A frozen zoo is a storage facility in which genetic materials taken from animals are stored at very low temperatures in tanks of liquid nitrogen. Material preserved in this way can be stored indefinitely and used for artificial insemination, in vitro fertilisation, embryo transfer, and cloning. Some facilities also collect and cryopreserve plant material. The first frozen zoo was established at the San Diego Zoo by pathologist Kurt Benirschke in 1972. At the time there was no technology available to make use of the collection, but Benirschke believed such technology would be developed in the future. The frozen zoo idea was later supported in Gregory Benford's 1992 paper proposing a Library of Life. Zoos such as the San Diego Zoo and research programs such as the Audubon Center for Research of Endangered Species cryopreserve genetic material in order to protect the diversity of the gene pool of endangered species, or to provide for a prospective reintroduction of such extinct species as the Tasmanian tiger and the mammoth. Gathering material for a frozen zoo is rendered simple by the abundance of sperm in males. Sperm can be taken from an animal following death. The production of eggs, which in females is usually low, can be increased through hormone treatment to obtain 10–20 oocytes, dependent on the species. Some frozen zoos prefer to fertilize eggs and freeze the resulting embryo, as embryos are more resilient under the cryopreservation process. Some centers also collect skin cell samples of endangered animals or extinct species. The Scripps Research Institute has successfully made skin cells into cultures of special cells called induced pluripotent stem cells. It is theoretically possible to make sperm and egg cells from these IPS cells.
Existing frozen zoos
The Frozen Zoo at the San Diego Zoo's Institute for Conservation Research currently stores a collection of 8,400 samples from over 800 species and subspecies. Frozen Zoo at San Diego Zoo Conservation Research has acted as a forbearer to similar projects at other zoos in the United States and Europe. However, there are still less than a dozen frozen zoos worldwide. At the United Arab Emirates' Breeding Centre for Endangered Arabian Wildlife in Sharjah, the embryos stored include the extremely endangered Gordon’s wildcat and the Arabian leopard . The Audubon Center for Research of Endangered Species, affiliated with the University of New Orleans, is maintaining a frozen zoo. In 2000 the Center implanted a frozen-thawed embryo from the highly endangered African wildcat into the uterus of a domestic house cat, resulting in a healthy male wildcat. The Frozen Ark is a frozen zoo established in 2004 and jointly managed by the Zoological Society of London, the London Natural History Museum, and the University of Nottingham. The University of Georgia's Regenerative Bioscience Center is building a frozen zoo. RBC Director Steven Stice and animal and dairy science assistant professor Franklin West created the facility with the thought of saving endangered cat species. The scientists have already extracted cells from a Sumatran tiger, which could be used for artificial insemination. Artificial insemination provides a remedy for animals who, due to anatomical or physiological reasons, are unable to reproduce in the natural way. Reproduction of stored genetic material also allows for the fostering of genetic improvements, and the prevention of inbreeding. Modern technology allows for genetic manipulation in animals without keeping them in captivity. However, the success of their restoration into the wild would require the application of new science and a sufficient amount of previously collected material.
