The Knoxville Zoo lost one of its most beloved inhabitants on Christmas Day.
BiBi was one of the zoo's four Western lowland gorillas, and its only female.
"She had been feeling poorly for about a week or so, and on Christmas eve, there was swelling of her face and neck," said Lisa New, the zoo's director of animal collections.
Zoo officials decided to do an emergency immobilization in order to examine her as thoroughly as possible. That was started on Christmas Day, by Dr. Ed Ramsay and Dr. Stephanie McCain of the University of Tennessee College of Veterinary Medicine. BiBi, who was under anesthesia, died during the procedure.
"It was not exactly the way you want to spend Christmas, but you can't pick the day when an animal gets sick," New said.
A necropsy performed Wednesday at the UT veterinary school revealed that BiBi was suffering from an infection at the back of her throat that would not have been detectable and likely contributed to her illness. But her exact cause of death is not known, New said.
BiBi would have been 40 years old next month, "which definitely puts her in the geriatric category (for apes)," New said, although apes can live into their 50s.
Bibi never had offspring, possibly because of an abdominal health issue several years ago.
She had been showing signs of age in recent years, including a bout with arthritis. But she never lost her appetite, kept a feisty, active personality, and was especially vocal when anticipating being fed.
One of the three male gorillas, Ernie, 25 years old, had been BiBi's regular companion since 1989. They came to the Knoxville Zoo together in 2001, from the zoo in Denver.
Ernie clearly misses BiBi, New said.
"He's still looking for her, he's still out of sorts," she said. "He is being very quiet, and he is inhibited and confused."
Ernie is not the only one missing BiBi. The other two apes, Kwashi, 25, and Bantu, 9, have shown signs of being upset and agitated. And the zoo employees who worked with her are feeling sad as well.
"Apes are so intelligent, and they get so attuned to their keepers," New said. "It is a huge loss, to lose an ape."
It has not been determined what will be done with Bibi's remains. Zoo officials will later decide if Bibi will be replaced.
New said a number of single female gorillas may be available through the Gorilla Species Survival Plan of the American Zoo and Aquarium Association.