It's one of Kenya's most critically endangered species, and scientists want to know just how many remain.
They're doing it by looking at their stripes.
Every zebra's stripes are unique, it turns out: a natural bar code. Now with new technology, scientists can read them like a bar code as well.
At the beginning of the month, around 120 teams of scientists, amateur scientists, schoolchildren and even the U.S. ambassador to Kenya were given GPS-enabled cameras, and they fanned out across 25 square kilometers of rangeland to photograph every Grevy's zebra they saw for two days.
Organizers called it the Great Grevy's Rally
, and the zebra enthusiasts took more than 100,000 photographs.
"It's amazing," Princeton professor Daniel Rubenstein said, snapping pictures. "Historic. Magic."
Rubenstein, one of the chief researchers organizing the rally, is taking the photos back to the United States to be analyzed.
Researchers feed the photos into a "hotspotter" computer program, which is able to identify animals based on coat design.
The computer focuses on where the stripes meet and branch, such as where the leg meets the body, the backside and the face.
Once identified, researchers can understand when a particular Grevy's was spotted, and where.
That information can make conservation programs smarter.
"We will be able to tell governments that this type of landscape is where they like to be. Let's preserve it. This landscape is an important corridor. They move through there, they don't stay there, but without it they can't get from A to B," said Rubenstein.
Once that is done, researchers plan to use hotspotter technology to study the traits of other animals, including giraffe's spots and elephants' ears.
The Great Grevy's Rally lasted for two days, so the scientists expect resightings of the same animal. The rally will help in estimating population size.
"So we're going to get a very accurate estimate of the population size in a particular area. Then we're going to aggregate this for Kenya, and for the first time we're going to know how many Grevy's zebras there are," Rubenstein said.
From the pictures, scientists will also be able to tell the sex and age of the animal.
A Grevy's zebra is about 50% larger than a plains or common zebra. It also has thinner, more intricate stripes, and a white belly and buttocks.
Most Grevy's zebras also live in the arid lands of Kenya, which don't fall inside the country's protected national parks, adding to the need to get local communities to protect them.
Perhaps oddly for an East African animal, it's named after a 19th-century French president.
It was initially named the imperial zebra, until a skin was presented to France's then-President, Jules Grevy, and naturalists decided to name the animal after him.
"They are one of our most beautiful endangered species, but also very emblematic of this part of the world," said Dino Martins, director of the Mpala Research Center, a Kenyan organization that partnered in the study.
That beautiful hide has turned out to be a particular disadvantage, since it's often used to make ornate carpets.
U.S. Ambassador Bob Godec explained as he scanned the bush for animals during the rally.
"One of the reasons there are fewer Grevys is because they have been hunted over time and the structure of their society doesn't protect them as much," he told CNN. "Unlike the common zebra, the Grevys don't hang out in large groups, so they are more subject to hunting and other challenges."
The U.S. government is funding large anti-poaching and wildlife trafficking initiatives in Kenya and across the continent.
Census estimates will take weeks, but researchers say they will pay off in the end. With the data calculated, they will be able to advise governments how to best preserve the Grevys.
And they will be able to tell Kenya, and the world, how worried they should be about these rare, disappearing animals.