A Fecal Pellet’s Worth A Thousand Words

Scientists can learn a surprising amount about an animal just by analyzing its poop

Important information about a cheetah can be found in its feces. Mehgan Murphy, Smithsonian's National Zoo via Flickr

Scat, dung, guano, frass, manure, night soil. We have a lot of fancy words for feces, don’t we? Perhaps it’s because even uttering the word poop somehow feels unclean.

But for scientists, poop is not something to recoil from—it represents unexplored data. Each nugget, cow patty and meadow muffin is brimming with information that can be used to divine all sorts of interesting things about not only the animal that left it, but also the world in which that animal lives.

For instance, a fresh splat of bear scat full of berry seeds and fruit stones might be used to predict how cherry trees will adapt to climate change.

Researchers recently scoured the mountainsides of Japan for scat from Asiatic black bears, particularly deposits that were laden with cherry pits. By analyzing forms of oxygen atoms found within the pits, the scientists could determine at what elevation the seeds originated from and how far the bears carried them before excretion. The bears are carrying the seeds higher into the mountains as the seasons change, the team recently reported in Current Biology. This means that as climate change warms the world below, the cool-loving cherry trees may be able to escape by colonizing new territory on the mountain slopes.

But this is just the tip of the dung heap when it comes to poop science.

At the Smithsonian Conservation Biology Institute, reproductive biologist Janine Brown uses plenty of poop in her studies of hormones and what they say about animals’ breeding cycles and stress levels.

“Hormones circulate in the blood and are secreted in urine, feces, saliva and hair,” says Brown. “But I will say, for better or worse, most of the work we do relies on fecal collections.”

In one study of captive clouded leopards, Brown’s lab determined from scat that the cats became stressed if they weren’t provided with hiding places to escape the peering eyes of zoogoers. What’s more, clouded leopards that are housed in tall enclosures—that is, habitats where the cats have somewhere to climb—have much lower levels of stress hormone than those without.

Perhaps that’s not so surprising for a species that spends most of its life in trees, said Brown. What is surprising is that you can learn all of that from a piece of poop.

Another fecal hormone study showed that female cheetahs can be housed together in the same enclosure without any fights breaking out, but something about the arrangement suppresses the cats’ reproductive cycles. Similarly, a closer look at the poop of Pallas’s cats—everybody’s favorite frumpy recluses—revealed that bright lights can discombobulate their reproductive cycles.  

Obviously, working with poop all day can have its drawbacks, and Brown says some samples are worse than others. Herbivore dung is mostly made up of undigested plant matter, so it has a mild smell. But carnivore crap can be quite “challenging,” she says.

“You’ve got people working on species like fishing cats, which of course eat fish, and their poop reeks to high heaven,” says Brown.

Odor doesn’t seem to bother Jesus Maldonado, a research geneticist with the Smithsonian’s National Museum of Natural History. What gets him down are exoskeletons.

Maldonado’s studies rely on teasing genetic markers out of fecal samples to learn about the animals that left the material and what they ate. He’s found that something about chitin—the material insects and crustaceans use to make their shells—can interfere with the reactions required to perform his experiments. This makes doing genetic work particularly difficult on certain animals, such as river otters, which eat a lot of crayfish.

River otter
The feces from a river otter can be difficult to analyze because the animals eat a lot of crustaceans. Jim Jenkins, Smithsonian's National Zoo via Flickr

But Maldonado is not easily deterred. He has conducted fecal sample analyses on everything from kit foxes and coyotes to tigers and jungle cats. With enough samples, he can puzzle out estimates of population size, gender ratios and the interrelatedness of all the animals in a given area. He can peer into a turd and tell you not just what species that animal is eating, but what parasites and pathogens it might be carrying.

“You can get all that information from just a sliver of poop,” says Maldonado. “It’s an incredibly powerful thing.”

Best of all, unlike studies that rely on hair, teeth or blood, this information comes at no cost to the animal, Maldonado notes. For animals in captivity, that means less handling and probing. And for animals in the wild, there is no stressful trapping or darting. Scientists benefit, too, since they can conduct their work without wasting time and resources trying to find rare or elusive creatures.

“Noninvasive” sampling also comes in handy when trying to gather information about an animal that can weigh 14,000 pounds and has 10-foot spikes growing out of its face, as Brown and Maldonado recently learned while working on a study of African elephants.

There’s no way they would ever be able to collect urine, saliva or blood from a whole herd of elephants in the wild, says Brown.

DNA analysis is just one way to determine the owner of a fecal sample. And in more controlled circumstances, such as those found in a zoo, researchers may turn to a less technical approach. Like glitter.

If keepers know they want to test the fecal samples of an animal that’s being housed with other animals, they will sometimes lace its food with the same stuff your toddler uses to make Mother’s Day cards. Best of all, glitter comes in multiple colors, which means keepers can work with several animals at once. One study conducted at the National Zoo in Washington, D.C., managed to keep track of 10 different lions using nothing more sophisticated than sparkly scat.  

In fact, the first “fecal marker” used by zoo personnel was even more commonplace. During the clouded leopard study, Brown says they were looking for a way to differentiate between the feces of male-female pairs.

“This was back when my kids were little,” says Brown, “and I noticed that when they were drinking grape Kool-Aid, it turned their poop green.”

You see, where most of us would see a soiled diaper, scientists like Brown see a potential wildlife management breakthrough. 

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