MONKEY BUSINESS; CHIMP'S BIRTH A REAL WHODUNIT.

Byline: Yvette Cabrera Daily News Staff Writer

The chimpanzees at the Los Angeles Zoo made monkeys out of their handlers - again.

One of the chimps gave birth over the weekend, without the zookeepers even being aware she was pregnant. What's more incredible: All the male chimps of siring age have been given vasectomies, while the others are either too old or too young to reproduce.

In the eight months that Yoshiko was pregnant, only once did her handler even suspect her condition.

``I looked at her a couple of weeks ago and said, Hmmm, she's looking kind of heavy,'' said Vicki Bingaman, head chimpanzee keeper. ``Then I said, Naahh, she can't be, and put it out of my mind.''

Tiny Toshi, a female, was discovered about 7:40 a.m. Sunday by animal keeper Mark Atha.

``She's beautiful. She's as cute as she can be,'' said Bingaman. ``Yoshi cradles her and loves her. Most of the morning, it was grandmother and mother and baby. They stayed together and groomed and hugged.''

As for the lucky father? Another case of monkeyshine by the chimps.

Befuddled last summer when the chimpanzees escaped from a newly built exhibit, which has required tighter security to keep them inside the Mahale Mountains, now the handlers are trying to figure out how 8-year-old Yoshi became pregnant with her first.

They suspect that 8-year-old Jerrard was sitting in a tree k-i-s-s-i-n-g with Yoshiko, and there was other monkeying around.

``He's a feisty little devil. He's just full of himself,'' said Bingaman, who described him as one of the more handsome and dominant of the zoo's chimps. ``He's a pistol.''

DNA tests can determine the paternity of the baby, but because mother chimpanzees tend to be very protective of their young, Bingaman doesn't expect to be able to conduct the blood tests until the baby is older.

If possible, the zoo will try to use hair samples for the DNA testing and will be checking all the vasectomized males to see which one is Toshi's father.

Three of the zoo's six males aren't vasectomized, but they include 4-year-old Glenn and Ripley, 2, both of whom are too young to reproduce, said Bingaman, who estimates that males are mature enough to reproduce at about age 5.

The third chimp, Toto, is a 44-year-old male who has never produced offspring, and nobody suspected he ``had it in him,'' said zoo spokeswoman Judy Shay.

``He has never shown any interest,'' said Shay. ``They're assuming he's not the father - but you never know.''

The zoo began controlling its chimpanzee births at the request of the American Zoo and Aquarium Association. The association oversees a nationwide species survival plan, created to control the genetic population of animals in captivity so that certain breeds are not overrepresented.

At first, the zoo put the female chimps on birth control pills and then hormonal implants, which resulted in two births. When the chimp keepers tried the Norplant implant, Ripley was born. Finally, the zoo resorted to vasectomies for the males shortly after Ripley's birth two years ago.

While the possibility that Yoshi might be pregnant did pass through Bingaman's mind when she noticed the mother chimp had gained weight recently, she explained that just as some women gain very little weight during pregnancies, chimps can likewise hide their pregnancies. The gestation period for chimps typically lasts eight months.

The baby chimp, with her tiny pink feet, is healthy and spent Monday cuddling with her mother under the gaze of zoo visitors. Yoshiko's mother, Regina, at age 7 became the youngest female chimp to give birth at the zoo.

Toshi was named by Los Angeles resident Jeanette Vachon, a longtime zoo supporter who contributed $25,000 on Monday through the zoo's ``adoption'' program and will have a plaque in her name placed at the exhibit.

Ripley was named after Ripley's Believe It or Not show because his conception when all the female chimps had the Norplant birth control implants was such a surprise, said Shay.

With Sunday's birth, 11 of the zoo's 14 chimps have been born at the zoo. The rest were either brought from other zoos or caught in the wild.

``We have such a history with this group (of chimps),'' said Bingaman. ``Other zoos in the United States cannot get their groups to reproduce. Our group, they're wonderful socially. It's just the way it should be.''

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PHOTO (color) Yoshiko cradles her 1-day-old baby chimpanzee, Toshi, Monday at the Los Angeles Zoo.

Michael Owen Baker/Daily News