MANAGERS of zoos across North America are facing a mammoth problem: the gene pool among captive African elephants has grown woefully small. A single bull named Jackson (pictured above) has sired many of the calves born in the United States in the past decade, and scientists say new bloodlines are needed to avoid future inbreeding among his many progeny.

So the Pittsburgh Zoo, which keeps Jackson at a conservation centre a little way outside the city, has joined an international effort to establish North America's first elephant sperm bank. The plan is to distribute from it semen collected from wild elephants in South Africa and frozen. Project Frozen Dumbo, started two years ago and led by a German researcher, has already set up an elephant sperm bank in France in the hope of resolving a similar predicament in Europe.

But the elephant semen painstakingly gathered for America has been sitting in Pretoria for well over a year because of bureaucratic red tape. South African officials have been slow to grant a permit to export the semen to America simply because they have never done it before, according to Barbara Baker, the president of the Pittsburgh Zoo. Meanwhile, the zoo continues to receive requests to breed Jackson or to collect his semen for artificial insemination, a technique first used successfully at the Indianapolis Zoo in 1998. One benefit of artificial insemination is that it does not require elephants to be transported from zoo to zoo, which is expensive and can be traumatic for the animals.

Project Frozen Dumbo seeks to create a genetic link between wild and captive elephants without taking more animals out of the wild, says Thomas Hildebrandt, the project's leader and head of reproduction management at Berlin's Leibniz Institute for Zoo and Wildlife Research. There is a catch, though: artificial insemination in African elephants with semen that has been frozen, as opposed to the fresh stuff, has not so far been done successfully. But the technique has worked perfectly well in other species, such as rhinos, so researchers remain hopeful.

Just 39 of the 213 African elephants believed to live in North America's zoos, circuses and a few private parks are bulls, and even fewer of them are suitable for breeding. Jackson stands out for his “fantastic libido” and highly productive semen, says Deborah Olson, who heads International Elephant Foundation, a conservation group. But this means that too many of the existing elephant stock are now related to him. The 15 litres of semen from South Africa, from assorted males not related to Jackson, would be enough to inseminate some 324 elephants and thereby freshen up the gene pool. If it can be successfully unfrozen, that is.