The South American bush dogs — which resemble chubby, furry Chihuahuas — were born in January following a successful, first-of-its-kind vasectomy reversal on the pups' father, named Brent.
The procedure was performed in August 2003 by St. Louis infertility specialist Dr. Sherman Silber, who had done the operation on more than 4,000 humans before trying it on Brent.
The reversible vasectomy holds the best hope for the world's zoos to manage animals genetically and behaviorally, said Ingrid Porton, co-director of the American Zoo and Aquarium Association's Wildlife Contraception Center at the St. Louis Zoo.
"It allows us to manage reproduction in a responsible way, and meet (animals') behavioral and social needs," Porton said. "It's so much more preferable not to isolate animals to prevent breeding; with a reversible contraception, we can allow them to live in a social group."