As cryptozoologists, we at the Centre for Fortean Zoology (CFZ) are frequently contacted by researchers from TV companies wanting to make monster-related programmes. While many of these projects come to nothing, a call from Bang Productions, who were working on a Discovery Channel series called Mysteries of Asia, led to my boarding a flight to Thailand in October 2000 to go in search of the legendary monster of the Mekong river, the naga.

The naga is essentially a gigantic snake, usually found in Hindu and Buddhist mythology rather than in present-day Thailand. It is supposed to bear an erectile crest on its head – rather like that of a cockatoo, but made of scales – which it holds menacingly aloft when angry, just as a cobra opens its hood.

According to Buddhist scriptures, the naga is dangerous and can kill by biting and injecting its venom; by spitting venom (again, like certain species of cobra) and thus paralysing its victim; by constriction with its powerful coils; and by the power of its baleful glare, much like the basilisk of mediæval Europe and the Middle East.

Legend says the nagas possess immense intelligence and magical power. They can, for instance, transform themselves into humans and walk unnoticed in the world of men. It was believed they inhabited grand underwater palaces, rather like the dragons of China. Unfortunately for folklorists of the Michael Meurger school, the naga is not satisfied with being a legend and still rears its scaly head, being sighted up and down the Mekong river even today.

The flight from England via Amsterdam took an uncomfortable 10 hours, but finally I arrived in Bangkok, to be met by Peter Daniel, the programme’s producer, and the rest of the crew, including hugely experienced cameraman Derek Williams and the equally dedicated soundman, Somyot Pisapark.

Bangkok is a strange city; for all its exoticism, it bore, for me, an uncanny resemblance to Birmingham. It even has an office block shaped like the famous Rotunda. Gaining planning permission in Bangkok is easy, so buildings spring up like fungi. Often, small things like foundations or strengthening rods are forgotten, and a half-constructed building is simply left abandoned. Unlike Birmingham, though, here one often comes across an elephant wandering nonchalantly down the street or rooting through a bin outside a bakery!

Later that evening, I was shown some film of the giant Mekong catfish (Pangasianodon gigas, the largest freshwater fish – in terms of bulk – in the world), which has sometimes been mooted as an explanation for the naga. The sequence showed four men catching an 8ft (2.4m) specimen (above). The silvery-grey fish is of massive bulk and has tiny eyes, bizarrely situated very low on the head. The men manually stimulated the fish’s cloaca to collect its milt for use in captive breeding programmes. It was strange to think I had travelled all the way to Thailand to watch film of a fish being masturbated.

The following day brought a visit to the Samutprakarn crocodile farm, home to the largest crocodile in captivity, a 20ft (6m) Indo-Pacific-Siamese cross named Yai. Yai in Thai means big, which demonstrates the imaginative bent of his keepers. They swore that Yai was the largest crocodile on the farm, but out in the main lake I saw a number that appeared to be even bigger and one which looked a good 25ft (7.6m) long. It would not be tempted closer to the bank and showed only the end of his huge jaws and a portion of his tree-trunk like tail, so no accurate measurement could be made.

I had a theory that the Mekong monster might be a large (30ft/9.1m +) Indo-Pacific crocodile (C. porosus). I abandoned this idea after hearing eye-witness accounts, but at least this was a chance to view these creatures at close quarters. A chance to feed them (from a bucket of chicken carcasses) brought a pang of nostalgia for my days as a zookeeper.

Samutprakarn would not past muster as a zoo in the West, but worse was to follow. Pata zoo, housed, believe it or not, on the roof of a department store in downtown Bangkok, was far worse. The animals’ living conditions are truly appalling, but the visit was at least worthwhile for a look at a preserved specimen of a creature I had only read about in Karl Shuker’s The Lost Ark, the giant freshwater stingray (Himantura chaophraya). Only discovered in 1987, this fish is a monster in every sense of the word. The best description of this piscine titan I can give is an organic flying saucer! Greenish grey in colour, its flattened body disc measures some 7ft x 6.5ft (2.1m x 2m), big enough to cover a double bed. Its eyes are tiny, like those of the Mekong catfish with whom it shares its habitat. These bottom-feeders have to rely on touch, scent and electro-reception in the Mekong’s muddy waters.

We had come to interview the zoo’s director, who had allegedly taken some film of a naga swimming in the Mekong. However, he had fallen over and banged his head and was now in critical condition in the hospital. After the horrors I had witnessed in his zoo, I was tempted to see this as an instance of karma in action. We talked instead to a Dr Apicsart, a fish expert unconnected to the zoo. He had spent many years on board Japanese trawlers studying rare fish, often from the deep seas, and was sceptical about the naga, believing that witnesses had merely seen shoaling fish.

The following day, we left Bangkok and flew north to Udon Thani; this would be our base of operations for the rest of the expedition. We were met at the airport by the author Pongpol Adireksarn, better known by his pen name, Paul Adirex. Pongpol specialises in action thrillers and has written four best sellers, one of which, Mekong, features the naga, in which he firmly believes. Pongpol, at the time of my visit, was the campaign manager of Thailand’s opposition party; now, he is the country’s deputy prime minister. Charming and witty, he was a joy to work with.

That evening, a banquet in Pongpol’s honour was held at a local restaurant. He seemed to be genuinely popular (unlike most Western politicians) and a local celebrity. We also met Pongpol’s friend Pracha Manakarn, known as “Pang” to his friends, who became an enthusiastic and valuable member of our team from this point on.

A particularly delicious fish soup was served at the meal; I had no idea, until I was already halfway through, that it was made with the Mekong catfish. It’s not good for a zoologist to admit that he has eaten an endangered species!

Our first destination the following day was a local statue garden, where gigantic statues, some more than 150ft (40m) tall, stand surrounded by jungle. It was a scene reminiscent of some lost Rider Haggard city, but the statues are only about 20 years old. They reflect Thailand’s peculiarly Hindu-influenced Buddhism: alongside sculptures of the Lord Buddha, one also finds gods such as Kali, Ganesh and Hanuman. (This is an important factor to which I shall return later.) There were several massive statues of nagas, including the multi-headed naga king shading a meditating Buddha. Thai monsters were well represented; as well as the naga, there were statues of Garuda, the bird-man, who is said to bring the rains on his wings, and a magical golden lion. A giant water-serpent, a bird-man and a mystery big cat all living in the same country. It reminded me of home.

Later, in the town of Nongkhai, we spoke to Malinee Phisaphan, an old lady who ran an antique stamp shop and a cybercafé and who had seen a naga five years earlier. Malinee was intelligent and well educated, and she read, wrote and spoke English perfectly. She and a friend had been riding through town on a bus when they passed by a bridge. They saw a huge black snake in the water beneath the bridge. Malinee described it as around 17ft (5m) long and as large in diameter as a soccer ball.

The next day was an important one. The naga mystery, with its complex folklore, has become entangled with many mysteries over the years; one of these is the naga fireballs.

On 13 October each year, balls of red light are seen shooting out of the Mekong river. Locals believe these to be the breath of the naga, heralding the end of the rainy season. Huge crowds assemble to celebrate and view the phenomenon from the banks of the Mekong. The fortean in me recalled the balls of blue light associated with giant snakes in the Amazon (believed to be their bioluminescent eyes) and I thought, too, of the earth lights often reported over water. Perhaps two fortean phenomena were occurring here side by side.

During daylight, before the appearance of the nocturnal lights, a huge parade took place, with hundreds of people in traditional dress, bands playing, and floats carrying images of the naga. It ended with a temple made entirely from bamboo leaves being floated upon the river.

By nightfall, I found myself surrounded by 100,000 screaming Thais shining spotlights and laser pointers on the water and letting off fireworks. Traditional long boats illuminated with candles and lamps passed by as we waited for the phenomenon to begin. Suddenly a shout went up: a fireball had been spotted. Shortly after I saw a red light spring upwards from the opposite bank, then fade away. Soon, more followed – first in ones, then in twos, threes and fours. Swiftly, something dawned upon me; if this were a natural phenomenon, it would surely be occurring across the entire width of the river. The lights were springing up from the far bank – the Laotian side – in what appeared to be an extremely orchestrated fashion. They also seemed to be coming from areas where lamps were visible and people, presumably, were present. The fabled naga fireballs seemed to be nothing more mysterious than fireworks of the relatively noiseless kind that fade away rather than exploding, much like maritime distress flares.

So, the fireball mystery bit the dust. I was satisfied that the Laotians were having a good chuckle at their friends across the river. But other riddles awited me.

Our next stop was the village of Phon Pisai, whose spectacular temple is adorned with dragons and nagas. Here, Pongpol interviewed a Buddhist abbot (who bore an uncanny resemblance to the late Brian Glover) and his monks about a strange naga encounter. Eight years ago, an ancient temple (on the site where the new one now stands) had become unsightly and dangerous, so it was decided to pull it down and replace it. Whenever workmen approached, a huge black snake would appear and rear up to strike them. The workers, monks, and abbot all saw it. Its body was very thick, but they couldn’t estimate the creature’s length as it kept most of its coils inside the building. Finally, an offering was made to the monster, and it disappeared overnight.

We were back in Phon Pisai the next day to interview another witness – Officer Suphat, the village’s chief of police (left). Three years previously, he and a group of 30 people had been walking on some cliffs overlooking the Mekong when they saw what they thought was flotsam in the river. As it drew closer, they became aware that the ‘flotsam’ was moving against the current. Looking down, they saw a gigantic black snake swimming with a horizontal flexation (indicative of a fish, amphibian, or reptile). I asked Officer Suphat how long the monster was. His answer staggered me: 70 metres. Thinking there had been a mistranslation, I asked again, but he was quite clear: 70 metres, or 230ft. It had been a monster of Toho Studios dimensions.

The spectators had watched the naga swim by, then were overcome by fear and fled. Officer Suphat later told a Buddhist monk about his sighting. The holy man confirmed that what he had seen was a naga. He explained that some years ago a boat carrying a statue of Buddha across the river had capsized, and the statue had fallen to the river bed. Since then nagas had come to protect it.

The officer’s monster seemed to me excessively long. Perhaps he had seen several of the Buddha-guarding nagas swimming in line, or a long wake that had made the already huge serpent appear even more monstrous.

Another enigma awaited me in Phon Pisai, an exciting one for a zoologist. It was said that the bones of an actual naga were kept as holy relics in the village! A strange story was attached to these bones. Their current owner had once had a dream in which he was visited by a naga. The serpent told him to cross the bridge into Laos, where he would meet a man who owned some naga bones, which he was told he should buy. The next day, the man duly crossed the bridge and, indeed, met the bone owner, who refused to sell the bones. The Thai returned empty-handed. The next night, the naga came to the man in his dreams once again, and told him to ask the Laotian if he would sell just half the naga bones. Once again, the Laotian refused to sell, and the man came home with nothing. One final time, the serpent entered the man’s sleeping mind and told him to try again; this time the Laotian would relent. The man crossed the bridge a third time and, indeed, the Laotian sold him the bones.

This was a fine story, but I was mostly excited at the prospect of laying my hands on real physical evidence of the creature’s existence. We were told that the owner did not want to be filmed and would not let us remove the bones for DNA analysis as I had intended. However, we were allowed to film and touch them. I was confident about being able to identify snake bones and hoped we had stumbled across evidence of a titanic new species. The relics were brought to the police station and kept under lock and key until we arrived. They were brought out in a silver chalice and we waited anxiously as the lid was removed to reveal… an elephant’s tooth! (above) Quite how, in a country absolutely jam-packed with pachyderms, anyone could mistake an elephant’s tooth for giant snake bones is beyond me; but it was another mystery shot down in flames.

My final full day in Thailand turned out to be the most exciting and fruitful. We drove north for hours, along dirt tracks through the jungle, and then trekked on foot to an extremely remote village in the forested hills. I don’t know if this place even had a name – I never found out. We’d come to talk to Mr Pimpa, a sprightly old man of about 70 who’d had a frighteningly close encounter with a naga in some local caves. Obligingly, he offered to take us underground to the naga’s lair, scene of his terrifying experience some 10 years ago. He led our party to a small, hidden cave mouth in a hillside. It didn’t look like much, but Mr Pimpa told us that it led to a network of caves which stretched for some 10 miles (16km) beneath the hills and connected with the Mekong.

We followed Mr Pimpa (pictured right) into the first cave, which was roughly 15sq ft (4.5sq m) by 4ft (1.2m) high. By flickering candlelight, our aged guide showed us a tiny triangular tunnel in one corner. Peter, with his expensive hand-held camera, went no further, and I left my bulky camera behind as Pang and I followed Mr Pimpa.

The tunnel was half filled with water and so low one had to crouch. It led on for some 40ft (12m) into the main network. These caves were by far the strangest and most alien place I have ever been in; a labyrinth of dank, unwholesome passages about 4ft (1.2m) high and often only 2ft (60cm) wide. Occasionally, they widened out into spaces of 15ft (4.6m) across. Unearthly rock formations like giant coffins or Greek pillars were festooned with jasmine wreaths in honour of the great serpent. It was as if we had entered the fevered imagination of Clark Ashton Smith.

We crossed icy subterranean rivers and avoided the razor-sharp stalactites which hung like guillotines from the ceiling. When not crouched, we were on all fours or slithering like worms on our bellies through the primal slime. No bats hung from the ceiling, but I saw what looked like tiny glowing strings of pearls hanging from the cave ceiling. These were drops of luminous saliva suspended on strands of silk by carnivorous midge larvæ like ghoulish fishing rods.

We travelled for about a mile, until we came to the spot where Mr Pimpa had encountered the monster 10 years before. It was a long, tubular cave. The old man had been exploring by candlelight when he had turned into this cave and come across a giant snake. Its head was in the shadows, but the visible portion of its body was 60ft (18m) long. Mr Pimpa had pressed himself against the wall in terror as the giant reptile crawled past at an agonisingly slow pace. Its scales were black, with a glossy green sheen, and it was around 2.5–3ft (76–91cm) thick. Finally, it had disappeared along the passage, and Mr Pimpa had collapsed gasping in relief. In the dark, his hand fell against a tiny, semi-precious stone which he had pocketed. Scrambling back out of the cave system, he returned to the village and told his weird tale. He later had the stone mounted onto a serpent-shaped ring which he showed to us. He believed that despite the fear he had felt at the time, the naga had since brought him luck. Before his adventure, he had hardly been able to feed his family. After it, he had inherited land and become a successful farmer. The caves were now considered sacred to the villagers.

Mr Pimpa led us back along a different set of passages and I regretted not having brought a ball of twine. Suddenly, daylight streamed in and I looked up to see a vertical shaft 10ft (3m) high, with perpendicular, slime-covered walls. Mr Pimpa shot up it like a monkey, but a portly cryptozoologist is not the most agile of creatures. After several attempts, I was forced to climb on poor Pang, as he if he were a living ladder, and be dragged the rest of the way by our guide. We then pulled up trampled Pang and trekked back off through the jungle to our crew.

I was impressed by Mr Pimpa’s testimony. He had nothing to gain from lying to us, was not paid for his story and seemed genuinely suprised that people from the outside world were interested. He was a very nice man who went out of his way to be helpful.

That night, back at our hotel, I was finally shown the film taken by the director of Pata zoo and showing a supposed naga swimming in the Mekong. Most film of cryptids is pretty poor – fuzzy, pixelated, out of focus – but this took the biscuit. It was a badly-filmed log being bobbed up and down by the current; nothing more, nothing less.

The director believed the naga to be an oarfish (Regalecus glesne), an elongate, silver-scaled fish which indeed has a naga-like blood-red crest. The oarfish is reputed to grow up to 45ft (14m) long, though none as big as this has ever been measured. It is, though, a saltwater fish and lives at extreme depths, only turning up on the surface when dead or dying; it’s hardly likely to be swimming in the Mekong river. It is, incidentally, totally harmless, but one could see how it could add to the naga legend if a specimen turned up in the nets of a fisherman at sea or washed up on the coast.

The expedition was over. After sad goodbyes all round, I prepared to return to a cold and wet Britain. As my plane took off, I asked myself what conclusions I’d come to.

First, the ‘naga fireballs’ seem to be man-made, possibly in order to attract money into the area. Secondly, the naga bones were elephant teeth. Thirdly, the naga film was of a floating log.

But one mystery remains unsolved; that of the naga itself. The witnesses I’d spoken to fell into two categories – those who’d seen something in the river and those who’d seen something on land. Both types of account, though, shared spiritual or superstitious overtones: serpents guarding temples and statues or bringing good fortune.

Perhaps the Hindu influence on Thai Buddhism is the key. Nagas originated in Indian legend and were only later transplanted to Indo-China. I suspect that all of the mystical elements of this original, legendary naga have been grafted onto a real, local animal – one that has always inhabited the Mekong. But what is it?

There was once a group of primarily aquatic snakes which reached immense sizes. The Madtsoids, which first evolved in the Cretaceous period and were found worldwide, were at first believed to be giant Boids. It is now known that they were a primitive basal group of snakes. They were highly successful for such archaic beasts and some (such as the Australian Wonambi) flourished until the end of the Pleistocene epoch, only 10,000 years ago. Some of these species dwarfed today’s anaconda; a vertebra from South America indicates a 60ft (18m) snake as thick about as an oil drum.

Reports from all over the tropics suggest that some species may have survived to the present day. As well as their great size, all these monster snakes seem to share strange ornamentation on the head. The lau of the swamps of Sudan is said to have facial tentacles. The mano tauro or sucuriju gigante of the Amazon is believed to have horns, and Indo-China’s naga has a crest. Horns are not unknown on snakes; the rhinoceros viper of Africa and the horned viper of the Middle East are just two examples, although their horns are actually modified scales. Madtsoids – none of which were venomous – killed their prey by constriction with huge muscular coils, so how do we explain the nagas’ supposed use of venom? Posessing both constriction and venom would seem to be evolutionary overkill. Perhaps this, like the widespread belief that the harmless salamanders of Europe were deadly poisonous, is a facet of folklore.

This is, of course, only a theory, and will remain so until a well-financed expedition with a lot of time makes a concerted effort to find a specimen.

The Naga fireballs

The annual appearance of the mysterious naga fireballs – on the full moon of the 11th lunar month each year and coinciding with the Buddhist equivalent of Lent – has become an important part of Thailand’s tourist industry. Celebrated in the Bang Fai Phaya Nark festival, the phenomenon is a huge boon to the local economy of the north-eastern border province of Nong Khai. 2002’s event saw in excess of 400,000 visitors, both Thais and foreign tourists, joining the celebrations along the Mekong river, mostly in the districts of Phon Phisai, Sri Chiang Mai, Pak Khad, Rattana Wapi and Bung Kan. The mysterious balls of red, pink and orange light were supplemented by a special light and sound show over the festival’s four-day run, bringing in more tourists than ever before.

At the height of festivities, a total of 829 fireballs was reported – noticeably less than in some previous years, when thousands were seen. The largest concentration was in the Rattana Wapi district, where 483 of the mystery lights were seen rising from the river. 188 fireballs were reported from Phon Pisai, 86 from Bung Kan, 62 from Pak Khad, seven from Sangkhom and a rather disappointing three from Bung Khong Long. One newspaper report blamed the “unusually poor show” in some areas on the weather; a heavy downpour and strong winds also dampened the spirits of visitors, many of whom had made the trip after seeing the recent hit Thai movie Mekong Full Moon Party, a comedy centred around the fireball festival.

The Thai government has apparently commissioned an investigation into the mystery orbs, whose cause remains unknown. While they are traditionally believed to emanate from the naga – some legends say they are the serpent’s eggs - scientists have suggested that the fireballs are produced by flammable natural gas deposits in the river bed drawn to the surface by the moon’s gravitational pull; although this hardly explains why it should happen only in the month of October or early November.

A recently-aired TV documentary has further muddied the waters, suggesting that the entire fireball phenomenon is a hoax perpetrated by the Tourism Authority of Thailand (TAT) to bring money to the region and that the ‘fireballs’ were created with tracer bullets from AK-47 rifles on the Laotian side of the Mekong. Prasit Chanthathong, a Nong Khai MP, responded that since the fireballs had been seen for hundreds of years, this wasn’t a very convincing debunking:“How did anyone have a gun back then to create this show?” he asked, apparently forgetting the earlier Chinese use of gunpowder and rockets.