LOS ANGELES (AP) -- The Los Angeles Zoo has had it with all the monkey business among the chimpanzees.
After the surprise birth of Toshi a month ago and tests confirming two more pregnancies, four of the adult female chimps at the zoo are being given birth control pills.
The mystery is that the three breeding-age males have had vasectomies. The oldest male, 45-year-old Toto, didn't have a vasectomy because he's never produced offspring or showed an interest in breeding.
Two other males -- 2-year-old Ripley and 4-year-old Glenn -- are believed to be too young to breed.
Blood samples from Jedeo, 20, Shaun, 10, Herrard, 9, and Glenn will be taken to determine paternity. They will also take a blood or semen sample from Toto.
``He hasn't been ruled out, but it's unlikely,'' said Vicki Bingaman, the zookeeper who crushes the birth control pills and mixes it with the chimps' morning strawberry yogurt.
Tests show 12-year-old Gracie will likely give birth at the end of the month and 15-year-old Regina should deliver sometime this summer.
``We thought we had a fail-proof method with the vasectomies. But the urologist who helped with these vasectomies told me that there is a 1 percent failure rate in humans. The rate for chimps is unknown,'' Dr. Cynthia Stringfield said Wednesday.
The zoo now has 14 chimps, 11 of them zoo-born.
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