In 2016, Paola Nogales-Ascarrunz, a biologist and National Geographic Explorer working in Bolivia, received a call from a local wildlife sanctuary that had just been given what they described as “a weird cat.” It came from a local man who found it as a kitten on a road near a forest. The man took the animal home, believing it to be a domestic breed. But after about a year of living with the clearly wild animal, he realized it would be better off at a sanctuary.

As the lead scientist and founder of the Bolivian Felids Research Program (Programa de Investigación de Félidos Bolivia), Nogales-Ascarrunz was intrigued. The animal had a small, scrunched-up face, short and round ears, and long whiskers. It was, indeed, too small to be a housecat, and, most notably, it was covered in leopard-like spots. So she went to visit the creature at the Senda Verde wildlife sanctuary on the subtropical flank of the Bolivian Andes.

“I took a hundred pictures of it,” remembers Nogales-Ascarrunz. “I was so fascinated.”

What she couldn’t know at the time was that this curious cat had a secret. It would become the first new species of felid (i.e. the cat family) discovered in over 100 years, according to a study published today in the journal Current Biology. What’s exciting is the discovery is not a validation of a species proposed in the distant past, nor a previously recognized subspecies raised to species status—which are both more commonly reported and important findings. No, this cat was something totally new to science.

At the time though, Nogales-Ascarrunz assumed the unusual cat was a member of the species Leopardus tigrinus. Sometimes called tigrinas, oncillas, tigrillos, or little spotted cats, this species was described back in 1775 from a single illustration of an animal seen in French Guiana and was subsequently presumed to exist across Central and South America, including, at the time, Bolivia.

But then in 2019, while she was preparing a booklet about Bolivia’s cat species, she realized the cat she’d photographed didn’t look like a guidebook reference photo from neighboring Brazil. Her tiger cat had rosettes that were much larger than the ones across the border. “This is so wrong,” she thought.

It would take another few years before Nogales-Ascarrunz developed her skills in genetic analysis to the point where she could investigate the mystery cat’s genome with any accuracy. Then, working with Eduardo Eizirik, a geneticist at Pontifical Catholic University of Rio Grande do Sul in Brazil, and study co-lead author Jonas Lescroart from the University of Antwerp, the team was able to find its distinct place on the cat family tree.

In their paper, the researchers propose the cat should be known as Leopardus tilcayo, in honor of the word local people know it by. “We asked the local people, ‘Why do you call it tilcayo?'” says Nogales-Ascarrunz, who is herself from Bolivia. “And they said, ‘I don’t know! My grandpa called it tilcayo, so I call it tilcayo.” (The name does not appear to mean anything particular in Spanish or the Quechua language spoken in Bolivia.)

So far, all scientists can say is that L. tilcayo lives in Bolivia’s Yungas forest ecoregion, which lies on the eastern slope of the Andes Mountains. But as to what these cats eat or get eaten by, how they reproduce, and many other facets of their day-to-day lives, much mystery remains. “So many basic things are not known,” says Nogales-Ascarrunz, who is co-lead author of the new study.

But the discovery is monumental, and not just because it’s the first new cat discovered since the pampas cat in 1923. The new paper doesn’t just name a new species; it redraws the cat family tree to have a lot more branches than previously thought. What’s more, the researchers hope the methods used to identify L. tilcayo may soon be used to find even more cat species spread across the world, and even transform how we protect them.

While physical differences such as tail length, rosette size, or teeth shape are always important indicators for scientists looking to delineate species, genomic analyses are increasingly the gold standard, simply because they can tell a story hidden from the naked eye.

“We’ve been working on tiger cats for 25 years or so, trying to sort out the whole genus, Leopardes,” says Eizirik. The deeper these scientists look into these cat’s genomes, the more hidden variation they find.