The red-crested tree rat hadn't been seen by scientists for more than a century — until this May.
The guinea pig-sized creature, with a fiery-red patch of fur on its head and a long, fuzzy black and white tail, was spotted by two conservationist volunteers working in Colombia.
One of the conservationists was Lizzie Noble. "We were just heading off to bed one evening," she tells NPR's Jennifer Ludden, "and it just crawled up the stairs toward us and just quite happily sat there and looked at us."
She snapped some photos of the fuzzy interloper, but had no idea quite how special his appearance was. She emailed the photos to Paul Salaman, director of conservation at the World Land Trust in Virginia.
"When I opened up the picture I was just ecstatic," he says. He instantly knew what it was — in fact, Salaman sent a team to look for the critter in 2007 in the El Dorado Reserve in northern Colombia.
The red-crested tree rat is so important because it's only found in the Sierra Nevadas, and because it's a monotypic genus, which means it's more than just a unique species, Salaman explains. "It's at a higher taxonomic level."
He's absolutely sure Noble found the rat he's been looking for, and Noble's hopeful she'll see the little mammal again. Next they want to gather samples to test its DNA and determine the size of the population.