This story originally ran in bioGraphic, an online magazine about nature and sustainability powered by the California Academy of Sciences.

Story by Ben Goldfarb

Ocelot 331 embarked on his life’s most perilous journey on January 25, 2020 – a warm night, scattered clouds against moonless sky. He was five years old, and like young males of most species, he was restless. The ocelot – a feline no larger than a bobcat, clad in a leopard’s bewitching spots and blotches – had spent his short life roaming the Laguna Atascosa National Wildlife Refuge in South Texas; he’d shied from coyotes, pounced on rats, blundered into box-traps, and worn the tracking collars that biologists buckled around his neck. This scrubby patch of forest had sustained him. But cats are inclined toward wanderlust, particularly mate-seeking males. Thus OM 331 – O for ocelot, M for male – decided, that January night, to leave his shard of forest and seek his fortune in the refuge’s southern reaches.

With only 100 or so individuals living north of the U.S.-Mexico border, the ocelot is thought to be the most endangered feline in America. Image: Aflo/NPL 

This was dangerous for one principle reason: OM 331 would have to cross a road. A road that humans knew as FM 106 funneled traffic through the refuge, and busier highways loomed beyond. Cars are the leading cause of death for Texas’s tiny population of federally endangered ocelots, responsible for around 40 percent of all mortality, and impetuous, lovesick males like OM 331 face the most risk.

But OM 331 had advantages that past ocelots had lacked. As he approached FM 106, he reached a chain-link fence that blocked him from slipping onto the road. Instead he turned 90 degrees and followed the fenceline to a tunnel. Although built expressly for his kind three years earlier, the dark, concrete-walled culvert was unnerving. OM 331 likely paused to sniff the traces of other travelers: raccoon, javelina, armadillo, opossum. He took a tentative step forward, then another and another, at last emerging at the tunnel’s south exit. Where other cats had perished, he’d found passage.

As 331 exited the tunnel, he broke the invisible beam of a camera trap, which snapped his photo, his shoulders hunched and eyes agleam. When researchers checked the camera, they discovered they’d documented history: the first American ocelot known to have strolled through a wildlife crossing. “It was kind of the shot heard ‘round the world,” Hilary Swarts, then a refuge biologist, told me.

Swarts and her colleagues had reason to be thrilled. Wildlife crossings and fences represent the most reliable solution to roadkill, which claims an estimated million vertebrates per day in the United States alone. Around the world, biologists and engineers have built tunnels, underpasses, culverts, and bridges to guide animals from European hamsters to African elephants across highways. Texas’s ocelots seemed likewise to be adapting to the road’s dangers by using the passages humans had installed for their benefit.

Yet OM 331’s story isn’t unambiguously cheery. Although the state of Texas began building ocelot crossings in the 1990s, the passages had long gone unused; a fair response to the news that an ocelot had walked through one might be, What took so long? Moreover, crossing a single road hardly guarantees an ocelot’s long-term survival: One biologist has described the highways, towns, and farms beyond the Laguna Atascosa refuge as an “ecological killing-zone.” Wildlife crossings have likely made South Texas safer for ocelots – but what will it take to sustain America’s rarest cats?

While it may look innocuous, highways like this one present one of the greatest risks to the country's most endangered feline. Image: Thomas J. Yamashita 
As this road sign warns, highway fatalities present one of the greatest threats to America's remaining ocelot population. Image: Ben Goldfarb
While the South Texas thornscrub presents a formidable challenge to human travel, it serves as prime habitat for the United States' remaining ocelot population. Image: Wildnerdpix/Shutterstock 

Few wild felines are as adaptable as Leopardus pardalis. Ocelots slink through landscapes as diverse as Mexican deserts, Brazilian rainforests, and Andean slopes, picking off rodents, reptiles, birds, even the occasional deer fawn. At one time they roamed Texas, Louisiana, and Arkansas, before the usual cataclysms – fur trapping, habitat loss, the indiscriminate slaughter of predators – shrank their U.S. range to a few patches of forest in the Lone Star State. Today fewer than 100 ocelots likely survive north of the Mexican border, in only two areas. One is a collection of private ranchlands that have escaped development, and the other is Laguna Atascosa, a reserve perched on the state’s southern tip.

I went in search of ocelots on the refuge one March morning with Daniel Scognamillo, a biologist at the Caeser Kleberg Wildlife Research Institute at Texas A&M University-Kingsville. After driving for two hours past cottonfields, lethargic cows, and wind turbines, we turned into the refuge and were promptly enveloped by thornscrub – a forest type native to Texas that’s as forbidding as its name suggests. Mesquite, hackberry, ebony, acacia, and other low trees and shrubs formed an inhospitable weave of needles, spines, and briars. A year earlier, Scognamillo had captured a big male ocelot, dubbed the Duke, whose face was etched with scars – wounds he likely sustained during skirmishes with other ocelots in heavy brush. “You can see in the Duke’s face how much it takes to survive in this patch,” Scognamillo said admiringly.

Fewer than 100 ocelots likely survive north of the Mexican border. Their range in the U.S. is currently limited to a collection of private ranchlands that have escaped development and Laguna Atascosa, a reserve perched on the state’s southern tip. Image: Rolf Nussbaumer 

Although no one knew precisely how many ocelots shared Laguna Atascosa with the Duke, Scognamillo hoped to find out. He’d scattered camera traps around the refuge to photograph ocelots and thus estimate their numbers. (The hypnotic patterns that adorn ocelot fur also permit scientists to differentiate individual animals.) “The idea is to capture the flank,” Scognamillo explained: the more spots he could see, the more easily he could tell one ocelot from another.

Scognamillo parked along a dirt road. Up close, the thornscrub seemed less hostile: creaturely trails and apertures punctured the understory, and it was easy to picture a small, furtive cat weaving through dappled light. We pushed into a pebbly clearing where Scognamillo had set two cameras. He opened one and flicked through motion-triggered photos. “Raccoon, opossum, rabbit, opossum, armadillo, coyote, bobcat,” he droned.

A thin smile creased his tanned face. He handed me the camera. “What do you think of this?”

On the screen: an ocelot, head raised, round ears lifted, the universal posture of the curious feline. A constellation of spots and rosettes swirled across his flank, a pattern somehow both random and artful – the delicate play of sunlight and shade rendered on fur. Where form and function converge, there lies the ocelot.

Scognamillo glanced around, as though the animal would suddenly appear. He’d been studying wild cats for three decades, from pumas in his native Argentina to leopards in Botswana. In Venezuela he’d been charged by a jaguar after his tranquilizer dart missed, and a massive paw had raked his lip and hand; like the Duke, he still bore the scars. I’d thought he might be indifferent to a mere photo of such an unimposing cat. Yet there was something about the ocelot – its elusiveness, its beauty, its grit – that left Scognamillo smitten. “It was right there,” he said with wonder. “We were standing in the same spot.”

We spent that day and the next inspecting cameras around the refuge. Ocelots appeared at two more sites, including, thrillingly, a mother and kitten. Scognamillo couldn’t yet estimate their numbers, though past surveys had pegged the local population at fewer than fifteen cats. They were clinging to life, yet they remained marooned within a terrestrial sea of agriculture, development, and roads, and tended to die not long after setting paw beyond the refuge. “We need to create a landscape that is safer for them to move,” Scognamillo said.

The refuge’s ocelots represent a classic conservation crisis: a tiny, isolated cluster of animals teetering on the precipice of local extinction. Ocelots need more of everything – more space, more security, more opportunity to mingle and breed. If the problem is straightforward, however, the solution is anything but simple.

Biologists are using camera trap images like this one to get a better sense of ocelot population size as well as the cats' use of wildlife crossings. Image: Ben Goldfarb 
South Texas ranchlands provide some of the few remaining pockets of habitat for America's most endangered feline. Image: Chris and Hans/Shutterstock

As recently as the 1980s, no one knew whether ocelots still lived in the United States. When a biologist named Michael Tewes set out to look for them, many researchers assumed they’d been extirpated; one professor bet Tewes a fifth of Jack Daniels that he wouldn’t find one. Tewes won the bottle on March 2, 1982, when he caught a live ocelot in a padded leg-hold trap. Over the next two years, he captured 11 more in box traps baited with chickens.

While he’d proven that ocelots persisted, however, he didn’t know how many survived, nor their range. “It was this big black hole of information,” recalled Tewes, Scognamillo’s colleague at Texas A&M.

The black hole posed a particular challenge for the Texas Department of Transportation. Every time the state upgraded a road in ocelot country, it was bound by the Endangered Species Act to protect the cats. Unfortunately, nobody knew where ocelot country was. Alleged sightings and old roadkill records suggested that their range might extend 150 miles north of the refuge. Erring on the safe side, TxDOT began including wildlife crossings on practically every road reconstruction in the region. In the 1990s and 2000s, it built 33 ocelot underpasses.

This was a sound strategy, but for one detail: None of these early crossings was anywhere near a flesh-and-blood ocelot. As Tewes affixed more ocelots with tracking collars, he discovered that their range was smaller than he’d thought. Texas’s crossings might be helping raccoons and opossums, but they weren’t doing anything for their target species. Between 1983 and 2002, Tewes and his colleagues tracked 80 ocelots, more than a third of whom were killed by cars. One collision hotspot, where eight ocelots died over several years, lay more than 15 miles from the nearest underpass. The irony was cruel: Texas had built plenty of crossings where ocelots didn’t need them, and none where they did.

Gradually, that began to change – thanks in part to the brutal guidance provided by roadkill itself. In 2017, TxDOT completed a dozen crossings beneath FM 106, the road that runs through Laguna Atascosa’s heart, and Highway 100, where ocelots often died as they tried to disperse south from the refuge. Altogether, the new underpasses cost $8 million. The agency later added more passages along FM 1847, which flanks the refuge to the west. Ocelot habitat and ocelot crossings had finally begun to overlap.

Despite that progress, the region’s roads remain perilous. Although the state better understands where to situate crossings, it tends to install them only in combination with other maintenance or road upgrades – “partly because they are less expensive when carried out as part of a construction project,” a TxDOT spokesperson told me in an email. This cost-conscious approach means that many roads remain treacherous, including one highway that cleaves ocelot populations on private ranches and prevents the cats from mixing.

“Crossings there would promote landscape and demographic connectivity,” Tewes told me. “It’s a shame we have to wait for road modifications to do it.”

The prickly pear cactus is one of many thorny species that dot the South Texas landscape. Image by Joel Trick

The day after my visit to Laguna Atascosa, I climbed into a Ford F-250 pickup with Thomas Yamashita to tour the highways fragmenting ocelot country. Yamashita was a PhD candidate in the same research group as Scognamillo and Tewes, and had the grisliest assignment: to survey roadkill along fifty miles of U.S. 77, a highway being upgraded into a massive interstate. The road’s facelift will include 10 new crossings, and Yamashita was tasked with pre-construction monitoring. You can’t tell whether underpasses are saving animals unless you know how many are dying in the first place.

The research was straightforward, albeit gruesome. We cruised the highway at 55 miles per hour, stopping to note crushed bobcats, barn owls, deer, opossums, and, surreally, nilgai, a huge Asian antelope introduced for hunters and since gone feral. (We didn’t find any ocelots, though we didn’t expect to: They’re so rare that, in more than a year of weekly surveys, Yamashita had only seen one.) We paused at each carcass to record species, location, and other data; then an undergraduate dashed through traffic to mark the body with orange spray paint so that it wouldn’t be counted in future surveys. Yamashita had once been interrogated at a Border Patrol checkpoint, where he informed the agent he was studying roadkill. The agent’s face lit up. “Oh,” he said, “you’re the ones painting all the dead animals!”

As well as tallying roadkill, Yamashita took me to visit some of TxDOT’s newer wildlife crossings. All of the underpasses adhered to the same basic principles – a passage beneath a road, flanked by fencing – though the design details varied. Some crossings were so capacious you could have driven a Hummer through, others so low and narrow that even a toddler would’ve had to crawl. Some were shrouded by thornscrub, others lacked cover; some were floored in dirt, others had muddy streams coursing through them. Several boasted elevated concrete shelves, which allowed animals like bobcats to walk through without wetting their paws.

Yamashita had tallied roadkill around many of these passages since their installation, and, in general, they worked. “After about a year, mortalities go way down,” he said. “Animals learn to use these crossing structures. It just takes time.”

Yet the patchwork nature of these lands posed challenges. For one thing, the preponderance of private property along the roadside made it difficult to keep animals off the highway: every driveway represented a gap in the fence that ocelots and other creatures could theoretically exploit. Even worse, ill-advised land management rendered some passages ineffective. At one site Yamashita showed me, TxDOT had installed an underpass where a drainage ditch intersected a road. The dense brush that lined the ditch should have guided animals to the crossing like a trail of bread crumbs, but the local flood control district, perhaps fearing that vegetation would clog the ditch during a storm, had demolished the scrub. Only a few sad brush piles remained, and the underpass was left stranded in an open field.

Even if an ocelot somehow discovered this underpass, would he walk through it? OM 331, and the several cats who’d followed him, had proven that some ocelots used some wildlife crossings, some of the time – but ocelots had been known to shun passages, too. After all, Yamashita pointed out, underpasses and culverts were “just so unnatural”: echoey, concrete-lined, bereft of plants.

Animals do acclimate to these eerie structures over time; in Wyoming, for example, research has shown that migrating herds of mule deer trot through underpasses more readily every year. But while deer encounter the same underpasses repeatedly on their migration routes and teach their fawns to use them, a young ocelot dispersing from the refuge might only stumble upon a crossing once, and never have the chance to habituate to it. In 2019 cameras had recorded an ocelot approaching a crossing on Highway 100, turning away, and slipping beneath a roadside gate onto the highway – never to be seen again.

Biologists document roadkill victims along stretches of highway to better understand the need for and effectiveness of wildlife crossings. They mark animals with orange spray paint to make sure those individuals aren't counted twice. Image: Ben Goldfarb 
A camera trap captures the image of a coyote as it safely exits a wildlife crossing in South Texas. Image: Thomas J. Yamashita
A better understanding of the dangers posed by highways has put safer wildlife crossings in the public consciousness in a way they never have been before, according to the National Wildlife Federation's Beth Pratt. Image: Wirestock Creators

If ocelots can take comfort in anything, it’s that they’re not alone: They share their vulnerability to roads with nearly all wild cats. Like most carnivores, felines roam large territories that overlap highways, and their naturally low numbers and slow reproductive rates mean that even a few collisions can spell doom. Motorists are responsible for more than 60 percent of Iberian lynx deaths in eastern Spain and, in 2021, more than three-quarters of Florida panther deaths. When a car killed a pregnant Asiatic cheetah named Majrad in Iran this March, conservationists declared it “one of the final nails in the coffin” for her disappearing species.

Against this grim backdrop, wildlife crossings offer reason for optimism. Beginning in the 1980s, the state of Florida installed 37 underpasses and 40 miles of fencing along Alligator Alley, an 80-mile stretch of federal highway that’s notorious for panther roadkill. Cat collisions virtually ceased, and researchers declared that the project had “facilitat(ed) panther population expansion.” Today wild cats are the impetus for the largest critter overpass in the country: the Wallis Annenberg Wildlife Crossing, a bridge, slated for completion in 2025, that will vault over U.S. 101 in California and connect inbred cougars with genetic reinforcements.

“Wildlife crossings are in the public consciousness in a way they never were before,” Beth Pratt, the National Wildlife Federation’s regional executive director who led the campaign to build the overpass, told me. “There should be a future where these are just part of transportation budgets everywhere.”

There’s no doubt that wildlife crossings are vital. But my time in Texas was also a reminder that they aren’t enough. Less than one percent of South Texas supports ocelot habitat; even if a cat did manage to cross beneath Highway 100, he’d find himself lost in a maze of development, sorghum fields, and still more roads. Without adequate land protection and restoration, wildlife crossings can become bridges to nowhere.

Given these immense hurdles, I couldn’t help but wonder: Does it matter whether an ocelot uses an underpass if it merely delays his death? Hilary Swarts, the refuge’s former biologist, countered my skepticism. “It’s not a silver bullet solution, but every action you take that adds some measure of safety or protection counts,” Swarts said. Take Ocelot 341, a dispersing male who slunk through an underpass only to be killed by a car eight months later. Although the crossing hadn’t permanently saved 341, it may have protected him long enough to breed.

“He might have snuck back into the refuge and passed on some of his genetic material in those eight months,” Swarts said. “That wouldn’t have happened otherwise.”

As this dead bobcat illustrates, roadkill makes up a significant portion of mortality among a variety of wildlife species in South Texas. Image: Ben Goldfarb

As perilous as South Texas remains, it’s not for lack of conservation effort. Over the past two decades the U.S. Fish & Wildlife Service and environmental groups have purchased more than 100,000 acres of land in hopes of expanding core ocelot habitat and forming corridors between isolated cats – even, perhaps, linking American ocelots with their cousins in Tamaulipas, Mexico, more than fifty miles away. Whether it’s possible to connect such far-flung populations is a matter of debate; Tewes has opined that we’re better off helping ocelots “shelter in place” on the refuge than facilitating their dispersal into the dangerous lands beyond. Either way, the cats won’t survive without more space – and a lot of it.

One afternoon, I toured Laguna Atascosa with Sergio Vasquez, the refuge’s deputy refuge manager. We stopped first at a sunbaked swath of crop furrows: a one-time sorghum farm of about 3,600 acres that the Fish & Wildlife Service bought in January 2020. Thousands of white plastic tubes picketed the field, each a sleeve that protected a young native tree or shrub – the slender origins of a new thornscrub patch. In the hazy distance, hunched workers planted ebony and prickly ash, a forest being made before our eyes.

We drove a quarter-mile to another erstwhile farmsite where restoration was further along. Waist-high lope bush, Mexican olive, Texas sage, and dozens of other species thrust their arms above the field; orange granjeño berries beckoned fruit-eating birds whose droppings would propagate seeds faster and cheaper than human hands could. Vasquez, who’d grown up hunting on the refuge, inhaled through his nose. “Nothing smells like this place,” he sighed. “That palo verde that’s blooming? Ah, so good.”

I asked Vasquez how long it would take for this site to support ocelots. “As soon as we get something that’s not bare ground, somebody’s going to use it,” he said. Just because ocelots dispersed through these sparse, early-stage plantings, however, didn’t mean that they could live here full-time. It would take years, if not decades, for this forest to mature. “Everyone wants to plant trees, walk away, and say, where are the ocelots?” Vasquez said. Like a true Texan, he compared restoration to barbecue: You couldn’t rush perfection. “Let it do its thing, slow and low, like a big juicy brisket.”

But ocelots may not be able to wait. The landscape around the refuge is among Texas’s fastest-growing regions: Its human population is predicted to double to 3 million by 2050, auguring more houses, more businesses, more cars. A proposed causeway to South Padre Island may someday funnel thousands of vehicles past the refuge daily; gas export terminals servicing Texas’s fracking boom could likewise beckon more traffic into ocelot country. Roads are even being built to accommodate the SpaceX personnel flocking to the company’s Brownsville launch site.

As far as anyone knows, OM 331 – the feline pioneer who first slunk through a crossing in 2020 – hasn’t had to navigate this explosive development. After crossing FM-106, he likely carved out his own territory on the refuge, where he may remain to this day: middle-aged, now, perhaps with a few scars and progeny of his own. As young males like him strike out on their own, it’s imperative that they, too, find habitat where they can thrive. Wildlife crossings may help ocelots traverse highways, but it would be even better to engineer a landscape so large and intact they never have to cross roads at all.

The palo verde tree is one of many species that make up the South Texas thornscrub habitat. Image: jflower74/iStock
A green jay looks out across the South Texas landscape. Image: Wilfred Marissen 
Evening rain lily, South Texas. Image: Rolf Nussbaumer