What makes a chimpanzee's heart skip a beat? That's what Dr. Kathryn Gamble is asking the chimps themselves to help her find out.
Chimpanzees at the Lincoln Park Zoo in Chicago, where Gamble is chief veterinarian, eat a healthy diet and get plenty of exercise, but they still can suffer from heart problems. Gamble saw that firsthand in 2008 when a female chimp named Donna died after a health exam. The death from a hidden heart rhythm problem made her think: How can we catch warning signs earlier, before it's too late?
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The chimp named Donna "had some really serious heart disease that had been invisible, completely invisible, on the ultrasound" that was used during the exam, Gamble said. "Because we couldn't see that using ultrasound, I wanted to find another technique that would allow us to measure what was going on."
She found the technology she needed in a small heart monitor. It is designed for human use, but Gamble implanted the devices in eight chimps at the zoo. Three animals so far have been trained to present their chests to a scanner to upload data from the monitors.
Other chimps, such as a male named Optimus Prime, are still learning the ropes. He gets treats offered by zoo staffers as rewards when he cooperates with a mock health exam.
More than one-third of deaths in adult zoo chimpanzees are caused by complications of heart disease, Gamble said. It's unclear how many are from heart rhythm problems, but that seems to be the predominant condition, rather than the clogged arteries more common in humans.
It's also unknown what's causing cardiac trouble in apes, Gamble said, or whether it's more common in zoo apes than in wild animals. The problem could be linked to diet or physical activity or stress.
Data from the implanted devices is uploaded every 10 to 14 days from the chimps who've learned to cooperate. The zoo also collects information about the chimps' behavior and activity levels, so the heart monitor data and the behavioral data can be analyzed together for patterns.
"All of the apes are watched virtually every day and have been for the past seven years, so we have reams and reams of behavioral data," said Steve Ross of the zoo's Lester E. Fisher Center for the Study and Conservation of Apes.
"We know how they act with each other. We know about their activity levels. We know how much of the exhibit they're using," Ross said. "So it's a really unique opportunity to match what we know about their behavior with what's going on inside them."
Someday, the research may lead to new recommendations for zoos on chimpanzee diet or physical activity, said Dr. Hayley Murphy, director of the Great Ape Heart Project based at Zoo Atlanta.
"The work at Lincoln Park Zoo is really groundbreaking," Murphy said. "It's super cool and I think it will tell us a lot."