Caught on camera for the first time, this image shows the newly identified Marohita mouse lemur. (Credit: Photo courtesy of Peter Kappeler) Enlarge

The new study brings the number of recognized mouse lemur species to 20, making them the most diverse group of lemurs known. But because these shy, nocturnal primates look so much alike, it's only possible to tell them apart with genetic sequencing.

The new mouse lemurs weigh 2.5 to 3 ounces (about 65 to 85 grams) and have grey-brown fur. "You can't really tell them apart just looking at them through binoculars in the rainforest," said senior author Peter Kappeler of the German Primate Center in Goettingen, who earned his PhD at Duke in 1992.

The researchers named one of the new species the Anosy mouse lemur, or Microcebus tanosi. Anosy mouse lemurs are close neighbors with grey mouse lemurs and grey-brown mouse lemurs, but the genetic data indicate they don't interbreed.

The researchers named the other new species the Marohita mouse lemur, or Microcebus marohita, after the forest where it was found. In Malagasy, the word "marohita" means "many views."

"Despite its species' name, this mouse lemur is threatened by ongoing habitat destruction, and 'many views' of its members are unlikely," the researchers write.

The two new species were first captured by co-author Rodin Rasoloarison of the University of Antananarivo in Madagascar during trips to the eastern part of the country in 2003 and 2007. Rasoloarison weighed and measured them and took tiny skin samples for genetic analysis in the lab.

Co-authors Anne Yoder and Dave Weisrock, both at Duke University at the time, analyzed two mitochondrial and four nuclear DNA genes to figure out where the animals fit into the lemur family tree. Their genetic analyses were published in 2010, but this is the first time the species have been formally named and described.

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