When it comes to holding the interest of 10-year-old boys, mother-baby relationships can't hope to compete with screeching lemurs and rough-housing lions.

But even James Clark and Bo Bridges were enamored Saturday with the rare gorilla twins at Zoo Atlanta, during a party for the primates' first birthday, which is actually today. (Celebratory banana muffins were served to the crowd, not the gorillas.)

Photos by JOHN SPINK/Staff (ENLARGE)

Year-old gorilla twins Kazi (top) and Kali hitch a ride with their mom, Kuchi, who zoo officials say is doing an excellent job of raising her offspring.

(ENLARGE)

Tara Stoinski (left), a Zoo Atlanta researcher who studies gorillas, and Charles Horton, curator of primates at the zoo, say they're thrilled with Kuchi's maternal instincts.

RELATED LINKS: • Photos: Happy birthday, babies! • Video: See twins in action! GORILLA BABIES • Kali and Kazi. Male and female. Born to Kuchi. Oct. 31, 2005. Kali is Swahili for "strong"; Kazi means "treasure." • Macy Baby. Female. Born to Kudzoo. Dec. 11, 2005. Named by zoo sponsor Macy's. • Gunther. Male. Born to Sukhari. July 6, 2006. Named by keeper Charles Horton, in honor of his 35 years of zoo service. It's a tribute to Horton's inspiration, famed animal trainer Gunther Gebel-Williams.

Standing on a packed observation deck at the Ford African Rain Forest, the boys, students at the St. Luke School in Columbus, laughed as mom gorilla Kuchi tried to keep track of her growingly independent offspring, Kali, a male, and Kazi, a female.

"I think it would be hard enough to have a baby," said Bridges, who nominated lions as his favorite zoo animals. "But it would be even harder to have to chase them when they're running away."

Clark, who favors lemurs, was equally enthused, if less analytical. "Their names are cool," he said.

Zoo officials would agree, even as they underscore the importance of ape conservation.

Overlooked in the excitement over the zoo's newborn panda cub, the prolific western lowland gorillas are making history of their own: Kali and Kazi are the first gorilla twins on record in North America entirely reared by their mother.

But they are only half the newborn gorilla act at the zoo, where four pint-sized gorillas are on the ground — and riding on their mothers' legs, backs and stomachs.

Of the three moms, who include first-timers Kudzoo, 12, and Sukhari, 8, Kuchi, 22, is the experienced and model caregiver.

"She has never faltered once with them," says Tara Stoinski, a Zoo Atlanta researcher who studies the endangered species here and in Africa. "Literally, there is no other captive facility in the world where you have ever been able to see what you're seeing right now — twins being reared by their mom in a normal social group."

With 24 animals, Zoo Atlanta has the second largest gorilla population in North America, after the Bronx Zoo in New York.

The four babies; their father, Taz, a 17-year-old silverback; and four adult females constitute one family group. The zoo has four gorilla family groups. Silverbacks Ozzie and Ivan also lead families, and there is one collection of "bachelors" — males with no females.

Even with that many animals, twins are exceedingly rare. And chances of survival are slimmer.

Of the six previous sets of gorilla twins born in North America since 1956, three died and three were hand-reared at zoos, Stoinski said.

"There has never been a female that had successfully raised twins in captivity before," Stoinski said, "so we didn't have a lot of precedents to work from."

Zoo Atlanta's policy is not to interfere with maternal care, as long as newborns are being properly reared. That's why even after one year, Kali and Kazi remain physically close to Kuchi — except for when she's chasing them around trees, now that they are trying to scamper off on their own.

Kali and Kazi were the first arrivals in a baby boom last Halloween. Macy Baby, a female, was born to Kudzoo on Dec. 11. A male named Gunther was born to Sukhari on July 6.

As they become more mobile in coming months, the zoo expects lots of animated activity among the younger set. "It's going to be fun to watch," says Charles Horton, a gorilla keeper in his 35th year at Zoo Atlanta. "We're going to have four kids all growing up about the same time, running and playing and jumping. We can put a bale of hay out there and they will just have the biggest party with it, something that simple. They just groove on each other."