When Brookfield Zoo employees learned that three of their bottlenose dolphins were pregnant, many planned their vacation early in anticipation of help with the December births.
Their eagerness gave way to disappointment last month as they now await results from necropsies — animal autopsies — to determine the cause of death for two of the calves, said Bill Zeigler, the zoo’s senior vice president of collections and animal programs.
The deaths emphasize the uncertain nature of dolphin breeding, a complicated science for zoos and aquariums, as a dolphin birth is not considered successful until a calf is one year old.
In the most recent death on December 19, a 7-day-old male calf was neglected by his 9-year-old mother, Allison. The calf, which had not yet been named, was sometimes abandoned and unable to slipstream or swim alongside its mother to conserve energy.
“The calf worked hard to stay upright and it swam just as fast as she did,” Zeigler said. “That is not easy for a calf in the first week of life.”
Zeigler employees at the Brookfield Zoo provided the treatment after noticing a change in behavior between the pair, but were unable to save the calf, Zeigler said.
The calf was the eighth bottlenose dolphin born at the zoo’s Seven Seas Dolphinarium since it began breeding the animals in 1999. Three of those calves have died, including a male, who died shortly after he was born to 11-year-old Noelani on December. 5.
Brookfield Zoo has up to 20 employees who monitor dolphins during the birthing process. After the calf is born, a staff of at least four members observes around the clock and checks the animal’s vital signs every six hours.
But high infant mortality, especially within 30 days of birth, is not uncommon for new moms like Allison and Noelani.
“Everyone hates seeing a baby die, but this isn’t what you would call unexpected based on what we see in the wild,” said Randall Wells, program manager for the Chicago Zoological Society. “Some make it, many don’t.”
Wells has been studying dolphins for 44 years with the Florida-based Sarasota Dolphin Research Program, the world’s longest-running research on bottlenose dolphin populations. He said 42 percent of dolphins born to first-born mothers in the wild do not survive the one-year mark. They face man-made dangers – such as getting entangled in discarded fishing gear – and attacks by other dolphins, as well as abandonment by their mothers.
While dolphin calves in zoos and aquariums don’t face the dangers of the wild, negligence by inexperienced mothers and breastfeeding problems are the main factors determining their survival rate, experts say.
Shedd Aquarium has also experienced complications in the birth and rearing of Pacific white-sided dolphins — fewer than 20 are in North American facilities. The species is relatively common in the wild, but little is known about its reproductive biology because birth rate research focuses mainly on bottlenose dolphins.
Since Shedd began a breeding program in 1995, four of the five dolphin calves have died. Two mothers who raised stillborn calves for the first time, and two other calves died after breastfeeding problems.
Shedd Aquarium’s fifth dolphin pregnancy in 2012 turned out to be the first successful birth as the calf, named Sagu, is now 2.
Tim Binder, vice president of collection planning at Shedd, said successful calf births have become more important as 70 percent of dolphins are born in accredited facilities in a zoo or aquarium.
Calves intervention is generally a last resort, he said.
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“We’re normally hands-off,” Binder said. “It’s always better and more efficient to let mommy do things.”
But a calf at Brookfield Zoo defied convention when his mother rejected him, forcing zoo staff to care for him. Magic turned one year old in October and became the country’s only successfully hand-reared calf at a zoo, Zeigler said.
Brookfield Zoo and Shedd Aquarium try to give calves a better chance of survival by placing inexperienced mothers with dolphins who already care for calves. In some cases, experienced dolphin mothers can start suckling and intervene if necessary to feed other dolphins’ calves, Binder said.
Though Allison and Noelani lost their firstborn calves, Brookfield staffers continue to expose them to experienced mothers, including 27-year-old Allie, who gave birth to last month’s third calf on December 16. Zeigler said she’s fine. “
“She does all the nursing and slipstreaming we’d expect,” he said.