Mysterious frogs from the high Andes
During a conservation project in Bolivia I was asked to help monitor the Titicaca water frog (Telmatobius culeus). For every person passionate about amphibians, there is only a single answer to this question. So in late October, I found myself in a bus towards Copacabana, a touristic town on the Bolivian shores of lake Titicaca. The lake, by volume the largest in South America, is situated at approximately 3800 meters in the Andes, on the border of Peru and Bolivia.
During the trip, a ferry took us across the narrow strait that separates the southern “lago menor” from the northern “lago major”. The water was clear and several Andean gulls were following the boat. Copacabana itself is a charming, but touristic town, with not too much to see. The next morning, I wandered around the streets to look for people selling frogs. One of the biggest threats to the endangered Titicaca water frog is overharvesting. Locals catch them to sell the legs to touristic restaurants or blend the frogs into juices that are claimed to be an aphrodisiac. I was however told that these practices came to an end in Copacabana and that I should go to Peru to buy them. Besides plenty of fish, I indeed did not encounter a single frog for sale in the entire town. When the coordinator of the Bolivian Amphibian Initiative – Arturo Muñoz – arrived, we headed towards a smaller village along the coastline from where we continued by boat towards Isla de la Luna. People have been living for ages on this relatively small island, as been proven by the remains of an Inca temple.
Several expeditions have been held in the region, in search for lost treasures. One of them, led by the famous French explorer Jacques Cousteau in the late 1960’s, even used small submarines. They did however not find many historical objects. Instead plenty of Titicaca water frogs were seen, even at depths of over 100 meter, quite unique for frogs. The animals that can grow very big have prominent skin folds, which gave it its nickname of “scrotum frog”. The extensive skin flaps are an adaptation to a fully aquatic life. At these altitudes the oxygen concentration is low and the frogs rarely surface to breath with their reduced lungs, but instead absorb the required oxygen from the water trough their skin.
Nowadays only a single settlement is found on the island. We stayed in the house of Don Francisco and enjoyed a beautiful sunset from the terrace. As the trip had been long and we needed to get up early in the morning, we went to bed early. During sunrise, several Titicaca flightless grebes (Rollandia microptera) were swimming between the reed and trout culture facilities. These endangered birds are endemic to Titicaca and as their names suggests, have lost the ability to fly. Different trout species were introduced to the lake several decades ago and breeding them is now one of the main sources of income. These introduced fish are however a threat to the native fish, from which many are endemic. At least one species, the Titicaca Orestias (Orestias cuvieri), is now believed to be extinct as a consequence of the trout introduction. Breeding them is so lucrative, that most fishermen use their catches to feed their trout, before selling them to restaurants. It is believed that these trout also have a negative impact on the frog population, probably mainly trough predation of eggs, tadpoles and juveniles.
We embarked a small fishing vessel that brought us to the tip of the island, from where we would follow a transect of one kilometer counting all the frogs. With the Bolivian Amphibian Initiative, Arturo has been monitoring these frogs for several years now. Our young guide rowing the boat assured us that the weather would be good, despite dark clouds covering the sky and a cold wind increasing in strength, causing the waves to smash the boat harder and harder. When we reached our location, the first drops started to fall down and the boy began having difficulties to keep the boat in position. Arturo and me entered the water. It felt cold, but a double wetsuit protected me and soon I felt warmer in the water than outside. Frogs were counted along the transect and data of depth, substrate, vegetation and temperature were written down. After a while the boat had to return as the wind was becoming too strong and the boy, unprepared for the bad weather, completely wet of the harsh rain and shivering of the cold. We continued our transect and despite the bad weather conditions, visibility under water remained relatively good and I was impressed by the high number of frogs. In some parts of the transect, we counted as many as seventeen frogs per ten meters. Arturo however warned me that this is one of the best known localities and I should not be expecting to see as many on the other two places we would visit the following days. Further along the transect, we encountered a pair in amplexus and two males attending their egg clutches, a rare sight. Having finished, we swam back to the village, enjoying the frogs below us. The variation in color is remarkable. Some are entirely brown, others whitish with grey speckling or greenish with a yellow pattern. Surprisingly, these colorations make them very well camouflaged when sitting still between rocks or on the sandy bottom.
The weather remained precarious for the rest of the day, hindering good opportunities to photograph the frogs with natural light. When the night fell, Don Fransisco invited us near the fire for dinner. He showed pieces of ancient pottery he had found on the beaches of the island and told us stories about the frogs. Fishermen are often in contact with the frogs, as nearly daily, these get stuck in their fishing nets. Nowadays, most of them release the frogs unharmed and some even take notes of how many they catch and assess the gender of the frogs, data that is passed on to scientists. Frogs seemed to be very important in some legends and traditions as well. A toad entering your home is a sign that you will get financial benefits in the near future. Or when there is a period of severe drought, people would catch a Titicaca water frog and keep it in a small tank on the top of the island, which would be good to make it rain. The recent decline of big toads on the island was explained by the toads having left to go to war, a story we heard in other places in Bolivia as well. How this war ended or when they will return is something nobody could answer. The frogs seem to play a role for the fishermen as well. Some claimed that schools of small fish can be located using frog concentrations. We were therefore not surprised when a local fisherman suggested that we should bring an offer to the frogs before our next visit. As during the last monitoring visit too, the weather had been very rainy.
The next day we would leave the island to do another transect close to the mainland. Waves were high and the number of frogs significantly lower. It was however only the next day that I would be really surprised of seeing almost no frogs, in the southern “lago menor”. Arturo told me that some years ago, they had found large numbers of dead frogs here and since then, numbers on this location had been extremely low. The presence of mud and algal growth, both only encountered on this transect, suggests that this part suffers from contamination. That I got an itchy rash on the parts of my face that had been in direct contact with this water also pointed in that direction. Next to contamination, the deadly chytrid fungus might also play a role in the decline of these frogs. On several frogs we encountered along the transects, we also found external parasites. Some frogs even with several dozens and those animals were often skinny and in poor condition. Those factors, together with an uncontrolled catch for human consumption are believed to be the key factors having caused a steep decline, by the IUCN estimated by over 80% of their original number. The frog, therefore listed as critically endangered, is now also being bred in captivity at the natural history museum d’Orbigny in Cochabamba. During a visit to this breeding facility, I also witnessed several other species of the water frog genus (Telmatobius). Arturo explained me that many species in this genus underwent serious declines and are threatened with extinction, the Titicaca water frog being the best known, but not necessarily the most endangered among them.
On the bus back towards my conservation project near the high Illimani, I wondered what the future would bring for these animals? Would these creatures, that have been in this remarkable lake much longer than even the earliest of human civilizations, withstand all the problems they are facing? Or would they be the next victim in a by mankind caused mass extinction? Having seen the efforts undertaken by local and international conservationists, I could only hope for the best.