RALEIGH, N.C. — The zookeepers just didn't think Stormy the male rhinoceros had it in him. Now, they owe him an apology.

Stormy had often tried to breed with the four female rhinos at the North Carolina Zoo, but the zookeepers had never seen him succeed. So color them surprised when Linda turned up pregnant, then gave birth July 2 to a rare southern white rhinoceros.

"Stormy was waiting until we were gone until he actually turned on the charm," said Guy Lichty, the outgoing curator of mammals at the zoo in Asheboro. "The keepers are apologizing to him for doubting him."

The birth of the as-yet-unnamed female is a special gift for Lichty, who arrived at the zoo 25 years ago with the goal of having a rhino born there. He's leaving the zoo Sunday, taking his accrued time off before he officially retires this fall.

The calf weighed about 80 to 90 pounds (36 to 41 kilograms) and will be on public view as soon as possible. Zookeepers expect her to gain 100 pounds (45 kilograms) a month in the first year. She could weigh anywhere from 3,500 to 5,500 pounds (1,600 to 2,500 kilograms) when fully grown

The International Rhino Foundation estimates that about 20,000 Southern white rhinos survive in the wild. The northern white rhino has been declared extinct, although researchers said earlier this week that they've succeeded in creating embryos using frozen northern white rhino sperm and eggs from a southern white rhino.

The North Carolina Zoo got Stormy in 2014 from a facility where he had only lived with his brother and with no other females so the keepers knew from the start that his breeding skills might be a tad awkward — and they were.

"We saw lots of foreplay and breeding behavior, but his actual mechanics were not correct," Lichty said.

About two weeks ago, Lichty got a daily report that said a female rhino named Linda showed physical signs of a possible pregnancy. Zookeepers confirmed the pregnancy with a blood test that showed high levels of progesterone.

The baby was born a few days later. Since the rhino gestation period is 16- to 18-months, Linda must have kept her svelte figure for some time.

The zoo was in negotiations to trade Stormy to another facility, but now those are plans are out the window. "He's locked in now," Lichty said. "He's not going anywhere."

And there's the possibility that Stormy could become a dad again. "I feel strongly that there may be more babies on the way," Lichty said cryptically.