Brookfield Zoo Chicago's newborn dolphin dies suddenly just days after birth

Bottlenose dolphin calf born at Brookfield Zoo Chicago

For the first time since 2014, a bottlenose dolphin calf was born at Brookfield Zoo Chicago on Saturday.

CHICAGO - The excitement surrounding the birth of a bottlenose dolphin at Brookfield Zoo over the weekend turned to heartbreak when the calf died unexpectedly Wednesday night.

What we know:

Brookfield Zoo announced Thursday that the male calf, born early Saturday morning, had died at just four days old. He was the first calf born at the zoo in over a decade.

According to zoo staff, the calf had been showing positive signs of development and had appeared healthy up until the moment he became unresponsive.

The calf was born to Allie, a first-time mother, who was being supported by Tapeko, another dolphin with experience raising young. Since the calf’s birth, zoo veterinarians and animal care staff had been monitoring him around the clock.

Brookfield Zoo Chicago welcomed a new member to its family early Saturday morning with the birth of a bottlenose dolphin calf. (Brookfield Zoo Chicago)

The zoo said the calf had been nursing well and reaching expected milestones. Staff noticed a sudden change in his behavior Wednesday evening. Within minutes, the calf was unresponsive and died shortly after.

What we don't know:

The cause of death is not yet known. A necropsy—an animal autopsy—is being conducted to learn more.

What's next:

Veterinarians and animal care teams continue to monitor Allie and the rest of the dolphin group as they process the loss.

In a statement, Dr. Rita Stacey, the zoo’s senior vice president of programs and impact, called the loss "devastating" and praised the care teams for their dedication.

"While the calf was progressing well, dolphin neonates face immense biological challenges," she said. "This calf’s birth brought hope and joy, and his sudden loss reminds us of the delicate balance of life."