Like many a new mom, Monifa the gorilla hasn't figured out what she has gotten herself into.

Monifa, an endangered western lowland gorilla, gave birth Monday to a healthy male baby in the San Francisco Zoo gorilla house, the first gorilla birth at the zoo in 10 years. And for about two hours, mother and baby seemed to be getting along just fine.

Then Monifa decided to take a short stroll to eat and have a drink - and she did not return to her baby.

Gorilla keepers and veterinarians have been watching from the other side of the bars, and they say they will be forced to step in and begin feeding and caring for the baby themselves - or perhaps see if one of the other females is interested in being a surrogate mom - if Monifa continues to forsake her maternal duties.

"The baby is healthy, with a strong grip and his eyes open," said zoo spokeswoman Gwendolyn Tornatore. "But Monifa is not mothering the infant. We're going to have to wait and see what happens next. This is not the best-case scenario."

The drama began around 8:40 a.m., when Monifa went into labor. About three hours later, the baby was born. And about 1:30 p.m., Monifa left the baby alone in the nest to go get a snack of fruit and veggies.

Later in the day, the keepers locked Monifa inside her enclosure, where the nest with the baby is suspended from a hammock. But Monifa has remained on the ground, a few feet from the baby.

"We're going to have to make a decision within 24 hours about what to do," Tornatore said.

The father is the king of the gorilla house, a stately male who goes by the name of Oscar Jonesy.

Like many such affairs, the pairing of Oscar Jonesy and Monifa was something of an arranged relationship. Both are loaners from other zoos. Monifa, 10, came from the Seattle zoo in 2007. Oscar Jonesy, 27, came from the Buffalo, N.Y., zoo in 2006.

The whole thing was arranged by the love gurus at the Species Survival Program, a Maryland menagerie matchmaker that works to increase zoo populations and maintain genetic diversity. Gorillas are no longer being taken from the wild, so it is vital to make sure that gorillas are proper strangers to one another, not first cousins or some such.

The first thing the matchmakers had to do was break things off between Oscar Jonesy and Nneka, another San Francisco lady gorilla that the big guy had taken a fancy to.

"Nneka's family line is already well represented," said curator of primates Corrine Macdonald, which is a zookeepers' way of saying that Nneka has cousins by the dozens and that Oscar Jonesy and Nneka would not be going to the big dance.

So Nneka, along with two other females in Gorilla World, stayed on birth control pills - the ones discreetly sneaked into their morning banana.

At first it wasn't clear that Oscar Jonesy was interested in species survival program. Macdonald said she could tell his hormones were on idle, because a male gorilla who is ready for action smells enticingly like armpits.

"It's a repulsive smell, unless you're a gorilla," zoo veterinarian Jacqueline Jencek said.

For months, Oscar Jonesy smelled relatively good, which was bad. Then one day it happened. Jencek opened the gorilla house door.

"It reeked of armpits," she said. "It was a very happy smell to me."

It was then that Oscar Jonesy was left alone with Monifa. "Oscar Jonesy understood his job and he performed it," Jencek said. "Diligently."

In the last several days, Monifa had taken to tossing and turning, trying to get comfortable. Monifa, keepers said, apparently did not know she was pregnant or what she was in for. And zoo animals live under different stress from animals in the wild, regardless of their parental status.

"She doesn't understand what's going on," Macdonald said.

In the hours since the birth, Monifa has decided to build a second nest of her own, below the nest where her baby has been left alone.

"Who knows why she's doing that or what she'll do next," Tornatore said.