Look at your navel. Do you know what it is? It is a scar, or mark, that remains where your umbilical cord attached you to your mother before you were born. Your navel is technically named the umbilicus and is commonly called the “belly button.” All humans have them. Other mammals have them as well, although theirs are usually smooth or flat—often just a thin line hidden by fur.

Look at your belly button again. Are you an “innie” or an “outie”? If you have an indentation or depression—if you can put the tip of your finger in—then you are an innie. Most people are innies. If you have a bump or protrusion, then you are an outie.

What do you think is in your belly button? In 2011, a team of scientists launched the Belly Button Biodiversity Project to find out. These scientists were from the biology department of North Carolina State University (NC State) and the Nature Research Center (NRC) at the North Carolina Museum of Natural Sciences. “We're interested in helping people understand and appreciate the microscopic species with which we share our daily lives,” says team member Dr. Holly Menninger, an entomologist and NC State’s director of public science. Usually when we think of body bacteria, she says, we think of the bad microbes that cause illness. But in reality, most of the organisms on our skin are our first line of protection from pathogens—organisms that can cause disease.

It’s a Jungle in There!

For this project, people wiped cotton swabs in or on their belly buttons. The first group of 66 samples was collected from visitors to the museum and other participants. Dr. Meg Lowman, a team member and director of the NRC, says, “This project was not only inclusive of all visitors, but also helped teach them about the challenges and techniques behind the collection of scientific data.”

The research team discovered that belly buttons are very diverse habitats! In total, they discovered 2,368 different species. More than half of those may be new to science. “The belly buttons reminded me of rain forests,” wrote Dr. Rob Dunn, a biologist at NC State and the project’s leader, in a blog post. “They differed more than we expected.”

Each participant’s belly button hosted about 67 different species. Yet not one was common to every person, and only eight were found on at least 70 percent of participants. The team considered factors including age, sex, and whether the person had an innie or an outie. Despite this research, the scientists can’t quite explain why some belly buttons had a particular species, while others did not. The researchers did learn, however, that the eight most common species were among the most abundant. This means that if a species was found in a belly button, that belly button usually had a lot of that species!

In November 2012, the team published their first findings in a paper called “A Jungle in There: Bacteria in Belly Buttons are Highly Diverse, But Predictable.” They will soon have 600 samples from people all over North America. “With this variety, we may well begin to explain the differences among people in terms of the intimate forests of their umbilicus,” Dunn wrote.

Citizen Science

Menninger’s team is passionate about engaging people of all ages in the whole process of science, from collecting and analyzing data, to making observations, producing new hypotheses, and determining what to study next. Both NC State’s biology department and NRC have multiple citizen science initiatives to get the public involved. These include Armpit-pa-looza, a study of armpits; a census of camel crickets (also known as “sprickets”); and School of Ants, which is identifying ants and mapping their biodiversity across the United States.

“One doesn't have to go off to the Amazon rain forest to experience biodiversity. It exists in your backyard, your basement and even your belly button!” says Menninger. “This biodiversity is critical to the functioning and health of our ecosystems—be that on our skin, or our forests and streams.”

So, will you be a citizen scientist? Join up here! Armpit Microbes! Camel Cricket Census! School of Ants!