THE HYBRIDISATION ISSUE IN CONSERVATION

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Jun 13, 2006 5:32 AM

THE HYBRIDISATION DEBATE IN CONSERVATION

journalistandanimals

 

DISCOVER Vol. 22 No. 3 (March 2001)

Table of Contents

 

Wild Cats in Carolina

Is the Carnivore Preservation Trust creating a genetic future for threatened

species— or genetic junk?

By Barry Yeoman

Photographs by Harry Benson

 

 

 

Fleet-footed caracals are able to chase down gazelles and knock birds from

the air, but to African and Asian farmers, they are merely crop-destroying

pests.

Lori Widener opens the gate of the 12-foot-high fence that surrounds the

Carnivore Preservation Trust outside Pittsboro, North Carolina, and walks

toward the home of her favorite resident, Scooter. " Where's my boy? " she

coos, peering into an enormous walk-in cage that holds two binturongs— Asian

bear cats. Slowly, a whiskery black head with blond tipping pops out of a

wooden den, and Scooter's pupils contract as they adjust to the brightness.

When Widener slips inside the cage, Scooter nuzzles her to mark her with his

scent. Then he climbs her body and hangs from her neck by his muscular

prehensile tail. Four years ago, when they were 2 weeks old, Scooter and his

littermates were taken from their mother and given to Widener to hand raise

in her trailer just outside the 35-acre compound's fence. Four times a day,

she bottle-fed the animals a specially prepared formula of milk substitute,

vitamins, and bananas. Most of the cats stayed two months, but the anemic

Scooter required a blood transfusion from his mother and ended up

recuperating inside the mobile home for an additional four months. During

that time he developed a laid-back personality that made him very easy for

his keeper to handle. " He is not tame, " insists Widener, an energetic

38-year-old who wears her hair in three waist-length braids. " He is not

domesticated. He is merely socialized. "

 

Scooter certainly lives more comfortably than his wild cousins do in the

rain forests of southeast Asia. Binturongs, a threatened species of

tree-dwelling civet cats, are hunted for their meat. Males are also

slaughtered for their genitalia, which are used as an aphrodisiac. At the

same time, land development is shrinking their natural habitat. Yet

binturongs, which don't have the mass appeal of, say, elephants or tigers,

have not been the focus of massive conservation efforts. Most American zoos,

if they have any binturongs at all, have two or three. So the Carnivore

Preservation Trust stepped in and now has the largest captive population in

the world, as well as sizable populations of a handful of other threatened

species of small wildcats. At last count, the nonprofit organization had 50

binturongs, 50 caracals, 39 servals, and 33 ocelots. The goal is to maintain

large numbers of a few overlooked species, says the trust's executive

director, Margaret Tunstall. " Then, when somebody realistically tries to

protect these animals and their habitats, we will breed a generation of

animals that can be reintroduced into the wild. "

 

Laudable as that mission sounds, not every wildlife conservationist has

embraced it. That's because the Carnivore Preservation Trust has upended

scientific orthodoxy, defiantly dissenting from the principles and methods

used by most zoos to raise and breed animals in captivity. While mainstream

animal conservationists adhere to the doctrine of having mothers raise their

own litters, the trust follows a policy of raising young carnivores by human

hand. And while most scientists believe in keeping subspecies lines as pure

as possible, the trust intentionally disregards those lines, creating

" generic " animals not found in nature.

 

" You're not going to hear me say, 'Hey, these people don't have a clue,' "

says Dave Wildt, head of the department of reproductive services at the

National Zoo's Conservation and Research Center in Front Royal, Virginia.

" They know about science, and they are amazing about putting resources into

housing large numbers of animals. Their animals are healthy and in great

shape. " But by refusing to fully coordinate their breeding efforts with the

greater zoo community, he says, the trust is creating " genetic junk " — hybrid

animals whose descendants can never be reintroduced into the wild. He is

blunt: " These people are not contributing to conservation. "

 

The Carnivore Preservation Trust grew out of the personal passion of the

late Michael Bleyman, a gray-bearded geneticist who left his University of

North Carolina faculty job in 1975 to follow his real love: studying tigers,

jaguars, and other large felines whose survival was threatened in the wild.

His interests were only partly academic. " Mike was a scientist who had a

strong interest in wildcats, and he wanted to save those cats, " recalls

Wildt. " But he also liked the excitement of having a 500-pound Siberian

tiger in his backyard. "

 

 

 

 

A baby ocelot gets a careful checkup from veterinarian Anneke Moresco and

vet tech Laurie Chafey (left) and is bottle-fed by keeper Kathryn Bertok

(right).

From the time he got his first felines, Bleyman tried to learn everything he

could about taking care of them. He knew that some large cats had trouble

breeding in captivity, and he wondered if different husbandry practices,

including a more natural diet and more secluded environs, could improve the

animals' reproductive success. In his quest for information, he traveled the

world and began to grasp the broader connections between animals and their

habitats. " He saw that in order to do good, you have to have a full-out

effort to save the environment as well as the animals, " says his daughter,

Anne Bleyman. " There has to be land set aside that people would not develop.

At the same time, he thought if he could start breeding these species, and

do it in such a way that there would be an outbred, genetically sustainable

population in captivity, then down the line people might start setting aside

land. "

 

The trust formally began in 1981, on the farm where Bleyman was living.

Lacking money, he rallied an enthusiastic platoon of volunteers, drawn by

the organization's mission and Bleyman's own charisma. By all accounts, even

the cats responded to his powerful personality. " All the tigers thought he

was God, " says Widener, the trust's development director. She remembers

being in a cage with Bleyman, who was only about 5 feet 7 inches tall, and

looking on with awe as he tried to separate two angry cats. " This tiger had

its ears back, snarling, growling, " she recalls. " And Michael was standing

there, three feet away, his hands on his hips, yelling back, 'You want a

piece of me? Come on!' "

 

Over time, Bleyman decided he was breeding the wrong animals. He couldn't

possibly keep enough tigers, leopards, and jaguars on his parcel of land to

make a difference in the species' survival. Instead, he switched his focus

to animals he could house in large numbers. The trust never got rid of its

big felines, but it stopped breeding them and concentrated instead on

smaller carnivores. In addition to binturongs, Bleyman selected caracals,

lightning-fast hunters from Asia and Africa with long, tufted black ears and

powerful jaw muscles. Capable of taking down large animals such as gazelles—

and of jumping into the air to knock down birds with their front paws—

caracals are considered pests by farmers. Ocelots were another choice.

Coveted for their lush pelts, they were hunted nearly to extinction during

the 1960s and 1970s and remain rare throughout the Americas. Bleyman

completed the small-cat menagerie with long-necked servals. Natives of

Africa, servals are also hunted for their fur, which can be passed off as

cheetah or leopard, and their habitat is shrinking from human encroachment.

Bleyman described his efforts as " an insurance policy. " The mission of the

Carnivore Preservation Trust, he said, " is to provide a living time capsule,

holding these animals in trust for the world until the world is able to

protect them. "

 

Even as he amassed disciples, however, Bleyman clashed with animal

conservationists. " He fell out with people with whom he should have used

words of honey rather than vinegar, " says Trudy Raumann, a retired physicist

who has volunteered at the trust for the past 10 years. " Like so many

geniuses, he wasn't so easy to be with all the time. "

 

But it was his scientific principles that really irked the conservation

community. Bleyman believed that too much value is placed on keeping

subspecies breeding pure. " Generic animals are virtually useless for

reintroduction purposes, " says Michael Hutchins, director of conservation

and science for the American Zoo and Aquarium Association. The reason? " We

don't know whether subspecies are important ecotypes— how closely adaptive

they are to a certain environment. If you don't know, it's better to

maintain the differences. "

 

Bleyman maintained that endangered subspecies' genetic pools were often too

small to propagate healthy offspring indefinitely. In his view, the only

hope of survival for tigers and some other wildcats was to breed across

subspecies lines— to purposefully create specimens that would be more

genetically diverse than their parents. " He was very unpopular with the zoo

community for this, " says Widener. " They called them 'mutt tigers'— American

generic tigers. " When animal-conservation organizations established breeding

protocols for certain animals, Bleyman ignored them.

 

 

 

The ocelot nibbling on Allison Larios's fingers , like the other 30 at the

trust, has no fear of humans. Hunted for its lush pelt, the cat has all but

vanished from the Americas.

So how important is it to keep a subspecies pure? And what defines a

subspecies, anyway? Nineteenth-century mammalogists " named populations with

little more criteria than a hide or skeleton from a particular geographic

locale, " says Stephen O'Brien, who heads the genomic diversity laboratory at

the National Cancer Institute. Nowadays, however, researchers are

distinguishing animal groups by their DNA. Some subspecies, it turns out,

are distinctly different from one another, while others are almost

identical. " They're closer, in many cases, than human ethnic groups, and

nobody argues that we should keep the ethnic groups separate, at least not

anymore, " says O'Brien.

 

One example of how dicey divisioning has been is the traditional sectioning

of leopards into 27 subspecies. Scientists studying the DNA of 14 of these

groups have found justification for only eight of the partitions. In

particular, the African subspecies of leopards are almost indistinguishable.

" There's no obvious line at which you say these are different subspecies, "

says Jonathan Ballou, population manager at the National Zoo. " So far,

though, there isn't a consensus. "

 

Indeed, wildlife conservationists tend to fall into two camps: lumpers, who

aggregate similar animals, and splitters, who keep them more strictly

separate. Splitters, who dominate the mainstream conservation community,

have decided on occasion to lump. The most famous case of the last decade

involves the Florida panther, a type of cougar whose population dwindled to

a few dozen because of hunting and habitat invasion. With such small

numbers, the cats were dangerously inbred— more prone to infectious disease,

low sperm production, and life-threatening heart defects. After considerable

debate, scientists agreed to introduce Texas cougars into the Florida cats'

habitat. Preliminary field reports indicate the project has been a success.

About a fifth of the 36 kittens born since the program's 1995 start are the

offspring of Florida-Texas pairings. " Is it admirable to mix them naturally?

Sometimes, " says geneticist O'Brien, who collaborated on the project. " That

Florida population was doomed otherwise. "

 

More often, scientists prefer to err in the other direction. " We take a

conservative approach: When in doubt, don't breed them, " says Jill Mellen, a

research biologist at Disney's Animal Kingdom in Orlando, Florida. For

instance, the American Zoo and Aquarium Association has asked members not to

crossbreed ocelot subspecies. Instead, the association is focusing on

propagating a particular Brazilian ocelot. There will be a scant 18 in

captivity in North America— if several can be imported from their native

continent. At the trust, things will go predictably in the opposite

direction: Members are convinced the zoo community will not get enough

specimens for successful outbreeding and therefore plan to continue breeding

their own generic ocelots.

 

" In an ideal world with large and healthy captive populations of all extant

subspecies and an infinite number of zoos and wild animal parks in which to

breed these subspecies, it might be prudent practice to maintain these

populations as genetic breeding isolates, " Bleyman wrote. But, he added, the

animal conservation community needs to " face reality " and aim to preserve

species rather than subspecies. " If we look, for example, at the registry of

all ocelots in captive breeding, we see a rather pathetic scattering of

subspecies spread out throughout the world's breeding institutions. Many

subspecies are represented by only one or two individuals in captivity in

the whole world. The entire weight of practical experience suggests that

these fragments of breeding populations cannot be maintained with any

success at all. "

 

 

 

The arboreal binturong helps other species survive in Asia's rain forests by

eating the fruit of the strangler fig. The vine wraps around trees, cutting

off nourishment and killing them; frogs, geckos, and other animals move

inside the hollows. But the fig's seed has a hard outer coat; it takes the

binturong's digestive fluids to dissolve the shell and allow the fig to

germinate.

Who's right? Based on the available science, there's no clear answer. The

National Zoo's Ballou, who is not involved in the ocelot project, says 18

founding animals might be sufficient to maintain 90 percent of the gene pool

for 100 years, but only if the descendant population can eventually grow to

400 or more. " We usually think of 25 or 30 [founding] animals as necessary, "

he adds. With fewer, " it wouldn't take much time to run into all sorts of

problems. In that case, some people might argue to combine them. "

 

Michael Bleyman always expected to die young, and his loved ones didn't

doubt him. " I always assumed he'd be off in some other country, tick

somebody off, and get killed there, " says his daughter, Anne. Still, it came

as a surprise when he was diagnosed in 1996 with kidney cancer, which killed

him within three months. He was 58.

 

For a couple of years after Bleyman's death, the organization foundered. The

Carnivore Preservation Trust was so much Bleyman's personal project that he

had never laid the groundwork for anyone to succeed him. At one point, the

compound was down to one keeper, who was stretched to the limit trying to

care for more than 200 animals. But during the past two years, the trust has

been professionalized, hiring its first staff veterinarians, boosting the

number of keepers, and working to strengthen its ties with other

conservationists. It even participates in American Zoo and Aquarium

Association meetings. One result: Following the recommendation of a zoo

official, the trust is paring its populations, keeping only the most diverse

breeding stock.

 

At the same time, the trust has sharpened its research mission, inviting

scientists to come to North Carolina to work with its large samples of

understudied animals. " If you think that research on how things vary among

carnivores is important, then the trust provides a real resource, " says Bill

Peake, a professor of electrical and bioengineering at the Massachusetts

Institute of Technology. Peake has traveled to Pittsboro to examine the ears

of the trust's large and small cats as part of a study of feline acoustic

sensitivity. His findings indicate that the middle ears of large tigers and

jaguars are structured to respond better to the low frequency sounds emitted

by the large prey they favor, like buffalo. In contrast, the middle ears of

smaller caracals, servals, and ocelots are more sensitive to the high

frequencies of mice and the other small animals they hunt.

 

 

 

The African serval also is killed for its fur, which resembles leopard and

cheetah. The trust shelters 40 servals.

Still, even with its forays into the mainstream community, the Carnivore

Preservation Trust hasn't lost its reputation as a renegade operation. Five

years after Bleyman's death, the organization clings closely to his

heretical principles— and not just in its generic breeding program. Bleyman

believed strongly in hand rearing young animals. Every animal born at the

compound is separated from its mother after two or three weeks of receiving

the protein- and antibody-rich colostrum, or first mother's milk. Then each

animal is raised by the trust's keepers in their homes and in the

farmhouse's nursery. Eureka and J. Edgar, two 4-week-old servals, received

typical treatment. They slept in a blanket-lined playpen next to an electric

heating pad set on low to mimic the heat their mother would generate, sucked

low-lactose infant formula from handheld bottles, and were burped.

 

Caretakers at the trust say such care not only makes animals more

manageable, it reduces their stress around humans, making them more

reproductive. The trust doesn't have statistics to measure that success, but

it evidently has no problem getting animals to mate. Recently, the compound

crawled with 22 babies, all simultaneously hand reared. " Here, breeding is

very natural, " says Allison Larios, who until last month served as the

trust's head curator. " In fact, we can't get them to quit. " She agrees that

hand-raised animals aren't candidates for reintroduction into the wild, but

she maintains that the trust is no more than three generations away from

producing animals that can fend for themselves.

 

Zoos vehemently oppose hand rearing, trying instead to keep young mammals

with their mothers for as long as possible. " It's well documented that hand

raising has long-term behavioral effects, " says Hutchins of the American Zoo

and Aquarium Association. " Animals become socially attached to human

caretakers, and later on in life can develop a sociosexual attachment to the

species that hand raised them. In a popular sense, you can say they are

confused about their species identity. This can have a long-term effect on

breeding. " The most oft-cited study, conducted by biologist Mellen,

indicated that maternally reared domestic cats were more likely to breed

than cats separated from their littermates and raised by humans. Cats hand

reared with their siblings— like the animals at the trust— fell somewhere in

the middle. But Mellen notes that her findings are not conclusive: The

results for the hand-reared sibling group were not statistically significant

compared to the other two groups.

 

Even so, as long as the trust continues separating babies from their

mothers, it will not be a welcome player in mainstream efforts to conserve

the species it wants to save. That is a consequence the trust is willing to

accept. " If mortality rates are going to increase when babies are left with

their mothers, I'd just as soon hand raise them, " Larios says.

 

The Carnivore Preservation Trust is willing to ruffle still more feathers by

following Bleyman's breeding agenda. The American Zoo and Aquarium

Association wants to reduce the world's captive caracal population from 250

to 75, noting that their numbers remain healthy in the wild. " Caracals are

not an endangered species, " says Alan Shoemaker, collection manager at the

Riverbanks Zoological Park in Columbia, South Carolina. " They have huge

ranges. They are never going to become extinct in your lifetime or mine. "

 

Nonetheless, the trust, which owns about a fifth of all captive caracals,

says it has no plans to stop breeding them. Larios points to an earlier

lesson. " When we started working with ocelots and binturongs, they weren't

endangered either, " she says. " If we don't take strides to preserve the

caracals here, then what will happen when those numbers drop off in the

wild? It's only a matter of time. "