The giant otter returns to Argentina after more than 40 years of extinction.

Madrid, July 1 (EFEverde). Nima, a giant otter ( Pteronura brasiliensis ) born at the Madrid Zoo Aquarium in 2020, heads the first family group of this species reintroduced in the Great Iberá Park (Argentina), after more than four decades of extinction in the country and thanks to a project

Her reintroduction, along with her partner Coco and two offspring, marks an unprecedented advance in the ecological restoration of the Argentine wetland and highlights the cooperation between institutions in situ and ex situ, the Madrid zoo reported in a statement.

The initiative was led by the Rewilding Argentina Foundation with the support of European zoos, as part of the European Giant Otter Conservation Programme (EEP), coordinated by the European Association of Zoos and Aquariums (EAZA).

Since their transfer in January 2023, Nima and Coco have lived in a pre-release enclosure in Iberá National Park, where they learned essential natural behaviors such as fishing and parental care. Their adaptation culminated in their final release after more than two years of preparation.

A perfect candidate born in Madrid

“Nima had a shy personality and wasn't very sociable with humans, which made her a perfect candidate for the reintroduction project,” explains Eva Martínez, a veterinarian at the Madrid Zoo. “This is one of the happiest endings we pursue in zoos: returning an endangered species to the wild.”

The last time a family group of giant otters was sighted in Argentina was in 1986. According to Sebastián Di Martino, Conservation Director of Rewilding Argentina, their return is key to the balance of aquatic ecosystems: “The giant otter is the main predator of these wetlands, and its piscivorous diet contributes to the maintenance of healthy water systems.”

The reintroduction project began in 2017 and required meticulous planning. It included searching for breeding pairs, designing health protocols, conditioning enclosures, and developing a special harness for post-release monitoring.

Diverse genetics and restored habitat

"The key to a project of this kind is not only breeding, but also ensuring diverse genetic lines and healthy specimens," emphasizes María Delclaux, head of conservation at the Madrid Zoo. The species is classified as Endangered by the IUCN, and its decline is primarily due to habitat loss and degradation.

Restoring this habitat has been one of the priorities of Rewilding Argentina, which has led large-scale ecological restoration projects since 2010. In Iberá, more than 158,000 hectares have been donated by the foundation to guarantee the necessary environment for emblematic species such as the jaguar, the anteater, and now, the giant otter.

Nima's reintroduction is a symbol of this restoration and the collaborative effort between organizations, governments, and local communities. Her story represents the possibility of reversing local extinctions through concrete actions and international cooperation.

Giant otter with pups in San Alonso-02_reworkweb

Global participation for an endangered species

The return of the giant otter to Argentina would not have been possible without the collaboration between the National Parks Administration, the Corrientes government, Rewilding Argentina, Projeto Ariranha of Brazil, and EAZA member zoos.

Participating in this first reintroduction include Givskud Zoo (Denmark), Budapest Zoo (Hungary), Eskilstuna Zoo (Sweden), Doué La Fontaine (France), Halle Zoo (Germany), and Los Angeles Zoo (USA), among others. EAZA currently maintains a population of 104 giant otters across 29 European institutions.

Furthermore, the future addition of Tama, Nima's sister, also born in Madrid, is already being planned. The goal is to form new family groups and continue the recovery process of this emblematic species of South American wetlands.

The Great Iberá Park: a sanctuary for wildlife

The Great Iberá Park, with more than 700,000 protected hectares, has become the epicenter of rewilding in Latin America. Species such as the peccary, the ocelot, the pampas deer, and the emblematic jaguar have been reintroduced there.

Since 2007, the project has integrated active conservation and local development, involving communities in ecotourism, environmental education, and scientific monitoring.

To learn more

Key facts about the giant otter