When Professor Drew Gardner returns from his forays into the UAE's hinterlands and replays his recordings, which must be converted from an ultrasonic frequency to something humanly audible, he strains his ears for new sounds. If he hears something different, it means he may have successfully notched another small victory in an ambitious project that has become his passion: to log the calls of all eight of the UAE's known bat species.
His goal is to create a data bank of their sounds and sonograms that will help researchers better identify which species is which when the uncooperative little mammals are flying overhead or flitting about the rocks. To date he has recorded three UAE species: the naked-bellied tomb bat (Taphozous nudiventris), the Muscat mouse-tailed bat (Rhinopoma muscatellum) and the pipistrelle. These happen to be the UAE's most common bats, so there is still plenty of work to do.
Last week found him on Sir Bani Yas Island, ultrasonic bat-detector at the ready, on the trail of the seldom seen and even more rarely heard Sind serotine bat (Eptesicus nasutus). When he pressed the darkened sky for its secrets, his bat detector registered something a little more familiar than anticipated. The call's sound and appearance, when graphed later with special software, is reminiscent of an old friend, Kuhl's pipistrelle (Pipistrellus kuhlii), perhaps the most common bat in the country.
And maybe it was the Kuhl's, except that the calls didn't exactly match his other pipistrelle recordings, some of which were made as the species hunted over the ghaf trees along Abu Dhabi's 19th Street, not far from the office he has occupied for nine years at Zayed University. "They are close to Kuhl's pipistrelle, but the Sind serotine looks almost identical, other than an extra tooth, and I have no idea what its call is like," Dr Gardner said. "I managed to get a few photos of the bats in flight, but not good enough for a certain identification."
Despite such difficulties, the 53-year-old professor of natural sciences and chairman of the Abu Dhabi branch of the Emirates Natural History Group remains enthusiastic about his part-time bat project. All insect-eating bats use echolocation to pinpoint their prey, sending out sounds usually in the range of 25 to 100 kilohertz frequencies, although some species can hear ultrasound up to 200 kHz, Dr Gardner said.
By comparison, a healthy, adult human will be lucky to hear between 40 and 17 kHz, and regular conversations tend to occur around 1 kHz. Bats do make sounds audible to humans, perhaps when jostling about their roosts or getting ready to fly, but when they are on the hunt they're using ultrasound. "What they are doing," Dr Gardner said, "is producing these calls, at say 40 kHz or something, that then get reflected off flying insects, rocks or trees or whatever, and the echoes come back and they pick those up. By analysing time and loudness and the quality, they get a lot of information."
They can also analyse Doppler shifts, the rise or fall in frequencies caused by an increase or decrease in distance between the source and receiver of a sound. "If a bat is stationary making a call and it's bouncing off a wall, the echo is going to come back at the same frequency. But if there is a relative movement, then the frequency that comes back will be changed and, by analysing the frequency of echoes, flying bats can track a flying moth, for example."
Some bats, like the UAE's trident leaf-nosed bat (Asellia tridens), have echolocation abilities so sophisticated they can detect wires thinner than a strand of hair stretched in a laboratory maze. The Persian leaf-nosed bat (Triaenops persicus), another local, sports similar nasal adaptations that help them make the most of their echolocation calls. "It's pretty amazing," Dr Gardner said. "Their brain has to take all of this information and build a sort of sound picture, just like we do with the light information that is coming back into our eyes. Our brain builds that into something which we can see; well, the bat is building a sound picture, a moving sound picture of its surroundings."
And while the echolocation skills of bats are astonishing, their aerial abilities are another claim to fame. "They are very efficient fliers," Dr Gardner said. "In some ways, almost more efficient than birds. A bat has much more control over its wing, over the shape of the wing, the size. It has a double membrane with these long fingers going through it, which have muscles attached, so they can really change the flight characteristics of the wing very, very effectively."
And there are still other things that make the bat a particularly fascinating creature for study. Dr Brock Fenton, a Canadian bat researcher with more than 40 years of experience and more than 200 scientific papers to his credit, said "in some ways, bats are just a magic well, full of all sorts of intriguing biology. Every time you turn around there is something else of interest and excitement on the horizon".
Dr Gardner agrees, citing a 2005 discovery that a bat had somehow managed to live 41 years in the wild. "How a small mammal with a high metabolic rate can live 41 years goes completely against the grain of what you are taught in comparative animal physiology and zoology courses," he says. "It is just bizarre. I mean, most small mammals, shrews and such, live a couple of years." But despite an explosion in bat research elsewhere in the world, even the basic natural history of most of the UAE's bats remains shrouded in mystery. Gary Feulner, one of the country's top naturalists and Dr Gardner's counterpart with the Dubai Natural History Group, sums up the present state of knowledge succinctly: "Good luck finding much to say about individual bat species."
With a few exceptions, Dr Gardner said, the Egyptian fruit bat (Rousettus aegypticus), and Kuhl's pipistrelle have both been well studied in other countries, though not here. The level of knowledge here is "very, very poor", he said. "We just don't know anything really about their status, and about any trends or changes in their populations, or what effects insecticide spraying might be having on them. We don't know how long they live, when their breeding seasons are. We don't even know where they roost. Basically, no one has done any real ecological or behavioural studies on them."
Dr Fenton is one of the out-of-country researchers who has taken under his wing one of the UAE's bats - Hemprich's long-eared bat (Otonycteris hemprichii) - though not here and not without some difficulty. "For years I had wanted to see these bats and work with them," he says. "In the early 1980s, I tried to negotiate going to Tashkent along the Silk Road, but the Soviets would not give me a visa."
Since then, he has had several opportunities to work with the bats and "radio tracking indicated that they roost in crevices and holes in rock faces and may cover at least 10km in search of prey". The availability and abundance of such roosting sites are absolutely critical for the bats of the UAE. Typical sites here, says Dr Gardner, might include caves, holes, falaj systems and undisturbed buildings such as old forts and watchtowers. But, he said: "The problem in the UAE is there are not that many, and they tend to get knocked down or restored."
Holes sometimes sealed for the safety of goats or children might also spell a quick end to a thriving bat colony. A grate through which the bats could pass would be a more ecologically sensitive solution. Each of the Emirates Natural History Groups, from Abu Dhabi, Dubai and Al Ain, usually include a yearly trip to a known bat roost, though never in the early summer, when nursing mothers and babies might be present, and always with strict limits placed on numbers to ensure the bats are not overly disturbed.
Dr Gardner often leads an autumn sunset trip to a particularly interesting rock formation where hundreds of the large, strong-flying naked-bellied tomb bats pour out of the crevices over a period of minutes. And for a particularly atmospheric and subterranean adventure, Brien Holmes, the chairman of the Al Ain Natural History Group, leads the odd trip through an ancient but still used 100 metre-long falaj system, up to 15m deep and perhaps 4,500 years old, near an oasis community at the foot of the Hajar mountains.
The tunnel system, calf-deep in water, is completely dark and quite narrow in sections, but access shafts bored for light and ventilation offer some respite and the chance to view the several dozen mouse-tailed bats, along with the geckos and spiders that have also made the falaj their home. Talk of such roosts sets Genevieve O'Farrell, 35, once a bat ecologist and now an environmental consultant in Abu Dhabi, on a trip down memory lane, a lane that has led her to hundreds of the deepest, darkest and dankest spaces in Britain, including cold mineshafts, the sewers of Bristol and Dartmoor prison.
"The way bats have been portrayed in the movies has made them a misunderstood and feared animal, a reputation they don't deserve," she said. "Bats avoid contact with humans, and if they accidentally come into contact with them are far more scared of us than we are of them." * The National