Enter children’s doctors, who are used to dealing with wriggly and unco-operative patients.

In 2000, Bodley and her team approached cardiologists at the Royal Children’s Hospital for help monitoring the hearts of great apes while they are awake.

Director of cardiology at the Royal Children’s Hospital, Professor Michael Cheung, said his team was “familiar with examinations where the patients aren’t completely co-operative”.

“There has to be a greater level of patience and acceptance that you may not be able to get all the images that you want, and you may have to do it in a different order to how you typically acquire the images,” he said.

After years of training with both hospital and zoo staff, two gorillas – Werribee Open Range Zoo’s Motaba and Melbourne Zoo’s Otana – now willingly allow staff to use hand-held devices to conduct echocardiogram and electrocardiogram ultrasounds.

Motaba – who at 40 is considered geriatric – was diagnosed with clinical signs of cardiovascular disease in 2007, making regular monitoring crucial.

In audio recorded at Werribee Open Range Zoo, Motaba can be heard letting out a bone-chilling grumble as he pushes himself towards the bars separating him and his keeper, to allow them to examine his heartbeat.

Motaba has already outlived many of his wild counterparts, who have a life expectancy of 35. In captivity, if his heart disease is kept in check, he could live for another 20 years.

Unlike an adult human patient, for whom an echocardiogram could take 30 minutes, vets and sonographers are limited by the gorillas’ patience in tolerating ultrasound testing. Some tests take multiple attempts.

“This is an entirely voluntary process on the part of the gorillas,” Bodley said. “We’re asking them to do something using positive reinforcement techniques like some food … if Otana does not want to sit for his cardiogram on a particular day, then he doesn’t do it.”

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Despite the challenges, the success of the consent-led approach – borne from four years of training and careful collaboration – has been hailed by zoo staff as remarkable.

“I could never have imagined us being able to achieve this diagnostic procedure with an animal volunteering,” Bodley said. “The amazing development of training as a way of doing proactive health monitoring in zoos is just really remarkable.”

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