IBERÁ, Argentina — Driving along the rutted dirt track into Iberá National Park, it is not hard to see why this vast subtropical wetland stretching from horizon to horizon makes for ideal jaguar habitat.
Capybara the size of sheep seem to be chewing the tall grass everywhere. Some even snooze in the middle of the path and only move grudgingly after vehicles stop in front of them.
These outsize rodents, the world's largest, might be a curiosity for visitors. But for jaguars, they spell something very different — lunch.
That abundance of prey makes Iberá the perfect setting for the groundbreaking Jaguar Reintroduction Project. The brainchild of the late Douglas Tompkins, an American conservation philanthropist better known as the co-founder of the North Face clothing brand, it represents the first attempt to repopulate the big cats, which are highly aquatic, into an area in which they were previously hunted into extinction.
The first stage was to completely rewild Iberá, beginning with replacing the cattle that once dotted the landscape with endemic species including anteaters, peccary and otters.
Now, the time has come for jaguars, which will be the first to roam the marsh in 70 years.
Two cubs, Juruna and Marina, are being carefully prepared for freedom in a complex of sprawling enclosures with tall electric fences that resemble something out of "Jurassic Park." If things go well, they will, by the end of the year, become the first jaguars released into Iberá in the reintroduction effort.
The project's specialist team hopes to eventually release up to 20 jaguars in Iberá. The goal is for them to then breed in the wild, with the wetland capable of sustaining a population of around 100 — and generating tourism revenue for locals.
Overall, jaguars — and Iberá in particular — represent a rare big-cat good news story. While lions and tigers are seriously endangered, the new world's biggest feline is in relatively good shape, thanks largely to the sheer scale of its principal stronghold, the Amazon.
Nevertheless, jaguars continue to face threats across their range, including hunting and habitat loss. They have been entirely wiped out from two countries, El Salvador and Uruguay.
Iberá, hundreds of miles southeast of the Amazon, teems with life. Flat as a pancake and roughly four million acres, it is the world's second largest wetland. Families of howler monkeys pack into the small, forested islands that occasionally pop out of the marsh. Tapirs barrel through the grass, caymans sun themselves on rocks and the array of brightly colored birds is breathtaking.
Eric Sanderson, a scientist at the Wildlife Conservation Society, a U.S. environmental group, describes the Iberá project as hugely important. "For a long time, conservation has been about just holding the line. This project is trying to push it back out again," he said.
Sanderson is monitoring its progress with a view to one day emulating it at the northernmost end of the jaguar's former range — the southern United States, where the cats roamed until the 20th century.
Two-year-old siblings Juruna and Marina prowl a seven-acre pen into which a live capybara is released once a week. There are two essential elements for them to survive and thrive in the wild: knowing how to hunt and maintaining their natural aversion to the only species that threatens them — humans.
That means they may only be observed by remote camera as they jump one of the giant rodents. After some toying with the capybara, one of the cubs finally, instinctively begins the jaguar's trademark kill technique, clamping its powerful jaws onto the back of the animal's neck.
"They are slowly getting there," Natalia Mufato, a biologist managing the small onsite team of veterinarians, scientists and volunteers, said. "They need to be able to kill their prey but also to do so without getting injured. A jaguar that breaks a tooth will not survive in the wild."
The next phase for the cubs will be living in the complex's largest enclosure, a 70-acre stretch of wetland that is already a permanent home to several capybara families. It is large enough for the felines to perfect their tracking and ambushing of prey in conditions identical to those in the wild.
When work needs to be done near their current enclosure, staff carry pepper spray and foghorns to ensure the cats do not acclimate to humans.
A key part of the project is the pool of breeding adults that were brought up in captivity in various zoos in Argentina, Paraguay and Brazil. They are too old to learn how to catch their own food but will, hopefully, continue to produce the new generation of wild cats.
Currently, three females and one male are each kept in their own spacious enclosures, packed with tall grass and trees, near enough to the cubs for the animals to be able to call out to each other.
The adults prowl excitedly as handlers approach with their food, pieces of feral pig that are still being culled to make way for native species.
The jaguars are temporarily lured into small pens while the meat is hidden around their compounds. Requiring them to sniff out the food is just one of many important details staff have developed to ensure these jaguars remain stimulated.
As the brawny cats, each weighing around 160 lbs, press up against the metal fence, their muscles ripple beneath rich dappled coats, their imposing presence almost tangible.
The jaguar reintroduction has required extensive work with local people. Jaguars actually rarely attack humans, but hunting, including by farmers concerned about their livestock, was the reason jaguars disappeared here in the first place. Given that any new felines would also stray beyond the park boundaries, buy-in from locals was paramount.
"We did a lot of work with the communities," Mufato said. "They were actually a lot more positive than we expected. A lot of people are really proud of the jaguar."
A local biologist surveyed 400 people in the region around the reserve and found 90 percent support for reintroducing the big cats, according to the project, which added "they also see it as a potential touristic attraction."
Sanderson anticipates the Iberá project will work: "Jaguars are such good generalists. People think of them as living in the jungle. But the truth is they can adapt to all kinds of different habitats and prey."
He is working, with other environmental nonprofits, on a similar project in Arizona and New Mexico, although he emphasizes that it will be years, if not decades, before the first jaguar could be released in the United States.
According to Sanderson, the U.S. Fish and Wildlife Service believe jaguars could roam as far north as Interstate 10, which runs through Phoenix, but he suspects they could go further than that, including as far north as Flagstaff, Arizona. One potential problem, given that the animals would cross back-and-forth into Mexico, would be President Donald Trump's border wall.
"They are on a much faster track in Argentina," Sanderson said. "But it would be wonderful to see a sustained jaguar population both in Iberá and in the U.S. once again. We have to remind people that they are part of our natural fauna and have as much of a right to be here as we do."