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Taking A Great Ape's Blood Pressure Isn't Easy. The Dallas Zoo Has Been Trying For Years

Courtesy of the Dallas Zoo
Zoos across the country have been working to get blood pressure readings of great apes to better understand their heart health.

For the past few years, the Dallas Zoo has been trying to get an accurate blood pressure reading for their gorillas – without having to put them to sleep.

It’s part of a national effort across several accredited zoos to better understand cardiovascular health in apes to prevent heart disease in captivity.

But that’s been quite a challenge. Getting a gorilla to voluntarily put his arm into a blood pressure cuff takes months of training – and trust.

Progress but no numbers yet

Sarah Villarreal spends her mornings with a 450-pound gorilla.

She's the primate supervisor at the Dallas Zoo. She’s been training 15-year-old Juba to put his arm into a blood pressure cuff. It’s just your average cuff — the ones human doctors use at checkups or the ones you see by the pharmacy at supermarkets.

In this case, the cuff is inside a rectangular metal sleeve that fits Juba's arm.

“We have him target his arm right in it. He pushes his hand, and the sleeve comes up just above probably his wrist bone,” she explains. “And then we start inflating, while the keepers feed him to reward him.”

If Juba stays still, he usually gets grapes, dried pineapples or apricots. His favorite treat is Gatorade. But Villarreal says getting a blood pressure reading on Juba has been a years-long endeavor — and she still doesn’t have a number.

Credit Stephanie Kuo / KERA News
Sarah Villareal, the primate supervisor at the Dallas Zoo, adjusts the blood pressure sleeve for Juba, a 15-year-old gorilla.

“Gorillas haven’t had something like that squeezed on their arm so tight, so you can imagine it’s pretty uncomfortable,” she says. “They don’t know English so you can’t explain what’s happening. They just have to have trust in us.”

Heart disease threatens great apes

This delicate process is happening at several zoos across the country in an effort to track cardiovascular health in great apes worldwide, like gorillas, chimpanzees, bonobos and orangutans. It’s called the Great Ape Heart Project.

Since the project launched at Zoo Atlanta in 2010, more than 70 institutions with geneticists, nutritionists, vets and cardiologists have gotten involved. From this project sprung a huge database that researchers hope will establish reliable baseline metrics.

“We knew that great apes across the United States had heart disease and that it was actually, in males at least, one of the No. 1 causes of morbidity and mortality,” says Dr. Hayley Murphy, the vice president of animal divisions at Zoo Atlanta and director of the Great Ape Heart Project. “But no one was really looking at it cohesively across all institutions in all of the great apes."

Murphy says a combination of blood pressure readings and ultrasounds of the heart will help zoos figure out why great apes are dying of heart disease and how to prevent it. Until recently, many zoos could only safely take blood pressure while their apes were under anesthesia. 

Murphy says the Great Ape Heart Project has collected over 1,800 pieces of data that they’re analyzing.

“We don’t know what a normal blood pressure is yet. We’re going with an assumption and that’s really what it is, that it should be fairly close to what a normal blood pressure in a human is because we are great apes,” Murphy says. “But we don’t know that for sure.”

In humans, the normal range for blood pressure is anything less than 120/80 mm Hg, according to the American Heart Association. High-blood pressure — readings over 140/80 mm Hg — may indicate underlying heart disease or other systemic disease, like kidney disease.

Every gorilla is different

At the Dallas Zoo, Villarreal has been patient with the gorillas because a medical procedure can be a scary thing for them — especially since gorillas tend to be very observant.

Credit Courtesy of the Dallas Zoo
Juba, a 15-year-old gorillas at the Dallas Zoo.

“Slowly we add piece by piece by piece because it’s all about desensitizing them,” she says. “You have to assume that even if I held a blue pen and then I had a black pen the next day, they might be a little nervous. And every gorilla’s personality is very different.”

Juba has made the most progress with the blood pressure cuff. He’s the independent one, Villarreal says. She still has seven other gorillas to train: B’Wenzi, Zola, Shana, Hope, Megan, Shanta and Subira.

Until they get comfortable with the blood pressure cuff, the zoo will continue to feed them fresh food, provide enough space for them to roam and stay active and give them their daily vitamins — all the same ingredients humans need to live heart healthy.