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."
Vasectomies on zoo and wildlife species up to this point were designed for permanent contraception, said Paul Calle, senior veterinarian with New York-based Wildlife Conservation Society and a scientific adviser to the contraception center.
This was done with the intention of reversing it, which opens more opportunities for wildlife management, he said.
The method is not controversial, he said, but reflects a shift in zoos' focus to selective reproduction as the world's wild areas disappear.
Brent's pups — Mariana, Turi and Sherman — will probably go on public display next week.
On Tuesday, after being vaccinated and weighed, the pups were returned to their waiting parents in the zoo's makeshift den, where they pawed at their dad's mouth to indicate they were hungry. He chews their food before giving it to them.