Bob Jenkins, the zoo's vice president of external affairs, said the zoo had planned on selling the giraffe since her birth.

Giraffe herds usually only have one male, who will breed with each female. Since the only male in the current herd is Barbro's father, that wouldn't work. Both the father and Barbro's half-brother had starting showing a non-platonic interest in the young female.

The zoo's giraffe exhibit is also getting crowded - two others are expecting babies in the next couple months. Barbro was orphaned last year when her mother, Gezi, died of cancer.

Officials said Barbro is doing well in her new digs with four other giraffes.

But Deniz Bolbol, an animal welfare activist who is often at odds with the zoo, criticized the transaction.

"This is exactly like the animal welfare problems we've had in past," she said, adding that the Discovery Kingdom giraffe exhibit is much smaller than the zoo's and was the site of a fire in 2007 that killed one giraffe.

"I can assure you that the local community, which cares about animals, would not agree that an amusement park is an appropriate place for a giraffe to live," she said.

Jenkins said the zoo settled on Six Flags Discovery Kingdom in Vallejo because of its proximity and the fact that the zoo's veterinary staff and animal keepers have contacts there.

Nancy Chan, a spokeswoman for Six Flags, noted that the park has a new giraffe facility, and is accredited by the Association of Zoos and Aquariums and regulated by the U.S. Department of Food and Agriculture.

"The animal-care staff vetted the facility," Jenkins added. "Everything was done with animal welfare in mind."

The money from the sale also can't hurt: The zoo has faced a number of financial problems over the past year and needs millions of dollars worth of upgrades to its aging animal facilities.

E-mail Marisa Lagos at mlagos@sfchronicle.com.

This article appeared on page B - 2 of the San Francisco Chronicle