A family of four otters, including two pups born in captivity, have been set free in the Iberá wetlands in north-east Argentina, the first step in reintroducing the species to its original habitat.
Endangered globally, the giant river otter (Pteronura brasiliensis) has been absent in Argentina for over 40 years, after habitat loss and illegal hunting led to its decline.
The milestone release is also the first time a top predator has been brought back from nationwide extinction in the country.
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The project is a collaboration between the provincial government of Corrientes, Argentina’s National Parks Administration, and Rewilding Argentina, the offspring organisation of Tompkins Conservation.
Rewilding Argentina’s planning for the giant river otter program began in 2017. But they’ve faced steep challenges, including obtaining suitable mates from zoos around the globe, processing authorisations for their international transfer, and establishing breeding pairs to form the gregarious family units that live and hunt together in the wild.
Charismatic and playful, the giant river otter is the world’s largest otter, measuring up to 1.8m and weighing 33kg.
They live and hunt in family groups, and once inhabited nearly the entire watershed of the Paraná River in the northern and eastern regions of Argentina. The last breeding population was seen in 1986, with only occasional solitary individuals, most likely dispersed from nearby countries, spotted since then.
Wetland return
Located near the borders of Paraguay and Brazil, the Iberá wetlands is one of South America’s largest (3.2 million acres, including two million acres of protected area) and most important watersheds.
As droughts and massive wildfires increase in frequency, the disturbances threaten the freshwater resources of the region’s diverse wildlife, alongside millions of people in Argentina. Having functional, intact ecosystems is considered crucial in order to combat these changes in climate.
Sitting at the top of the wetlands’ aquatic food chain, the giant river otter has a key role to play in the health of the wetlands. "The giant river otter is one of the largest aquatic predators in the wetlands of South America, and it’s a particularly active and voracious species,” says Sebastián Di Martino, conservation director of Rewilding Argentina.
“They mainly prey on fish, so their presence will likely impact the fish populations here. It’s a dynamic we need to better understand because, more than recovering one species, we want to recover its ecological role in the ecosystem, so we’re measuring the diversity and abundance of fish species in Iberá, via a procedure that assesses DNA in the water and tells us the species that are present and their numbers. We will be monitoring these fish populations for differences post-reintroduction.”
Wildlife translocations are complex and potentially dangerous for the animals. "There are many challenges, especially when working with animals that were born in captivity and have spent their whole lives there, like these giant river otters we’re setting free,” explains Di Martino.
"In this case, the animals have spent long periods acclimatising, years in this case, in pre-release pens, in the same environment that they will inhabit once free.
"They have learned to dig their own dens, and capture live prey, and know the vegetation and water of the region. They have spent a substantial amount of time learning to adapt to the environment they will live in.
"As with our other reintroduction projects, they will be monitored, so we can follow their adaptation and the challenges that they will encounter. We’ve had to develop special technologies, since satellite GPS had never been used to monitor this kind of otter, and we’ve had to design a new kind of harness with special materials, since regular collars wouldn’t work on them.”
What's next?
To help the permanent recovery of the species, additional releases are planned in the Iberá wetlands and the Chaco region. "The species will not recover with the release of just one family,” says Di Martino.
"Rewilding Argentina have been working to bring back the species for eight years with the world’s first reintroduction program, breeding giant otters for wild release. We’ve paired multiple adult giant otters gifted from zoos around the world, and they’ve successfully formed families and are living in pre-release pens in the wetlands.
"Soon, when these individuals are ready, we hope to release them as two family groups into the wetlands."
Main image credit: Rewilding Argentina
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