As the moon rises on the island of Sulawesi in Indonesia, saucer-eyed primates with a face like Yoda emerge in search of food. Males and females sing to each other in a cacophonous duet, strengthening their bonds and advertising territories.
Now, these songs have helped scientists identify two new species of these tiny tree-dwellers, called tarsiers, according to a study released on May 4, or Star Wars Day.
The newly named critters, Tarsius spectrumgurskyae and T. supriatnai, bring the total number of tarsier species on Sulawesi to 11. (See a picture of a new tarsier species found in 2014.)
“They look almost identical, but their calls are very different,” says study leader Myron Shekelle, a primatologist at Western Washington University, whose team confirmed the discovery with DNA analysis of 10 previously collected specimens.
Tarsiers evolved from a diurnal, or daytime-dwelling, ancestor, splitting from other monkeys and apes around the time the dinosaurs died out, about 64.2 to 58.4 million years ago. Once found across Asia and North Africa, about 18 known species of tarsier are now scattered across the islands of Southeast Asia—which more likely out there. (See "New Species Found: Thai Fossils Reveal Ancient Primate.")
Tarsiers have some unusual physical traits. Their diurnal ancestor lost the tapidum lucidum, a reflective layer of cells on the back of the eye that helps amplify light. So, to compensate, tarsiers evolved massive eyes—each is as big as its brain—that allow the creatures to see at night. Because its peepers are too big to rotate in their sockets, the tarsier rotates its entire head, similar to the owl—the only primate that can turn its head 360 degrees. (See a picture of the tube-nosed bat that's also compared to Yoda.)
“They always startle me in the jungle,” says Rafe Brown, a herpetologist at the University of Kansas who was not involved in the study. “You can see the glowing eyes of wild cats even in the dark, but not tarsiers. They’re like little furry forest goblins.”
Living in trees has also made tarsiers very nimble: Though adults weigh only about four ounces, they're skilled jumpers.
“No one expects an animal that’s the size of a stick of butter can jump three meters from a standstill,” says Shekelle, who received funding from the National Geographic Society. The new study was published in the journal Primate Conservation.
Race Against Time
Tarsiers look alike—even to their ancestors. “I’ve seen fossils from 50 million years ago that look nearly identical to modern tarsiers,” says Gursky.
But their physical similarities have also hindered efforts to identify new species, including on Sulawesi.
Sulawesi originated as several different islands that merged together into a single landmass around a million years ago, and geological evidence indicates that a species of tarsier evolved on each ancient island before the merger. (See "Photos: 'Smiling' Tarsier Among New Most Endangered Species.")
But he's in a race against time to identify them before they go extinct due to deforestation.
“Some probably already have,” he says.
Follow Carrie Arnold on Twitter.