A jaguar named Jatobazinho has been released back into the wild at a national park in Argentina as part of a program to boost the numbers of the endangered species, which faces significant hurdles after it has suffered a marked decline in recent years.

This was the eighth jaguar freed in the past year into Ibera National Park but the first adult male, said the environmental group Rewilding Argentina, which is behind the project.

Jatobazinho weighs about 90 kilograms (200 pounds) and has brown fur peppered with black spots.

He first appeared at a rural school in 2018 in Brazil, looking skinny and weak after crossing a river from Paraguay.

The big cat spent a year in an animal refuge in Brazil until he was sent to a jaguar reintroduction center operating since 2012 in Argentina's northeast Corrientes province, where the species had been extinct for 70 years.

Sebastian Di Martino, a biologist with Rewilding Argentina, said that the jaguar needed to be nice and relaxed as it left its enclosure and entered the wild.

"If the animal is stressed it can become disoriented and end up anywhere," he said.

He said these jaguars were fed live prey while in captivity because they have to know how to hunt.

In the Ibera park, there is plenty of wildlife for them to feed on such as deer.

The jaguars are tracked with a GPS device they wear.

There are plans now to release a female that was born at the reintroduction center.

The park is also awaiting the arrival of three wild jaguars from Paraguay, and two more raised in captivity in Uruguay and Brazil.

Jaguars are native to the Americas.

It is estimated there were more than 100,000 jaguars when Europeans arrived in the 15th century, their habitat ranging from semi-desert areas of North America to the tropical forests of South America.

Conservation groups say the jaguar population of South America has fallen by up to 25% over the past 20 years as deforestation eats up their habitat.