The 4-month-old, spotted female dolphin had struggled all last week but experienced "a very rapid deterioration last night," said Margaret Akamine, the protected species program coordinator for the National Oceanic and Atmospheric Administration.

"She became weak and disoriented and unresponsive and became unable to swim on her own," Akamine said today. "So, for humane reasons, the veterinarians euthanized her."

The decision was made about 11 p.m. yesterday, she said.

The dolphin was found Christmas morning frantically swimming in circles at Poka'i Bay in Wai'anae.

The dolphin was being treated at Marine Mammal Research rehabilitation facility at Marine Corps Base, Hawaii.

A team of veterinarians and biologists with the Hawaiian Islands Stranding Response Group diagnosed the dolphin with severe pneumonia. It received antibiotics all week.