One Tiny Wasp Turns a Fig Tree Into a 150-Foot-High Eden

Birds, bats, monkeys by the dozen: A fruiting fig tree is a riot of life. It all goes back to the tree's ancient partnership with an insect.

“This is what makes them very special: At any point in time in the tropical forest, there is a fig that has fruit.”

German photographer Christian Ziegler, a tropical biologist by training who lives on the edge of a Panamanian rain forest, is talking about one of his obsessions. Where other trees have distinct fruiting seasons, Ziegler explains, figs are always available somewhere in the forest. And so especially in lean times—even a rain forest has a dry season—a fruiting fig can become a mob scene, like a watering hole in the Serengeti. Birds, monkeys, bats, insects—dozens of species congregate on a single tree, feasting in a noisy frenzy.

The origins of the feast go back 75 million years. That’s when figs first evolved, probably in Eurasia, possibly in China—but certainly in conjunction with the tiny wasps that pollinate them. Since then, as figs have spread around the world and diversified into between 750 and 1,000 species, the wasps have diversified with them. Each species of fig has just one or two wasp species that pollinate it.

Tree and wasp are totally dependent on one another. And all over the world, from Peru to Gabon to Indonesia to Australia, countless other species depend on a strange accident of their intersecting life cycles: While other species of tree tend to fruit in synchrony in a given area, fig trees do not.

“They are like pop-up restaurants,” says Michael Shanahan, author of Ladders to Heaven, a new book on the science and cultural history of fig trees. “Everything comes and feeds on them for three or four days. And you come back a couple days later, and it’s like nothing happened.”


Two carpenter ants forage on fig fruit. Bats are the primary consumers of this particular fig, but in the Amazon, ants are never far away.
PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

Crazy, but in a Good Way

Ziegler wants to capture what may be the wildest fig feast of all, and so he dreams up an outrageous idea. He brings $90,000 worth of steel scaffolding to the Peruvian Amazon, moving it 200 miles down the Alto Madre de Dios River and up the Manu River in motorized canoes. His destination is one of the most diverse places on Earth: the Cocha Cashu Biological Station in Manú National Park. On the 2,500 acres of the station, there are more than 500 bird and 70 mammal species. And many of them eat figs. The scaffolding will allow Ziegler to get to where most of them live, high in the forest canopy. (Read all about Manú and its inhabitants in National Geographic magazine.)

“I’ve seen a hundred monkeys in a single tree,” says John Terborgh, an ecologist at Duke University who has spent more than 40 years studying the intricacies of the Peruvian Amazon at Cocha Cashu. “On moonlit nights, if they are hungry, they’ll get up at two in the morning and be there at four a.m.”

Once Ziegler arrives at Cocha Cashu, he begins searching for a fruiting fig within a mile or so of the river, where his scaffolding lies gleaming on the beach. As soon as he finds one, the race is on to reach the party while it lasts. The scaffolding is erected in a flash by eight young men from the Matsigenka tribe, the indigenous residents of Manú, under the supervision of Antonio Gerra, a Cocha Cashu staffer from Lima. The team wear hard hats provided by Ziegler, but for the most part no shoes. Born and bred in the forest, they’re excellent, confident climbers. (They also have very interesting conceptions of nature and the afterlife.)

Once fruiting slows down, Ziegler looks for a second tree, and the entire metal structure is disassembled and schlepped through the jungle so he can have another chance to get the photographs he wants.

Here in the Amazon, days from a hardware store, they improvise when construction challenges arise. They lash beams together with vines; they use bow and arrow and slingshot to try to loop guidelines over dizzyingly high limbs. As they carry the scaffolding from place to place and set it down, indigo and tomato-red butterflies, genus Panacea, alight on the beams, sipping the sweat that has rubbed off their shoulders.

Once the tower is erected, Ziegler has to climb it. He’s a pleasant sort of obsessive, short and intense, with jaw-length hair and a perpetual smile—and, as it turns out, a deep fear of heights. He takes it floor by floor. It is on the second tower, while spending some time clinging to a fig limb that crosses floor 10, that he admits there is perhaps just a touch of craziness in his plan.


To immerse himself in the canopy, Ziegler photographed from a platform 100 feet above the forest floor.
PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

A red howler monkey eats a fig. These monkeys spend more than half their day sleeping or snoozing in the treetops.

White-fronted capuchin monkeys, including this juvenile, were curious about Christian Ziegler and his giant lenses, but their first priority was to vacuum up as many figs as they could fit into their mouths. PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

But once he’s at the top, 12 stories off the ground, Ziegler finds himself in another world. The tree is hopping. He sees hungry howler monkeys, spider monkeys, and brown capuchin monkeys—sometimes all at once. A white-fronted capuchin monkey—fuzzy, elegant, tail curled under—detaches small figs with nimble fingers and pops them in its mouth like popcorn. Anole lizards flash their bright neck flaps at rival males. Ziegler observes butterflies and damselflies and bees that never descend to the ground, and dozens of species of birds: barbets, paradise tanagers, scarlet macaws that arrive in pairs, and fat, piping guans, which look like elegant turkeys. He also catalogs 17 species of insect that bite or sting him. “Here, you become part of the food chain very fast,” Ziegler says.

Despite its dizzying height, the scaffolding is shorter than the tree; at the top, the fig’s crown is still overhead. But much of the forest canopy is spread out below, a sweeping green expanse of trees, lianas, and their inhabitants. One hears birds and insects, distant whoops and unidentifiable descending notes. The wind rocks the scaffold just a bit and, in the heat of the late morning, one feels dozily as if one is rolling on a small boat. Above the green sea of leaves, parakeets sing.


A cloud of mimosa yellow butterflies is attracted to small figs on a beach alongside the Manú River.
PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

The Evolution of a Miracle

Nothing in the scene is more amazing than the fig tree itself—and especially the way it reproduces. Its partner is a wasp the size of a lowercase i. The wasp pollinates the fig, and in return, it doesn’t get food, as most pollinators do. It gets a snug nursery.

Fig wasps deposit pollen—and lay their own eggs—in the fig’s egg-bearing ovules. The ovules are inside the flowers, as they are in other flowering plants. But on a fig tree the flowers themselves are tucked inside an unripe fruit. It’s an inside-out bouquet of up to 10,000 tiny flowers packed in a tight orb.

When the wasp eggs hatch, males emerge first. They immediately mate with their sisters through holes in the walls of the unhatched eggs. After the impregnated females emerge, the males nibble an escape tunnel through the fig for their sister-wives. The females take off, full of fertilized eggs and coated with fig pollen from the flowers they brushed by on the way out. The males die, never having left the tiny world in which they were born.

(So if you eat a ripe wild fig, there’s an excellent chance you’ll ingest a few minute male wasps. Perhaps not coincidentally, many familiar varieties of fig do not require pollination; there are no tiny corpses in supermarket figs.)

After the females leave the fig, they must find another fig tree with receptive fruits in which to lay their eggs. Following trace chemical signals in the air, they often fly more than six miles, and on rare occasion more than 100. Once a female finds a likely fig, she wriggles in through a tiny opening that, because fig and wasp have evolved together, is just large enough for her head. She proceeds to pop her eggs in about half the available ovules, dusting the rest with the pollen she brought with her. The pollinated ovules become seeds as the fruit ripens.

Birds or monkeys eat the fruit, and when they excrete the seeds, chances are they’re far away, perched or lazing in a different tree. This is ideal for many fig species—they actually germinate in the canopy, perhaps in a little bit of earth in the crotch of a branch, and send roots down to the forest floor. The growing roots twine around the host tree, and ultimately they engulf, strangle, and replace it. Looking at a mature fig, with its smooth trunk hurtling toward the sky, one would never know it conceals the ghost of the tree that supported it as a seedling.

But the key to fig trees’ outsize ecological role is their partnership with wasps, and the timing that imposes. It takes about a month for wasp eggs to mature and hatch. When the females emerge, they have only a day or two to find another receptive fig before they die—which means there needs to be one available within a two-day flight. To hold up their end of the ancient partnership, figs have to reproduce all year long, like the wasps. And so unlike nearly every other fruiting tree, they don’t all fruit in a single season. Each individual tree fruits at a random time, thus ensuring that there is always a receptive fig—and a party going on—somewhere in the forest.


An ocelot walks across a fallen log at Cocha Cashu Biological Station, one of the most biodiverse places on Earth.
PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

A urania butterfly, a kind of swallowtail, feeds off the sap of a tree. In the Amazonian rain forest, much of the food web is in the canopy.

Fig trees benefit from birds and monkeys eating their fruit and spreading their seeds—but probably not from this caterpillar, which is eating fig leaves. PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

A Rain of Figs—and Dung

The most boisterous action unfolds in the tree’s canopy, more than a hundred feet up. Many monkeys up there never touch the earth. Even from the ground, one can hear the cracks and rustles and hoots. But there’s a lot going on underneath the tree too.

It sounds like rain under a fruiting fig, as the copiously falling fruit hits broad tropical leaves. The ground is blanketed in fruit. Even as figs continue to pelt the ground, the first to fall have begun to rot and are enveloped in a nimbus of diaphanous white fungus. Minute white flies hover over the figs, bouncing in place, like the impatient bobbing of a foot. It smells like wine dregs and mold.

In Manú, if one sits quietly at the foot of a fruiting fig at dawn or dusk, one might see a small, pointy-nosed mammal, the paca, coming to eat, or a herd of pig-like collared peccaries. During the day, a neat file of waddling chicken-size birds with white rumps—the pale-winged trumpeters—might come through. They might be followed by human hunters, looking for monkey meat. The waves of energy from a fruiting fig ripple up and down the food chain.

One morning I watch a family of howler monkeys having breakfast in a fig tree by the river. After the meal they move to another tree, then line up—mom, dad, and two kids—and hang their posteriors over a branch. The feces hit broad heliconia leaves with a series of loud slaps. I go over to inspect the dung. The fig seeds are clearly visible.

Within five minutes, several dung beetles have landed and begun to excavate portions of the figgy substance, rolling it into balls with which they will woo females. If a female is sufficiently impressed, she’ll accept the dung ball and use it to incubate her eggs. For their first meal, the baby beetles will have fig seeds.

Figs feed more wild animals than any other type of fruit. Ziegler would like to chase that ephemeral feast in other tropical forests, in Gabon maybe or in Indonesia. At Cocha Cashu he experiences the thrill of arriving at the height of the party—and also the letdown when it's over too soon. Just a couple of days after he and his Matsigenka crew erect the scaffold around his second tree, the fruit is all but gone. “It was after a day of rain,” he says with a sigh. “One day the tree had maybe 50 monkeys, and after it was over.”


Cocha Cashu, the biological station where figs have been studied for decades, is named for this oxbow lake, seen here just before heavy rains set in. PHOTOGRAPH BY CHRISTIAN ZIEGLER, NATIONAL GEOGRAPHIC

Follow Emma Marris on Twitter.

Discuss this article

Newsletter

Never miss a Nat Geo moment

Your email address
Submit