Every day, thousands of people visit the Milwaukee County Zoo to see the animals they love — whether it’s the adorable otters, roaring tigers or giant elephants.
These animals live their lives on display, but most of us don’t know what happens after they die.
That prompted Bubbler Talk listener Terry Puhek-Sandberg to ask:
“What happens to the bodies of the animals that die at the Milwaukee County Zoo? The big ones and the small ones.”Bubbler Talk listener Terry Puhek-Sandberg
To find out, I took a trip to the Milwaukee County Zoo to meet Tim Wild, the zoo’s large mammal curator. In his nearly 25-year career working with zoo animals, he says it’s a question he gets asked every so often.
“Well, the first thing we do is we call the vet staff, and they confirm everything that we know and we get that animal ready to transport,” Wild says.
He says every animal that meets its end at the zoo is required to get a necropsy — a fancy word for animal autopsy. The smallest to biggest creatures you can think of get one — from starfish to giraffes. Wild animals that die on zoo grounds, like birds or squirrels, sometimes get a necropsy, too, to check for diseases that could have spread to the zoo’s inhabitants.
The dead animals are usually taken to the Wisconsin Veterinary Diagnostic Lab at the UW-Madison School of Veterinary Medicine for a necropsy.
“[Depending] on the size of the animal, [they’re transported in] anywhere from a van to a pickup truck to a larger dump truck style,” Wild says.
The science behind a necropsy
This is where veterinarians like Dr. David Gasper come in. He’s an anatomic pathologist at UW-Madison, which means he searches for clues about an animal’s health — a sort of disease detective.
As the Zoo & Wildlife Pathology coordinator, he sets up necropsy and biopsy procedures with zoos across Wisconsin, including the Milwaukee County Zoo. He also performs necropsies alongside faculty and students and teaches at the veterinary college.
Gasper gave me a tour of the necropsy lab, which he describes as “cavernous, like a gymnasium.”
The large room is filled with different-sized tables, and the walls are lined with medical cabinets, sinks and various cutting tools. Gasper says a few tables are hydraulic, which is necessary to lift heavier animals.
“It actually goes up and down, so you can imagine if we needed to reach over the top of a hippopotamus, we could lower the table down,” he says. “Especially if we needed to open up the abdomen and have to reach in and maybe look up at the diaphragm to make sure that the lungs were properly inflated.”
A necropsy starts with a “gross examination” — in which the pathologist reports everything they can see about the animal with just their eyes.
“For example, if a cheetah comes in, the first thing that we do is we go through its [medical] history — it probably had X-rays, a CT scan, or it may have had an MRI,” Gasper says. “Then we look at the actual body. So we do a complete external physical exam just like your veterinarian would when you bring your dog in, head to tail. So everything gets measured and described. Then we'll do an internal examination.”
After the internal examination, parts of the animal are preserved and processed on microscope slides to get a closer look, also known as histopathology.
“We try to match up what we found grossly and every one of those changes, whether it's normal or abnormal, it could be an age-related change, a tumor or it could be an abscess — all of those things we look at under the microscope,” Gasper says. “This giant microscope sitting next to us is where I spend three or four times as much time as I do [performing] the necropsies.”
Gasper says what veterinary pathologists find can be used to improve the care of living animals, both in the zoo and in the wild.
How animal remains are disposed of
After the necropsy is done, Gasper says there are four different ways to dispose of an animal’s remains: cremation, burial on zoo grounds, composting and alkaline digestion.
“Alkaline digestion is a process where we put the remains into lye solution under high pressure, and it dissolves pretty much everything except the bones," he says. "And the bones at the end of the day are basically dust. It's essentially a giant Instant Pot filled with lye.”
It’s important to note that animal bodies aren’t disposed of whole. Gasper says that during the necropsy process, animals are taken apart to examine each of its tissues thoroughly.
“So I will look at the ankle bones, joints and digits, we'll take the wings off, and we'll look at the joints in the wings,” Gasper says. “So the entire animal is disarticulated by the end of [the necropsy]... so what's left is much smaller portions of the remains that we can then pick a disposition for.”
Certain parts of an animal may be disposed of in different ways. Gasper says the digester is used in particular to destroy things like an elephant’s ivory tusks or a tiger’s teeth, which poachers might try to find. The Milwaukee County Zoo also doesn’t publicly disclose burial sites as a way to prevent poaching.
“If we have remains, like a skeletal system going to the museum for permanent collection, or if it's going to go back to the zoo — perhaps they want the cheetah's pelt to use it as an educational thing — we'll separate those things out,” Gasper says. “So we can have different parts of the animal going for different purposes, and then the remains can be disposed of as requested.”
The impact of zoo animals
The Milwaukee County Zoo doesn’t hold memorial services for dead animals, but Gasper says they’re still mourned.
“Animal keepers at the zoo, their lives are devoted to taking care of these animals,” he says. “They're extremely important animals to them.”
Gasper creates keepsakes for zookeepers by taking paw or hoof prints of nearly every animal that arrives for a necropsy.
“The human-animal bond is something that deeply affects everyone,” Gasper says. “They're taken care of in the same capacity, with the same concern, as I would my dog or my cat. So these [prints] are important things to give back.”
Tim Wild with the Milwaukee County Zoo says an animal’s remains continue educating people, not just in Milwaukee but across the country.
“The UW Zoological Museum takes a lot of the skeletons for their collection for educational reasons, and we might bring horns, antlers or parts of hides back for education classes,” Wild says. “There’s also a lot of samples that might go to researchers throughout the country. A lot of the species have pre-existing requests so that when an animal dies, we know that this tissue or organ can be put it on ice and sent to the researcher right away because they're doing a research project.”
Bubbler Talk question-asker Terry Puhek-Sandberg says she’s surprised to learn about all of the work that happens after an animal dies at the zoo.
“I got far more information than I ever thought was going to be possible,” Puheck-Sandberg says. “I thought it was just, ‘Put them on a truck’ and off they go somewhere. I had no idea there were all those different ways. I had no idea about the necropsy — no concept!”
So, the next time you go to the zoo, take a moment to appreciate not just the living animals in front of you, but all that happens behind the scenes when they’re gone.
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