In addition to Hank, six other animals died recently at the zoo.
• A male muntjac, a small type of Asian deer, died after a visitor at the Chattanooga Zoo noticed the animal was struggling in the koi pond. The deer apparently had been frightened by barking dogs, which were brought by visitors to the zoo on "pet night."
The deer died of hypothermia, zoo officials said. The zoo board decided after the incident to ban dogs from the zoo.
• A second male muntjac involved in the incident died days later of a twisted colon. Board member and veterinarian Mickey Myers said the twisted colon was not connected to the dog-barking incident.
• Two marmosets died while their regular keeper was off and another keeper was not scheduled to tend to them, the whistleblowers said.
A U.S. Department of Agriculture inspector, checking the zoo in wake of complaints and with a zoo invitation, confirmed that zoo logs stated that the marmosets indeed were not attended for two days.
Myers has said final necropsies are still pending on the marmosets, but he does not believe they died from going two days without food. He said preliminary necropsies show they had a type of hepatitis virus commonly carried by mice.
• Two baby cub snow leopards were found dead shortly after being born outside in freezing temperatures while the cats were locked outside their shelter.
USDA inspection reports confirm the female leopard was locked with the male leopard outside the den. Zoo veterinarian Tony Ashley said he performed necropsies on the leopard cubs and could not determine if they were stillborn or died later.
A third cub, born later inside the den, survived and made her six-week debut at the zoo last weekend.
Hank the chimpanzee died in January at the Chattanooga Zoo from fluid around his heart and "sudden cardiac death," according to necropsy results.
"We know he had a great life here at the zoo, and the report points to the fact that Hank was simply facing challenges of aging," said Chattanooga Zoo Director Darde Long in a prepared release Monday.
The necropsy on Hank, who was 42 when he died, was performed by the University of Tennessee College of Veterinary Medicine's Department of Pathobiology.
Hank's final diagnosis was "Idiopathic myocardial fibrosis and sudden cardiac death," according to zoo veterinarian Tony Ashley.
"Myocardial fibrosis occurs when the normal muscle tissue of the heart is replaced by scar tissue," Ashley said. "This prevents the heart from pumping properly, and it interferes with the electric pathways through the heart. Hank died because fluid built up in the sac around the heart."
The veterinarian said the fluid prevented Hank's heart from filling properly.
"If the heart cannot fill with blood, it cannot pump blood. This is called cardiac tamponade, and it is lethal within minutes," Ashley said. "Alternatively, the scar tissue could prevent the electric impulses from going through the heart properly. This could have caused a fatal arrhythmia."
Hank was found dead on the morning of Jan. 24. Zoo officials said he had appeared to die in his sleep. He was the seventh zoo animal to die in a period of about a month over the holidays.
The chimpanzee's unexpected death, coupled with the other recent zoo animal deaths, caused an outcry from a number of former zoo keepers and former zoo volunteers.
Some whistleblowers wrote to regulators and told the Chattanooga Times Free Press that they had concerns about the management and incidents at the zoo.
The U.S. Department of Agriculture's Animal and Plant Inspection Service made a follow-up inspection and cited the zoo with several violations of animal care, including feeding concerns.
On Monday, Ashley said chimpanzee research has shown that 81 percent of chimpanzees have some evidence of the heart problems shown on Hank's necropsy, and one in three die of sudden cardiac death because of the disease.
"So it is a fairly common disease in common chimpanzees," he said. "The disease is called 'idiopathic' because there is no known cause for the scarring."
Ashley also said there are no signs of sudden cardiac death in chimpanzees, except at the time of the death.
"Hank did not have your typical heart failure found in people, where there is a lot of coughing or abdominal swelling beforehand," Ashley said.
The release of Hank's necropsy was contained in an e-mail from zoo spokeswoman and board member Robin Derryberry. She said a fax of the necropsy would follow, but it was not received Monday.
Sandra Harbison, spokeswoman for the University of Tennessee's College of Veterinary Medicine, said she was awaiting zoo permission to talk about the necropsy.