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Science

Widening the gene pool with wild frozen sperm

Researchers have successfully impregnated an elephant with frozen sperm from a wild male for the first time. They want to broaden the genetic pool of animals in captivity.

This is just the start of a 22 month process - but it is success all the same.

Tonga, a 26-year old African bush elephant who lives at Vienna's Tiergarten Schönbrunn, is the first captive elephant to be inseminated with frozen sperm from a wild elephant bull.

Steve, the lucky man, lives on a game reserve in South Africa. Tonga is nine months pregnant and will have to go through a further 13 months before she gives birth.

Previous attempts to inseminate elephants with frozen sperm have been unsuccessful. The elephants became pregnant but failed to deliver.

So the success at this point is the mix of the captive and the wild.

"This is the first time that sperm of a wild elephant has been used for insemination of a zoo elephant," says Thomas Hildebrandt of the Leibniz Institute for Zoo and Wildlife Research in Berlin. His team worked on the project.

Ultrasonic scan of elephant fetus at Vienna Zoo

This ultrascan shows the elephant fetus at about four months of age

"For the first time, we've shown that it's possible to combine populations of wild and captive elephants this way," says Hildebrandt.

In the last 15 years, 40 elephant calves have been fathered in Europe using artificial insemination. But until recently, researchers had only used fresh sperm from other zoo elephants.

Male to female imbalance

At European zoos, male elephants are in short supply.

For every five female elephants there is an average of just one male - or bull. And not all of them are able to produce offspring. This means the genetic pool of zoo elephants is narrow. The researchers want to widen the gene pool by bringing in genetic material from wild elephant bulls. They also hope it will make the zoo animals healthier and stronger.

Hildebrandt says Steve and other bulls were being transferred from the Phinda Private Game Reserve near Durban to another park near Capetown when the sperm was extracted.

"So they were narcotized anyway," says Hildebrandt. "We stimulated a nerve plexus near the prostate with electricity and the bull ejaculated."

The researchers decided to give Steve's sperm to Tonga.

"He had the best sperm and he is also particularly beautiful," says Hildebrandt.

Elephant bull Steve, who provided the sperm for Tonga at Vienna Zoo

The sperm came from this wild living South African elephant bull

His team from Leibniz worked on the project with the scientists from the zoo in Vienna, veterinary doctors from Zooparc de Beauval in France, South Africa's National Zoo in Pretoria and Pittsburgh Zoo in the US.

Easy sperm

It is easier to use frozen sperm for artificial insemination than fresh sperm.

"Frozen sperm can be stored and used when the time is right," says Harald Schwammer, vice director of Tiergarten Schönbrunn.

Researchers and conservationists have successfully inseminated other mammals like rhinos with frozen sperm. With elephants, however, Hildebrandt says the process can be problematic.

"The membrane of the elephant sperm is very sensitive to cold - much more than that of human beings," says Hildebrandt.

To make the elephant insemination possible, Hildebrandt's team developed a gentle freezing method.

"We freeze the sperm gradually rather than abruptly," Hildebrandt explains. "But it has taken years to find out at which stages it works the best. And also which solution the sperm has to be placed in."

If Tonga's baby is born it will be the first time an elephant is fathered using frozen sperm.

"Only two elephant pregnancies have ever been achieved with frozen sperm and both ended at an early stage when the fetus died," says Hildebrandt.

But he says the failed pregnancies had nothing to do with the frozen sperm. Instead, they were as a result of the mother's poor condition.

The international team behind the project - Frank Göritz (IZW), Robert Hermes (IZW), Thomas Hildebrandt (IZW), Romain Potier (Associated Beauval Conservation and Research), Harald Schwammer (Tiergarten Schönbrunn)

The international team behind the project wants to try its method on other animals in capitivty

"With Tonga, everything is perfect," says Hildebrandt, "she is healthy and has no social stress in her group. We are very optimistic."

Healthy elephant fetus

The team took daily blood readings from Tonga to determine the right time for her insemination. When it was time, they inseminated her four times on two consecutive days.

An ultrascan in the fourth month of the pregnancy showed an elephant fetus that was more than ten centimeters.

"Trunk, head and legs can be recognized clearly," the zoo announced at the time.

It will now be about twice as large. On Tuesday, Tonga had her second ultrascan.

"It looks super," says the zoo's Harald Schwammer.

If everything goes well, the researchers plan to adopt their method for use with other kinds of animals, who would also receive sperm from wild males.

"We need a healthy captive population in case wild populations break down - because of things like poaching," Schwammer says.

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