VIRGINIA KEY, Fla. -- Researchers who performed a necropsy on a whale that died Monday after stranding itself in shallow waters off Hollywood Beach said the animal was ill.

Biologists at the NOAA's National Marine Fisheries Service examined the body of a beaked whale Tuesday. They said the whale was suffering from pneumonia, an indication that it was sick with some sort of virus or disease, Local 10's Roger Lohse reported.

The examination was a rare opportunity to learn about beaked whales. The 13-foot mammal could provide important data about the species, about which researchers know little.

"They do come ashore once or twice a year here in Florida," said Blair Mays of the NOAA. "They're a little bit of a mystery to us because they're very deep divers. They're deep-ocean dwellers, and they're hard to study in the wild."

Marine biologists and veterinarians are trying to find out why the rare whales came so close to shore. The reason whales beach themselves and die is one of the oldest mysteries in the study of the animals. Sometimes scientists attribute the behavior to viruses, illnesses or ingested debris, but 70 percent of the time, they never come up with a cause, Lohse reported.

The female beaked whale beached itself near Johnson Street Monday afternoon. A few blocks away, her calf was spotted, roaming the shallow waters and searching for its mother.

Marine rescue workers corralled the calf and herded it to its ailing mother, which struggled to shake free of its rescuers when it spotted its calf so close. Beachgoers said they could relate to the maternal bond.

"It's sad -- even though they say it's a natural thing of nature -- to see the baby looking for its mom," said beachgoer Nancy Acosta.

Soon after the mother and calf were reunited, the mother whale began to thrash in the water and died, leaving the calf orphaned. Biologists decided to euthanize the 6-month-old calf, as well, which Mays said was the most humane thing they could do.

"This is a deep-ocean dweller. There are no animals like this in captivity, and it needs its mother to survive. It needs its mother to teach it how to hunt and survive in the wild. So even if we were to bring it in for a little while, give it formula, we could never release it back into the wild because we don't have the skills to teach it to be a wild animal," Mays said.

Mays said the calf was likely malnourished because its mother had not eaten in a week. In their search to find out why the mother whale was sick, researchers hoped to learn how they can help the next stranded mammal survive.

The calf's body was sent to a laboratory at the University of Florida in Gainesville. Researchers there will focus on the whale's vascular system in the hope of learning how beaked whales can hold their breath for up to an hour and live in deep waters of 2,000 to 3,000 feet.