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For me, it all started with a small black harlequin frog, a creature no bigger than my thumb. Named after the local word for sadness, the frog was special, because it appeared to no longer exist.

It was an emblem of all the frogs that had disappeared from bubbling streams and cool forests of South America and beyond, as hundreds of species of amphibian succumbed the world over to a fungus responsible for the greatest disease-caused loss of biodiversity in human history.

I’d set off to scour a high mountain pass in southern Ecuador, seeking signs of the frog’s survival. I never did find it. The following year a team of local scientists returned to resume the search, and they made an astonishing rediscovery – of the black harlequin, clinging to life. But I had taken my first step of what would become a global quest for answers.

The black harlequin frog was not the only species to make a comeback - in Costa Rica and Australia frogs were also reappearing years, sometimes decades after they were thought to have vanished. What were these survivors among the carnage telling us? What clues did they hold that could help us stem the hemorrhaging of life from our planet?

In 2010 I decided to try to find out. As Director of the amphibian programme at Conservation International I was uniquely positioned to spearhead the largest coordinated global search for species lost to science. Over several months more than 120 scientists were deployed in 21 countries in search of frogs and salamanders that had not been seen for at least 15 years. Some had not been sighted for 160 years. The stories, discoveries and rediscoveries that they brought home captivated a global audience and shed new light on the biggest loss of biodiversity in 65 million years.

But first let’s address the question on so many lips: so what if frogs are disappearing?

Amazing creatures

To convey just why I care, let me travel back 30 years. As a young boy growing up in Scotland, long before I knew that amphibians were in trouble, frogs and newts granted me an entry point to nature – an invitation to study and understand my own little corner of a vast world. They opened my mind to scientific inquiry and inspired curiosity.

Every spring I would arrive at our neighbourhood pond to collect spawn and transfer several black pearls encased in jelly to a tank in my bedroom, where I would nurture rounded tadpoles as they floated belly up, smiling at me as they devoured fish flakes hovering like sheets of ice on the water’s surface. As they sprouted legs, hind ones first, and their tails began to shrink like a melting ice lolly, I would release the froglets into the tangle of grass next to the pond to embark on their life on land, and each and every time I would wonder: how do they do that?

Watching black eggs transform into tadpoles and then froglets was like bearing witness to evolution – the great exodus of life from water to land - in miniature. Frogs are the largest animals to undergo such a dramatic metamorphosis.

I may no longer be a child (debatable, some may say), but that doesn’t mean that amphibians cease to amaze me.

Just when I think I am getting a handle on the diversity of colours, shapes, sizes and behaviours, another frog, salamander or caecilian (a kind of long, worm-like amphibian that lives underground) comes along that blows my mind.

I remember vividly the first time I learned about the axolotl – the Peter Pan of the animal world – a salamander that spends its entire life (and even breeds) in the larval form, with feathery gills billowing from either side of its head. From browns to whites and pinks, their ability to exist in such an eclectic array of colour forms is a subject of research, as is their remarkable ability to regenerate limbs.

While many more of us are drawn to the furry and the feathered than the scaly and moist, frogs and salamanders have always resonated with me because they extended an invitation to develop a personal relationship with them from an early age.

Had I raised a panda cub in my wardrobe my life may have played out differently. But amphibians were simply more tightly woven into my life, as they are into the lives of many people around the world. To some they are consumers of crop pests or of mosquitoes, to others they are a source of medicinal compounds. But to many they represent a source of wonder – and thankfully, I am not alone.

The late Wangari Maathai, a Kenyan social and environmental activist who was awarded the Nobel Peace Prize of 2004, made a special place for frogs in her acceptance speech when she spoke of growing up in rural Kenya; “I saw thousands of tadpoles: black, energetic and wriggling through the clear water against the background of the brown earth. This is the world I inherited from my parents.” Protecting frogs is an investment in the future of our children and children’s children.

Back from the dead

As a child I never imagined that frogs would, or could, suddenly disappear. It was a couple of decades later when I really became aware that frogs and salamanders were in trouble, and that understanding deeply saddened me.

After gaining a PhD (studying frogs, of course), I joined Conservation International in the hope that I could play my part in protecting these underappreciated creatures. Amid stories of loss, I found myself increasingly interested in an emerging phenomenon that provided a glimmer of hope: the reappearance of frogs that had been given up as extinct.

The first Lazarus frog that captured my imagination was the Variable Harlequin Frog of Costa Rica – a beautiful animal with lemon yellow to flame-red against mottled black (their name came from the variability in their colouration), that disappeared suddenly and rapidly throughout Costa Rica and Panama in the 1990s. After years without trace the species was considered to be extinct.

To increase our chances of discovering the toad, we pushed further into uncharted forest

But then, in 2003, a young herpetologist by the name of Justin Yeager was doing a study abroad program on poison dart frogs in Costa Rica, when his guide started to talk to him about a yellow and black frog living in the rainforest. You must be mistaken, Yeager had told the guide, who was clearly describing the Variable Harlequin Frog. Two days later, the guide appeared holding a pair of the very frogs that were believed extinct.

Further surprise reappearances over the following years, including the black harlequin frog in Ecuador, a couple of species from Costa Rica and a couple of species in Australia, suggesting that the Variable Harlequin Frog was not a unique case. And so the question started to grow in my mind: how many frogs were out there, waiting to be rediscovered?

The quest begins

Early in 2010, the seed was planted for a global hunt for lost species. First, I solicited the help of experts around the world to compile a list of frogs, salamanders and caecilians that had not been seen in at least a decade and were feared extinct. As the list grew to 100, I produced a top ten “Most Wanted” poster of the most iconic species. We rallied some funding and within a few months more than 120 researchers in 21 countries were on a quest to find some of the most elusive creatures on earth.

Following the launch of the campaign, my own journey in search of lost species took me first to the steamy jungles of Colombia – preserved by years of armed conflict – to search for the Mesopotamia Beaked Toad, one of our top ten Most Wanted and last seen in 1914.

In my new book, In Search of Lost Frogs, I describe how the hunt proved to be both tragic and joyous.

For three days we searched, without success. To increase our chances of discovering the toad, we then pushed further into uncharted forest, plunging into the steamy depths of the Chocó, one of the wettest places on earth, where steam rises from thick jungle undulating as far as the eye can see. The rugged terrain and 16 to 18 metres of rainfall a year prevented even the conquistadores from settling here.

As night fell, we were greeted by a chorus of frogs, a soundscape of chirps and wheeps. We homed in on the calls of glass frogs with translucent bellies, finding many of them up the first river - a good sign that the forests are healthy, for these amphibians are among the most sensitive to change.

The following day and night became a blur of frogs of all shapes and sizes. Large tree frogs clasped thick stems with toes separated by a shock of red webbing, and small rocket frogs with red thighs skipped through the shallows. Masked treefrogs peered from behind elephant ear leaves, and splendid poison dart frogs with yellow splashed on black induced “oohs” and “aahs” from the team. A more colourful assortment of frogs would be hard to imagine.

We never did find the Mesopotamia Beaked Toad, however. The last embers of hope died with the final day of the search, as the light was sucked from the forest, the last leaf had been turned and the mud had been kicked off the boots. The realisation that you are not going to find a lost species seeps in imperceptibly, like cold into tired muscles.

It is now a century since the last sighting of this animal.

But we did get a big, and extremely happier, surprise. During the search, one of the team found another species of beaked toad – one entirely new to science. In the search for one lost beaked toad we had found another, new one.

Musical frogs and tiny frogs

After Colombia I swapped lush jungle for the remote limestone peaks of southwest Haiti, whose cloud forests boast more than a dozen frogs found nowhere else in the world. Most of these had not been seen in close to two decades.

A week spent scouring the forests during hurricane season resulted in six rediscoveries, including Mozart’s Frog (named because an audiospectogram of its call resembled the musical notes of a Mozart symphony), the Ventriloqual Frog (named because – yup, it can throw its voice) and one of the smallest frogs in the world, the miniscule Macaya Breast-spot Frog. The frogs became beacons of hope for the preservation of the last remnants of cloud forest.

My journey in search of lost frogs then led me to India, where I rediscovered a small frog that had not been seen in 30 years inside a rubbish bin in a tiger reserve, Israel, to try to find the Hula Painted Frog which had reappeared after being missing for 55 years, and Costa Rica, on a quest to find and photograph the iconic Variable Harlequin Frog.

Overall, the Search for Lost Frogs produced over a dozen rediscoveries of species thought to be extinct.

These Lazarus frogs have provided an opportunity for scientists to investigate what sets them apart from all those that died around them, feeding into efforts to combat a fungal disease that has caused the biggest loss of biodiversity in human history.

Some frogs survived by raising their temperature to fight the fungus, others seemed to have moved to more conducive habitats. But most promising is the discovery on the skin of some survivors of beneficial bacteria capable of staving off infection. By augmenting the skin of other frogs with these bacteria – in the same way that we augment our stomach bacteria with probiotic yogurt – we may, so the thinking goes, be able to give Lazarus frogs a second chance.

Beyond the science, the Search for Lost Frogs achieved something that I had previously failed to do in my attempts to communicate the plight of amphibians – it captured the imagination of the global public.

The way in which it did so opened my eyes to the reality that the way in which we deliver information is as important as the information itself.

The Search for Lost Frogs drew people in through stories of discovery, disappointment, perseverance and ultimately of hope, delivered in a package decorated with striking photographs. It opened the eyes of battle-weary adults to the wonder and awe of the natural world, and reminded us that the world still holds secrets.

By speaking to hearts – and not just minds – around the world, the Search for Lost Frogs continues to grow our army of supporters and give many frogs a second chance.

Robin Moore is an award-winning photographer, author and conservationist.

Having gained a PhD in biodiversity conservation, Robin is currently Conservation Officer with the Amphibian Survival Alliance, Rainforest Trust and Global Wildlife Conservation.

He is also a Senior Fellow of the International League of Conservation Photographers

In Search of Lost Frogs is published in September 2014.