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A Siberian-Bengal tiger rests in its enclosure at the Oakland Zoo on Wednesday (D. Ross Cameron/The Oakland Tribune)
OAKLAND _ The tigers at the Oakland Zoo were the focal point of the facility Wednesday as visitors pondered the possible escape techniques of the violent predators.

Scores of patrons viewed Oakland's tigers the day after one of the big cats escaped its enclosure at the San Francisco Zoo and killed a boy and mauled his two friends.

Just how Tatiana, the San Francisco Zoo's 300-pound female tiger, got out of her grotto about 5 p.m. Christmas Day remained unclear Wednesday. Police investigators were still trying to determine if the Siberian tiger escaped on its own, received inadvertent help or had provocation.

But the horrific incident did not stop people from visiting the Oakland Zoo and its own two female tigers _ an 18-year-old Bengal tiger weighing 230 pounds and a 10-year old Siberian-Bengal mix weighing about 305 pounds.

Still, Oakland Zoo visitors were on high alert. ``You gotta be careful. They are real animals,'' said Lara Kueppers of Mariposa. ``It's tough to have cats in these small habitats.''

Even with news of the mauling across the Bay, Oakland Zoo officials said attendance was up Wednesday -- possibly due to the winter break school holiday -- but maybe because people wanted to get a look at the type of animal that did such damage to three unsuspecting people.

"I wasn't that shocked. I was more shocked that it happened on Christmas," said Jill Briggs of La Honda, visiting the Oakland Zoo with five children and her sister.

Briggs said she had been at the San Francisco Zoo in October on a school field trip.

"The way (the tiger exhibit) was situated ... I didn't think it would be that difficult to get out of," she said.

The big cat did not leave through an open door, said Robert Jenkins, director of animal care and conservation at the San Francisco Zoo.

``There was no way out through the door,'' Jenkins said. ``The animal appears to have climbed or otherwise leaped out of the enclosure.''

The tiger's enclosure is surrounded by a 20-foot-wide moat and an 18- foot tall wall.

The barriers at the Oakland Zoo are lower -- a 15-foot high chain-link fence surrounds most of the habitat and a 15-foot high smooth, flat cement wall encloses about one-quarter of the exhibit, zoo officials said. There are no moats in Oakland.

Oakland's tigers have lived in captivity since they were rescued from the circus about eight years ago, ``so they don't have overt aggression,'' said Oakland Zoo Executive Director Joel Parrott.

Experts say tigers -- depending on their size, weight and other factors -- can leap between 15 feet and 30 feet and run up to 35 mph. Siberian tigers prefer prey weighing more than 100 pounds and need to eat at least 20 pounds of meat a day to sustain body temperature in the cold weather, experts said.

But Tuesday's attack likely had little to do with hunger, said Chris Austria, an animal trainer who has worked with tigers at Marine World in Vallejo and with bears at the San Francisco Zoo. Just like a house cat who jumps the backyard fence, a captive tiger would be very interested in the outside world, Austria said.

Austria said San Francisco Zoo has always been very safety-conscious and its staff well-trained but ``when they're working with wild animals, they're very hard to control. When they escape their habitats, they can be very aggressive.''

Still, Parrott said patrons should feel safe.

``Right now, the zoo is as safe today as it was yesterday and our barriers are designed to keep animals where they belong.''

Oakland Zoo visitor Pat Leach of Milpitas felt safe at the zoo with her grandchildren. ``We've been to this zoo many times. They have really high (barriers on the) exhibits,'' she said.

Parrott said they will be ``reexamining their safety standards'' in the wake of the San Francisco Zoo incident.

``We always do,'' he said. ``When a jaguar attacked a zookeeper in Denver we looked at them. Generally nothing changes, but it sure freshens our procedures.'' In the Denver incident, it was later determined that a zookeeper had violated zoo rules by opening the door to the animal's cage.

Tuesday's attack happened around closing time on the east end of the 125-acre zoo grounds near Ocean Beach. About two dozen people were still in the zoo when the attacks happened, zoo officials said.

It appears the tiger jumped out of the grotto and attacked and killed 17-year-old Carlos Sousa Jr. of San Jose. Then she attacked his friends, who are brothers, ages 19 and 23. The injured men were upgraded to stable condition Wednesday at San Francisco General Hospital after undergoing surgery to have their wounds cleaned and closed, said surgeon Rochelle Dicker. San Francisco police officers shot and killed the rogue tiger.

Tatiana, the San Franciso tiger, ripped the flesh off a zookeeper's arm just before Christmas last year. After that attack, the zoo added customized steel mesh over the bars, built in a feeding shoot and increased the distance between the public and the cats.

But some Oakland Zoo patrons, such as Briggs, said the zoo did not go far enough after that attack.

``The zookeepers know the animals, they feed the animals and they know their temperaments so they should have known that that particular animal was going to be a problem,'' she said.

San Francisco Zoo Director Manual Mollinedo said he did not consider euthanizing the animal after the 2006 incident, which occurred when the keeper was feeding the tiger through the bars surrounding the enclosure.

That is not the way tigers in Oakland are fed.

Parrott said they are given their food inside a rock structure by trainers who enter through two doors. Each door has a lock on it and zookeepers go in to the feeding area two at a time, he said.

But Parrott acknowledged Wednesday that if a zookeeper "broke protocol" -- or made a mistake _ a tiger could escape quickly.

To try to prevent that, the Oakland Zoo allows only its most experienced animal keepers -- those with two-plus years on the job -- to become predator keepers, Parrott said.

Parrott said he and other zoo employees are thinking and praying for those impacted by the attack.

``The immediate response is that your heart goes up in your throat,'' he said. ``And there is deep sympathy for them.''

Parrott said he knows what it's like to deal with a zoo fatality. In January 1991, Oakland Zoo supervisor Loren Jackson Sr. was shoveling elephant manure when something set off one of the African elephants and it fatally trampled him. Jackson had worked at the zoo for 25 years. The fatality prompted Oakland to become the first zoo in the nation to exclusively use ``protected contact'' in its handling and feeding of elephants.

The approach has trainers tend to elephants only when they are in protective chutes. The elephants are lured in by treats, and there is never punishment for not cooperating.

Wire services contributed to this report. Contact Kristin Bender at kbender@bayareanewsgroup.com or 510-208-6453.