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My classmates explored the treetops with binoculars and a thermal imaging monocular. I stared at the branches and leaves, pretending I knew what to look for. It was a cool June afternoon shortly before sunset on a village road on the island of Langkawi, Malaysia.
"There's one! Up there," called one of the biologists. I looked sideways at the spot, about five feet from the trunk of the tree, and saw only a brown button dotted with gray. Where? Then the button shook. Her upper edge rose and turned, and I was looking at a pair of bulging eyes placed on a small head with a short snout.
My first colleague. The size of a domestic cat, colugus are nocturnal mammals that live in trees. Collugos are also called "flying lemurs," which is a bad name because they can't fly and they're not lemurs. A colugo has a layer of skin that extends from the neck to the tips of its four limbs and tail. That skin, hairy at the top, helps the colugos slide away and hide well in the canopy.
"Wait … Oh, you have a baby!" called zoologist Priscillia Miard of Universiti Sains Malaysia in Penang and leader of the same night search. He handed me his binoculars while the team discussed the identity of this colleague.
A small head came out from under the mother's skin, like a child peeking out from under a blanket. Baby colugs cling to their mother’s hairless bottom until about 6 months of age, breastfeeding on the nipples near the mother’s armpits.
He had seen two colugos just 15 minutes from our search.
Recent observations by zoologist Priscillia Miard and others have shown how nocturnal colugas interact with their young, as well as their mating efforts.
The colugo mother raised her tail. “It’s poop,” Miard said, without the slightest concern that we were underneath. Later Miard told me that colugo feces are like dried lentils, nothing messy.
For an animal that is the closest living relative to all primates, which branched out about 80 million years ago, colugos remain a great mystery (SN: 9/3/16, p. 17). Today, the two living species of colugos are only found in Southeast Asia, although recent studies suggest that two are an imperfect number. Miard and other scientists have begun to trace the little knowledge of these mammals, revealing how their colleagues communicate and how they plan more than the length of a football field.
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The night
Colugos appeared unexpectedly in Miard’s life three years ago. The then 28-year-old French researcher had spent five years in Borneo studying nocturnal primates, including tarsiers and slow lorises. In 2017, Miard visited Langkawi, famous for its beaches and rice fields, where he saw colugas “everywhere,” in well-traveled orchards, golf courses, resorts, and village paths. Because the colugos were abundant and easy to find and observe in Langkawi, Miard pivoted to study them. In August he successfully defended his doctorate. thesis at Universiti Sains Malaysia for his research on colony ecology.
But while he was beside her looking up, Miard did not mention his doctorate. He focused on the colugo mother – now some slightly slower dry – who seemed ready to start her night. The colugo climbed to the end of a branch and turned his head toward the road. Then he jumped.
The colugus turned, stretched his legs and tail, and glided like a magic carpet down the road to another tree trunk. Then he jumped, jumped, climbed the tree to the leaves and out of sight.
She glanced at four other trees for the next 15 minutes. By then, Miard and his teammates – biologists Muhammad Fizri bin Ahmad Zubir and Celia Lacomme – had recognized the coloration of the colugo's mother's skin. They had been following her for a long time, calling her “Batwoman” because, months ago, residents thought investigators were looking for bats in the trees.
Streetlights and passing cars and motorcycles lit up the road, but a few feet away the trees were dark. Miard and Lacomme turned on the red light bulbs to light the treetops. Something moved on a nearby tree trunk. Another colleague! Miard pointed to the camera, saw testicles, and announced that the colugo was male.
Master gliders
All colugos are master gliders, considered among the best species of 60 mammals that can glide. A Sunda colugo (Galeopterus variegatus) was recorded gliding 145 meters, almost the length of three Olympic pools.
That sustained plain was reported in 2011 in the Journal of Experimental Biology by Gregory Byrnes, a biologist at Siena College in Loudonville, New York, and colleagues. At the time, most researchers considered the planar to be an energy-efficient way to travel to colleagues. Byrnes ’team tested that idea by pasting data loggers into wild Sunda colugos in Singapore and recording nearly 260 shots between four individuals.
Sunda’s colleagues usually climb before planning. In the study, a Sunda colugus could climb a total of 320 meters and slide 1,342 meters in one night. “No one ever took into account that to plan you have to climb,” Byrnes says. His team fed the colugo data on metabolic models of other mammals inhabiting trees to estimate the amount of energy the colugos spend on planning and climbing. When climbing is included as part of gliding behavior, and in forests where tree tops overlap, a colugo could save energy by crawling across the canopy instead of gliding, he says.
The “big advantage” of gliding is that it saves time for colleagues, Byrnes says. Planar allows an animal to cross space in seconds so it can spend more time feeding or traveling even further, he says.
The colugos take out those long-distance shots with their slippery skin, known as patagium. While other gliders such as flying squirrels have a path that extends to the hind feet, a colugo’s path continues to the tip of the tail. A more expansive patagio gives an additional “wing area” a colugo, which lifts and slows the animal, allowing for a smoother descent than other gliders, says Byrnes. The extra skin also helps the animal move away.
And there is more to the pathology than skin and skin. Byrnes and his collaborators found that the thin pathway is rich in muscle and some parts are stiffer than others. A colugo can flex those muscles to change the shape and stiffness of his paddock and thus adjust his aerodynamics to half an hour. Understanding the slippery biomechanics of cuckoos can help in the design of robotics and wing technology, says Byrnes.
That night in Langkawi, Batwoman glided down the road, crossing the road and climbing the road. Never a sound. Once, he was gliding towards a tree and just before the impact, he turned, cut a sharp bow and landed on the next trunk. Wow.
Writer Yao-Hua Law along with zoologist Priscillia Miard and her colleagues set out to follow colugas on the island of Langkawi, Malaysia, as they glided from tree to tree along a busy village road.
High conversation
When Batwoman reached her fifth tree of the night, another colugo jumped out of the darkness and climbed the trunk toward her.
Colugos were once thought to be solitary animals, Miard says. Social interactions were brief and rarely seen. But new observations by Miard and others suggest that colugos form loose social groups of females or a mother and her offspring, even those who are weaned. Miard saw up to six colugos in a tree. However, males appear to travel alone, joining groups of females only temporarily.
Miard trained his camera in the newcomer, who passed by Batwoman and continued toward the canopy. Not a glance. Miard looked disappointed. "Oh no, he didn't even say hello."
To my ear, Batwoman made no sound. But he may have been calling for ultrasounds, inaudible to humans. Miard and colleagues discovered ultrasound calls from colleagues, reporting the finding in 2019 in Bioacoustics. A microphone picked up the ultrasound signals during a bat survey and Miard tracked the source down to the colugos. Many nocturnal animals, including bats, tarsis, and slow lorises, communicate by ultrasound, probably to avoid detection by predators. Probably colleagues do the same. In November, Miard and colleagues will play ultrasound calls in the field and listen to the colleague’s responses.
It’s 8:15 p.m., dinner time. Batwoman crawled toward the thick foliage and carefully pulled out some leaves to give her a scent. Miard explained that colugos eat mostly leaves. Batwoman put some leaves in her mouth and started chewing. Fizri and Lacomme recorded the observations in a behavior checklist on their smartphones.
"Wait, the baby is trying to eat leaves," Miard said, looking through the binoculars. Lacomme shone his red light bulb against Batwoman. The baby colugo stretched out his hand under his mother, pulled out some small leaves and tried to bite them. Maybe the baby is learning what to eat from his mother, Miard said. It was too dark to tell if the baby was actually eating the leaves. Lacomme's red light bulb wasn't bright enough. White light could offer a better view.
But Miard will not shine white light on nocturnal mammals. “When we use white light on our collars, they freeze, but not when we use red light,” he told me later. Freezing, she says, is a sign that white light is disturbing nocturnal mammals.
Miard's concern makes sense. White light, commonly used in nocturnal animal studies, can quickly saturate sensitive optical cells in nocturnal animal eyes and cause temporary blindness, says primatologist Amanda Melin of the University of Calgary, Canada. “These moments of blindness are probably disorienting and potentially harmful,” Melin says. “Red light is likely to be much less disturbing as it will have a much lower intensity” than white light.
The large surface of their slippery skin, or patagium, helps colugos achieve some of the longest planes among mammals. This three-image compound shows a colugus gliding to the right and preparing to land on a tree.Chien C. Lee
Anxious pursuit
Around nine in the evening, another colleague glided and joined Batwoman in a tree. This one seemed more interested than the previous one; he tapped Batwoman and bit her sides. The newcomer, a man, wanted to mate, Miard said. But every time she approached, Batwoman pulled away.
Miard gripped the camera tightly. Colugo's romance makes images much appreciated. Looking at the canopy, Miard stepped back toward the tree and headed for the road toward the path of an approaching car that had just stopped before hitting it.
On an early night in Malaysia in June, zoologist Priscillia Miard uses a thermal imaging device to look for cuckoos, which have coats that camouflage them well against the bark of lichen-covered trees.Y.-H. Right
“F—, let’s miss the most important part. We know they're going to make babies, but I can't see them, "Miard said. She turned to Fizri," Where's the thermal chamber? "
Minutes later, Miard spotted the colugos near the top of the tree. “You’re very lucky,” he told me. "Lots of exciting things tonight."
Batwoman kept testing the male, which I decided to call "Anxious." She glided toward another tree, then another and the other with Eager far behind. The colugos remained in a tree. Miard sat by the side of the road, camera in hand, eyes fixed on Batwoman.
"Come on guys …. Please let me do it, please … Batwoman," Miard murmured.
Our small group aroused the curiosity of the locals. A couple, standing on the porch of a nearby house, watched them for about 10 minutes and then approached. “He’s a kubong,” Fizri told them, giving the local Malay name to colugo.
The couple knew the name but not the animal. They thought the colugos only lived in the woods. “Do you eat fruit? Is it like a bat? They asked in silent tones. Fizri lowered his smartphone and began explaining the ecology of the colugo. The opportunity to talk colugo with local residents and correct misconceptions is one of the reasons Miard likes to study colugo in villages.
Conservation of the colugo
Perhaps because they are nocturnal and well camouflaged, colugos live hidden from view. Zoologist Dzulhelmi Nasir, now with the Malaysian Palm Oil Board, studied colleagues in Borneo. Most residents have never heard of colugos, he says. People often confuse animals with flying squirrels or a giant fruit bat called a kluang in Malay.
Confusion or misconceptions about colugos can be deadly to animals. In parts of Malaysia, garden and plantation owners see colugos as pests of fruit and kill them, Miard told me. But colugos rarely eat fruit and flowers, according to a study published in 2006 in Biodiversity & Conservation, as well as Miard’s own unpublished research. Fortunately, here in Langkawi, there are few commercial orchards and the locals leave their colleagues alone.
But across Southeast Asia, colugos are losing their forest homes to agriculture and development. The region lost 293,000 square miles of forest between 2000 and 2014, an area the size of Arizona, according to a 2018 report published in Nature Geoscience.
In the International Union for Conservation of Nature's Red List of Threatened Species, the Sunda's and the Philippine's (Cynocephalus volans) are classified as "less worrying" because of the risk of extinction. It is particularly likely that the Sunda colugo, with its wide distribution from Vietnam to Indonesia, is threatened.
Colugos live all their lives in trees. Gliders visit several trees in one night, eating mostly leaves instead of fruit.Night Spotting Project
But that assessment may be too rosy. Those two species can have eight or up to 14, based on genetic evidence reported in 2016 in Science Advances. If so, instead of the Sunda colugo being a widely distributed species, there are several colugo species confined to smaller areas that may be more susceptible to local extinction.
Zoologists have always observed that colugos look different in Southeast Asia. In the 1950s, about 20 species and subspecies were recognized based on physical differences. But zoologists have decided to simplify things and group all subspecies into two species, says geneticist Victor Mason, author of the 2016 report, which studied the phylogeny of the colugo at Texas A&M University College Station.
Mason and colleagues looked for signs of hidden species diversity in the genetic composition of colugos, a task that required colug DNA samples from all over Southeast Asia. Researchers have turned to museum specimens in Singapore and the United States. “There are hundreds of colugo skulls just sitting in drawers in small boxes collecting dust” accumulated over a century ago by European explorers, says Mason, now at the Institute of Cell Biology at the University of Bern in Switzerland.
Using DNA from the museum’s specimens, Mason and colleagues found up to 14 groups of colugo with significant genetic differences. More work is needed to weigh these differences and review the diversity of colugo species. And more surveys are needed on colugo populations and their whereabouts, Miard says, to reliably say if and where colugos are threatened.
The good news is that colugos seem to adapt well to human environments with forests, including the villages of Langkawi. The animals feed on leaves from five to seven different trees each night, according to Dzulhelmi based on his studies in Langkawi and Borneo. He says if a municipality could plant enough trees in gardens, parks and zoos to support free-living colleagues, residents could see and learn about the animals and appreciate them.
After 50 minutes of courtship, Eager the male colugo gave up. Batwoman went back up the road – with four humans on her tail – and started feeding again. We saw a few more colleagues that night, but we stayed close to Batwoman.
Around eleven o'clock at night, Batwoman was still plucking leaves. Suddenly, I felt the air brush against my hair: a colugo was gliding to land on a tree about three feet away. I moved to look closely at the only colleague I warned in front of my guides. But it started to rain and we ran to the shelter.
The next morning, we moved our survey to a leafy resort on the island. In two hours, we found 17 colugos, all embracing the trees, motionless in the light of day. I saw two before Miard did and tried to hide the joy. But the excitement was not my only. Shortly after we found colugo 11, Miard could no longer stand it: "I love colugos!"
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