Later this year, reproductive biologist Betsy Dresser will check some rather extraordinary luggage on a flight from New Orleans to Kenya: Two thermoses containing about 50 bongo embryos, cryogenically frozen at –385° F (–232° C) in liquid nitrogen. Hopefully, these embryos will develop into healthy calves that will repopulate bongo herds—endangered antelope that are rapidly disappearing from their African range.
Upon arrival at the 10,000 acre (4,047 hectare) Mt. Kenya Game Ranch, Dresser and her team will implant these bongo embryos into about 25 surrogate eland mothers that have received three weeks of hormone injections—like those given women preparing for in-vitro fertilization (IVF). After a few weeks, the eland will be pregnancy tested—and the researchers will wait out the 11-month incubation period.
Dresser, director of the Audubon Institute Center for Research of Endangered Species (AICRES) in New Orleans, is a pioneer in "cross-species embryo transfer," an experimental method of breeding endangered species with the help of their more-plentiful—or domestic—relatives. "Nobody has ever done this (embryo transfer) in the wild before," she said.
Conservation's New Front
As Earth's wild places vanish and the numbers of animals facing extinction rises, the fight to save dwindling wildlife is expanding on a new front: in the laboratory. Researchers are adapting techniques like artificial insemination, cloning, in vitro fertilization and inter-species embryo transfer for use in threatened species.
Dresser has successfully "incubated" bongo calves in eland mothers before in captivity, with fresh, not frozen, embryos. This current project follows her 20 years of reproductive work with endangered species—including the birth of the first "test-tube" gorilla in 1995 when Dresser was with the Cincinnati Zoo.
"There is a rapidly growing interest in assisted reproduction technologies in conservation," said Oliver Ryder, a geneticist at the San Diego Zoo's Center for Reproduction of Endangered Species (CRES).
For some at-risk species, biotech conservation represents the last chance to preserve precious genetic diversity, a benchmark of species health and well-being. Toward this end, zoos have become genetic repositories for cryogenically frozen eggs, embryos, sperm and tissue.
The Frozen Zoo
The first so-called "frozen zoo" was created in 1975 by Kurt Benirschke, a visionary physician who switched from his human practice to work with endangered species at the San Diego Zoo, studying gene pools and genetic diseases made prevalent by inbreeding.
Today, in zoos around the world, these deep-freeze tanks act as a high-tech Ark, housing cells from the planet's most endangered animals, including chimps, cheetahs, pandas, California condors and hundreds more.
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