By Laura Fairman
Our group was lucky enough to spend several days in the Peruvian Amazon, hosted by Rainforest Expeditions at Posada Amazonas Lodge. On March 17, 2024, we spent about four hours at an oxbow lake to observe wildlife in their natural habitat of the Amazon Rainforest, the world’s most biodiverse ecosystem. We trekked from the Tambopata River into the Tambopata National Reserve, arriving at Tres Chimbadas Lake, named after the slang word “chimbadas”, or river crossing, after about thirty minutes. There, we hopped on a large raft vessel which was guided by a wide, manual rudder rather than an engine, and on to the lake. This freshwater lake is roughly one mile long and 12 feet deep. Tres Chimbadas is an oxbow lake, meaning it naturally split off from a river bend to create a shallower lake as the water found a shorter course.
The calm, mid-sized Tres Chimbadas is absolutely teeming with animal and plant life, including piranhas, caimans, and eels in the water, and hoatzins and toucans in the sky. It has tall, swamp-like grasses on some sides of the lake, where we observed birds, and in the water, a black caiman crossed the lake with its nose halfway out of the water. Above us, three howler monkeys huddled on a tall tree branch, sitting very still. Our group became very excited when the guides pointed out some otters distantly visible on a far shore. We followed them with our binoculars as they swam gracefully along the lake, their little heads held above the water as they swam with their bodies and tails beneath the surface. Our boat crossed the lake to observe the otters, keeping a safe distance from them and keeping our noise levels low, as is required on the lake due to the otters’ sensitive nature.
Observing the Giant Amazon River Otter
We were very lucky to observe seven otters, including two baby otters estimated to be about 20 days old, for over half an hour. We watched silently as the otters flipped above and below the surface of the water, sometimes pulling up fish to share with the babies or eat themselves. The baby otters were just learning to fish and struggled to catch them. The otter family crawled up and off the land, traversing the shoreline to sit on the lake’s edge and swim. They growled and made other loud noises, to which the guides explained that they are a very communicative species. We were all fascinated by the giant otters and grateful to observe all seven of them for as long as we did. The remainder of this blog post provides some context on this amazing animal, their habitat, and forecasts for the future of this endangered species.
Background on the Giant Amazon River Otter
Giant Amazon River Otters (Pteronura brasiliensis), also known as Giant Otters, Giant Brazilian Otters, and locally as the “River Wolf” (lobo del río), are apex predators that sit at the top of the food chain and have few predators. They typically measure about five feet, weigh around 50 pounds, and live for roughly 8 years. They have a white spot that runs from their jaw to their chest which serves as a unique identifier for each otter, similar to the human fingerprint. Otters are social, family-based animals, displaying complex emotions which researchers have studied, and which we were able to see and hear in action. Otter families have one breeding couple, and the female otter is the matriarch of the family. Otters also practice alloparenting, meaning non-parents of the family unit help raise the younger otters.
According to the Rainforest Expedition guides, giant otters eat up to 4 kilos of fish per day. This high demand for food requires the family unit to sometimes force out a few of its own, only once the baby otters are at least two years old. By keeping the family of otters smaller, the family can meet its food needs without overwhelming the environment. Otters who are pushed out by their family unit have a difficult journey to find a new home, as navigating the land is not their strong suit compared with the water. Otters in transit are vulnerable to land predators, and some do not survive the journey to the river or to find a new partner.
Giant Amazon River Otters (photo by Delaney West)
Otter Habitat Forecast
After spending time observing them, I was interested to learn from our Ese’eja guides and do further research on how giant otters interact with their habitat, the oxbow lakes. How have giant otters been affected by human activity, and how is climate change projected to alter the course for the future of this important species?
The giant otter population was heavily impacted by pelt hunting in the 20th century until Peru’s national government instituted a ban in 1973. In 1975, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed the species as an Appendix I animal, halting international trade. Researchers observed population recovery once protections were increased for the otters, such as in Manu National Park, where a study running from 1991-2006 found that the species count jumped from a low of 42 in 1994 to a high of 88 in 2004.
Today, giant Amazon river otters remain endangered as gold mining and deforestation for timber threaten the oxbow lake ecosystem. The process of gold mining creates mercury runoff, which contaminates the water in the Madre de Dios region. A 2013 study of the Tambopata River, where Tres Chimbadas Lake is located, measured water contamination levels by mercury in fish. Although mining activity did not take place at the study site, the authors found mercury in several species of fish at levels higher than the U.S. Environmental Protection Agency (EPA) guidelines for human consumption. Mercury accumulation in otters and their food sources may impact their reproductive health and survival. Logging and mining activities also impact the quantity of fish which live in the oxbow lakes, reducing the giant otter’s food source.
To protect the giant otters in the face of future climate change, conservationist Jessica Groenendijk asserts that artisanal gold mining activity in the region must be reduced, education should be provided to locals and visitors on best practices when entering an otter’s habitat, and protected areas expanded. Future infrastructure development such as hydroelectric dams should take into consideration local wildlife populations that may be harmed if built. Further research may support a greater understanding of the giant otters and the risks humans and climate change pose to the species. Our group was very lucky and thankful to observe this giant otter family and reflect on its important status in the Amazon.
Public Policy Peru 