How This Young Bonobo Survived Two Brain Surgeries

Neurosurgeons and animal docs teamed up to save the life of Milwaukee County Zoo’s endangered bonobo.

When Qasai, a precocious, fun-loving 5-year-old male bonobo, started clinging more to his mother and tugging at his lip and face, his keepers at the Milwaukee County Zoo became increasingly worried about a potential health issue. 

“The keepers are very in tune with their animals, and they noticed that Qasai was not coming as readily to them,” said Dr. Pam Govett, the zoo’s senior staff veterinarian. “When I examined him, he also had kind of a head tilt.”

Tests eventually traced the problem to a pair of abscesses in Qasai’s brain, one near the surface and another more troublesome one deep in the organ that required a pair of time-consuming and groundbreaking surgeries to address the issue.

In the weeks to come, a team made up of the zoo’s veterinary experts would join forces with neurosurgeons and others who have perfected their skills on human patients to save Qasai’s life. 

Photo from Qasai’s third birthday party in 2019; Photo courtesy of the Milwaukee County Zoo

At first, Govett figured Qasai’s troubles stemmed from a dental issue, so she started him on a course of antibiotics and ibuprofen.

“He seemed to do better but then when the ibuprofen waned, he’d go back to pulling at the side of his mouth and touching the side of his head,” Govett said.

After a week with little or no improvement, Qasai underwent a more intense physical examination along with a CT scan at a local specialty veterinary clinic. 

“The reason we wanted to do a CT is oftentimes inner ear infections that you might not detect during a physical exam could be causing the pain,” Govett said.  

The scan didn’t appear to show anything unusual on initial review.



The zoo sent the advanced imaging studies to the radiology department at the University of Wisconsin-Madison School of Veterinary Medicine. Radiologists there studied the scans and discovered two lesions in the left cerebellum of Qasai’s brain. 

Next, Dr. Leighton Mark, head of neuroradiology at Froedtert & The Medical College of Wisconsin examined the imaging study. He recommended an MRI with spectroscopy, which sends magnetic waves into the brain.

“That’s when we knew it was consistent with an abscess, which is basically pus formation due to an infection,” Govett said. 

Concern for Qasai’s health began to grow after the MRI revealed that the abscesses had expanded the cerebellum to the point where it threatened to herniate through the back of the brain, which could have been fatal for Qasai.

Zoo staffers then met with Dr. Wade Mueller, a neurosurgeon at Froedtert, who quickly mobilized his team for an initial surgery on March 7 that lasted about five and a half hours. 

“Dr. Mueller coordinated this effort to save Qasai’s life,” Govett said. 

Mueller offered a simple explanation as to why he agreed to be part of Qasai’s surgical squad. 

“I did it because it’s cool,” said Mueller, who once performed a biopsy on a larger primate but has spent nearly his entire career operating on humans. “My wife is also a big fan of animals and she’s a doctor, too. I had an opportunity that plays well at home and it’s something I was interested in.”

Qasai in the treatment room before surgery.; Photo courtesy of the Milwaukee County Zoo

The close genetic relationship between bonobos and humans made for an easier transition of professional duties. But that didn’t mean any surgery on Qasai could be carried out absent any challenges, including accessing the deeper abscess. 

Mueller felt it best to perform the surgery at the zoo. 

“My thought was that the animal is best taken care of when their handlers are there,” Mueller said. “That was the challenge. But the people at the zoo were fantastic. It wasn’t dramatically more difficult than regular operations I do. But it was an away game instead of a home game.”

The first surgery involved making a small incision, known as a burr hole, in Qasai’s skull to access the surface-level abscess. Medical personnel drained the pus and took a culture from the abscess before sealing the hole. 

The team opted not to operate on the deeper abscess in the hope that it would resolve with additional doses of antibiotics.  

“There is a higher risk going deeper into the brain,” Govett said.

A collective sigh of relief came after a pathologist determined the abscess to be benign.

Qasai in brain surgery; Photo courtesy of the Milwaukee County Zoo

After surgery, Qasai remained in a medically induced coma for five days so caretakers could administer intravenous antibiotics while allowing the surgical site to heal.

“You can’t just tell a small, young primate not to pick at his stitches,” Govett said.

Qasai remained in a small enclosure after surgery to prevent him from falling and injuring his head. He continued to receive antibiotics and three weeks after the surgery a follow-up MRI showed slight improvement in his condition. However, the abscesses hadn’t completely disappeared. 

Because of the social nature of bonobos, keepers kept Qasai company and watched over him around the clock. Trish Khan, the zoo’s curator of primates and small mammals, spent about three months watching over Qasai throughout the night while periodically administering medication.

“It’s a huge emotional investment, but he’s a very special little boy,” Khan said. 

When it became apparent that Qasai wouldn’t soon be returning to his troop, the cooperative and peaceful groups in which bonobos live, keepers brought in Nadine, a 7-year-old female bonobo, to provide companionship. 

“It was a great decision. They really get along well,” Govett said. “The reason we didn’t put him back with the troop right away is we knew we’d have to pull him back out again. That’s a stressful situation for the animal.” 

“Qasai and Nadine immediately started playing together, swinging on ropes,” she said. “They were always hugging and cuddling. It’s been a really sweet relationship to watch.”

Qasai continued to receive oral antibiotics for another four weeks and then went back for yet another MRI.

“Unfortunately, while the lesions weren’t as bad as they had previously been, they had a grown a little bit,” Govett said. “This is not uncommon with children with brain abscesses. You might have to go back in two or three times, but this is a different situation. With kids, you can tell them to sit still and give them an IV with antibiotics for six weeks. You can’t do that with a bonobo.”

The team agreed that Qasai would need to undergo another surgery on May 2.

Qasai in the treatment room before surgery.; Photo courtesy of the Milwaukee County Zoo

“A decision was made to be aggressive and I’m glad,” Govett said. 

This time, the medical team used a surgical operating microscope, which provides high-quality magnified and illuminated images. A second Froedtert neurosurgeon, Dr. Nathan Zwagerman, joined the squad that would operate on Qasai. 

Surgeons first removed the superficial abscess and then took out the deeper one in the five-plus hour surgery.  

“I was able to look in and I thought how is this animal going to survive? I could stick my finger into the hole in Qasai’s brain. But the surgeons did such a great job,” Govett said.

Ever so resilient, Qasai was up and moving around a short time after surgery. 

Qasai received strong pain medication and injectable antibiotics along with a small dose of steroids to decrease brain swelling. Despite a generally positive prognosis immediately following the second surgery, the medical team remained cautious.   

“This is actually the first time that I’m aware of that a brain abscess has been diagnosed prior to death in a non-human primate,” Govett said. “It’s a very novel thing. It’s really been exciting to have this whole medical team come together for Qasai.”

As part of Qasai’s recovery, the zoo worked closely with the neurosurgeons while also bringing in Dr. Rainer Gedeit, a specialist in critical care and pediatrics at Children’s Wisconsin, to direct post-surgical care.

“We had a lot of questions about things like electrolyte imbalances,” Govett said.

Handlers also consulted with physical therapists who designed an exercise program for Qasai while he recovered at the zoo’s on-site hospital. 

For his fifth birthday on May 23, the zoo’s animal care staff treated Qasai to special treats and enrichment activities.

Qasai made a strong recovery from the second surgery and after a few more weeks reunited with his troop on June 5 after an MRI revealed some scarring on his brain, but no abscesses, leading to a positive prognosis.

At first, he was placed on a cushy bed of wood wool inside a mesh enclosure in the zoo’s Apes of Africa building and allowed to interact with his mother Claudine, grandmother Laura, brother K2 and uncle Murph. 

“Laura was there right from the get-go, vocalizing very loudly,” Khan said.

When the keepers opened the door to the enclosure, Qasai “flew into his mother’s arms,” she said. 

The Milwaukee County Zoo is home to the largest bonobo population in North America, with 19 in all, including Qasai, who was born at the zoo. Claudine is prominent in the troop, which are matriarchal in nature, which also means that Qasai, as her son, takes on a high-ranking role.

“The reason bonobos are so special is that they share 98.7% of the genetics of humans,” Govett said. “They are our closest living relatives, even closer than chimpanzees.”

Bonobos are native to the Democratic Republic of the Congo and are an endangered species due in large part to deforestation of their native habitat. Civil unrest in the country also has resulted in critical food shortages, leading to a demand for the meat of the bonobos. Their current estimated population in the wild stands at about 20,000, according to Khan. 

The species is also elusive and hard to study, often living in the dense tropical forest canopy. 

“What we do here at the zoo is evaluate the animal and behavior more closely than could be done in the Congo and hopefully what we find here can help the native population,” Govett said.

She flashed a broad smile as she spoke about her interactions with Qasai. 

“He’s a sweetheart. I have a 5-year-old myself. The comparisons are adorable,” Govett said. “He’s a very spunky animal. One of my techs calls him popcorn because he’s always jumping around. He’s very active.”

Govett regularly checked on Qasai during his recovery. 

“He loves fruit, so I would bring him a strawberry or a blueberry,” Govett said. “Sometimes at the end of the day I’m stressed, too, and I’d go in there and sing him lullabies and that calmed me, maybe more than him. He’s just a really incredible animal. All of them are, but it’s during these times that you develop that special personal relationship.”

Khan described Qasai as a mischievous acrobat. 

“He’s always flying around,” she said. “He’s also incredibly inquisitive, which most young bonobos are at that age.”

It’s been an emotional rollercoaster for those who know and care for Qasai, Khan said.

“The keepers adore him,” she said. “Not all bonobos at that age are what we would call sweet. Some are a real handful, but he definitely has everybody’s heart tied up. That was only amplified by all the one-on-one time we spent with him and investing so much in giving him the best chance that we could to survive all of this.”

Mueller had high praise for all those who volunteered their time, including Staci Gaulke, a neurosurgery service coordinator at Froedtert.

Photo from Qasai’s third birthday party in 2019; Photo courtesy of the Milwaukee County Zoo

“She’s the nurse in charge of neurosurgery services in the operating room. The nuts and bolts of the procedures,” Mueller said. “She was deeply involved in pulling this off.”

Mueller also noted the contribution of Thomas Davis, a long-time neurosurgery technician at Froedtert who retired last year. 

“He’s very good at assisting in surgeries so I asked him to come along,” Mueller said.

Others who served as part of the medical team included: veterinary surgeon Connie Hurley and veterinary neurologist Cassandra Williams; Carrie Schroeder and Kyle Bartholomew of the University of Wisconsin-Madison Veterinary Anesthesiology Department; Lakeshore Veterinary Specialists veterinarian Andrew Linklater; anesthesiologist Catherine Drexler from Froedtert & the Medical College; and professionals from the Wisconsin Veterinary Referral Center.

Team members who partnered with the zoo’s medical personnel provided their services free of charge. 

Operating on Qasai went beyond a mere sense of accomplishment for Mueller.

“I operate on humans all the time and I take it very seriously,” he said. “And I took this very seriously, too, but it had a little bit of a children’s storybook flavor to it. The fun was the teamwork. We melded together very well. The veterinarian crew at the zoo is awesome. They are cool people. It was great getting to know them.” 

Most important, the medical team is confident that Qasai’s brain health issues have been resolved through the novel surgery.

“He really had the cards stacked against him,” Khan said. “This surgery had never been performed on a bonobo. We really didn’t know what the outcome would be, so we are all just thrilled.”



Rich Rovito is a freelance writer for Milwaukee Magazine.