To Boost Gene Pool, Lions Artificially Inseminated
By Bijal P. Trivedi
National Geographic Today
|June 12, 2002|
It is a tough blow to a lion's pride when the jungle royalty must depend
on humans for its reproductive success. But in some parts of South
Africa, lions have lost much of their habitat and their roaming grounds
have been seriously constricted. The result: inbreeding, which
scientists believe cause genetic defects and infertility.
wildlife experts in some smaller reserves are experimenting with
artificial insemination and vasectomies to boost the lions' gene pool.
Artificial insemination has been used successfully with other big cats
in zoos but never before with lions, captive or free ranging.
Inbreeding has also plagued wild elephant, rhinoceros, buffalo, and antelope populations. One solution has been to simply move some individuals to another reserveinfusing the local populations with a blast of new genes. But this approach is not as easy for lions.
"You can't just dump a group of lions into a new area because the resident lions will chase them out or kill them," said Paul Bartels, a wildlife veterinarian and director of the Wildlife Biological Resource Center of the Endangered Wildlife Trust, outside of Johannesburg. "Lions have a very intricate social structure."
Before fences and highways lions roamed vast distances, sowing their seeds far and wide. But as their domain shrank, some parks could accommodate only a few prides, which then began to inbreed.
Need for New Blood
Lions live in prides, family groups made up of a number of females and one or only a few male leaders. Before their habitat shrank, young lions introduced new blood by challenging and replacing the dominant males every few years. But as parks accommodate fewer prides, older males remain unchallenged and mate with their offspring.
Hluhluwe-Umfolozi Park (HUP) in KwaZulu Natal, for example, has an unusually inbred population120 lions sprung from just three lions introduced to the park in the 1960s.
Genetic analysis of HUP lions revealed sperm abnormalities and increased disease susceptibility. The animals were also about 20 percent smaller than lions from other parks, says Rob Slotow, a professor at the University of Natal in Durban and leader of the Natal Lion Project, established in 1996 to unify conservation efforts.
Slotow favors introducing adult female lions and established prides to regions of parks where there are no resident lions. He is monitoring lions released in Hluhluwe-Umfolozi to test this approach.
Bartels said to move the genes without displacing the lions.
In a project begun a little over a year ago, Bartels sterilizes pride males that have sired around 20 cubs. The lion is darted and once asleep is given a vasectomy. During the operation sperm is collected for the tissue bank and will later be used to inseminate lions in another park. "Darting Safaris" are used to fund the work and have become quite popular, Bartels said.
But handling lions can be hair-raising, Bartels said. "I've had a male lion, who wasn't quite asleep, jump up and bite me." The lion chased Bartels to the gate of the enclosure and leapt toward him, jaws aimed at his head. Bartels blocked the attack with his arm, which became tightly locked in the lions jaw. Bartels ceased struggling, mimicking dead prey, and fooled the lion into relaxing his jaws. He escaped.
When the lion awakens, testes and libido intact, he has no idea that the key aspect of his masculinity has been removed, and he continues to behave as king of the pride. The scientists use the sterile lion as a "teaser" to determine which females are "in season" and ready to inseminate.
Slow Route to Success
Lions are exhaustive maters, mating every 12 to 15 minutes for up to five days.
The frequency of mating, researchers speculate, is meant to stimulate egg release in the female. Only after a "teaser" has stimulated the female can she be successfully inseminated with sperm from an unrelated male. "We are taking sperm from successful males and trying to emulate survival of the fittest," says Bartels.
So far, six lions from Pilanesberg National Park have received vasectomies. Of these, two lions became fertile again when their tubes rejoinedprompting a recent revision of the surgical technique. Four females were inseminated late last year but no pregnancies resulted. The new vasectomy procedure will be tested later this year.
David Wildt, who heads reproductive sciences at the Smithsonian Institution's National Zoological Park in Washington, D.C., isn't optimistic about immediate success.
"Bartels has an interesting concept, but this is not a trivial experiment," he said. "It took our lab 15 years of research into cheetah reproductive biology for us to develop a routine artificial insemination procedure for this cat."
Reproducing lions through artificial insemination, he added, will require much basic research because so little is know about lion ovulation.
Not everyone accepts the insemination approach.
Craig Packer, a veteran lion researcher at the University of Minnesota who has worked with Slotow, said: "The easiest way to introduce genetic diversity is to move animals about and let them do the rest. Artificial insemination is incredibly labor-intensive, expensive, and subjects the lions to a lot of handling."
Even if AI works there is only one litter, and there is no guarantee that the cubs will survive.
There is no doubt that for very small lion populations genetic management is required, said Packer, but it is probably easier to increase genetic diversity by strategically introducing adult females and whole prides into these areas and leaving the matchmaking up to them.
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