For years, the Florida panther, a majestic creature that lurks in and around the forests of the Everglades, has teetered on the edge of permanent disappearance. Closely related to the mountain lion, the panther once roamed across much of the South, but the ever-advancing modern world pushed it into a tiny corner of Southwest Florida. By the late nineteen-seventies, fewer than thirty survived.

Since then, the panther has been coming back, helped by a government- and privately backed expansion of its habitat. Florida panthers are now thought to number around two hundred. Indeed, there are so many big cats in the Everglades that they are venturing out in search of new territory.

This spring has brought the best news for the Florida panther in many years. For the first time since 1973, panther kittens were spotted north of the Caloosahatchee River, which had formed the northern boundary of the panther’s habitat. In March, a pair of panther kittens tripped an automatic wildlife camera in the Babcock Ranch Preserve, a forested expanse thirty-five miles west of Lake Okeechobee. That means that a female panther swam across the Caloosahatchee and recently mated with a male panther on the other side. (Male panthers, which are larger and have a bigger range than females, have been spotted north of the Caloosahatchee River for many years.) The news cheered scientists and state environmental officials, who have been trying to coax a female panther across the Caloosahatchee for more than two decades.

“We’ve been waiting for a female panther to cross the river for a long time,’’ Darrell Land, a scientist with the Florida Fish and Wildlife Conservation Commission told me. You can see the photos of the kittens here.

The kittens are small, of course, but adults are big. Male adults can weigh as much as a hundred and sixty pounds and stretch seven feet from tip to tail. Females are somewhat smaller. I’ve seen a Florida panther only once, in captivity on a Seminole Indian reservation inside the Everglades. Its paws were as large as baseball mitts.

There is a lot of open land north of the Caloosahatchee, and the hope is that the panther population will now have room to grow. The bigger the population gets, the greater its genetic diversity, which should boost its chances for survival. The history of extinctions is littered with examples of tiny populations that, because of inbreeding, are no longer fit enough to carry on.

Getting a female panther across the river was the culmination of years of effort—not just by conservationists but by the panther itself. Each Florida panther needs a huge area to live and breed; males need as many as a hundred and fifty square miles, females around a hundred. They eat possums, rabbits, white-tailed deer, hogs, and young cattle. The panthers’ home ranges often overlap, but they don’t like getting too close to each other. “Males fight to the death if they come into contact with each other,’’ Richard Hilsenbeck, a senior terrestrial scientist with the Nature Conservancy in Florida, said.

As the panthers have begun to multiply, they’ve been forced to search for new home ranges. Male panthers are especially adventurous; they crossed the Caloosahatchee River years ago. Male panthers have been found hundreds of miles north of the Everglades; three years ago, a male panther was shot and killed in the Okefenokee Swamp, in Georgia, more than four hundred miles away.

But, for the panther population to breed, females needed to cross the river, too. “Females are not as adventurous,’’ Hilsenbeck said. As the Everglades have grown crowded, more and more panthers have started to move out. That’s led to a dramatic increase in the number of panthers being killed by cars—thirty-one in 2016, the most ever recorded. The panthers needed somewhere else to go.

The solution, to conservationists, was to create a land corridor that would lead panthers to the river and then north across it. In 1994, the State of Florida and the Nature Conservancy began assembling the property for the corridor. Today it is about thirty miles long and fifteen miles wide, and spans both sides of the Caloosahatchee, but more money is needed to complete it.

Crossing is not easy; in most places inside the corridor, the river is seventy-five yards wide, and the banks are high and steep. But, at some point, the first female panther made the swim. In 2015, she was spotted on a remote wildlife camera north of the river. “They’re looking for territory, looking for food—they’re on the move,’’ Land said. It took more than a year for the first kittens to be born.

The Florida panther still faces many challenges—speeding cars, shrinking habitat, and the never-ending march of suburbia. But the prospects for the big cat are better than they’ve been in decades. “There’s a lot of open habitat north of the river,” Hilsenbeck said. “As long as they’ve got possums and rabbits and deer to eat, the panthers should be able to survive.”