NEW YORK (AP) _ After months of monkeying around, Timmy has finally done it: He's impregnated his Bronx Zoo ape-mate, Patty Cake.

Zoo keepers had become concerned that Timmy, a 33-year-old gorilla, was a primate past his prime.

But two tests confirming Patty Cake's pregnancy put their fears to rest.

Zoo-peepers have watched Timmy court his mate for months, and say they are certain he's the father.

The 500-pound silverback gorilla came to the Bronx in November 1991 from Cleveland's Metro Park Zoo, where Timmy was celibate for most of his life. Timmy's only mate there turned out to be infertile.

''He's one of the oldest gorillas to breed in captivity, and I think he's made a marvelous adjustment to living in New York after Cleveland,'' said Jim Doherty, curator of the New York Zoological Society.

The pregnancy is welcome news for the threatened lowland gorilla. They number 300 in zoos throughout the country.

Patty Cake, already the mother of five, was matched up with Timmy by the American Association of Zoological Parks and Aquariums, which created a survival plan for the species.