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CLEVELAND– For the past 22 years, Mokolo has called the Cleveland Metroparks Zoo his home. Visitors can find the iconic animal in his habitat at the primate, cat and aquatics building.

But like many male gorillas, Mokolo suffers from heart disease. The 29-year-old western lowland gorilla was diagnosed 10 years ago. It posed problems for veterinarians and zoo staff: How to monitor the heart condition of a 400-plus-pound gorilla?

“Historically, whenever we had to evaluate his heart, we’d have to knock him out to do that. And to do that for an animal that’s got a heart condition, that’s not that exciting of a thing to do. There is a real risk of an adverse problem during the procedure,” Dr. Mike Selig said.

That’s why Mokolo gets bimonthly ultrasounds on his heart. It’s a non-invasive way to keep tabs on the leading cause of death for male gorillas in zoos.

With a little motivation, in the form of a bag of grapes, Mokolo learned to cooperate in the procedure.

“One of the behaviors that he is trained for is voluntary blood draw, which I’m not even good at giving my blood. It scares me every time and he loves it. It is one of his favorite behaviors,” said Julie Good, lead keeper.

Mokolo is trained for physical exams and getting his teeth brushed. He also knows how to present his chest for the cardiac ultrasound.

“He knows he’s the center of attention right now and he knows there is a bunch of fruit here. And all he needs to do is be relatively well behaved and he is going to get it. So I think that’s his major motivation,” Good said.

The procedure also required the right staff. Joan Cramer was a cardiac ultrasound technician and spent years performing echocardiograms on humans. Now she’s a volunteer at the Cleveland Metroparks Zoo.

“They said, ‘Do you want to do ultrasounds on our gorillas?’ And I said, ‘Sure.’ And they’re like, ‘They’ll be awake,’ and I went, ‘What?'” Cramer said. She said she had to train keepers to use the ultrasound probe and find the proper position on Mokolo’s body. After all, “There’s no text book on giving gorillas ultrasounds.”

It took the gorilla and the zoo staff two years to perfect the procedure, which typically takes 10 to 15 minutes.

Selig said the main reason they do the procedure so often is to keep the behavior fresh for Mokolo, who does not like the ultrasound gel. It’s a problem at other zoos, where keepers tried using applesauce until the gorilla started eating it.

“I think it really kind of points to how intelligent these animals are that they are able to understand what we are trying to do, and be able to sit there and cooperate,” Selig said.

This gorilla takes two heart medications to keep his condition under control. He also is on a very heart-healthy diet, consisting of 22 pounds of greens, plus 2 pounds of green beans and a starch mix of ground flax seed to mimic the fiber he would eat in the wild.

The Cleveland Metroparks Zoo recently started its “Future for Wildlife” campaign, which focuses on the need for education and conversation. That’s especially important for the critically-endangered western lowland gorilla.

“As you saw, he has a very dynamic personality and people really connect to him. And we hope he can serve as an ambassador for his wild counterparts,” said Elena Less, associate animal curator.