San Diego’s Frozen Zoo Offers Hope for Endangered Species Around the World

The last male northern white rhinoceros—his name was Sudan—died in March, leaving only two members of the subspecies behind: his daughter and granddaughter. In the past, those stark facts would have spelled the end. But researchers at the San Diego Zoo’s Institute for Conservation Research—home to a frosty menagerie known as the Frozen Zoo—are working to give northern white rhinos a second chance. Since 1975, the institute has been collecting tissues from creatures, some endangered and some not, then growing the cells in the lab and preserving them at a chilly 321 degrees below zero Fahrenheit. Zoos already use reproductive technologies such as in vitro fertilization for animals like gorillas, and artificial insemination for pandas. (Elsewhere, scientists are considering the merits of resurrecting extinct species such as the woolly mammoth and the passenger pigeon, though they’d have to use ancient DNA for that.) The Frozen Zoo has used its preserved sperm to create pheasant chicks, for example, and has gone as far as making embryos of cheetahs and fertilizing the eggs of southern white rhinoceroses. Now its zookeepers hope that their dozen northern white rhino samples will become parents to a new generation in a different way: using stem-cell technology to turn preserved white rhino skin tissue into eggs and sperm.The institute’s research goes beyond baby-making. Scientists there are working on methods to genetically identify meat from primates and duiker antelopes that have been illegally hunted. And in the future, they might use its collection to restore genetic diversity to endangered black-footed ferrets...MORE