Duke Lemur Center
Duke Lemur Center
News Article | April 20, 2017
Researchers are working to digitally preserve the bodies of lemurs that have died so future students and scientists might learn more about lemur anatomy—and “virtually dissect” them. Almost all of the roughly 100 species of lemurs are facing extinction in the wild due to logging, mining, hunting, and slash-and-burn agriculture. Which is why, when an animal at the Duke University Lemur Center dies from illness, injury, or old age, a licensed veterinarian performs a postmortem exam within 24 hours of death, organs are removed, and tissue samples are collected so that other researchers can make use of them. Cadavers of each species go into storage freezers or are preserved in formalin—not for ghoulish curiosity, but so that years from now their bodies could be still be useful for research and education. And though these animals are gone, their bodies are now being preserved for present and future generations with help from an X-ray imaging technique called micro-computed tomography (microCT). Soon, anyone will be able to go online to MorphoSource.org and get 3D views of the internal anatomy of dozens of lemurs and other rare and endangered prosimian primates, in micrometer detail, without disturbing the original specimens. “Even when they’ve passed, these animals continue to contribute valuable scientific data,” says former Duke graduate student Gabe Yapuncich, who has been leading the effort to scan the specimens with assistant professor Doug Boyer. Yapuncich got the idea for the project while earning his doctorate in evolutionary anthropology. He was scanning the skeletal remains of present-day primates to see if certain foot bone measurements could help to reconstruct how much their extinct relatives might have weighed. Researchers can learn about many aspects of primate biology from fossils, but most fossil specimens consist of isolated teeth or fragments of bones. Complete or even partial skeletons are rare. “It seemed like a waste just to scan the foot and send it back,” Yapuncich says. “Once I had a specimen on loan, I tended to scan the whole thing.” Yapuncich demonstrated how the technology works at Duke’s Shared Materials Instrumentation Facility. A giant lead-lined box there looks like an airport security scanner. Inside, a Styrofoam cooler filled with dry ice contains the frozen remains of Beauty, a female bamboo lemur who died in 1985. The microCT scanner blasts a cone-shaped beam of X-rays at the cooler as it spins slowly on a rotating platform. The X-rays that pass through Beauty’s body hit a detector on the back wall, which records a snapshot. The scanner takes thousands of snapshots for each full rotation. The data go to a computer, which uses the images to reconstruct two-dimensional cross sections of Beauty’s insides, and these are stacked like slices of bread into a 3D model. Yapuncich peers at the result on a nearby computer screen. It’s a 3D close-up of Beauty’s head built from 1,900 cross-sectional images. With the click of a mouse, he digitally dissects away Beauty’s fur, skin, and soft tissue to reveal the skeleton underneath in stunning, three-dimensional detail. He can also look at any 2D slice to see internal structures in cross section. The Duke Lemur Center is committed to studying lemurs without harming them. Imaging cadavers makes it possible to perform “virtual” dissections that would never be allowed on living animals. With standard microCT researchers can visualize hard tissues such as bones and teeth, but by using special iodine-based stains, they can also see soft tissues such as muscles, nerves, and blood vessels in the deceased animals. Yapuncich has scanned the remains of more than 100 animals so far. A fat-tailed dwarf lemur named Jonas is one of them. When he died in 2015 at age 29, suffering from cataracts and other signs of age, he was the oldest of his kind. The scan shows his tail curled around his body, the roughly two dozen tail bones neatly lined up one after the other. “If you go to a museum collection, the tail vertebrae are just a bunch of bones in a box,” Yapuncich says. The Duke Lemur Center fields dozens of cadaver requests from researchers each year. But these rare and fragile specimens can only be examined so many times using traditional methods. Repeated shipping and handling may expose them to damage and freeze-thaw cycles that would inevitably speed their decay. By creating high resolution 3D scans and putting them online, researchers hope to reduce destructive sampling and insure the availability of specimens for future study. “There aren’t that many available,” says Duke R&D engineer and microCT specialist Justin Gladman. “If one researcher dissects and destroys one, the next researcher can’t do anything with it.” “By scanning them in the microCT and creating these beautiful 3D models, we can digitize the specimens and share them online,” Gladman says. “Instead of being locked in a museum drawer, they’re freely available.” In the digital afterlife, Merlin’s bony appendages are no longer nimble but still intact. He was one of four of the fewer than 60 endangered aye-ayes living in captivity worldwide that died suddenly over 36 hours at the Duke Lemur Center in October 2016. Staff and researchers were devastated. The culprit, tests later revealed, was a natural toxin found in avocados, not previously known to be harmful to lemurs, which damaged their heart muscles. In assistant professor Doug Boyer’s lab on Science Drive, recent Duke graduate Darbi Griffith uses software to stitch together nearly 3,000 2D images of Merlin into a 3D rendering. Merlin was very popular with lemur center staff, and often enjoyed using his incredibly slender and dexterous middle finger to gently tease mealworms from his keepers’ closed fists. The 3D volume rendering shows his body cloaked in skin and muscle. With a click his flesh fades away, and Griffith can zoom in on Merlin’s skull to examine the complex wear patterns on his teeth, or peer inside his cranial cavity to estimate the size and shape of his brain. Griffith has uploaded these 3D images to an online database Boyer created called MorphoSource. Because the digitization is ongoing the Lemur Center scans haven’t been made publicly available yet, but when they are, visitors to MorphoSource will be able to compare Merlin to other individuals, or measure anatomical variation across species. Anyone will be able to browse the specimens, measure them, download the raw data, and even create their own 3D lemur models, both of bodies and skeletons, on a 3D printer. “It’s the largest collection of 3D lemur scans. That’s pretty cool,” Griffith says. Grants from the National Science Foundation supported this research.
News Article | January 27, 2016
In a study led by Duke University, researchers used a technique called whole-transcriptome sequencing to screen for blood-borne diseases in wild lemurs, distant primate cousins to humans. The animals were found to carry several strains or species of parasites similar to those that cause Lyme disease and other infections in humans. This is the first time these parasites have been reported in lemurs or in Madagascar, the only place on Earth where lemurs live in the wild outside of zoos and sanctuaries, the researchers report in the Jan. 27, 2016 issue of Biology Letters. The approach could pave the way for earlier, more accurate detection of future outbreaks of zoonotic diseases that move between animals and people. "We can detect pathogens we might not expect and be better prepared to deal with them," said co-author Anne Yoder, director of the Duke Lemur Center. In 2012, Duke Lemur Center veterinarian Cathy Williams and colleagues started performing physical exams on lemurs in the rainforests surrounding a mine site in eastern Madagascar to help monitor the impacts of such activities on lemur health. "Lemur populations are becoming increasingly small and fragmented because of human activities like mining, logging and clearing forests to make way for cattle grazing and rice paddies," Williams said. "If an infectious disease wipes out a lemur population it could be a huge blow to the species." Researchers took small amounts of blood and tested them for evidence of exposure to known viruses and pathogens, but nothing turned up. The problem is that standard diagnostic tests tend to target known pathogens, Williams said. You can check for antibodies to certain viruses, or look for specific snippets of genetic material in an animal's blood, "but you have to know what you're looking for." The end result is that new or exotic diseases often go undetected. And with hundreds of thousands of viral and bacterial species that lemurs and other mammals harbor still awaiting discovery, "we could be looking for anything," Williams said. To cast a wider net they tried a new approach. Lead author Peter Larsen, senior research scientist at Duke, analyzed blood samples from six lemurs in two species, the indri and the diademed sifaka, both of which are considered critically endangered by the International Union for Conservation of Nature (IUCN). With advances in high-throughput sequencing, the ability to read genetic code rapidly, Larsen was able to look at all the gene readouts, or RNA transcripts, that were present in each animal—an alphabet soup containing billions of nucleotide bases. The team found more than just lemur RNA in the animals' blood. Using computer algorithms that compared the genetic material to sequences already catalogued in existing databases, they discovered several new types of parasites that had never been reported in lemurs. These included a new form of the protozoa responsible for babesiosis, a disease spread by bites from infected ticks, and a new kind of Borrelia closely related to the bacterium that causes Lyme disease. They also found the first known case in Madagascar of a bacterium called Candidatus Neoehrlichia, which can be deadly in humans. Further analyses revealed that the new types of Babesia and Borrelia they found didn't begin in lemurs, but were likely introduced to Madagascar in infected pets and livestock such as cattle and then spilled over to lemurs. The researchers don't yet know if the new parasites are actually dangerous to lemurs. But they caution that what is infecting lemurs could potentially infect people, too. Human health officials and veterinarians in Madagascar may want to consider screening their patients to see if any test positive for the same parasites, the researchers say. The majority of emerging infectious diseases that affect humans, including recent outbreaks of SARS, Ebola and bird flu, are zoonotic—they can spread among wildlife, domestic animals and humans. "Next-generation sequencing will be an important tool to identify emerging pathogens, particularly vector-borne diseases," said Barbara Qurollo, a research assistant professor at the N.C. State College of Veterinary Medicine who was not affiliated with the study. "A clinician cannot treat an infection that he or she does not know exists," said veterinarian and infectious diseases researcher Edward Breitschwerdt, also of the N.C. State College of Veterinary Medicine. "The kindest form of therapy is an accurate diagnosis." More information: Blood transcriptomes reveal novel parasitic zoonoses circulating in Madagascar's lemurs, Biology Letters, rsbl.royalsocietypublishing.org/lookup/doi/10.1098/rsbl.2015.0829
News Article | January 27, 2016
Advances in genetic sequencing are uncovering emerging diseases in wildlife that other diagnostic tests can’t detect. In a study led by Duke University, researchers used a technique called whole-transcriptome sequencing to screen for blood-borne diseases in wild lemurs, distant primate cousins to humans. The animals were found to carry several strains or species of parasites similar to those that cause Lyme disease and other infections in humans. This is the first time these parasites have been reported in lemurs or in Madagascar, the only place on Earth where lemurs live in the wild outside of zoos and sanctuaries, the researchers report in the Jan. 27 issue of Biology Letters. The approach could pave the way for earlier, more accurate detection of future outbreaks of zoonotic diseases that move between animals and people. “We can detect pathogens we might not expect and be better prepared to deal with them,” said co-author Anne Yoder, director of the Duke Lemur Center. In 2012, Duke Lemur Center veterinarian Cathy Williams and colleagues started performing physical exams on lemurs in the rainforests surrounding a mine site in eastern Madagascar to help monitor the impacts of such activities on lemur health. “Lemur populations are becoming increasingly small and fragmented because of human activities like mining, logging and clearing forests to make way for cattle grazing and rice paddies,” Williams said. “If an infectious disease wipes out a lemur population it could be a huge blow to the species.” Researchers took small amounts of blood and tested them for evidence of exposure to known viruses and pathogens, but nothing turned up. The problem is that standard diagnostic tests tend to target known pathogens, Williams said. You can check for antibodies to certain viruses, or look for specific snippets of genetic material in an animal’s blood, “but you have to know what you’re looking for.” The end result is that new or exotic diseases often go undetected. And with hundreds of thousands of viral and bacterial species that lemurs and other mammals harbor still awaiting discovery, “we could be looking for anything,” Williams said. To cast a wider net they tried a new approach. Lead author Peter Larsen, senior research scientist at Duke, analyzed blood samples from six lemurs in two species, the indri and the diademed sifaka, both of which are considered critically endangered by the International Union for Conservation of Nature (IUCN). With advances in high-throughput sequencing, the ability to read genetic code rapidly, Larsen was able to look at all the gene readouts, or RNA transcripts, that were present in each animal -- an alphabet soup containing billions of nucleotide bases. The team found more than just lemur RNA in the animals’ blood. Using computer algorithms that compared the genetic material to sequences already catalogued in existing databases, they discovered several new types of parasites that had never been reported in lemurs. These included a new form of the protozoa responsible for babesiosis, a disease spread by bites from infected ticks, and a new kind of Borrelia closely related to the bacterium that causes Lyme disease. They also found the first known case in Madagascar of a bacterium called Candidatus Neoehrlichia, which can be deadly in humans. Further analyses revealed that the new types of Babesia and Borrelia they found didn’t begin in lemurs, but were likely introduced to Madagascar in infected pets and livestock such as cattle and then spilled over to lemurs. The researchers don’t yet know if the new parasites are actually dangerous to lemurs. But they caution that what is infecting lemurs could potentially infect people, too. Human health officials and veterinarians in Madagascar may want to consider screening their patients to see if any test positive for the same parasites, the researchers say. The majority of emerging infectious diseases that affect humans, including recent outbreaks of SARS, Ebola and bird flu, are zoonotic -- they can spread among wildlife, domestic animals and humans. “Next-generation sequencing will be an important tool to identify emerging pathogens, particularly vector-borne diseases,” said Barbara Qurollo, a research assistant professor at the N.C. State College of Veterinary Medicine who was not affiliated with the study. “A clinician cannot treat an infection that he or she does not know exists,” said veterinarian and infectious diseases researcher Edward Breitschwerdt, also of the N.C. State College of Veterinary Medicine. “The kindest form of therapy is an accurate diagnosis.”
News Article | April 19, 2016
The results appear online April 20 in Royal Society Open Science. The "perfume" of the ring-tailed lemur could never be confused with Chanel. Male ring-tailed lemurs, our distant primate cousins, produce their distinctive musky odor with help from a pair of glands on their wrists that give off droplets of clear, fast-evaporating fluid, and a second pair of glands on their chests that secrete a brown, foul-smelling paste. Males use their scents to mark territories and tell rivals to back off. Sometimes they deposit wrist secretions alone, rubbing their wrists directly onto branches and saplings. Other times they mix the two, pressing the insides of their wrists against their chest glands to mingle the scents. They also smear the pungent mixture on their tails, waving them in the air and wafting them at opponents to see who can outstink the other in a ritual called "stink-fighting." Many animals combine odors from sources such as glands, urine, feces and saliva, but why they sometimes blend and layer these fragrances, and other times deposit them alone, is not well understood. To find out why lemurs mix their scents, researchers presented pure and mixed scent secretions from unfamiliar males to 12 ring-tailed lemurs at the Duke Lemur Center in Durham, North Carolina. The secretions were collected with cotton swabs and then rubbed onto three wooden rods—one rod with wrist secretions only, another with secretions from the chest, and a third with a mixture. Each male participated in two sets of trials, one set with fresh secretions and another in which the secretions were allowed to air out and evaporate for 12 hours first. The researchers found that the lemurs paid more attention to the mixtures, spending more time sniffing rods covered with mixed secretions than pure ones. Surprisingly, the lemurs showed an even stronger preference for mixed secretions after the scents had aired out, shifting from sniffing them when fresh to licking them intently when dried. The results suggest that mixing scents serves two purposes. First, like blending perfumes with complementary notes, blending secretions may increase the amount of information conveyed by a single dab of scent, said Christine Drea, a professor of evolutionary anthropology at Duke who led the study. The wrist and chest secretions of male ring-tailed lemurs differ somewhat in composition, previous studies show. Chemical analyses have identified dozens of odor molecules in the wrist secretions alone. Mixing wrist and chest secretions may also lock in the more fleeting aromas and boost their staying power, said co-first author Lydia Greene, a graduate student at Duke. The greasy goo from the chest glands contains a chemical called squalene, an oily substance produced by many plants and animals and commonly used as a preservative in perfumes and skincare products. The longer-lasting mixtures that result may send a signal to males from other groups, who may not wander by a scent-marked tree or sapling until days later, the researchers say. Explore further: Primate's scent speaks volumes about who he is More information: Mix it and fix it: functions of composite olfactory signals in ring-tailed lemurs, Royal Society Open Science, rsos.royalsocietypublishing.org/lookup/doi/10.1098/rsos.160076
News Article | July 21, 2016
Just like humans, primates may be hardwired for happy hour in the jungle, a new study has revealed. Nectars and fermented fruits are nature's organic cocktails, and it appears that some of our relatives actively indulge in them. Indeed, researchers in New Hampshire have found that two species of primate enjoy drinking "booze" and they consume it like intoxicated drunkards — the stronger the content, the better. Scientists from Dartmouth College put to test two species of monkey-like primates — the aye-aye and the slow loris species — and provided representatives a selection of beverages with different degrees of alcohol. Researchers borrowed a slow loris named Dharma and two aye-ayes named Merlin and Morticia from the Duke Lemur Center in North Carolina to find out which were more naturally inclined towards heavily fermented forms of nectar that resemble booze. Drink receptacles were placed in slots cut into a round table with lids that left a hole big enough for the animals to insert their fingers to taste the drinks. This simulated the nectar-gathering process that these primate species perform in native habitats of aye-ayes and the slow loris: Madagascar and the Southeast Asian jungle, respectively. The nectar substitutes contained 1 to 4 percent alcohol content, with tap water as a control. In the end, researchers found that in all cases, even when they mixed the order in which the beverages were given, the primates preferred the nectar substitute with the strongest content. In fact, Dharma the slow loris not only enjoyed booze, but had even had a "relative aversion" to tap water. Morticia and Merlin, the aye-ayes, reportedly went directly for the drink with the highest alcohol content and continued searching the receptacles for more even after emptying them. Nathaniel Dominy, a co-author of the study, says the primates perhaps relied on their sense of taste and smell to distinguish which drinks contained the higher alcohol levels. And because the aye-ayes stuck their fingers into the receptacles over and over again, this suggests a "strong attraction," says Dominy. Can It Pinpoint The Roots Of Alcoholism? Although the level of eagerness was unexpected, researchers say the results of the study were not surprising because nectar or fruit is the primary source of food of primates. But the findings have left scientists intrigued, especially those who study the origins of alcoholism. Experts say gorillas, chimps and humans carry a gene that helps us take in decent amounts of alcohol without getting too intoxicated. Matthew Carrigan, an expert from Santa Fe College who was not involved in the study, found that this certain gene had evolved from an ancestral ape about 10 million years ago long before humankind learned how to make alcohol. Researchers propose that this metabolism trick dates to the period when some apes started hanging out on the ground and taking lots of fermented fruit under the trees. George Perry, who has collaborated with Dominy but is also not involved in the new study, says aye-ayes carry the gene that helps process strong drinks efficiently. The species' preference for alcohol possibly corroborates with the idea that the gene helps animals adapt to drinking booze, he says. The findings of the new study are published in the journal Royal Society Open Science. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.
News Article | September 5, 2016
Contrary to many adorable children’s stories, hibernation is so not sleeping. And most animals can’t do both at the same time. So what’s with Madagascar’s dwarf lemurs? The fat-tailed dwarf lemur slows its metabolism into true hibernation, and stays there even when brain monitoring shows it’s also sleeping. But two lemur cousins, scientists have just learned, don’t multitask. Like other animals, they have to rev their metabolisms out of hibernation if they want a nap. Hibernating animals, in the strictest sense, stop regulating body temperature, says Peter Klopfer, cofounder of the Duke Lemur Center in Durham, N.C. “They become totally cold-blooded, like snakes.” By this definition, bears don’t hibernate; they downregulate, dropping their body temperatures only modestly, even when winter den temperatures sink lower. And real hibernation lasts months, disqualifying short-termers such as subtropical hummingbirds. The darting fliers cease temperature regulation and go truly torpid at night. “You can pick them out of the trees,” Klopfer says. The fat-tailed dwarf lemur, Cheirogaleus medius, was the first primate hibernator discovered, snuggling deep into the softly rotting wood of dead trees. “You’d think they’d suffocate,” he says. But their oxygen demands plunge to somewhere around 1 percent of usual. As trees warm during the day and cool at night, so do these lemurs. When both a tree and its inner lemur heat up, the lemur’s brain activity reflects mammalian REM sleep. Klopfer expected much the same from two other dwarf lemurs from an upland forest with cold, wet winters. There, C. crossleyi and C. sibreei spend three to seven months curled up underground, below a thick cushion of fallen leaves. “If you didn’t know better, you might think they were dead because they’re cold to the touch,” Klopfer says. Unlike the tree-hibernators, the upland lemurs take periodic breaks from hibernating to sleep, Klopfer, the Lemur Center’s Marina Blanco and colleagues report in the August Royal Society Open Science. The lemurs generated some body heat of their own about once a week, which is when their brains showed signs of sleep (REM-like and slow-wave). “My suspicion is that sleep during torpor is only possible at relatively high temperatures, above 20º Celsius,” Klopfer says. Sleep may be important enough for cold-winter lemurs to come out of the storybook “long winter’s nap.”
News Article | December 28, 2015
When you get a phone call or a text from a friend or acquaintance, how fast you respond — or whether you even bother to pick up your phone — often depends on the quality of the relationship you have with that person. If it’s your best friend or mom, you probably pick up right away. If it’s that annoying coworker contacting you on Sunday morning, you might ignore it. Ring-tailed lemurs, it seems, are even pickier in who they choose to respond to. They only respond to calls from close buddies, a new study finds. These aren’t phone calls but contact calls. Ring-tailed lemurs live in female-dominated groups of 11 to 16, and up to 25, animals, and when the group is on the move, it’s common for one member to yell out a “meow!” and for other members to “meow!” back. A lemur may also make the call if it gets lost. The calls serve to keep the group together. The main way ring-tailed lemurs (and many other primates) build friendships, though, is through grooming. Grooming helps maintain health and hygiene and, more importantly, bonds between members. It’s a time-consuming endeavor, and animals have to be picky about who they bother to groom. Ipek Kulahci and colleagues at Princeton University wanted to see if there was a link between relationships built through grooming and vocal exchanges among ring-tailed lemurs. Contact calls don’t require nearly as much time or effort as grooming sessions, so it is possible that animals could be less discriminating when they respond to calls. But, the researchers reasoned, if the vocalizations were a way of maintaining the relationships built through painstaking grooming sessions, then the lemurs would be as picky in their responses as in their grooming partners. So they watched four free-ranging lemur colonies — two at the Duke Lemur Center in North Carolina and two on St. Catherine’s Island in Georgia — and mapped out who groomed whom and which lemurs responded to which calls from other lemurs. The researchers also played back recorded lemur calls to see who responded. The team reports their findings in the December Animal Behaviour. Not all lemurs were alike. Some were extremely social, grooming lots of other animals and calling back to plenty of their brethren. Others were loners, hardly grooming anyone and rarely responding to contact calls. But regardless of how social an animal was, the lemurs tended to respond vocally only to lemurs that they groomed most frequently and probably have the strongest social bonds, the researchers say. In other words, they may have groomed their friends, but they only responded to the contact calls of their besties. The contact calls may allow the lemurs to “groom-at-a-distance” and maintain their social bonds, the team concludes. And maintaining those bonds is important. If I were dependent on others to pick dead skin, insects and other bits and pieces off my body, I’d probably answer the phone when they called.
News Article | April 15, 2016
Scientists from the German Primate Center (DPZ), the University of Kentucky, the American Duke Lemur Center and the Université d'Antananarivo in Madagascar have described three new species of mouse lemurs. They live in the South and East of Madagascar and increase the number of known mouse lemur species to 24. As little as 20 years ago, only two species of these small, nocturnal primates were known. New genetic methods and expeditions to remote areas have made the new descriptions possible (Molecular Ecology).
News Article | September 26, 2016
Duke professor Brian Hare remembers his first flopped experiment. While an undergraduate at Emory in the late 1990s, he spent a week at the Duke Lemur Center waving bananas at lemurs. He was trying to see if they, like other primates, possess an important social skill. If a lemur spots a piece of food, or a predator, can other lemurs follow his gaze to spot it too?
News Article | March 24, 2016
She would much rather sleep in than participate in Duke alum Joe Sullivan's early morning vision tests. "I can't blame her," said Sullivan, who graduated from Duke in 2015. Elphaba is one of 14 aye-ayes at the Duke Lemur Center in Durham, North Carolina, where researchers like Sullivan have been trying to figure out if these rare lemurs can tell certain colors apart, particularly at night when aye-ayes are most active. But as their experiments show, testing an aye-aye's eyesight is easier said than done. Aye-ayes don't see colors as well as humans do. While we have genes for three types of color-sensing proteins in our eyes, aye-ayes and most other mammals have two, one tuned to blue-violet light and another that responds to green. In all animals, the eyes' color-detecting machinery depends on medium to bright light. In a version of "use it or lose it," the genes responsible for color vision in some nocturnal species have decayed over time, such that they see the world in black and white. But in aye-ayes, research shows, the genes for seeing colors remain intact, and scientists at Duke and elsewhere are trying to understand why. One possibility is the aye-aye's color vision genes are mere leftovers, relics passed down from daylight-loving ancestors and no longer useful to aye-ayes today. Or, the genes may have been preserved because color vision gives aye-ayes an edge. Wild aye-ayes live by eating fruit, nuts, nectar and grubs in the rainforests of Madagascar. Wouldn't an animal that could distinguish the blue fruits of a favorite snack like the Traveler's palm from the green of the surrounding foliage have an advantage? Understanding what aye-ayes can see is no easy feat. One of the most common tests for colorblindness, the Ishihara, requires the subject to recognize and identify numbers hidden within a patch of colored dots of different sizes and brightness. Aye-ayes don't read numbers, so Sullivan tests for color vision using food and colored cards. The first tests were simple enough. In a dimly lit enclosure, a trainer held up two cards: a white card and a black one. Each time the aye-ayes chose the white card over the black one by reaching out and touching it with their hand, the animal got a peanut. Even animals with no color vision can tell white from black, so Sullivan was confident they'd ace the test. But aye-ayes aren't programmed to please. Just getting them to sit still, instead of running around their enclosure, was a challenge. One aye-aye, 29-year-old Ozma who was born in the wild in Madagascar, never got the hang of even the most basic task, a warmup involving a single white card. "That's when I realized that aye-ayes don't always play by my rules," said Sullivan, who started working at the Duke Lemur Center as an undergraduate research intern in 2012. After four months and 200 trials, all five of the aye-ayes in Sullivan's study started picking the white card more often than not, with Merlin, Elphaba and Grendel passing the test at least 70 percent of the time. Norman and Ardrey tended to reach for the card on their left, no matter what the color. Sullivan isn't giving up. Still working at the Duke Lemur Center post-graduation, now he's trying to see if aye-ayes can distinguish a purplish card from a green one, in brighter light more similar to dawn or dusk. So far, Merlin and Grendel are getting it right just over half the time, leaving Sullivan still unsure if the aye-ayes are choosing the cards by their colors or by some other cue. "I came in thinking that the aye-ayes were going to play nice and do everything I wanted. That was so wrong," Sullivan said. "Still, they've been very good sports." Explore further: The aye-ayes have it: The preservation of color vision in a creature of the night