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Heading south on Florida's I-75 from Tampa to Naples, traffic oozes with countless sun-sparkled sedans, silvery SUVs, and trucks filled with the trappings of a large state undergoing big changes. Tractor-trailers carrying turf rolls, two-by-fours, masonry, and ornamental palms pull off the highway, replaced by dump trucks heaped high with palmetto brush cleared from construction sites. From frontier to vacationland to home for 17 million people, Florida now welcomes some 1,000 new residents each day.

Florida panthers need space—each resident male's average territory covers 250 square miles. (South Florida Water Management District)

Instead of new tourist attractions, signs trumpet new housing developments with names like The Preserve, Malibu Lakes, and Cypress Falls. In the midst of this human circus, it's easy to forget that Florida provides the last refugia for dozens of endangered and threatened species and subspecies. The king of them all is the Florida panther, an apex predator and the last of the eastern pumas, or cougars.

The Florida panther (Puma concolor coryi) once lived across the Southeast United States, and its range joined that of other puma subspecies to the north and west. Now endangered with extinction, this reddish-brown, up to seven-foot-long phantom is pigeonholed into just five percent of its historic range, making its last stand in Florida's southern tip. As it beds down by day and travels and hunts by night, the panther lurks in the shrinking shadows of Florida's building boom. But for how much longer?

The Florida panther was listed as endangered in 1967 by the U.S. Fish & Wildlife Service, and received thorough federal protection with the 1973 enactment of the Endangered Species Act. Over the decades, as the panther population shrank, conservationists realized that saving an animal that can roam 12 miles a night takes more than a few large parks and protection from hunting. It takes a multi-disciplinary marriage of genetics, conservation biology, land-use planning, and veterinary science. While the panther's odds don't always seem great, thanks to strong conservation efforts the known Florida panther population is now more than double what it was 30 years ago.

Big Cats, Big Cities
After battling more than three hours of heavy traffic, I find Darrell Land standing in his Naples office. I'm lucky: For up to 12 hours each week he's far above it, circling in a single-engine Cessna 172 to pinpoint radiocollared panthers with radiotelemetry gear. This tiring work is just one of Land's responsibilities as panther team leader for the Florida Fish and Wildlife Conservation Commission (FWC).

On Land's office wall hangs a satellite photo of South Florida stippled with hundreds of yellow dots that look like giant pollen grains. A huge smear of spots runs right over the Fakahatchee Strand State Preserve, indicating the striking number of times Land and his colleagues have locked onto radiocollared cats there over the last 25 years. But that doesn't mean panthers only pop up in natural areas. As he shows me the map, Land explains.

"They use practically every habitat out there in one shape or form, as long as it provides all the elements they need for food, denning, and stalking cover," Land tells me. "Young males that don't know where they're going end up in the darndest places. They find thick cover, wait until evening, then start working their way out," he says. Cover can include a copse of trees in suburbs, a thicket on a ranch, a citrus grove, or a stand of introduced Brazilian pepper bushes.

To illustrate his point, Land points to a spot on the map noting that a panther was located in the late 1980s right near the building in which we stand. Although Naples lies west of the core part of the Florida panther's range, wandering cats have popped up in areas much farther afield. Last year, for example, Land and his colleagues located a radiocollared male almost as far north as St. Augustine, within 100 miles of the Georgia border. Since 1988, four other radiocollared males and at least five other panthers—detected via their tracks, pictures, or roadkills—have been located north of the Caloosahatchee River, which is considered roughly the north end of the panther's current breeding range. Over the last 30 years, however, no panther breeding, nor any female panthers, have been noted north of the river.

Panthers are solitary and seldom meet up with others of their kind, except during brief mating encounters and the 14 months it takes for females to raise their cubs to independence. While young females usually stay inside or close to their mothers' home ranges, newly independent males have to find unoccupied areas or risk the wrath of resident, territorial males. In fact, the number-one cause of death among panthers is territorial males killing others that wander into their declared space. With each resident male holding an average home range of 250 square miles, and with each territory likely overlapping that of several females and their young, a few panthers cover a lot of real estate. "Certainly south of Lake Okeechobee, all of the areas that could support panthers are supporting panthers," says Land.

On average, young males disperse 25 miles, but the longest recorded peregrination was by a male that wandered 139 miles in seven months, followed by another trek of 145 miles. Except when females are tending their young or when an individual remains at a kill site to savor its prey for a few days, panthers are not only loners, but restless ones at that. They bed down in different locations at night, and patrol, scent mark (by urinating on piles of ground litter), and hunt throughout their home ranges. As they move around, many—especially young, dispersing males—risk encountering the panthers' second-greatest killer, cars and trucks. Between five and ten panthers die on Florida roadways each year (and between January and March 2006, five panthers had already been killed on Florida roads). "The number of road kills is up," Land told me, "but that's not surprising given that we believe the population has doubled or tripled since the 1980s."

Florida panthers prey on white-tailed deer.

Ideal panther habitat has minimal human disturbance, dense vegetative cover (such as palmetto), and ample prey, especially white-tailed deer (Odocoileus virginianus) and feral hogs (Sus scrofa). Panthers also hunt northern raccoons (Procyon lotor), nine-banded armadillos (Dasypus novemcinctus), marsh rabbits (Sylvilagus palustris), and American alligators (Alligator mississippiensis). Pets sometimes fall onto the menu as well. A few weeks before my visit, I spoke with Land on the phone and he told me that his office occasionally receives reports of panthers killing domesticated emus and turkeys, and that in the last few weeks, a few dogs had been attacked—the first such reports since the late 1980s. "Most of the depredation events," he told me, "are more of a chance meeting and not a true act of predation. Once panthers are locked in on something like that, it's kind of hard for them to break their attention. Unfortunately, we might be expecting to see more of these kinds of encounters given the tremendous increase in the human populations and small but steady growth in panthers, although the cats are hitting the ceiling in terms of space," said Land.

His prediction seems to be proving true during our meeting, which is cut short by incessant beeping. "I'd better get this," Land says, reaching for the black radio sitting on his desk. A woman's voice tells him that a domestic turkey was reportedly killed the previous night, and that she suspects Panther 79, which frequents the area. "All the classic signs [indicate] that this was a panther, not a bobcat," says the voice. (Land later tells me that his colleague suspected the panther because she found panther tracks and could hear the cat's radio signal.) "The media [are] on the way. We need to get someone from the state out here to talk with them," crackles the voice.

I leave Land to his work and head east from Naples. To go from the sprawling city to the heart of panther country takes just half an hour.

Bring on the Texans
Genetic sleuthing has played a major role in the panther population's recent growth. From the 1970s into the '90s, only 20 to 50 Florida panthers were thought to survive. Confined and dwindling, they had become inbred. Visible signs of their lack of genetic variation included crooked tail tips and cowlicks of fur on their backs. But more serious problems lurked beneath the surface. JoGayle Howard, a reproductive physiologist at the Smithsonian National Zoo's Department of Reproductive Sciences, has helped monitor the reproductive health of Florida's panthers for more than 20 years. She was shocked when she began examining panthers in 1985. "It turns out they had the worst sperm quality of any cats we'd found—even cheetahs. They were sort of a textbook of abnormal sperm. We'd never seen such high percentages of sperm defects," says Howard. Florida panther males had 94 percent abnormal sperm.

Another problem came to light when Howard and her colleagues examined panther acrosomes, membranes that cover sperm heads and release enzymes that bore into eggs during fertilization. Forty-two percent of all the Florida panther sperm they analyzed had abnormal acrosomes. Puma samples from other regions had far lower percentages: 19 percent in Colorado, ten percent in Texas, and just six percent in Latin America.

Another worry was the growing rate of cryptorchidism in male panthers—the failure of one or both testes to descend from the body. "Around 1985, about 30 percent of the population's males had only one descended testis," says Howard. "By the late 1990s, 80 percent of the population's males had one descended testis, and we were also starting to see males with no descended testes that were totally infertile." In addition to these reproductive woes, an atrial septal defect—a hole in the wall between two atria that does not allow proper blood flow through the heart—began to show up in Florida panthers. This caused heart murmurs and could have proven fatal to many of the inbred cats.

In 1994, Howard and other geneticists, biologists, and land managers met at the White Oak Conservation Center in northeastern Florida to plan for the panther's future. At the time, one population model projected that the panther might go extinct within 20 years. "It was a very contentious period," recalls Howard. "Some of the field guys said, ‘Hey, these cats are breeding. There's nothing wrong.' They had doubted the studies. Then the data were presented and they said, ‘Okay, what are we going to do about this?'"

The next year, 1995, eight female pumas were captured in Texas and released into panther habitat in South Florida. Texas cats were chosen because they were the closest genetic fit, but were typically larger than Florida panthers. "We were worried that big Texas males would kill smaller Florida panther males, so it was decided to bring in just females," says Howard. Five survived and began breeding with the local males. The Texas females have since been removed from the Florida wilds, but not before they produced 20 offspring, which in turn gave birth to about 60 grand-offspring.

Pure Florida panther males average around 115 pounds; females average 75 pounds. The intercrosses—offspring of Texas and Florida cats—grew larger. In 2000, Howard collected samples from a treed, darted 154-pounder, a first-generation intercross male called Panther 79—the same one I heard mentioned on Land's radio. After she and her colleagues looked at sperm samples, they found that the Texas experiment paid off. "Many of the bad defects we had been seeing went away in the first breeding," says Howard. Panther 79 had only ten percent abnormal acrosomes, the same percentage as Texas cats.

There are no current plans to reintroduce more Texas cats, but panther conservationists now know they could if the panthers' genetic health heads south again. "The original plan was to get a flood of genes from Texas cats in there and see what happens," says Howard. "There's been no cryptorchidism seen after the genetic restoration," she says. Some critics say that the intercross cats compromise the genetic purity of the Florida cats. Howard does not think this is an issue. Neither do some other geneticists. The infusion of new blood certainly seems to have boosted the cats' productivity: The last published count from 2003 tallied 87 cats, not including kittens.

The Florida Space Race
The Endangered Species Act requires that plans be made for each listed species' recovery. On January 31, 2006, the third draft of the Florida Panther Recovery Plan was published. In addition to recommending steps to ensure the future of the panther, the plan provides a comprehensive summary of what is known, or not known, about these stealthy animals.

Reflecting recent criticisms, the third draft of the recovery plan mentions a weakness of the dotted map on Land's wall—years' worth of data on radiocollared panthers that were mostly recorded during the day, the only time it's safe to circle a small plane low over hidden panthers. The 2006 plan reads, "Since almost all data from radiocollars have been collected during daytime hours…and because panthers are most active at night, daytime radio locations are insufficient to describe the full range of panther habitat use."

Development in the Everglades and other parts of Florida reduces panther habitat. (South Florida Water Managment District)

Over the last few years, controversy has swirled around the way some past panther research was conducted or interpreted and how it factored into land-use decisions. A 2003 report for the FWC entitled An Analysis of Scientific Literature Related to the Florida Panther states, "The conclusions that panthers prefer large forest patches and are reluctant to travel from forests are unreliable because the analyses excluded (without mention or rationale) a large fraction of the available data, ignored errors inherent in telemetry data, and did not rigorously compare used habitats to habitats available to the [radiocollared] panthers." The authors of the report also believe that some building projects were approved based on these questionable data, and note that over the last decade, there has been little progress in researching future panther reintroduction sites.

While there are no current plans to reintroduce panthers to other parts of their former range, the latest recovery plan states that an important part of the panther's recovery will be "expanding the known occurrence of panthers north of the Caloosahatchee River, if feasible, and identifying potential reintroduction areas within the historic range… ." The aim is to establish and maintain at least two other viable populations outside of South and south-central Florida. Potential reintroduction sites include parts of Arkansas, Mississippi, Alabama, and northern Florida. As a reintroduction site, central Florida is given low priority due to its heavy development, large human population, and extensive road network.

With only one isolated population, Florida panthers have no "medical insurance"—they remain vulnerable to disease outbreaks and other calamities. In 2002, five panthers tested positive for feline leukemia virus, and two of them died from the disease. The cats' wild hog prey can carry pseudorabies virus, a neurologic disease that killed at least one panther in the 1990s, while rabies, which is present in raccoons in some areas, claimed another. Radiocollared panthers are now vaccinated for feline leukemia virus and rabies. But there are other concerns as well: Veterinarians examining panther blood samples found antibodies to feline immunodeficiency virus and feline panleukopenia virus. Right now, none of these ailments pose a grave threat to the panther population, but it's not hard to picture a dire scenario, especially given that one of the downsides of inbreeding can be compromised immunity to disease.

Meanwhile, in the panthers' current breeding range, the walls of development are beginning to close in. Between 1985 and 2003, for example, three of the five counties that were home to breeding panthers—Collier, Lee, and Hendry—lost more than 368 square miles of natural or semi-natural habitat to agriculture and development, an area half the size of the state's largest lake, Okeechobee. And some projections estimate that South Florida's human population will grow by more than 50 percent by 2030. "I think any acre of open land out there is vulnerable to pressure," Land says. In many areas, agricultural lands, which are not considered conservation priorities but are used by hunting and moving panthers, are giving way to housing, malls, and other development. "From a conservation standpoint, we prefer the land [remains] in agriculture," says Land, "but economic pressures are too great. The profit you get from agricultural activity pales in comparison to direct conversion [of the land for development]," he adds.

But the news isn't all bad. "Some recent state purchases are starting to make a more secure jigsaw puzzle for the panther," says Land. In recent years, due in part to the state's $300-million-a-year Florida Forever land acquisition program and to required mitigation when developers are permitted to build in panther country, some important land purchases and easements have been, or will be, set aside.

From the late 1980s through the 1990s, for example, the state purchased 70,000 acres along the west border of the Fakahatchee Strand State Preserve, including the former Southern Golden Gates Estates development. There, cypress forests were logged in the 1950s, and canals, roads, and 2.5-acre plots were carved into the landscape in the 1960s as part of an operation to sell seasonally flooded swampland to unsuspecting buyers. The area, now the Picayune Strand State Forest, is being restored as wildlife habitat. Not far north, at the boundary between Hendry and Collier counties, lies the 32,000-acre Okaloacoochee Slough State Forest, home to Florida panthers, Florida black bears (Ursus americanus floridanus), and other threatened and endangered species.

One important property that may soon be purchased with Florida Forever funds is the Babcock Ranch, a 91,000-acre mosaic of habitats that would link four other protected properties, forming a band of conservation land that nearly stretches from the Lake Okeechobee shoreline west to the Gulf Coast. These vital areas lie just north of the Caloosahatchee River and may some day provide a gateway for northern expansion of the breeding panther population.

Private mitigation banks and permanent easements will also help protect some panther areas, offsetting at least some of the changes wrought by planned development. The 5,000-acre Ave Maria University and mixed-use development planned just north of Fakahatchee Strand State Preserve will claim large agricultural lands adjacent to areas where radiocollared panthers have been detected. As part of Collier County's Rural Stewardship Plan, the developers will be required to set aside large permanent habitat blocks that will protect nearby panther habitat.

Several large pieces of conservation land form the current core of panther country, and I drive between them after my meeting with Darrell Land. As I head south on State Road 29, on my right I pass the 2,400-acre Florida Panther National Wildlife Refuge, followed by the Fakahatchee Strand State Preserve's 80,000 acres. On my left sits the 730,000-acre Big Cypress National Preserve, now marked by U.S. Department of Interior signs, although here and there I spot amid the foliage rusted real estate signs that could have spelled a different future for the land. Instead of houses, I find Spanish moss-draped cypress, cabbage palm, and a sprinkling of royal palm sheltering basking alligators below and croaking cormorants, egrets, and herons above.

After a rumble strip, flashing lights, and a series of signs warning, "Panther crossing next 7 miles," "Entering panther habitat," and "Speed limit 60/night 45," I pull off the road where chain-link fences frame a vine-plastered concrete underpass. Panthers and other wildlife find safe passage beneath the roadbed using this and almost 30 other underpasses, or wildlife crossings, scattered along this road and I-75. These structures serve as cat crosswalks in what is, in essence, the panthers' downtown.

From my tranquil vantage point, the future seems bright for Florida's panther. But much of Florida is not like this. Across the state, the human rush hour is just beginning. When sunset arrives outside protected areas, denning panthers will stir, then wander between clusters of new houses and endless lines of headlights in search of prey.

—Contributing editor Howard Youth's recent ZooGoer articles have explored the world of sharks, border parks, Florida's exotic reptiles, and the wildlife of Spain's Canary Islands.

More: Is the Florida Panther Really a Distinct Subspecies?

ZooGoer 35(3) 2006. Copyright 2006 Friends of the National Zoo. All rights reserved.