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December 19, 2019

The Maryland Zoo Joins Effort to Rescue Rare Bolivian River Dolphins

Veterinarians from The Maryland Zoo and the Saint Louis Zoo traveled nearly 4,000 miles to rescue dolphins in central Bolivia, where a group of approximately 15 endangered Bolivian river dolphins were trapped in a lake.

The dolphins, known in Bolivia as bufeos, were isolated in the lake surrounded by dense forest and expansive soybean fields, and had become cut off from the main river over the past several years due to run-off from environmental changes in the area.

"This species is endemic to Bolivia," said Dr. Ellen Bronson, senior director of animal health, conservation, and research at The Maryland Zoo. "They face many threats in the wild mostly due to the conversion of forest into soybean fields, which leads to erosion of dirt into rivers, along with potential contaminants and diseases. They are very secretive, and little is known about their biology and health, including how these environmental changes affect their survival."

In late 2017, Claudia Venegas, a biologist affiliated with the Noel Kempff Mercado Museum of Natural History in Santa Cruz, Bolivia, reached out to colleagues at Maryland Zoo and Saint Louis Zoo with whom she had worked previously to ask for assistance. "Having worked on wildlife health and conservation projects in Bolivia since 1999, I was happy to collaborate with Bolivian colleagues and Dr. Bronson to help address this increasing conservation challenge that threatens the long-term survival of the river dolphin of Bolivia," said Dr. Sharon Deem, director of the Saint Louis Zoo Institute for Conservation Medicine. "This rescue project also presented the opportunity to perform complete medical exams on the animals, which we believe is a first for the species — a species designated as separate from the Amazonian river dolphin in 2012."

A grant from the American Association of Zoo Veterinarians' Wild Animal Health Fund made the trip and unprecedented level of medical research possible for Dr. Bronson and Dr. Julie Sheldon, a veterinary resident from the Shedd Aquarium in Chicago, who was representing the Saint Louis Zoo's Institute for Conservation Medicine and whose travel was funded by the Animal Response Team at Shedd Aquarium. They purchased medical supplies and custom-built fishing nets made by Bolivian women in the department of Cochabomba, Bolivia. The veterinary team traveled to the remote location, 150 miles from Santa Cruz, in October 2018 with representatives of Noel Kempff Mercado Museum of Natural History, the Santa Cruz Regional Government, and the non-profit Bolivian group Faunagua, who have worked with the species in other parts of the country.

The first challenge for the group was finding a way to reach the dolphins, and then a way to transport them to a river release point.

Battling knee-deep mud, mosquitoes, extreme heat and rudimentary roads cleared by machete, the group worked with regional aquatic rescue experts and forest fire fighters to reach the lake. Once there, the dolphins' natural curiosity and the team's extensive planning helped to quickly and safely guide the dolphins into transfer nets. A full medical examination, including blood samples, an ultrasound examination and swab collection for culture and parasites, among other testing, was completed prior to loading each dolphin into the back of a specially rigged pick-up truck. Before release into the river, three of the dolphins received satellite transmitters connected to their dorsal fins, which is providing real-time information about their locations, movements, and survival.

Transport from the lake to the river took nearly two hours, and the dolphins were monitored closely the entire time. During their two weeks at the lake, the group relocated six dolphins and collected priceless information on the species.

"We believe that these were the first full health examinations done on this species with extensive diagnostic sampling. There have been research studies on this species in other areas of Bolivia, and they have also taken some limited samples, but not to this extent," said Bronson.

Results from many of the tests were recently received and could greatly impact future conservation efforts for the species.
"The six dolphins, one female and five males, including one juvenile, were in surprisingly good condition and overall appeared healthy on examination and on initial laboratory testing," said Bronson. "Having the opportunity to work hands-on with this amazing species and contribute to its conservation was a very gratifying and humbling experience."

"This dolphin rescue and translocation project is an example of the positive impact that zoos and aquariums accredited by the Association of Zoos and Aquariums (AZA) can have by working to ensure the health and conservation of endangered species, whether the species are living in world-class AZA zoos and aquariums or are in the wild living in habitats that are rapidly being modified by the growing human footprint," said Deem. "We hope to continue our collaboration in the near future on behalf of the river dolphins in Bolivia."

Plans are currently underway with the collaborating organizations to determine the next rescue mission for the remaining dolphins.

About The Maryland Zoo in Baltimore

Founded in 1876, The Maryland Zoo in Baltimore is the third oldest zoo in the United States and is internationally known for its contributions in conservation and research. More than 1,500 animals are represented in the Zoo's varied natural habitat exhibits such as the AZA-Award winning Penguin Coast, Polar Bear Watch, the Maryland Wilderness, African Journey and the award-winning Children's Zoo. Situated in Druid Hill Park near downtown Baltimore, the Zoo is accredited by the Association of Zoos & Aquariums. For more information, visit

Maryland Zoo : Claire Aubel, 410/454-1333

Saint Louis Zoo: Billy Brennan, 314/646-4633
Christy Childs, 314/646-4639