 It was the first to use a dart gun to implant a slow-release hormone into the thigh of a female giraffe; she is the daughter of the zoo's bull giraffe, and inbreeding is inadvisable.The zoo uses slow-release hormones to control its chimpanzee and mandrill populations, which are reproducing too quickly for the space they occupy; letting the animals multiply and sending family members to other zoos is unwise, according to veterinarians.Newborn animals that are threatened or ignored by their parents are raised by the veterinary staff.