Curious City: The secrets of Lincoln Park Zoo's poo

We get to the bottom of a question posed by a curious zoo-goer

June 20, 2012

Jennifer Brandel

WBEZ's collaborative project Curious City takes your questions about Chicago, the region and the people (or in this case, animals) who live here. As of mid-June, the project has been live for just under three weeks and we've received nearly 100 questions.  

Every few weeks we curate groups of questions that would make for great multi-media explorations and put them up for a public vote. So far two questions have emerged victorious from that process: one asked by Katie Conrad of St. Charles concerning the veracity of Al Capone's secret tunnels; the other posed by Gerard Fleming of Orland Hills about whether there are descendants of the original Native American Chicagoans still living in the city. We have two ace reporters on those cases right now: Alex Keefe and Odette Yousef, respectively. 

Curious City is a news-gathering experiment designed to satisfy your curiosities. You ask your questions about Chicago, the region and the people who live here, vote for your favorites, and together we discover answers. It’s your Curious City. 


Bonus track! Joe Shive writes a song about our story while serenading the camels on banjo:

But in between these bigger and more time-intensive investigations, the Curious City staff are taking on some of the seemingly less complex, but no less interesting, curiosities. We started by popular demand with the question that's garnered the most comments on the site so far, which is: "What happens to all the, um, 'animal waste' from the Lincoln Park Zoo?" That question was diplomatically posed by Kelley C., of the North Center neighborhood. 

Who could answer this? 

We got excited at the prospect of getting close as possible to the source of some answers, but we received some bad news from Lincoln Park Zoo Public Relations Specialist Tiffany Ruddle: Animal waste is considered bio-hazard material, so we could not actually go anywhere near it. Perhaps that was for the best given that, the day we hoped to arrive, temps were bumping close to 97 degrees.  But, we were able to corner the very knowledgeable General Curator of the Lincoln Park Zoo, Dave Bernier.

When we asked Bernier what happens to the zoo's supply of animal waste, we found the answer more complex than we expected. First off, he explained the zoo treats feces as a "management tool" to monitor animal health. For example, zoo keepers look for obvious changes in the consistency, color or amount of feces animals produce. 

"Recently we had a camel that had loose stool. Normally they're well-formed pellets of stool — just think of chocolate-glazed donut holes," Bernier said. He explained that they looked into that camel's diet and realized it was eating too much of the free-growing plant material in its space. "So we ended up cutting back some of the plants they could reach in their exhibit and then their stool normalized again," he said. 

But the zoo keepers take an even closer look at feces, too, performing diagnostic tests in an on-site laboratory. Bernier said over the past decade technology advanced considerably and zoos can now test feces for clues into an animal's emotional health. Equipment can detect changes in hormonal levels, for example, and that can indicate whether a female animal is in her menstrual cycle. Tests for the hormone cortisol can also give keepers a sense of whether an animal feels stressed.   

Bernier said those fecal tests can be used to make important decisions, such as changing an animal's living situation. "I had a singly-housed female antelope which normally lives in groups and she seemed perfectly fine. But she was alone because her cage-mate had recently passed away," Bernier said. He wondered if introducing another antelope to her cage would ultimately be a positive change, or if it would make her more stressed out. They tested the theory by slowly introducing a new antelope friend and by saving and testing samples of both antelopess feces before the introduction and after it.

Bernier said the cortisol levels spiked and then dipped with  introduction. "But ultimately both of their stress hormone levels went down below their baselines when they were together," Bernier said. He added that without this kind of testing, they could not have known whether it was a positive or negative change because the animals showed no outward signs of stress. 

"Animals are meant to mask any kinds of injuries illnesses or deficincies because a lot of them are prey animals or have to survive in a social setting. But the hormones don't lie," Bernier said. 

Beyond the science

As for what happens to all the animal feces that aren't collected for testing, which is the bulk of it, the bottom line is that it's pretty much handled like garbage. It's hand-removed by staff, thrown into dumpsters or bags, and compacted along with all the other garbage from the zoo. Bernier said the zoo uses a waste management company to cart it away. 

Some zoos have opted to use the feces for composting, even selling the material as fertilizer in their gift shops for use in home gardening. Bernier said he's heard talk of doing similar things at Lincoln Park, but he says there are some considerable barriers to doing so. He said it would require hiring staff and the park currently doesn't have space or a back-lot for such an operation. Besides, Bernier said, "We have a hard time getting people to like the smell of our ardvark, I can't imagine they'd like this feces brewing somewhere."