Scientists are hailing the birth of the world’s second cloned Przewalski’s horse as evidence that cloning might indeed be a useful tool in genetic rescue. According to an April 19 news release from the San Diego (CA) Zoo Wildlife Alliance, hopes are high that it will help foster the sustainability of endangered species (or subspecies) such as the one to which this youngster belongs.

A frozen cell line

The new colt, born Feb. 17, 2023 to a domestic surrogate mare and reportedly nicknamed “Trey,” is a clone of a male Przewalski’s horse stallion whose living cell line was cryopreserved over 40 years ago in the San Diego Zoo Wildlife Alliance Biodiversity Bank’s Frozen Zoo®.

As the news release explains, this new colt is the genetic twin of the world’s first cloned Przewalski’s horse, Kurt. This is because Kurt was born in August 2020 from the same stallion’s living cell line. The births of both horses are a result of a partnership between nonprofit Revive & Restore, the animal cloning company ViaGen Pets & Equine and the San Diego Zoo Wildlife Alliance. The goal of this partnership has been to add genetic diversity to the endangered Przewalski’s horse species.

“The most transformative moments in conservation happen when the brightest minds collaborate and discover new possibilities for wildlife,” said Paul A. Baribault, president and chief executive officer of the San Diego Zoo Wildlife Alliance. “Our work to rescue endangered species is possible because we’ve come together as an alliance of conservationists, whose goal is to help create a world where all life thrives. We are inspired by this incredible achievement and the impact it will have on Przewalski’s horses worldwide.”

A boost for conservation

Until the recent birth of this Przewalski’s horse, cloning had only successfully produced a single individual of any endangered species. “This is a big deal for conservation,” said Ryan Phelan, co-founder and executive director of Revive & Restore. “Cloning as a tool for genetic rescue has been underutilized. Here, we have increasing evidence that cloning is a viable strategy to revive lost genetic diversity in endangered species.”

“Having two stallions of a genetically valuable line is a huge boost for the conservation of the species,” explained Ben Novak, lead scientist at Revive & Restore. “It means twice the potential to revive genetic diversity in this species.” 

Formerly extinct in the wild, the Przewalski’s horse has survived for the past 40 years almost entirely in zoos around the world, and nearly all of the surviving horses are related to just 12 Przewalski’s horses born in native habitats. Ongoing reintroductions of Przewalski’s horses into their native habitats have established several herds in grasslands in China and Mongolia.

To maintain genetic variation, however, scientists believe more work needs to be done to ensure the species’ future survival. Advanced reproductive technologies are relatively standard for domestic horses and cattle. However, there have been few attempts to work with endangered species.

Learning to be wild

“He has been a healthy, amazing foal from birth,” Blake Russell, president of ViaGen Pets & Equine, said of the new Przewalski’s horse. “He was up and nursing within a few minutes, and only slows down for his regular naps. We are thrilled to be a part of this effort, and look forward to more milestones ahead.”

“Trey” will eventually be moved from his birthplace at ViaGen Pets & Equine’s cloning facility in Texas to the San Diego Zoo Safari Park. Kurt was moved from ViaGen Pets & Equine’s facility to the Safari Park in March 2021.

Przewalski’s horses normally live in groups, where a youngster secures their place in the herd from their mother. Because the new colt and Kurt were not born into a herd, San Diego Zoo Safari Park wildlife care experts are working to ensure that Kurt, and eventually his twin, gain the unique behavioral language they will need to interact and thrive among the larger herd of Przewalski’s horses at the Safari Park. Kurt is currently learning the language of being a wild horse from his companion, Holly, a young female of his own species. The plan is for Kurt and the new colt to become breeding stallions when they reach maturity at about 3 to 4 years of age.

‘Unprecedented step’

“Over the more than 100-year history of human management of Przewalski’s horses and their extinction in the wild, there have been multiple genetic bottlenecks that have diminished the gene pool of the species, including in its reintroduction into the wild,” said Oliver Ryder, Ph.D., Kleberg endowed director of conservation genetics at the San Diego Zoo Wildlife Alliance.

“It is an enormously hopeful, unprecedented step for the Frozen Zoo to have the capacity to restore genetic diversity and resiliency in the ongoing efforts to conserve the Przewalski’s horse.”

For more information about the partners involved in this conservation effort, visit the San Diego Zoo Wildlife Alliance, Revive & Restore and ViaGen Pets and Equine.

Landing page image copyright Jaimie Wells, San Diego Zoo Safari Park/San Diego Zoo Wildlife Alliance