“The Tough Life" - Louise Emmons and Treeshrews

By Chris Eckstrom
International Wildlife, 1996

On a moonless night in northern Borneo, ecologist Louise Emmons steps into the black maw of the rain forest and disappears. The air is steamy. Insects are screaming. Only the panning movement of Emmons’s flashlight beam identifies her position.

This is the hour when big mammals stir--clouded leopards, elephants, sun bears. But Emmons is after more ephemeral quarry. At the base of a white-skinned mengaris tree, she switches off her light and waits. When she flicks on her beam moments later, the tree sparkles with tiny diamonds of light, flashing up and down the trunk like electric fireflies. “Treeshrews,” she whispers. “Pentails.” Her light catches the eyeshine of four mini-mouse forms with bottlebrush tails before they all skitter off in a tangle of vines.

Few scientists who work in Borneo ever see a treeshrew, least of all the elusive pentail--the only nocturnal member of a family that includes sixteen species, “all neurotic,” says Emmons. Treeshrews are small animals resembling squirrels with glass-button eyes and cone-shaped noses. They bounce around like pinballs through the rainforests of southern Asia, moving so fast that you notice little more than a rustle and a musky whiff.

Misnamed and long misclassified, treeshrews are not shrews (which are strictly insectivorous), and most are ground-dwellers (though many retreat to trees when alarmed). For much of this century treeshrews were believed to be primitive primates, which stimulated great scientific interest in their shadowy lives. Now fallen from the lofty rank of primate, treeshrews are classed in their own separate order, Scandentia. But despite the earlier flurry of scientific attention, almost nothing was known about them in the wild until renowned field biologist Louise Emmons set her sights on them in 1989 and headed for the island of Borneo, home to more species of treeshrews than any place else in the world.

“I had heard a lot of stories about them,” Emmons says, “and I wanted to find out what was true.” What she discovered, after scientific sleuthing that most experts would write off as impossible, was a snapshot of a mysterious maternal care system and an understanding of how these tiny dynamoes subdivide rain forest niches and scamper a daily energetic tightrope to survive.

“I found out early on that life is tough for treeshrews,” Emmons says. “They work 12 hours a day, 365 days a year. There’s no excess in their lives. They live on the edge.” These words could easily apply to Emmons herself. One of the world’s foremost mammalogists, Louise Emmons has dedicated her life to fieldwork in tropical rainforests from Madagascar to Brazil. Her work with the under celebrated creatures and fine tunings of ecological processes often yields the kind of knowledge that finds its way into reference books. Although she holds positions as research associate at both the Smithsonian and the American Museum of Natural History, she lives on modest research grants, working at field camps from Gabon to New Guinea.

Emmons is also a member of Conservation International’s famous RAP team--for Rapid Assessment Program--an all-star ensemble of field scientists who drop in and out of wilderness hot spots around the world to do fast-sketch surveys of their biodiversity to help determine the most important areas to protect. Of Emmons’s work on RAP, Conservation International Presidebt Russ Mittermeier says, “What she can learn in two weeks would take anyone else years.”

Emmons herself is a rare breed, one of a dwindling number of hard-core field scientists whose work connects the scattered dots of what we know about the natural world to create an overall image of how life works. A champion of the world’s little critters--the squirrels, bats, mouse opossums, rodents, and pygmy everythings--Emmons likes working with the overlooked and unglamorous. “So little is known about the small fauna,” she says, “that everything is a new discovery. And I have the fun of putting the puzzle of their ecology together from scratch.”

When she set off for Borneo to ferret out the unknowns about treeshrews, Emmons carried some ideas from captive studies done in the 1960’s by a scientist named Bob Martin, whose work showed that treeshrews have a bizarre parental strategy unlike that of any other mammal.

“I was so intrigued by them,” Emmons said. “In captivity, mother treeshrews visit their babies once every two days--for two minutes. They nurse and run,” she said, explaining a maternal care system that has been called ‘minimalist motherhood.’ “I wanted to know, was this true in the wild? And why?” Emmons asked. “I knew it was going to be hard work. No one had ever even found a treeshrew nest. And nothing was known about the ecology of all these different species,” she added. “How do they all live together in one place?”

How do you find a nest of unknown description visited by an animal you can hardly see inside the most complex environment on earth? In Borneo, Emmons captured treeshrews in banana-baited traps, fitted them with radio collars, and began to track them. Most were females. “Think about it,” said Emmons. “You’re in the middle of the rain forest, following the radio signal of a tiny animal that’s too nervous to even be in your sight. She runs all day long. Once every forty-eight hours, she goes to one spot for two minutes. How do you find that spot? You can be standing right there with a radio antenna and see nothing. It’s a needle in a haystack.”

Just after she began her work, Emmons captured the same female two weeks in a row. The first time the treeshrew was pregnant; the second time, she was lactating. “So I knew--aha! Baby treeshrews. I decided to track her,” said Emmons. “The very next day I stopped by a trail, and right next to me, she popped out of a hole in a tree. What a piece of luck! I just knew, well there it is.”

Emmons set up a blind and watched. Every two days the mother treeshrew came--for two minutes. “So Bob Martin was right. It was all true in the wild. And this was the first time it was ever seen,” Emmons said.

But what happens inside the nest? Baby treeshrews are born helpless, hairless, and blind. How do they stay warm, avoid predators? During the month they spend in the nest, their mother visits them for a total of 30 minutes. No other mammal mothers do so little for their young.

While Emmons was tracking treeshrews in Borneo, back at the National Zoo in Washington, D.C., Emmons’s colleague, research zoologist Miles Roberts, was raising treeshrews in his laboratory. To see what was happening in the nest boxes, he placed video cameras inside--and discovered some amazing things. When a mother treeshrew visits her young, she springs inside the nest, raises her forelegs and presents herself for nursing. The babies grope for her, nurse fast, and roll back with balloon bellies full of milk as the mother leaps out two minutes later. Neither mother nor young makes a sound. Most treeshrews have two young, and Roberts found that energetically, two is the optimum litter size: In the absence of a parent, the babies snuggle up and keep each other warm.

Roberts also discovered that the fat content of a treeshrew mother’s milk may be second only to that of seals and other pinnipeds. The milk’s richness may enable the babies to grow fast with so few feedings. The video cameras revealed more. The babies groom each other--a job done by parents in most mammals--so that nothing soils the nest that might tip off a predator to their presence. That fact was borne out in the wild: The nest and baby treeshrews Emmons found had no detectable scent.

“Everything points to predator avoidance as one reason for this bizarre system,” Emmons explained. “Adult treeshrews have a strong smell that could lead predators right to the young. The mother I watched never took the same route to her nest,” she added. “I also found that treeshrew care is not as minimalist as we think. The wild treeshrew mother spent time with her babies for three weeks after they left the nest. No one ever knew that before.”

Emmons expanded her treeshrew work, radio-collaring males and females of five species, and steadily began to uncover the kind of subtleties that wow her colleagues. When Emmons worked in Gabon twenty years ago, her painstaking work showed that nine species of squirrels can all coexist because each consumes different foods in different layers of the forest. In Borneo, when she asked the same question about treeshrews she found that although all eat insects (and fruit when they can find it), the species separate on a very fine point: how and where they hunt. “Each treeshrew has a distinct feeding tactic,” Emmons says, observing that one treeshrew gleans black ants at night, another digs earthworms under leaf litter, while a third hunts caterpillars by looking up under the leaves of understory shrubs.

Emmons made more connections. Treeshrews have simple digestive tracts (“it’s just a tube”)--and she found that they pass food more quickly than any other animal but fruit bats. “What that means is that a treeshrew has to eat all day long,” she explained. “A treeshrew can never afford to rest.”

One grueling hallmark of Emmons’s fieldwork is continual tracking, for several days in a row, of an individual animal. “When I’m following an animal, I get a feeling for the shape of its daily life, where it goes, what it does all day long. I want to know what it means to be a small mammal out there in the forest,” she says. “This is the nitty-gritty of ecology.”

She once followed a female ocelot in the Amazon rainforest. “I found that an ocelot has to work up to eleven hours a day just to find enough to eat,” Emmons said. “But this particular female had young. I followed her once for twenty-three hours. She just walked and walked. She walked until there were no more hours left in the day before she finally stopped. She just couldn’t get enough,” Emmons remembered. “And she lost her young.”

“Treeshrews and ocelots have exactly the same problem,” Emmons said. “They both live on the edge.” Then how do female treeshrews find the extra energy they need--up to twice as much--to raise young? “In captivity, treeshrews breed continuously. In the wild they never do. The bottleneck is food,” Emmons explains. “If you already run all twelve daylight hours each day to find food, how are you going to get twice as much?” Emmons found that treeshrews breed when fruiting peaks occur in the forest: The additional calories from fruit provide the extra margin for raising young. “Energetics may be related to their maternal care too,” she said. “If the mother treeshrew doesn’t have to run back to the nest every night, the energy she saves may be crucial.”

The tough life has its rewards, both for treeshrews and hard-working scientists. During her fieldwork in Borneo, Emmons and two Malay colleagues made a serendipitous discovery: They found the fruit of the rare rafflesia, the world’s largest flower--a garish red blossom up to three feet wide. “No one had ever seen the fruit of this species before,” Emmons said. “We just hiked up and there it was.” It looked like a chocolate-brown canteloupe--and something had taken a few bites.

“So I said, ‘Let’s build a blind and watch!’ We did, and I took the four a.m. shift,” Emmons said. “Just before sunrise I saw something sneak up to the fruit. And what was it but a treeshrew!” she said. “He hung on to a tree with his hind feet and reached down inside this fruit, which looks like a bowl of custard filled with millions of tiny seeds. It tastes like fermented coconut, and it’s a pool of pure oil--a mother lode of energy for a tiny forest animal.”

Later, a squirrel made a brief visit. “Both are ideal dispersers of these seeds because rafflesias are parasitic to a certain vine, and that’s exactly where treeshrews and squirrels run. They would spread these sticky seeds on vines all over the forest. It makes perfect sense,” she said. “And it was so much fun. For us it was a twenty-four-hour mental fling,” Emmons added. “For the treeshrew it was like a big ice cream cone.”

It wasn’t until she returned home that Emmons realized that she had pushed the boundaries of science once more. The rafflesia fruit was a new discovery, as were its furtive consumers. “Most people think that everything in nature is known,” Emmons says. “The truth is almost the opposite--especially for the smaller animals. Nobody knows what a civet does all day long, or a jaguarundi.

“With small mammals like treeshrews I can study their whole lives, and several generations, in a short period,” Emmons says. “And because their populations rise and fall according to smaller environmental changes, they can tell us more about resources in the forest, and what the boundaries are for survival.

“I’m interested in these animals that live on the edge,” she says. “They make us ask, what are the limits?” What are the limits--for a treeshrew, a rain forest, or for bigger mammals and other ecosystems? There may be something of Louise Emmons in the tough cases she tackles, and something for us all in the answers she finds.

*Louise Emmons is one of the field biologist that i admire the most. Her works on Bornean Treeshrews is one of the important reference for the treeshrews ecology. As i said in my previous posts, it is not an easy work to become a good field ecologist.