Science News for Students: The Littlest Lemurs

Ziggy is not amused.

The tiny creature has already been trapped in a box and hauled through the rainforest. Some of his hair has been clipped. Now, he crouches on the floor of a cage, while three pairs of human eyes stare at him. One of those pairs is mine.

"He's so cute!" I say. But wide-eyed Ziggy clearly doesn't feel the same way about me. Still, he stares right back.

Ziggy is a mouse lemur, one of the smallest primates in the world. He's related to monkeys, gorillas, and humans, but he looks like a hamster. Weighing just 52 grams (1.8 ounces), he's actually heavier than the average mouse lemur.

Like nearly all wild lemurs, Ziggy lives in Madagascar, a Texas-size island 300 miles off the eastern coast of Africa. Scientists know surprisingly little about Madagascar's mouse lemurs, but they're busy collecting information. One reason is that if we learn more about mouse lemurs, these researchers say, we'll know more about ourselves.

Our earliest relatives might have looked like Ziggy and his pals, says Anja Deppe. She's an anthropology graduate student at Stony Brook University in New York. She studies mouse lemurs in Madagascar's Ranomafana National Park.

"We're using them as an ancestral primate model," she says. Mouse lemurs, along with other types of lemurs, might help explain what first set primates apart from other creatures.

Rodents and mouse lemurs, for example, look alike and are about the same size. But mice tend to be afraid of everything, Deppe says, while mouse lemurs fear only certain things.

This ability to differentiate is a sign of intelligence. Humans have it. For example, you know that a real bear is scary but a teddy bear isn't. It's still not clear, however, how mouse lemurs decide what to fear.

"What's interesting is that different mouse lemurs do different things," says Patricia Wright, an anthropologist and lemur expert at Stony Brook University. "That means they have the ability to learn."

Night life

Mouse lemurs are active at night, so Deppe and her coworkers venture into the forest just before sunset every day. They place banana slices inside 40 lemur traps scattered along a trail. After dinner, the scientists return to the traps.

The researchers close the traps that are still empty so that banana-loving lemurs won't get stuck in them overnight. They carry the traps with lemurs back to the lab. For the next 2 or 3 hours, the animals take part in the research team's experiments. Around midnight, the scientists return the tiny creatures to the wild.

In the lab, Deppe begins by checking to see whether any of the lemurs has a tag. During 4 years of research, she's tagged more than 80 lemurs and given them names, such as Foxy, Mickey, Medusa, Queeni, Roxy, and Anja. She assigns a new name and number to any lemur that doesn't already sport a tag.

Certain lemurs tend to show up again and again, so every night is like a minireunion.

"Omigod, it's Ziggy!" Deppe cheers. "I'm so glad we got Ziggy. He has beautiful green eyes, and he's so good in experiments."

Next, Deppe records each lemur's weight, sex, and eye color. She then places the animal into a clear plastic cage with snakeskin, feathers, or other objects. She uses these particular objects because she's studying how each lemur reacts to the sights, smells, and sounds of three of its major predators: snakes, owls, and mongooses. Because of the tagging system, she can see whether a certain lemur's behavior changes over months or years.

As much as half of the mouse lemur population gets eaten each year, Deppe says. So, recognizing predators is an important behavior for these animals. And the need to survive might have pushed the first primates to develop sharp eyesight. Along with hands that grip, keen vision is one feature that sets primates apart from other animals.

Disappearing act

The work is revealing in other ways too. At the beginning of every trapping season in September, Deppe says, she catches mostly males. Females show up only after they see the males coming home safely every night.

Then, around May, females disappear again. Scientists think that females might enter a hibernation-like state, called torpor, for half the year. The males, however, remain active.

"That means that [males] wear their teeth down twice as much," Wright says. "And they get exposed to predators twice as often."

Because males take twice as many risks, do they live only half as long? To find out, Deppe and Wright want to develop radio collars small enough to track mouse lemurs in the wild. As researchers continue to put tracking devices on ever-smaller creatures, including dragonflies, technology might soon make that possible.

New species

Scientists discovered three new mouse lemur species last year, bringing the total to more than a dozen. Altogether, there may be more than 50 lemur species in Madagascar.

And there's much more to learn. Brooke Crowley, a graduate student at the University of California, Santa Cruz is collecting and analyzing the hair of mouse lemurs in order to learn about their diet. The hair contains traces of the nutrients found in the food they eat.

"No one really knows [what lemurs eat]," Crowley says. "There are guesses, but no one is sure."

The list of unanswered questions will last for many years. If these creatures fascinate you, you might want to consider a future research trip to Madagascar. "I wish more people would come down here and study these things," Deppe says. After all, mouse lemurs are easy to work with, cooperative, and fun.

If that's not enough incentive, just look at a photo of a lemur. Like Deppe and her team, you'll be hooked.