe (Rhinolophus ferrumequinum) -– Picture by Carles Flaquer

Catalonia is also home to the Greater Horseshoe Bat (Rhinolophus ferrumequinum), which can live for up to 40 years -- the oldest recorded age for any European bat. The Greater Horseshoe bat is the largest bat in Europe and has a distinctive noseleaf -- a thin, broad, membranous fold of skin on the nose -- which has a pointed upper part and a horseshoe shaped lower part that gives it its name. The bat’s horseshoe noseleaf is an important adaptation -- it helps to focus the 82 kHz echolocation frequency calls the animal uses to 'see'. The Greater Horseshoe bat is between 5.7 and 7.1 cm long and has a  35–40 cm wingspan.

      The Barbastelle, a European bat with a short nose, small eyes and wide ears – Picture by Carles Flaquer

Two other favourites of  bat-lovers here are the Barbastelle (barbastellus barbastellus)  and the Parti-coloured Bat or Rearmouse (Vespertilio murinus). The Barbastelle, a European bat with a short nose, small eyes and wide ears, roost in damaged or dead trees and move between the roosts with great frequency. Its echolocation frequency is around 40 kHz. The Parti-coloured bats, which have a call similar to a twittering bird call, hunt for prey such as mosquitoes, flies and moths using ultrasonic cries of around 27 kHz. Its name comes from its two-coloured red to dark brown fur, and silver-white-frosted hair.

          The Parti-coloured Bat  with a bird-like call –Picture by Carles Flaquer

Bat-Hunting Via Ultrasonic Mike

The throng that tailed Toni Arrizabalaga down the narrow streets of Riells del Fai on Bat Night didn’t actually see any bats. But they did learn a lot about the Heterodyne Bat Detector he was brandishing. Nobody had ever seen one before. Toni explained that it was a gadget with an ultrasonic microphone that converted undetectable bat calls into sounds audible to the human ear – a sort of bat radio. The electronics is complex, but whenever a bat flew over the crowd, the detector gave out a series of  clicks that got everyone excited and focussed on the electronic box instead of the skies above. The sounds were not exactly meaningful, except to the expert user. They didn’t give us any real idea of the calls themselves,  but they did tell that a bat was around, what species it belonged to, and why it was making those sounds. Different sounds “reveal” to the expert different bat activity: normal navigational calls to identify and avoid hitting some obstacle;  calls of bats on the hunt for prey; calls indicating an attack sequence as the bat locates its prey and homes in on it; social calls and even calls revealing movement between roosts.

Click  to ‘hear’ a Kuhl´s pipistrelle (Pipistrellus kuhlii) making a social call. 

     Sound waves on a bat detector and revealing what the creature is up to –picture courtesy of Granollers Natural Science  Museum

An upside down world

Apart from echolocation, another fascinating feature of bats is their ability to roost upside down, virtually from dawn to dusk. To get into position, all a bat has to do is find a surface it can grip on to with its claws. With the surface held, the bat lets its body relax, an action with causes the weight of the upper body to pull down on the tendons connected to the claws, causing them to clench vicelike. The claws then close in, and the animal’s weight keeps them locked. To unlock the grip, the bat has to exert energy and flex muscles that pull the claws open. Since the claws remain locked when the bat is relaxed, a bat that dies while roosting will continue to hang upside down until something shakes it loose.Sleeping upside down enables them to launch into flight in an instant, especially when danger threatens.  The other alternative is to slowly crawl up to a high vantage point and then hurl themselves off into flight.

                                       Roosting wrong side up in a bat cave -- Picture: Granollers Natural Science Museum  

While Heterodyne bat detectors have opened up the secret world of bats, public awareness of the vital role they play in the environment in which they live is still poor. Most people find the creatures repulsive –they are ugly, grotesque, and there’s something sinister about the fact that they roost suspended upside down. The European Bat Night, involving more than 30 countries throughout Europe, has gone a long way, however, in breaking down some of the barriers between humans and bats by passing on information about the way bats live and their habitats. One myth that has certainly been buried is the belief that bats are rabies-carriers.They aren't.

                                                                                                                                     Report: Abul Fazil