BROOKFIELD, Illinois -- The Chicago Zoological Society announced Wednesday that twin river otter pups had been born at Brookfield Zoo in February.The male and female pups, born Feb. 23, are the first successful river otter births in the zoo's history.The mother, Charlotte, has been at Brookfield Zoo since 2012, and father Benny has been at the zoo since 2004. Otter pups are born with their eyes closed, fully furred and weighing about 4 ounces, the zoo said.The pups are being kept behind the scenes at the zoo to bond with their mother and learn how to swim. They are expected to make their public debut later in April.