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BBC Life in Cold Blood Land Invaders

about amphibians, salamanders, frogs, toads Amphibians were the first backboned animals to leave the water and colonize the land. Today there are some 6000 species of them and new ones are constantly being discovered. We may not often see them but during the breeding season we certainly hear them. Choruses like this ensure that we are well aware of frogs and toads. But there are others kinds of amphibians that don't make themselves so obvious. Newts and their close relatives the salamanders. And even ones that have completely lost their legs. But all amphibians have one thing in common a moist skin. If that dries they die. And dealing with that danger dominates their lives. How are they to survive away from water? Four hundred million years ago the only backboned animals on the Earth were fish. The land was empty except for insects and other invertebrates. But then one of those fish managed to haul itself out of the water and up on to the land. You can see what sort of creature that might have been if you go to north-east Australia. There the rivers only too often dry up. But one remarkable ancient and extraordinary fish manages to survive because it has a rare talent for a fish. It has lungs and can breathe air. And there's one at my feet right here. Fossils just like it date from precisely the time when the great invasion of the land took place. On occasion it rises to the surface and gulps air. The air goes into a pouch that opens from its throat where the oxygen from it is absorbed. This is a lungfish. It punts itself along the river bottom using two pairs of fleshy muscular fins placed low on its body just like simple legs. Sometime around 360 million years ago one of its remote ancestors used such limb-like fins to push itself up onto the land. That pioneer may have looked much like this strange monster that haunts the waterways of Japan. It's the giant salamander the biggest of all living amphibians that grows to a metre or more in length. It too has lungs and breathes air but even so it almost never leaves the water. Males make their dens in both natural and man-made retreats in the river banks and defend them against all other males. A newcomer arrives looking for a breeding den of his own. It won't be here. The resident male has good reason to be so defensive. He is guarding a batch of eggs left by a female who visited him a few days earlier. Like fish eggs amphibian eggs have no protective shell. They can only develop in moisture of some kind and amphibians no matter where they live must find ways to provide that. In North America in the eastern half of the country there are many kinds of small salamanders only a few inches long that has taken one further step away from the aquatic life. In spring the woodlands are drenched in rain and suddenly in response an amphibian army appears among the leaf litter. Marbled salamanders. First to emerge are the males. A form that is characteristic of amphibians. They are becoming tadpoles. They swim free equipped with feathery gills that enable them to extract oxygen from the water. They are truly aquatic creatures. But they have front legs as well as gills. And within days they develop back legs as well. As time passes they grow stronger. Their gills wither and disappear and at last they are miniature versions of their parents and are ready to leave the water forever and to start on their land-living lives. But what tempted those ancient fish to leave the water in the first place? Food. When the first amphibians moved out of water the land was already swarming with insects. And the amphibians have evolved a special weapon with which to catch them. Salamanders however have not yet developed the athleticism needed for a high-speed chase and a lightning pounce. Their hunts are rather solemn sedate affairs. A simple contraction of the muscles surrounding the tongue is all that's needed to shoot it forward. Some salamanders have a tongue that is about three-quarters the length of the body but most species has to get pretty close to their prey if they are to catch it. Although the adult marbled salamander lives entirely on land it nonetheless needed water at the very beginning of its life. But there are other species of salamander in North America that have managed to break even that link with their distant aquatic past. This is a gold mine. The people who dug it found nothing but biologists who came later found gold of their own special kind. They discovered a colony of a species called the slimy salamander that could be properly observed throughout the summer when normally they are hidden in the leaf litter. They were all females and their behavior proved to be very surprising indeed. These salamanders come down in early summer in about June and will travel several hundred metres down along this mine shaft to exactly the same ledge within an inch or so that they used the previous year. And they have been seen doing that for at least five or six years. And they don't eat. They will stay down here for six or seven months sustained only by the food reserves that they've accumulated in their fat tails. Down here there is permanent moisture however hot and dry it gets outside. The salamanders clearly prefer to cluster together close to one another for the rock walls of the mine shaft elsewhere are totally uninhabited. However this open plan way of life while it's clearly very successful nonetheless comes at a price. Some of the females here are up to no good. They failed to fatten up enough during the spring and they're hungry and in search of a good meal. And the eggs and young of the other salamanders will do very well. To see exactly what these creatures are doing we need to turn off our torches and turn on the infrared camera. Here comes one of those marauding females. She must have located this mother guarding her eggs by smell for all this is going on in total darkness. So some amphibians when needs be are neither sluggish insensitive nor lacking in maternal concern. And mother wins the day. The salamanders need to keep moist means that they seldom come out into the open but find their prey by pushing through the leaf litter. And to do that it helps to be slim. Very slim. Legs are less in the way if they're small. And one great group of burrowing amphibians has lost its legs altogether. The most numerous and successful of all amphibians however have kept their legs and developed them spectacularly. Some are walkers. Others are climbers. There are hoppers. There are even gliders who use the membranes on their feet like parachutes. If their skin is very moist we call these creatures frogs. If it's less so we call them toads. But they all belong to the same group. There are some 2200 different kinds of frogs and toads in the world today and here in the leaf litter in this Madagascan forest is the tiniest of them all. This is fully adult and in its tiny body which is only a centimetre long is packed a beating hearts a skeleton a gut a brain. It's a miracle of miniaturization. And this basic body plan not only comes in all sizes but many different shapes which have enabled frogs and toads to colonize all kinds of different environments. Out of water frogs found a new way to communicate with one another. Amphibian lungs are comparatively feeble so frogs amplify their calls with cheek or throat pouches which act as resonators. The call of a frog in this South African pool can be heard over a mile away. It's the painted reed frog the loudest caller of all for his size. But a female is not only impressed by the loudness of a male's call she also judges him by how frequently he manages to make that call. Calling is a very demanding activity requiring a male to increase his energy consumption by about 20 times. So in picking the loudest and fastest caller the female is also selecting the fittest and most vigorous male as the father of her offspring. He's the one. Success. And silence for a few minutes. In some circumstances however calls need reinforcing with gestures. The sound of rushing water could drown out the calls of a frog. However here in this stream in Panama there's a species living alongside that has developed a novel way of dealing with that problem. The rare and wonderful golden frog. It does have a voice but it's not loud. Individual males set up their territories beside the river and then wait for females to turn up. And since good positions in the territory are not common they may have to hold them against intruders. And here one comes. Just in case his call is inaudible he makes his message clear with a wave. And his rival waves back. He repeats his message so there's no misunderstanding. But rival is not deterred. Well that makes things perfectly clear. Another arrives. Perhaps at last this is a female. No it's another male. So there will have to be a wrestling match. That should teach him. And his rival signals submission by keeping his head down. Now where are those females? And here she is. She is pure unblemished gold and much bigger than he is. While he is fully occupied another challenger arrives. Since has already in position there is no point in breaking away for another wrestling match so he hangs on. The golden frog has a powerful poison in its skin so it can afford to be conspicuous. But most frogs find safety in camouflage. This is a South American red-eyed tree frog a close match for the leaves on which it habitually sits. This tiny poison-arrow frog is carrying his tadpole pig-a-back. It hatched on a leaf and now has taking it to a pool in a bromeliad high up in the branches. The tadpole wriggles off. He may have half a dozen babies each of which he puts into its own tiny pool. He makes regular tours of all his nurseries checking on his tadpole's welfare. This youngster is hungry and tells him so by nibbling his legs and vibrating against his body. But the male cant feed the tadpole himself. He needs help. He has to find a female. There she is. He calls. And she follows. He has to lead for only he knows exactly where he deposited each tadpole. This one is now very hungry indeed? He calls to the female encouragingly. She jumps in perhaps to assess the situation. Out she comes without having done what's required so he keeps calling. In she goes a second time. This time she produces food for the hungry tadpole an infertile egg. There. Out she comes and mother and father embrace. Baby has its dinner. Australia in the southeast has temperate rainforests. A cluster of frogs eggs on the damp ground. When these hatch the tadpoles will also need a moist nursery. Father a marsupial frog is on guard. The eggs are developing fast. The male has to keep a careful eye on them for he must be close beside them at the very moment when they hatch. It's going to be a long wait at least 11 days. He seems to have decided that the crucial moment has arrived and lowers himself onto the eggs. As he does so the tough egg membranes liquefy and the young wriggle free. He has two pouches in his skin one on each hip and the tadpoles start to squirm into them. Competition between the tadpoles is intense for there are more of them than he can accommodate in his pouches. At last has taken on board as many as he can manage. He will now look after them for up to six weeks. The young remain in his pouches continuing their development fuelled by the remains of the yolk in their infant stomachs. And then one night his behavior changes. His flanks are rippling. The first of his young is emerging. The profound transformation that converted a tadpole into this young frog took place entirely within its father's moist pouch. The parched bush country of Southern Africa. Here it rains only twice a year and then only briefly. But when it does the ground in places erupts. Rain frogs as they are aptly called have been waiting for months below ground for this moment. After starving for so long they are keen to feed. As darkness falls the males begin to call. Females are fat with eggs. The males are so much smaller that they can't embrace a female. So they produce glue from glands on their underside and stick themselves to their partners back. But sometimes that only results in a chain of enthusiastic but undiscriminating males stuck to one another. Their brief time above ground has come to an end. The female starts to dig. The diminutive male being stuck on goes with her. He will fertilize the eggs later below ground. Her stay on the surface is over. The female has excavated a little chamber for herself and below that she has made a second one which she has filled with frothy foam. This is the nursery for her tadpoles. The female stays underground away from the lethal heat for several more weeks. By now her offspring have almost completed their time as tadpoles. The rains return. Below ground the youngsters await their release. The female leads the way and her brood is with her. Rain is even rarer in Australia. There in the central deserts it may not fall for years on end. But there are amphibians even here little toads that remain underground in a state of suspended animation for years just to take advantage of a few rainy days. After the rains have fallen spade foot toads all emerge together. They must feed and breed if possible before the sun rises. But the desert dries only too quickly even after the heaviest of storms. Temperatures rise to 20 degrees centigrade. Now water will evaporate instantly. This is one of the hottest places on Earth. So the toads have to retreat once again below ground. The miracle is that they're here at all. A toad that can live in as parched a desert as this is impressive evidence of the versatility of the amphibians the way they can adapt their behavior and their anatomy to live so far away from water. But there is one group of animals that can really call the desert their own. The lizards. And well look at them in the next episode of Life in Cold Blood. Amphibians are the most threatened group of vertebrates on the planet. In recent years a strange and lethal fungal disease has started to spread among them. The golden frog which lives only in one small area in Panama was in particular danger as the disease is already on the frontier of its territory. If we were to film it at all we would have to move quickly. For series producer Miles Barton that meant mean cutting short Christmas. We had been told that in Panama the frogs few remaining breeding streams were being rapidly destroyed by the building of a new road making the last tiny population even more at risk from the disease. The fungus clogs the animal's moist skin. Since all frogs breathe through their skin infected animals die from suffocation. Frog biologist Erik Lindquist who first described the golden frogs signaling behavior helped the film team to thoroughly disinfect their kit before travelling into the frog's territory. Freshly scrubbed up Erik took the team to one of the golden frogs last known breeding sites. But would they still be there? Yeah you hear that? That's a male calling. Okay we have another male crawling up over here crawling up the rock face.


 
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The giant salamander the biggest of all living amphibians that grows to a metre or more in length
The giant salamander the biggest of all living amphibians that grows to a metre or more in length 		  He wafts a pheromone a sexual stimulant towards her with beats of his tail
He wafts a pheromone a sexual stimulant towards her with beats of his tail 		  A South American red-eyed tree frog a close match for the leaves on which it habitually sits
A South American red-eyed tree frog a close match for the leaves on which it habitually sits 		  The golden frog which lives only in one small area in Panama
The golden frog which lives only in one small area in Panama
 
But with the fungus approaching at a rate of up to 22 miles a year the frogs were rapidly disappearing from all their known breeding sites. The advance crew immediately set about filming as much of the behavior as they could. By the time I arrived there was only one remaining location where the frogs survived. Where exactly are we going? I would prefer not saying precisely. You see this is really the last population of the golden frog left in the wild. And historically the locals have been collecting out these animals as good-luck talismans. And so now left with just one population I'm concerned that if this secret locality gets given out there will be international collectors that would come. Really? Sure. They're rare enough now where many people would pay top dollar for these animals. Were they ever what you might call common? When I talked to people who had been here in the past the populations were so abundant that one would have to watch where they're stepping to keep from killing one. Really? Yes. Erik has his own low-tech method of finding them which he assures me normally works. See when you call sometimes they'll call back and they'll reveal their location. Sometimes they're tucked away behind leaves and they're really difficult to find. Hopefully we can elicit a response. It's the fastest way to get them to shut up. Was that him? Yeah. Listen. So they're here. They're here. There's one over here. See him right there. Looks like a male. Make him do it again. You have to hum and whistle at the same time. Cant does it. See if he can. Now we knew the frogs were still here we could complete the filming. The local people have always treasured their remarkable little frog but Erik was the first to document its signaling behavior. It was an animal that was just walking. I wasn't sure if the animal was trying to flush out prey or if it was using it in a communication role. And so a group of us set out to look at whether or not this was communication. We tried mirror presentations to the animals.     Some of us have looked specifically at an LCD screen a little television with a hand-waving semaphoring frog and it's elicited a number of responses specifically from males. You show a television picture to a male and he waves back? He waves back and hell even call really? To the male on the television screen. It's really fascinating. Yes. Absolutely. They then experimented with a life-size plastic model complete with waving arm the sort of high-tech gear I thought I might manage to operate myself. It's not as easy as you might think. Erik showed me how it should be done. You've got to get that slow-motion just right. The frogs waved. They called. They even attacked. So that wave really is a form of communication. So they're just saying Keep off keep off. Is that right? Were not sure. Sometimes there seem to be certain hand waves that may indicate appeasement showing that I'm just walking through perhaps your territory. Don't bother me. Really? Ah please. But how endangered is the golden frog? This is it what you see. You're going to be the last crew to film these in the wild. And indeed we were. Soon after finishing filming the local scientists decided the time had come to take all the surviving golden frogs into captivity before the fungus arrives here and kills them all. They and other rare species of frog also threatened were being brought back to a special frog hospital where I was introduced to some of the other patients. So what are these? They're nocturnal also Here they're being treated daily with a fungicide but without a vaccine to protect them and with the fungus still at large in the forest they cant be reintroduced into their proper home. Frogs so common in these humid forests are crucial links in the ecology. If they disappear all kinds of food chains will be broken and the effect could be little short of catastrophic to wildlife in general. And sadly for now at least it seems that the golden frog has waved its last in the wild.