Forget woolly mammoths. The business of copying cats is quietly making headway. First, scientists reprogrammed eggs from everyday house cats to contain instructions for building wild ones. Then they started churning out small endangered cats. Next up: Lions and Canadian lynx.
By Emily Anthes
On the surface, the idea is simple: Animal numbers dwindling? Let’s just use science to make copies of the ones that remain. But it will not be nearly as easy as it sounds. That much has been apparent since the birth of the very first endangered-species clone: a little gaur named Noah, an exact copy of a rare wild ox native to India and Southeast Asia. His birth in January 2001 was a headline-grabbing feat, proving that it was at least technically possible to mimeograph endangered animals. It was also a bittersweet accomplishment. Thirty-six hours after he was born, Noah began showing signs of a gastrointestinal infection. Twelve hours later, he was dead. The researchers at Advanced Cell Technology, the Massachusetts company that brought Noah into being, said cloning had nothing to do with the calf’s tragic fate, but it’s impossible to say for sure, given the health problems that have been documented in other clones. Noah’s death suggested that wildlife replication would not be immune to the challenges and complications that have plagued those cloning pets and livestock. But if we can get it right, cloning has the potential to be a useful, if limited, tool in conservation. When it comes to endangered species, Stewart Brand’s words from his 1968 Whole Earth Catalog still resonate: “We are as gods and might as well get good at it.”
With that in mind, I decide to take a trip to New Orleans, where a small number of researchers have positioned themselves at the forefront of endangered-species cloning. Their remarkable facility is hidden inside 1,200 acres of hardwood forest along the banks of the Mississippi River. At first glance, these woods look like any other slice of nature. But peek inside these thickets and you’ll find some surprising secrets: Some of the world’s most exotic animals—creatures that usually make their homes on the African savanna or in the mountains of Central Asia—are here, living quietly in this small patch of wilderness. Amble among these trees and you could find yourself face to face with a flock of preening snow-white ibises or a small spotted wildcat, pacing back and forth.
These are the grounds of the Freeport-McMoRan Audubon Species Survival Center. The entire compound sits at the end of a country lane, behind a locked gate. A guard checks my credentials, then allows me in. I drive slowly along a narrow gravel road that winds into the forest. Branches swoop over me, creating a lush canopy, and it’s impossible to see more than a foot or so past the trees that line the road. I half-expect a leopard to leap out in front of my car at any moment.
Suddenly, the forest opens up into a clearing, where a brick sign welcomes me to the sprawling Audubon Center for Research of Endangered Species (ACRES), the Survival Center’s 36,000-square-foot complex of genetic and veterinary laboratories. Each of the rooms inside is devoted to one small task in the much larger effort to save wild animals. Signs posted on the doors along one corridor announce, in succession: Gamete/Embryo Laboratory, Molecular Genetics Laboratory, Radio Isotope Laboratory, Cryobiology Room. For a state-of-the-art research facility, it feels awfully homey, with its dark wood paneling and bucolic views. I have just settled down into a plush armchair when Betsy Dresser, the reproductive physiologist who directs ACRES, emerges from her office. Wearing a gray blazer the same color as her closely cropped hair, she offers a warm handshake and a smile.
After earning a PhD in animal reproductive physiology, Dresser established the Center for Conservation and Research of Endangered Wildlife (CREW) at the Cincinnati Zoo in 1981. At CREW, Dresser and her colleagues made a number of breakthroughs, including producing a Persian leopard cub through artificial insemination and creating the world’s first test-tube gorilla. Impressed by the research at CREW, the Audubon Nature Institute, which ran a zoo in New Orleans, asked for Dresser’s help in creating a similar program. In 1996, Dresser became director of the brand-new Audubon Center for Research of Endangered Species, where she remained at the helm for 15 years. Now she continues to consult with its scientific team.
At first, the ACRES crew relied on the same techniques Dresser had honed in Cincinnati—embryo transfer, in vitro fertilization, and the like—and the walls of the research facility are hung with photos of tiny kittens and newborn whooping cranes that the scientists brought into being. Dresser acts every bit the proud parent, showing off each creature. “Here’s a caracal,” she says, pointing to an image of two kittens she created using in vitro fertilization. The otherwise sand-colored cats have tufts of black fur jutting straight out of the tips of their pointy ears. “Some people,” Dresser says, “call them Spock cats.”
Dresser goes down the line of photos, identifying each kitten: serval, fishing cat, Arabian sand cat, and more. Nearly all of these felines are under threat, a result of poaching and habitat destruction.
ACRES has made a name for itself for its work with these small exotic cats, and as the technology evolved, so did the scientists’ strategy. Though in vitro fertilization had allowed biologists to help exotic animals breed in new ways, the technique had limitations. Creating test-tube caracals, for instance, required harvesting sperm and eggs from wild cats, fertilizing the eggs in the lab, and then implanting them in surrogate mothers. Collecting and storing specialized reproductive cells is technically difficult—and potentially dangerous for the animals, since the females must be anesthetized and cut open in order for surgeons to recover their eggs.
Cloning has several distinct advantages. Scientists can get all the DNA they need for cloning from an animal’s skin cells; stealing a quick swipe of skin from a rare cat is a much easier proposition than surgically harvesting ova. Cloning also provides a way to propagate the genes of animals without viable sperm or eggs: old animals, infertile animals, even dead animals. To Dresser, the technique has an obvious role to play in rescuing endangered species. As she imagines it, scientists could collect skin samples from rare animals and then churn out new copies of them in the lab. Field biologists could take these creatures and release them into their native habitats, where the clones would mingle with their wild brethren—both socially and sexually—and the population would slowly rise again.
For her first cloning project, Dresser chose the African wildcat (Felis silvestris lybica), a tawny-colored feline with black rings circling its legs and tail. Native to northern and western Africa, the animals are thought to be the ancestors of domestic cats. Dresser decided to duplicate a three-year-old African wildcat named Jazz who already resided at ACRES, and technicians began by taking a tiny sample of the cat’s skin cells. To do the cloning, the researchers planned to employ a technique known as nuclear transfer—the same process that researchers had used to create Dolly the sheep and others—but with a twist.
Usually, scientists put the DNA of the animal being duplicated into an egg harvested from a female of the same species. Nuclear transfer presents extra hurdles for wildlife biologists, who may not be able to get their hands on enough females of an exotic species to provide eggs or act as surrogate mothers. And even if they rounded up a pack of wildcats, they’d be loath to put threatened animals through any unnecessary medical procedures. So when scientists clone endangered animals, they usually use a common, closely related species to serve as egg donors and surrogate mothers. This is known as interspecies nuclear transfer.
To clone Jazz, Dresser and her colleagues used everyday housecats. They collected ova from plain ol’ tabbies, removed the nuclei, and then used the standard nuclear transfer procedure to put Jazz’s genes inside. The eggs from the domestic cats now contained instructions for building a wild one. To maximize their chances of success, the researchers implanted the cloned embryos in 50 different lady housecats, and 12 ended up pregnant. The ACRES team carefully monitored the pregnancies, using regular sonograms to check on the developing kittens. Alas, cloning’s inefficiency reared its ugly head, and it was a long and sometimes heartbreaking slog. The first three cats miscarried. One went into premature labor; the kitten did not survive. Several kittens were stillborn. A few more survived their birth but died within 36 hours.
The string of losses was eerily similar to what other cloners had faced, and the incomplete genetic reprogramming associated with nuclear transfer likely contributed to these poor outcomes. But the ACRES team kept at it, and on August 6, 2003, they extracted a tiny wildcat kitten—weighing less than a stick of butter—from the womb of a housecat named Brooke. The vet cleared the male kitten’s nose and mouth and watched him take his first breaths. As soon as Brooke was sewn up, the staff placed the kitten beside her, and the newborn started to nurse. The researchers watched and waited, hoping that when the anesthesia wore off and Brooke came to, she’d bond with the fuzzy ball of foreign DNA pressed up against her.
The odd couple thrived. Brooke took to her maternal duties like a champ, and the little clone continued to suck down her milk. After several uneventful days, Dresser and her colleagues let out a sigh of relief; it looked like the youngster would make it. In a nod to their New Orleans home, they named the kitten Ditteaux (pronounced, in the French fashion, as “Ditto”), and DNA analysis confirmed that he was, indeed, an exact genetic replica of Jazz.
Ditteaux soon had company. That November, Miles and Otis, two more clones of Jazz, were born—as was Caty, a copy of a female African wildcat named Nancy. Spring brought four more Nancy duplicates: Madge, Emily, Evangeline, and Tilly. All the clones were raised by their surrogate mothers, and when they reached sexual maturity, they became swingers, mating in various combinations: Ditteaux and Madge, Ditteaux and Nancy, clone with clone. Their kittens were normal and healthy, and many were eventually sent to live at various zoos.
After these successes, the ACRES researchers moved on to other small exotic cats, cloning the caracal and the Arabian sand cat, the same species that Dresser so proudly showed off when we first met. Next up: lions and the Canadian lynx. They’ve created the embryos already, though no cloned lions or lynx have been born yet. Meanwhile, other labs and researchers have been busy making their own breakthroughs. A European team made a mouflon, a rare breed of wild sheep, using DNA extracted from a female found dead in a pasture, and Korean researchers cloned an endangered cattle species as well as the gray wolf. In 2012, scientists in India ushered Noori, a clone of the rare pashmina goat, into the world.
But that doesn’t mean we’re ready to stock the wild with clones. For every well-earned accomplishment, there are disappointing setbacks; nuclear transfer still produces failures and casualties, whether scientists are duplicating pets, livestock, or wildlife. If we want to use clones to prop up a population, we’ll need to figure out how to produce healthy animals with less collateral damage and learn more about the long-term health of clones. (Ditteaux is still alive and well at age ten, and as scientists rack up more successes, and more clones come of age, we’ll have the chance to close this knowledge gap.)
If and when we are ready to use clones for large-scale repopulation projects, what would such an endeavor look like? How would we go from a cloned kitten living in a lab to a sustainable wildcat population? In Dresser’s mind, the first task would be simply to create a lot of wildcats. Biologists would collect skin samples from as many of the felines as possible and send them off to a facility like ACRES. The laboratory scientists would turn the skin cells into cloned embryos, and a few months of gestation would turn the embryos into wide-eyed wildcat kittens.
But researchers couldn’t just let the clones loose; repopulation projects are major undertakings. Many endangered-species reintroductions fail—reviews have turned up success rates that range from 11 to 53 percent. Reintroduction projects require long-term scientific, economic, and political commitments. Captive-born wildcats would need to learn survival skills, such as how to hunt on their own, and biologists would need to work with African governments and agencies to secure a safe slice of land for the felines. That wouldn’t be an easy task, given the habitat destruction and other forms of human interference that have gotten small exotic cats into trouble in the first place, and the clones might need to start their wild lives on a sanctuary or preserve. After the cats were released, scientists would need to spend years monitoring the animals, analyzing mortalities and documenting how the lab-born cats were adjusting to their new lives. If all went well, the cloned felines would eventually integrate themselves into the wild population and begin to breed.
In addition, animal reintroductions can have ripple effects that help restore the environment itself. Every species is part of a complex ecosystem, and if an animal population suddenly disappears—or its numbers drop precipitously—it can throw the entire system out of whack. For example, some plants rely on animals to disperse their seeds; if these animals die out, the plants are vulnerable, too. When large herbivores disappear, dry shrubs and grasses accumulate, increasing the chance of wildfires. When predators disappear, herds of grazing animals swell, stripping the landscape of vegetation. Some scientists have proposed that by reintroducing animals to their native habitats, we can remodel landscapes and restore healthy ecosystems.
In the long run, boosting population size is just part of the task for scientists such as Dresser, since many endangered species are also handicapped by a lack of genetic diversity. Reduced diversity creates all sorts of problems. It means a rare and devastating mutation might proliferate. Small genes pools also invite other disasters; if an infectious disease comes roaring along, and every animal’s equally susceptible to it, it could wipe out a species in one fell swoop.
This is essentially what happens to a species whose numbers have dropped precipitously, such as the cheetah. Evidence suggests that some unknown catastrophe wiped out most of the planet’s cheetahs about 10,000 years ago, leaving just a small number of the cats to pass their genes along. The cheetahs alive today are a remarkably homogeneous bunch, with very little genetic variation. Their low levels of fertility and high rates of sperm abnormalities may be a result of generations of inbreeding.
Cloning, which just makes twins of the creatures that are already out there, won’t solve the genetic-diversity problem for cheetahs or any other species, but we could use the technology to prevent a gene pool from shrinking further. For instance, if scientists learn to clone the cheetah—something they have not yet attempted—they could create carbon copies of the animals that don’t reproduce. If one of the wild felines dies in infancy, and scientists can get their hands on a skin sample, they could clone the youngster, giving it another chance to pass along its genes. They could do the same with cheetahs that reach old age without ever having little ones. In a small population, every genome counts.
By stockpiling DNA from exotic animals, we can also prevent other species from developing such crippling diversity problems in the first place. At ACRES, these DNA samples are kept behind the door labeled “Cryobiology Room,” and Dresser takes me inside. The room is cold, dark, and unimpressive. There is no obvious high-tech lab equipment, just a cluster of metal tanks, the approximate size and shape of kegs, lined up along the wall. But appearances can be deceiving. “That is years of science in there,” Dresser says, gesturing at the tanks.
This is the Frozen Zoo, where an entire wild kingdom is packed into a few square feet. Dresser opens one of the tanks, which are kept at a frigid −373 degrees Fahrenheit, and nitrogen vapor comes swirling out. Suspended in the fog is a metal rack packed with tiny yellow straws. Each straw contains a cell sample from a different animal. They hold skin cells, sperm, eggs, and whole embryos from thousands of different individuals including gorillas, elephants, rhinos, monkeys, buffalo, frogs, storks, cranes, lions, tigers, and bears. If Dresser is a modern-day Noah, these tanks are her ark.
Frozen zoos provide us with the opportunity to preserve the genetic diversity of a species before catastrophe strikes. If they had existed when the cheetah population was at its most robust, scientists could have packed the tanks with hundreds or thousands of cheetah skin samples. If we had these cells available today, we could look through them for genetic variants that have disappeared from the wild. We could clone these animals back into existence and set them free on the African savanna, restoring genetic lineages that had died out.
Frozen zoos are popping up all over the planet. The San Diego Zoo has a well known one, and 18 institutions in eight countries are participating in the Frozen Ark Project, run out of Britain’s University of Nottingham. Together, these institutions have collected and preserved 48,000 DNA samples from more than 5,500 species; the collective goal is to hit 10,000 species by 2015. If we store these samples properly, we’ll be able to use them to pull off remarkable scientific feats, including resurrecting species that die out in the wild.
The closest that scientists have gotten to species resurrection is the cloning of the Pyrenean ibex, a Spanish mountain goat. By 1999, there was only one Pyrenean ibex left in the world. Her name was Celia, and the rest of her kind had been hunted to extinction. One day in January 2000, Celia found herself under the wrong tree in Spain’s Ordesa National Park. The tree toppled, crushing Celia and officially snuffing out the Pyrenean ibex for good—or so it seemed.
The year before Celia’s death, some forward-thinking researchers had swiped a sample of her skin and stored the cells in liquid nitrogen. Then, after the elderly goat was gone, the scientists thawed out her cells and used nuclear transfer to get the ibex DNA into a whole clutch of domestic goat eggs. For their surrogate mothers, the researchers used hybrids—female crosses between the domestic goat and the Spanish ibex, a subspecies closely related to the Pyrenean variety. After the five-and-a-half-month gestation period, one hybrid was still pregnant. Researchers opened her up and delivered Celia’s clone. The newborn kid opened her eyes and moved her legs, but she struggled mightily for air and died just a few minutes after her birth. A necropsy revealed lung abnormalities, a defect that’s been observed in other young clones. It was the briefest of resurrections, but the return of the Pyrenean ibex gave scientists hope that cloning could indeed bring back other extinct species.
To many biologists, cloning is all sizzle and no substance, a high-tech spectacle that fails to address habitat loss, poaching, pollution, and the other human activities that put wildlife at risk in the first place. David Ehrenfeld, a biologist at Rutgers, raised this concern in an article in Conservation Biology. (1) Cloning, he wrote, “is a glamorous technology, and there is the danger of creating the false impression in the mind of a technology-infatuated public that it offers an easy, high-tech solution to the problem of extinction. Not only can this divert resources from conservation methods that have a much better chance of success, but repeated cloning failures may disillusion the lay supporters of conservation.” Cloning, he concluded, “should never be a conservation strategy of first resort.”
But the time for first resorts has come and gone, and safeguarding species is an all-hands-on-deck enterprise. Indeed, for cloning to have a real shot, laboratory scientists must work with conservationists; researchers can make all the fauna facsimiles they want, but the lab babies will need somewhere to live. The prospect of unleashing a thousand clones in the planet’s forests and prairies may be pure fantasy, but it’s not so far-fetched to imagine using cloning to accomplish more modest goals, such as duplicating select animals from select populations to keep certain genetic lineages alive. If we use our scientific superpowers wisely, we can make life better for all living beings. It’s time to embrace our role as the dominant force in shaping the planet’s future, time to discover what it truly means to be stewards. Then we can all evolve together. ❧
Emily Anthes specializes in telling the stories of science. Her work has appeared in Wired, Scientific American Mind, Slate, Psychology Today, The Boston Globe, and elsewhere.
1. Ehrenfeld, D. 2006. Conservation Biology doi:10.1111/j.1523-1739.2006.00399.x.
Excerpted from Frankenstein’s Cat: Cuddling Up to Biotech’s Brave New Beasts by Emily Anthes, published in March 2013 by Scientific American/Farrar, Straus and Giroux, LLC. Copyright ©2013 by Emily Anthes. All rights reserved.