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The Yungas

by TFH Magazine on February 17, 2012 at 8:44 am

International explorer Heiko Bleher traveled to the Yungas in Bolivia in search of freshwater fish.

By Heiko Bleher

photographs by the author

It was a lovely day in Sarlat, which to me is the most beautiful city of France, in the Dordogne. Sitting in this beautiful old mansion just outside of the city limits, surrounded by greens, plants, trees, and bonsais I was having lunch with Jacques Géry and his wife Georgie. She had served pate du foi gras entier, the whole duck liver, and a delicious red wine, while Jacques was telling me about Nathan Everett Pearson, the student of the famous German/American Ichthyologist  Karl H. Eigenmann (1863–1927), one of the most talented and well respected men in the ichthyological world—the very same which applies to Jacques Géry. Jacques asked me why I had not been to the Yungas on the eastern slope of the Andes in Bolivia. There is very interesting research to be done there. Pearson alone, on the Mulford Expedition of 1921–1922, collected 6775 specimens, of which Characiformes (his lifetime speciality) represented about 50 percent of the collection and 77 of the total of 155 species, there. He found 25 new species and 2 new genera, most of them never seen alive until today.

This tiny characoid was (to me) something special. Less than an inch long, with the brightest golden color and a jet black stripe below the golden stripe all the way into the tail fin, this is a miniature tiny jewel.

Naturally that made me very curious, especially because I collected in Bolivia several times, but never in that region he mentioned. The only other person who did report of some field work in that region was Perugia, who published in Genova, Italy, in 1897 about the collection of 200 specimens Professor Luigi Balzani (Gymnogeophagus balzanii) found in Bolivia. They represented 37 species, out of which 5 came from the Marmoré and 32 from the Beni, in the Yungas. Haseman also collected in Bolivia, but only in the Marmoré/Guaporé region, not in the Yungas or the eastern slopes.

Actually I was very interested in seeing some of those new genera and species in vivo, especially after I researched and found out that no one has ever photographed and much less collected any of those species alive.

The only real predators were members of the wolffish family in a small pond.

Next thing I knew, I was on a plane from Milan to São Paulo and on to La Paz, the highest capital city of the world, which brings back childhood memories. My mother and I took a two-year expedition to South America when I was a child.

The Mulford Expedition

The Mulford Expedition of 1921–1922 was organized by Henry Hurd Rusby to explore the Amazon Valley from the headwaters of the Quime River in Bolivia to the mouth of the Amazon in Brazil. Dr. Rusby, then 70 years old, was a well-known explorer, a professor at Colombia University, and a member of the New York Botanical Garden staff. Funding was obtained from the H. K. Mulford Company. To assist him in collecting and handling plant specimens, Rusby hired Dr. Orland E. White, of Broclyn Botanical Garden.

The expedition started by crossing the high Andes on a mountain trail, passing through the Bolivian Yungas, down the Bopi River by balsa raft, and to the jungle town of Rurrenabaque by way of the Beni River. They searched the Beni savannas for a lake that was rumored to have an outlet to the Beni River. There was no such outlet, so they backtracked to Rurrenabaque. Along the way, five of the eight expedition members departed for reasons that vary from disillusionment to illness. That was in the first year. The remaining members traveled to Manaus in central Brazil, up the Rio Negro, to the Uaupes River, and finally to the Tiquie River where they were blocked by waterfalls and rapids and had to turn around. After a second full year of wandering, the expedition came apart when the final member was left to recover from poisoning in Manaus.


Rurrenabaque was the site of the expedition’s longest stop and the collection point for many specimens. Today it functions as a staging ground for eco-travelers in search of wildlife and adventure. It is a spectacular sight to enter Rurrenabaque by boat from upriver. The narrow gorge is now the grand entrance to Madidi National Park. Rurrenabaque is larger today, but the housing has probably not changed dramatically since the Mulford Expedition.

The expedition started in Rurrenabaque, an area that includes mountains in addition to two other ecosystems.

Rurrenabaque is at the intersection of three major ecosystems—the mountains, the rainforests, and the pampas. The result of this blending is a remarkably high diversity of wildlife, as revealed in the variety of animals collected during their long stay there.


The cries of red howler monkeys were heard every morning.

Every morning, red howler monkeys  made deep, guttural howls and, at sundown, hoatzins (a bizarre bird whose young have clawed wings), squawked in loud bunches along the waterside. The raucous chatter of macaws and parrots periodically penetrated the constant drill of cicadas. A jewel-like dung beetle, in particular, captured my attention. Its beautiful exterior seemed inconsistent with the job it performs in the rainforest animals. We also saw capybaras (a large rodent), a bright green parrot snake, toucans, and delicate butterflies.

The Bolivian government to establish Madidi National Park in 1995. The park is home to 85 percent of the bird species in Bolivia (11 percent of all the bird species in the world), 75 percent of Bolivian mammal species, and 40 percent of Bolivian reptile species. Endangered jaguars, giant otters, spectacled bears, and black caiman all roam within its forests. But, Madidi is not only important because of the rich biodiversity it protects within its borders, but because it is now part of a series of protected areas that stretch across international lines and an eclectic variety of habitats. Madidi, like other protected areas in the Amazon, will survive only if the people who live in and around the park have an incentive to keep it protected.

At the end of the road behind Alto Madidi I was lucky and found this tiny blue shiny tetra.

A proposed dam across the Beni at the entrance of Madidi National Park would flood Chalalan Lodge and surrounding rainforests. The proposal seems to be on hold for now, but there are road projects in the works and two companies hold concessions to search for and extract hydrocarbons within the park’s boundaries.

Posted in TFH Extras by TFH Magazine on February 17th, 2012 at 8:44 am.

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