The male dolphin calf born March 20 at Baltimore's National Aquarium was found dead yesterday morning in the Marine Mammal Pavilion's nursery pool -- being pushed through the water by its mother in a futile lifesaving effort.
Aquarium officials said mother Nani's instinctive attempt to keep her unnamed calf breathing could not save it from the pneumonia that appeared to be the cause of death.
Marine mammal curator Nedra Hecker said the calf was Nani's third; the others, born at Marine Park in Galveston, Texas, also did not survive -- one drowning at birth, the other succumbing to a bacterial infection at three weeks.
Ms. Hecker said the pneumonia likely set in as a result of some other illness, and that studies of blood and tissue samples will take several weeks to complete.
The calf had shown no obvious physical problem -- but even if it had appeared to be ill, Ms. Hecker said, there would have been no way for humans to intervene. A dolphin calf's immune system is not fully developed in the early weeks of life, and its survival depends entirely on the mother.
"Both in and out of the wild," the aquarium said in announcing the death, "high mortality is a fact of life for dolphin calves. Approximately 20 percent of the calves are stillborn; about 40 percent of those born alive die within the first month."
Since its birth 18 days ago, the calf and the 21-year-old Nani had shared the nursery pool with the aquarium's year-old calves, Cobie and Chessie, and their mothers, and had no difficulties with interaction.
A videotape of the birth showed the curiosity of the other dolphins, which within minutes began swimming alongside Nani and her calf.
Ms. Hecker said the surviving dolphins in the aquarium's nursery pool do not appear to be at medical risk.