It hardly seems possible that in 2011 new species of vertebrates continue to be discovered. Or rediscovered. But every year, one or two reports of an unknown or forgotten bird or frog appear, usually from the tropics.

So I shouldn't have been surprised when I learned that at 9:30 p.m. May 4, at the 2,000-acre El Dorado Nature Reserve in northern Colombia, a guinea-pig-sized rodent not seen since 1898 showed up at an eco-lodge there. The red-crested tree rat stayed for almost two hours while two research volunteers took the first photos ever of a creature the world thought was extinct.

The reserve was established in 2005 by Fundación ProAves, Colombia's foremost bird conservation organization, in cooperation with the American Bird Conservancy, World Land Trust-U.S., the U.S. Fish and Wildlife Service, Fundación Loro Parque and Conservation International.

A news release from the American Bird Conservancy reported on Tuesday that the nocturnal rodent was rediscovered by Lizzie Noble and Simon McKeown, volunteer researchers with ProAves who were monitoring endangered amphibians.

The red-crested tree rat, "just shuffled up the handrail near where we were sitting," said Noble, a ProAves volunteer from England, in a written statement that included comments from several people associated with the project. Noble had been on site for just a month.

"The El Dorado Nature Reserve represents the ultimate Noah's Ark, a living treasure trove like no other on earth," said Paul Salaman, the scientist from the World Land Trust-U.S. who confirmed the identity of the species.

A major concern, however, is that much of the tree rat's potential remaining range is overrun with feral domestic cats that prey on native fauna.

"Had we not worked with our partners to establish this reserve, it is reasonable to believe this species would remain something that was only talked about in science journals," said George Fenwick, president of American Bird Conservancy.

"We are so proud that our El Dorado Nature Reserve has provided safe haven for this enigmatic little guy to survive. The discovery illustrates why we buy forested properties known to be important for endangered wildlife," said Lina Daza, executive director of ProAves.

First Published: May 22, 2011, 4:00 a.m.