BROOKFIELD – Staff at the Brookfield Zoo are mourning the death of a second dolphin calf born at the zoo, the Chicago Zoological Society announced Monday.
The 7-day-old calf was born on Dec. 12 to 9-year-old Allison. The calf died Dec. 19 after zoo staff stepped in to provide supportive treatment.
A second dolphin calf born born Dec. 5 died suddenly that day after what was believed to be a normal birth.
The first 30 days of a dolphin's life are particularly critical, said Bill Zeigler, senior vice president of collection and animal care for the Chicago Zoological Society.
One of the three dolphins born at the zoo in 2013 also died in the days after it was born. The other two are now 1-year-old calves, Merlin and Magic, and are doing well at the zoo's exhibit.
Zeigler said the dolphin born Dec. 5 died very quickly after it was born. The zoo is still awaiting results of a necropsy – and animal autopsy – to learn more about the circumstances of the deaths.
In the most recent death, the 7-day-old calf appeared to be doing well. After the birth, the calf and its mother received round-the-clock care by zoo staff. Most important, Zeigler said, was making sure the calf was nursing and "slipstreaming" with its mother.
Slipstreaming is a critical behavior that allows the newborn calf to conserve energy by riding a wake created by its mother and being pulled along in her stream. However, days later the calf and mother began to show behavior changes in their swimming patterns. When it appeared the calf was experiencing problems, zoo staff stepped in and despite their best efforts, the calf died in the evening.
Both of the calves that died recently were born to inexperienced mothers. Zeigler said the zoo prefers to avoid hand-rearing dolphins to allow the mothers to gain experience. He added that the Brookfield Zoo is only zoo that has been successful hand-rearing a dolphin calf.
Zeigler said that inexperienced mothers have a higher loss rate than experienced mothers. He said that was especially true of dolphins born in the wild.
The Chicago Zoological Society has participated in a 44-year study of wild dolphin research in Sarasota, Fla. Zeigler said that the study shows that moralities of young calves during the first 30 days of life account for the largest rate of loss to dolphin populations in the wild.
The dolphins at the Brookfield Zoo, Zeigler said, get significantly better treatment than those in the wild.
"It's as much an issue out there as anywhere else," Zeigler said.
Zeigler said it was apparent that the mother of the calf that died Dec. 19 was making a good effort to raise the calf.
Members of the zoo's staff are heartbroken over both deaths, Zeigler said.
"Obviously, when this type of thing happens it is devastating for the staff."