Baby Shamu II, the killer whale born Jan. 5 at Sea World, died Thursday morning, apparently of a "respiratory or flu-like viral disease," a Sea World spokeswoman said.
The baby was the offspring of 27-year-old Shamu and his mate, 12-year-old Kenau. It had shown signs of illness late Wednesday afternoon and was moved to an intensive care pool but failed to respond to treatment, spokeswoman Jackie Hill said.
Baby Shamu II weighed 350 pounds at birth and appeared healthy, leading Sea World officials to express guarded optimism about the chances of survival of the female calf.
There is a high mortality rate among whales born in captivity. All five of the killer whales born at Marineland in Rancho Palos Verdes died. The only killer whale born in captivity to survive is Shamu's only other offspring, born in September at Sea World in Orlando, Fla.