Cat on the Spot
Of three endangered cats that roam the U.S.-Mexico border, only the ocelot still breeds on the northern side
- Laura Tangley
- Apr 01, 2006
JOCKEYING FOR POSITION, eight camera-wielding volunteers from the Dallas Zoo fanned out around a towel-draped cage at the edge of a thornscrub forest in northeastern Mexico. Slathered in insect repellent, their ankles wrapped in gaiters or duct tape to seal out swarms of tiny ticks, they were preparing to document the release of a seven-month-old female ocelot--one of just two of these secretive cats captured on a two-week research expedition to Los Ebanos, a large private ranch 150 miles south of Brownsville, Texas. Slowly, Mexican biologist Arturo Caso approached the cage and opened its door. But before a single team member could get a shot, the cat bolted out of the enclosure as if fired from a cannon and vanished into the thick tangle of prickly vegetation.
Though the ocelot, designated 31, had disappeared from the team's view, a tiny radio transmitter attached to her collar would allow Caso, a doctoral student at Texas A&M University–Kingsville, to track her every move over the following months. His work would reveal, among other things, the cat's activity patterns, the kind of vegetation she favors and the size of her home range.
What Caso learns about the ocelot, as well as 30 others he has tracked in Mexico, may help biologists bring back the species north of the border, where fewer than 100 cats survive at the southernmost tip of Texas. Even ocelot 31 herself--more specifically, her genes or those of her Mexican cousins--could determine the fate of Leopardus pardalis in the United States, suggests Caso, who has studied the elusive feline and two other border cats, the jaguar and jaguarundi, for the past six years.
Of the three cats--all federally listed as endangered--only the ocelot is confirmed to live in the United States today. Scientists believe that these sleek, spotted predators once ranged across the southern United States as far north as Arkansas and Arizona. But over the past 60 years, much of the cat's habitat has been destroyed to make way for farms, ranches and, more recently, subdivisions and shopping malls in the rapidly developing border region.
Even worse for the cats, Caso and other researchers have discovered that ocelots have very specific habitat requirements. "You can find them in many ecosystems, from tropical rain forest to dry deciduous forest," he says, "but they must have at least 75 percent woody cover." Thick vegetation provides ocelots abundant mice, rabbits and other food as well as camouflage, both from prey and predators such as coyotes and people. In Texas, less than 5 percent of the dense native brush that once sheltered the cats still stands.
As a result, scientists estimate that only between 80 and 100 ocelots remain in the United States today. More alarming, all of the cats are confined to one of two isolated populations, one in Laguna Atascosa National Wildlife Refuge and the other on private ranchland some 30 miles away.
"The problem with these kinds of populations is that they can go extinct very quickly," says University of Kentucky wildlife biologist Dave Maehr, coleader, along with Caso, of the federal government's ocelot recovery team. "All it could take would be a bad hurricane or disease outbreak to wipe them all out."
Today the automobile is the greatest cause of mortality; since 1994, nine ocelots have been killed on roads in Laguna Atascosa alone. Most victims are young cats searching for home ranges when they leave their parents' territories at about age one. Unfortunately, there is nowhere near enough space to accommodate them all. At Los Ebanos, which he considers "a natural situation," Caso has found that a pair of adult ocelots will occupy a home range of more then 2,000 acres; in Texas, most pairs have 80 acres or much less.
Small, isolated populations also are likely to suffer dangerous decreases in genetic diversity, a result of inbreeding that can lead to birth defects, greater susceptibility to disease and other problems. One study, called a population viability analysis, predicted that even without a hurricane or other disaster, ocelots in the United States "could be extinct in 50 years or even sooner if we do nothing to increase the genetic diversity of the animals," says Maehr.
In contrast to the ocelot's cuddly, house-catlike appearance, the jaguarundi hardly seems like a feline. With its long, low body, short legs and small head, the animal resembles a weasel or an otter--and was in fact dubbed the "weasel cat" by the first scientist to describe the species in 1803.
Jaguarundis range from Argentina to the U.S.-Mexican border, but whether they still exist on the northern side is doubtful. "I get reports every week from people who claim to have seen jaguarundis," says biologist Michael Tewes, a wild cat expert at Texas A&M University–Kingsville. But the last scientifically documented sighting, he adds, was two decades ago: a dead cat that had been hit by a car near Brownsville. Like the ocelot, the jaguarundi has been squeezed out by habitat destruction.
So, too, has the jaguar, the largest wild cat in the Americas. Biologists believe that in pre-Columbian times, this magnificent spotted cat may have thrived as far north as Oregon and Pennsylvania, and that at least until the early 1900s, populations existed in Texas, Arizona and New Mexico. Today, however, no jaguar populations are thought to remain in the United States.
The jaguar's distribution is also contracting south of the border. In addition to habitat loss, the major threat in Mexico has been run-ins with gun-toting cattle ranchers. "In many places, there is nothing left for the cats to eat but cattle," says Caso, who is researching possible solutions to the problem, including introductions of javelina or other native prey.
Over the past several years, remotely operated camera traps in southern Arizona have captured jaguars on film more than a dozen times. Although most biologists believe these cats are temporary visitors from Mexico, the photos have given conservationists hope that the species may still be on the prowl in some remote U.S. hideout--or could at least return or be reintroduced someday.
Nowhere to Run
Before considering reintroductions, of course, wildlife managers will have to identify and safeguard suitable habitat--a tall order given that a single male jaguar may occupy a home range of 6,000 acres. In the case of the ocelot, protecting additional habitat is critical to preventing the cat's extinction in the United States. But "the problem in Texas," says Tewes, "is that more than 95 percent of the land is privately owned, and there's not enough money on the planet to buy all the habitat that's needed."
One solution, Tewes and his colleagues say, would be to provide Texas landowners with tax breaks or other incentives persuading them to protect the cat's habitat. Even without such perks, a few large landholders already have made commitments. Just north of Laguna Atascosa, for example, Frank Yturria owns a large ranch housing a handful of ocelots. In the early 1980s, he granted the U.S. Fish and Wildlife Service (FWS) 600 acres of permanent conservation easements within the cats' habitat. Though he still owns the land, he has agreed to leave its native brush intact. Hoping Yturria can get other ranchers on board, FWS added him to its staff last November. A new ocelot recovery plan, the first in more than a decade, is also expected to encourage private conservation efforts when it is published later this year.
In the meantime, scientists say, emergency measures may be required to shore up dwindling U.S. ocelot populations. To increase genetic diversity of the cats, "we need to link existing population hubs in Texas with each other as well as with some in Mexico," says Maehr. But because no corridors of vegetation connect even the Texas cats, the only quick and sure way to create such genetic links would be to move ocelots from one place to another.
In Mexico, Caso is working on the first steps of such a bold experiment. After locating prime ocelot habitat not far from the border--habitat that currently lacks ocelots--he's testing at Los Ebanos satellite transmitters and other devices for remotely tracking introduced cats. If all goes well, he and his colleagues hope to begin a trial translocation project within a year. But even if a Mexico-U.S. gene exchange succeeds, warns Caso, "the same problem will happen again if there is no place for the cats' offspring to go."
Some hundred miles south of the border, ocelot 31 and her kind may provide inspiration. Bumping along rutted dirt tracks after releasing the cat, Caso noted that the dense thickets of ebony, coma and other native vegetation outside the truck's windows are thriving within a 4,000-acre cattle ranch--a place where relentlessly squawking brown jays and chachalacas are just 2 of more than 200 avian species that regularly attract birding groups to Los Ebanos.
"There's no reason that cattle and wildlife cannot coexist," explained Caso, who tracked ocelot 31 for three months before she lost her collar. By that time she was a year old, nearly ready to search for a home range of her own. "Around here, that's no problem," he said. "There's plenty of room for a cat to roam."
Senior Editor Laura Tangley visited Los Ebanos last spring with a group from the Dallas Zoo, which helps fund Arturo Caso's research.
Mexico's Mysterious Margays
Mexico's smallest wild cat, the margay may never have lived in established breeding populations in the United States. Today its range extends from northern Mexico south to Argentina and Uruguay. Working in Mexico's El Cielo Biosphere Reserve--considered the northernmost limit of the species' distribution--biologist Arturo Caso has launched the first comprehensive study of margays in the wild. So far he and his colleagues have captured and radio-collared five margays and are now tracking the cats.
While very little is known about margays in the wild, captive cats are famous for their agility. Margays have been observed climbing down trees headfirst, leaping 12 feet through the air, and hanging from branches by their hind feet.
The Secret Lives of Ocelots
While much about ocelots remains a mystery, biologists radio tracking the elusive cats over the past two decades have learned at least the basics of the species' natural history. Ocelots, for example, are opportunistic hunters, preying primarily on birds and small mammals such as rabbits and mice, but also chowing down on frogs, reptiles and insects if they come across them. Hunting mainly at night, the cats either sit still and wait for prey to pass by or move slowly through the dense underbrush searching for food. In either case, ocelots capture their prey by pouncing, much like a domestic cat pounces on a house mouse.
A female ocelot begins to breed when she is about three years old, giving birth to just one or two kittens every other year--a longer birth interval and smaller litter size than other cats the same size. At about the age of one, young ocelots typically leave their mothers to establish their own territories, as long as appropriate habitat is available. Although cats in captivity have survived into their twenties, scientists believe wild ocelots live for just five or six years.
Contributing to the species' sparse database, biologist Arturo Caso has been researching ocelots in Mexico since 2001--one of the most thorough studies of the species to date. For each cat captured (31 so far), Caso and his colleagues take blood samples and record baseline data such as weight, length, general condition, and the number and species of parasites while the animal is anesthetized. Next, they attach a radio collar, which allows the scientists to follow the cat over time. From radio tracking collared ocelots, Caso has learned, for example, the species' preferred habitat (dense vegetation with at least 75 percent cover), activity patterns (nocturnal), home range size (2,000 acres at his study site), and that the ocelot can coexist with the jaguarundi, another endangered border cat, due to subtle differences in hunting times and preferred habitat. Jaguarundis can survive, for instance, in more open habitats than can ocelots.--Laura Tangley