Giraffes at the Safari Park
February 12, 2020


Feb. 12, 202

San Diego Zoo Global
Public Relations



San Diego Zoo Global’s Frozen Zoo® Hits Milestone: 10,000 Cell Lines

Second-largest Number of New Species in a Single Year Added in 2019

Scientists at San Diego Zoo Global’s Frozen Zoo® have achieved a major milestone in saving wildlife species: This unique collection of genetic material now contains 10,000 individual cell lines from more than 1,100 species and subspecies—some of them critically endangered. The cell lines are established from tissue collected from a variety of mammals, birds, reptiles, amphibians and fish, which are then stored in liquid nitrogen freezers at a temperature of -320 degrees Fahrenheit. Akin to the Svalbard Global Seed Vault in Norway, which safeguards unique genetic material for thousands of the world’s food crops, the Frozen Zoo is a genetic cryobank that serves as a potent bulwark against wildlife extinction. The genetic material here can be used to study species, produce offspring, restore genetic diversity and possibly help rescue species on the brink of extinction.

“Achieving the milestone of 10,000 individual cell lines reinforces the significance of this unique repository of biodiversity that can be used to better understand and sustain endangered populations,” said Marlys Houck, curator of the Frozen Zoo at San Diego Zoo Global. “I’m incredibly proud of the tissue culture team’s efforts to successfully optimize the conditions necessary to establish, characterize and preserve these important animal cell lines. These living cells contain the genetic blueprint of the species—and they can be reprogrammed to create other types of cells, including reproductive cells. Not only are we banking biodiversity, but we are also providing hope and opportunities for current and future species conservation.” 

Established in 1975, the Frozen Zoo is the largest repository of its kind in the world. The collection includes irreplaceable living cell lines, gametes and embryos, providing an invaluable resource for conservation, assisted reproduction, evolutionary biology and wildlife medicine.

A team of three tissue culturists, led by Houck, work year-round to collect, grow and preserve cell lines. The team collects skin or other tissue samples from threatened and endangered wildlife, either after an animal has died or during a routine veterinary exam. From those tissues, living fibroblast cells are established and grown, which are then frozen in multiple vials and placed in the Frozen Zoo.

In 2019, the Biodiversity Banking team added 75 new species to the Frozen Zoo—the second-highest number of new species added in a single year since the collection began. A total of 80% of the new additions are bird species, 15% are reptiles and 5% are amphibians. “The volume of species added to the Frozen Zoo in 2019 underscores the Biodiversity Banking team’s expertise in developing the specific conditions necessary to bank biological material with the high quality that current conservation efforts require,” added Houck. 

Scientists at the Frozen Zoo are committed to sharing their knowledge and methods with other researchers around the world. Dr. Kurt Benirschke, who founded the Frozen Zoo in 1975, had this vision from its inception and predicted there would be future uses for the cells beyond anything imaginable in the 1970s.

“From the very beginning, we have shared our many resources and collaborated with other scientists to aid conservation efforts worldwide,” said Oliver Ryder, Ph.D., Kleberg endowed director of Conservation Genetics at San Diego Zoo Global. “The Biodiversity Banking Institute team provides cell lines to qualified researchers locally and internationally. In addition, they offer in-depth training on everything from how to acquire samples from deceased animals to establishing cell lines and studying chromosomes. We want to help scientists in other countries start collections like the Frozen Zoo to represent their local species.”

As an international nonprofit organization, San Diego Zoo Global works to fight extinction through conservation efforts for plants and animals worldwide. With a history of leadership in species recovery and animal care, San Diego Zoo Global works with partners in science-based field programs on six continents, and maintains sanctuaries and public education facilities in many places. Inspiring a passion for nature is critical to saving species, and San Diego Zoo Global’s outreach efforts share the wonder of wildlife with millions of people every year. Current major conservation initiatives include: fighting wildlife trafficking and the impacts of climate change on wildlife species; broad-spectrum species and habitat protection efforts in Kenya, in Peru, and on islands worldwide; preventing extinction in our own backyard; and expanding efforts to bank critical genetic resources and apply them to the conservation of critically endangered species. To learn more, visit or connect with us on Facebook.


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Link includes:

  • Archival image of Marlys Houck, curator of the Frozen Zoo at the San Diego Zoo Institute for Conservation Research, placing cell samples into one of the liquid nitrogen freezers inside the Frozen Zoo
  • Archival image of the liquid nitrogen freezers inside the Frozen Zoo, Credit: San Diego Zoo Global 
  • Archival image of cell samples in the Frozen Zoo, Credit: San Diego Zoo Global 
  • Archival video of researchers at the Frozen Zoo, Credit: San Diego Zoo Global