Five years of The Peru Giant Otter Conservation Program - what we have done and where we are

This journey started in lake Salvador, Manu National Park, five years ago. I was accompanied by collaborators Dr. Ron Swaisgood and Jessica Groenendijk, and by local jungle men Panchito Pizarro and Manuel Enriquez, each in a different capacity. We embarked on a catamaran and went into the large oxbow lake, looking for the object of this research program and what would become one of my favorite species – the giant otter.

It didn’t take us long to spot a family group, about 10 individuals of varying ages. The otters were swimming, fishing and vocalizing, as otters do. This was the first of many opportunities I had to observe giant otter behavior, something that would become routine for me.

Having Jessica on board, with her several years of giant otter experience, was crucial and made it easier to decide which lakes inside Manu would become our long-term study sites.

After Ron and Jessica left, the rest of the team went to an unprotected and not so pristine area based on the Madre de Dios river, where gold mining has been happening for the last few decades. We were surprised to find several giant otter groups and lakes which were suitable for research.

The Giant Otter Program has grown and evolved since. I had the opportunity to work with more than 20 Peruvian assistants, 10 Peruvian volunteers and four foreign students. At some points the crew was as large as 10 people.

Our focus has also evolved and grown over the years. It started as a study of giant otter behavior and demography. It is now also an investigation of fish, freshwater birds, black caiman, bank trees, plants and lake water algae.

The objective of our research activities is to understand how vulnerable Amazon freshwater ecosystems are to human disturbance, and what are the best solutions to secure their conservation.

We used gillnets to survey oxbow lakes for medium-sized and larger fish species. We found that lakes outside protected areas, in the gold mining region, had in general much lower fish richness abundance.

Differences in the composition of fish assemblages were also evident. Protected lakes were dominated by carnivorous fish (especially piranhas), whereas in lakes subject to human activity, fish that feed on organic material (detritivores) were more dominant.

We spent several hours in our rubber boats, following 15 giant otter groups to study their behavior. We found that in lakes with high fish abundance, giant otters forage more efficiently, and therefore need to spend less time looking for food.

We also found that giant otters that are more commonly exposed to people can become tolerant to their presence and show less vigilance and defensive behavior. This suggests that, when ecotourism is done responsibly with care not to disturb the animals, it is unlikely to pose threats to giant otter survival and reproduction.

Following the otters for several sessions also helped us understand which areas they prefer in the lakes where we study them. Using a drone, we were able to quantify both the terrestrial and aquatic portions of giant otter habitat in detail.

We found that giant otters prefer open water, free of vegetation. On land, otters were more likely to use areas where soil is well drained (which is understandable in a floodplain region, where water levels fluctuate regularly). They also preferred forest areas with good canopy cover. Therefore, mining and deforestation of oxbow lake banks are likely to create lower quality habitats.

Our studies on giant otters and their freshwater habitats show that outside protected areas, the impacts of gold mining include lower quantities of fish, polluted water and degraded bank habitats. However, there are also more optimistic signs regarding the ability of otters to survive outside protected areas.

We found giant otters in almost all oxbow lakes outside protected areas. We also registered some observations of otters in abandoned gold mining ponds. With the surprising recent finding of a giant otter in Argentina, we can conclude that this carnivore is more resilient than thought so far.

Also, the fact that giant otters can survive in degraded and lower-quality habitats like mining ponds and lakes with lower fish abundance suggest that, if we put some effort into restoring these areas, otters can rebound to strong, healthy populations.

Oxbow lakes also have rich and varied populations of birds, some more dependent on water than others. Our bird surveys showed that in lakes subject to gold mining, bird communities are not as rich. Also, the majority of birds are less abundant outside protected areas, especially those that depend on freshwater.

We also provide logistical support to a team led by Dr. Tali Magory Cohen, interested in understanding whether lake birds that feed on fish and insects are more exposed to mercury pollution in gold mining areas, and whether this exposure has consequences for their health and genomic structure.

The bird team is only one example for the flurry of research activity associated with the project at the moment. We are also doing nocturnal flashlight surveys to examine the abundance of black caiman and how they interact with giant otters, as two top predators which mostly feed on the same fish prey.

Our new plant team uses nets, microscopes, tree climbing gear and tree transects to examine differences in the abundance of algae and study the communities of bank trees and floating macrophyte plants in lakes with varying exposure to human activity.

Our field activities are not limited to collecting ecological data. We work in local communities which depend economically on gold mining. We try to understand how they perceive the impact of their activities on their environment and whether they are willing to work to conserve and restore the rivers and lakes many of them depend on.

Our work in local communities takes place in primary schools, where we conduct workshops showing the diversity of aquatic animals and the importance of protected areas. Our human dimensions team introduces school students to a conservation game, in which they are faced with resource-related dilemmas.

Our community work also has a creative aspect. Students make giant otters out of plastic bottles, draw thematic maps to showcase their knowledge on local plants and animals, and in some cases work in communal gardens to grow vegetables.

Several young Peruvian biologists have gained experience with the project. I was able to interview Alejandro Alarcon Pardo, who is still one of the project’s leading field assistants, and Romina Najarro, who moved on to a PhD program in Purdue university. Sol Fernandez Rodriguez, Alessandra Cuya and Lara von Hildebrand are currently doing environment-related Master’s programs in European universities.

Despite what we have achieved so far, our project is still young. Our main mission has been to understand the biodiversity of oxbow lake ecosystems, the ecology of the animals living in them, and specifically which species and ecological interactions are impacted by activities like gold mining and fishing.

Our findings on freshwater ecosystems so far indicate that animal communities are richer and more abundant within protected areas. We have also learned that some kinds of human activity, such as responsible ecotourism, can have lower impacts on the freshwater environment.

The next step is to figure out how we can work to mitigate these influences. There are several aspects to this: at the landscape level, in some areas it has been demonstrated that protection of bank areas in freshwater ecosystems and tree planting in deforestation scars and can promote their restoration.

From the perspective of the local people that inhabit the land, one of our objectives is continuing to familiarize them with the diversity of fish and birds, the beauty of trees and the behavior of charismatic species like giant otters.

We feel that better familiarity with the environment and a stronger connection with the freshwater ecosystems surrounding them can promote a more responsible treatment of these rivers and oxbow lakes, and ultimately more sustainable land use in this valuable Amazon biodiversity hotspot.