The oldest animal at the Houston Zoo, a radiated tortoise born nearly a century ago, is finally a father.

The zoo announced last week that Mr. Pickles and Mrs. Pickles welcomed three tortoise hatchlings: Dill, Gherkin and Jalapeño. (All three names are comfortably in the family of pickle preserves.)

It was an astounding feat, zoo officials said, not only because Mr. Pickles is 90 years old, but also because the critically endangered species rarely produces offspring.

Mr. Pickles has been a resident of the zoo for 36 years and partnered with Mrs. Pickles, now 53, since her arrival in 1996. While radiated tortoises can live for up to 150 years, exactly how long they can reproduce is unknown, said Jessica Reyes, a zoo spokeswoman.

The births were even more improbable because the hatchlings likely wouldn’t have survived if a zookeeper had not noticed Mrs. Pickles laying her eggs, the zoo said. The soil in Houston isn’t conducive to keeping the burrowed eggs that Madagascar native tortoises lay at the right temperature and humidity, so the keepers moved them into the Reptile and Amphibian House.

The eggs were closely watched and monitored for more than five months as the zookeepers cooled them off in a chiller at about 50 degrees to mimic what would happen in nature, before returning them to room temperature and eventually placing them in an incubator in the 80s.

The new trio will remain behind the scenes in the reptile and amphibian dwelling, until they are big enough to join their parents, the zoo said.

Jon Rold, supervisor of herpetology and entomology at the Houston Zoo, said it was a matter of luck that Mr. and Mrs. Pickles had bred successfully and that the eggs had been found in time.

“If you don’t see the female actually digging a hole and laying the eggs, it can very easily be missed,” Mr. Rold said. “And if it is missed and the eggs don’t get in the proper setup soon enough, they just won’t develop.”

Mr. Pickles was hatched in the 1930s and eventually made his way to Houston in the 1980s, after he was collected and traveled throughout Europe in the 1950s, Mr. Rold said.

It’s unclear how many radiated tortoises remain in the wild, according to the Smithsonian’s National Zoo and Conservation Biology Institute, but their numbers are declining and the species could become extinct.

Despite radiated tortoises’ being an endangered species, and an international treaty protecting them, the animals continue to be in demand on the black market because of the distinctive, intricate yellow star pattern on their shells that gives them their name. In Madagascar, they are sometimes given as wedding gifts, and in China, some people will pay about $50 to eat them, the Smithsonian said.

In 2018, nearly 10,000 of the tortoises were found inside a Madagascar home by local authorities who believed that the animals were going to be smuggled out of the country, according to National Geographic.