“Bug Poop Grows Trees” (BPGT)
By Lee Anna Sherman
In Andrew Moldenke’s forest ecology course, students get the BPGT acronym drilled into their heads from Day One. Oregon’s fabled old-growth forests owe their existence to insect digestion, and the professor wants to make sure nobody forgets it.
Chris Marshall had collected insects in a lot of unusual places. But scrounging for a rare species of moth in the fur of a three-toed sloth had to be the weirdest.
It happened one black, sweltering night in the unexplored rainforests of northern Guyana in 2006. The OSU entomologist, rousted from his hammock by a commotion in camp, switched on his headlamp. He found himself looking into the frightened eyes of a docile, moon-faced mammal captured by the native guides assisting the scientific expedition.
The two-foot tall creature, whose coarse, shaggy hair glistened with a green patina of algae, sat quietly as Marshall gently searched its back for specimens of the Bradipodicola hahneli (“sloth moth”), which lives exclusively in this hairy habitat. Then, without warning, the sloth turned to face the researcher. Before Marshall could react, the animal wrapped its powerful, apelike arms around him. With the sloth’s hot breath on his neck, Marshall felt a rush of adrenaline as he visualized its peg-like teeth and its four-inch hooked claws.
“I had a furry, wild animal clinging tightly to my body with its face inches from mine,” Marshall recounts. “I couldn’t have pried it off without great effort. It was then that I realized I didn’t really know whether these animals are friendly or aggressive.”
No blood was spilled that night. The guides disengaged the sloth and sent it slouching up the nearest tree. Marshall, meanwhile, sealed his hard-won specimens into tiny plastic vials. Before the journey was over, the zoology faculty member would fill thousands of such vials, as well as glassine envelopes and zip-locked, ethanol-filled polyethylene bags, with bugs destined for arthropod collections in Corvallis and the Guyanese capital of Georgetown. Among the specimens shipped out of the jungle were several beetles never seen by scientists. To identify his discoveries would require months of meticulous lab work and tedious database searching.
“It’s always exciting to identify a new species, but there’s no automatic definition of how that’s done,” Marshall explains. “Some scientists are turning toward using a certain percentage of difference in DNA, but there’s still skepticism about that approach. More traditionally, we look at things like shape, body structure, male genitalia, ability to interbreed and other attributes of an organism. Integrating all of this information into a coherent notion of a ‘species’ can take months or years. That’s the main reason it takes so long to identify everything from a trip like this.”
The expedition’s finds — which in addition to the beetles included new species of katydids, butterflies, catfish and frogs — will contribute to scientific understanding of the Guyana Shield and other tropical rainforests at risk from extraction industries such as drilling, mining and logging, as well as deforestation for agriculture. Conservation International, one of the expedition’s sponsors, has designated “biodiversity hotspots” like the Guyana Shield as “the richest and most threatened reservoirs of plant and animal life on earth.”
“The air was calm, full of the eternal hum of insects, a tropical chorus of many octaves, from the deep drone of the bee to the high, keen pipe of the mosquito.”
Sir Arthur Conan Doyle, The Lost World, 1912
Born to Love Bugs
Living a boyhood obsession
There are two kinds of entomologists: those who love insects intellectually and those who love them viscerally. Without a doubt, Chris Marshall fits into the second category.
Marshall and a team of researchers from Venezuela, Colombia and the United States had joined Guyanese scientists in this South American wilderness to seek insects, birds, reptiles, amphibians and fish that are unique to this place, a land so otherworldly, so untouched, that it inspired Sir Arthur Conan Doyle’s 1912 tale of remnant dinosaurs. In this “lost world” known as the Guyana Shield, vast plateaus of ancient granite rise 3,000 feet above a jungle canopy whose shadows hide jaguars as elusive as ghosts and snakes as thick as tree trunks. Mazes of rivers breed electric eels, stingrays and caimans (cousins of the crocodile). Also swimming in the teeming waters is one of the world’s largest freshwater fish, the arapaima, which can grow to 10 feet in length and weigh more than 400 pounds.
“Ironically,” Marshall notes, “the arapaima is related to the minnow.”
But it’s the bugs, millions and millions of them, that dominate the landscape. Like the “sloth moth,” which subsists on blue-green algae growing on the slow-motion mammal, each species exists in perfect adaptation to a precise niche in the biosphere. Scarabs scour the forest floor for dead things and manure. Mantises disguise themselves as sticks or leaves. Butterflies “puddle” on moist soil, resembling seas of pale-green petals as they ingest salts and minerals. Katydids clutch smaller bugs in their spiny legs and crunch them with their powerful jaws. Lightning bugs glow like sparks from campfires. Ants use their shovel-shaped heads to plug their burrows against predators. Other ants spy their prey with giant, high-resolution eyes.
Guyana’s butterflies, dragonflies, scorpions and spiders were intriguing to Marshall, who curates and manages the Oregon State Arthropod Collection (see sidebar). But his scientific investigations were focused elsewhere. While his fellow entomologists concentrated on ants and katydids, he attended to his specialty: beetles. The jungle boasts beetles that shine like obsidian and others that shimmer with rainbow iridescence. Even though he’s an expert on the glossy black beetles of the family Passalidae, Marshall admits to having a soft spot for the drabber members of the world’s vast and varied beetle species, estimated at 5 million. “I like the small, humble brown beetles better than the big, showy ones,” he says. “I find it more interesting to sift through the unobtrusive, obscure groups. Fewer collectors care about them, so they’re much less studied.”
Some of the bugs he encountered, however, were not so appealing. The ubiquitous ticks, for instance, forced him to soak his clothes in pyrethrins (pesticides made from chrysanthemum flowers). Malaria-bearing mosquitoes made sleeping nets mandatory. To foil swarms of sticky, persistent black flies, which can carry river-blindness disease in their painful bite, Marshall worked in long sleeves despite the oppressive heat. “The horsefly was everyone’s bane,” he says. “We couldn’t get away from them. One day we were hiking through a swamp of spiny palms. It was hard to walk, and it was real wet, very humid and muggy. That’s where the horseflies were the worst they could possibly be.”
Another perilous pest was the sandfly. Smaller than an ordinary mosquito, this insect transmits a disease called Leishmaniasis. The protozoan, a microscopic single-celled organism, can cause devastating wounds that destroy skin and mucous membranes, causing massive scars. Worse, some victims have lost ears and noses.
Why would Marshall and his fellow researchers risk life, limb and nose in this inhospitable place? Beyond the basic motives of science (delving into mysteries, uncovering clues, connecting dots) and beyond the more prosaic goal of beefing up the bug collections at Georgetown and at OSU, they were driven by the urgency of an endangered ecosystem. The expedition was part of an ongoing movement to protect the shield’s extraordinary biodiversity from human exploitation. In cooperation with a small group of Amerindians indigenous to the Guyana Shield, the Guyanese government has set aside a 1.5 million-acre swath of the rainforest as a preserve. Funded by the Smithsonian Institution, National Geographic and Conservation International, the expedition carried out a “rapid biodiversity assessment” — in essence, a marathon collecting binge for zoologists — to help document the scope of Guyana’s species diversity. One set of specimens would go to the Center for the Study of Biological Diversity at the University of Georgetown.
The mission had a cultural component, as well. The native guides and porters were naturalists-in-training. Members of the Wai Wai tribe have been tasked with managing the preserve, protecting the animals and plants living along the mighty Essequibo River and its tributary, the Sipu, against poachers, loggers and miners. Investigating their ecosystem along with the university-trained scientists, the Wai Wai were preparing to become para-biologists and rangers, formalized roles for the people who have been Guyana’s unofficial “forest keepers” for generations.
Expedition to the Edge
“Once some bandy-legged, lurching creature, an ant-eater or a bear, scuttled clumsily amid the shadows.”
The Proboscis Hypothesis
Very likely, argues OSU zoologist George Poinar in his new book, What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous.
Marshall first met his guides after the expedition embarked in early October 2006 from a small airfield on the outskirts of Georgetown. A reluctant flyer, he felt the color drain from his sweat-beaded face as the twin-prop plane lifted off and rose above a patchwork of small farms and scattered houses. Soon, from the window of the droning aircraft the entomologist saw nothing but the rainforest’s emerald canopy stitched to the sky in every direction.
The flight, it turned out, was just the first of Marshall’s many white-knuckle experiences in Guyana. The plane touched down near the banks of the Essequibo, where the Wai Wai guides, “druggers” (equipment porters) and “line cutters” (machete-wielding trailblazers) were waiting to take the team upriver. In this trackless forest, modes of travel are two: foot and canoe. Several dugouts, hand-carved of dark purple heartwood in the ancestral Wai Wai tradition, sat on the riverbank. But in a jarring clash of cultures, each primitive boat sported a shiny outboard motor. The 750-horsepower Evinrudes, lent to the expedition by Conservation International, have obvious advantages over paddles for transporting several entomologists, an ornithologist, an ichthyologist, a herpetologist, a mammalogist and a water-quality expert — as well as hundreds of pounds of food and gear — deep into the lost world.
The boats pushed off. The tangled green understory, lush and luminous in the filtered sunlight, closed around the travelers. It wasn’t long before Marshall noticed water pooling around his feet, apparently seeping through a crack in the heart-wood hidden under bulging bags of gear. During the two-day journey, whenever the canoe struck a submerged log with a loud crack! (as it did every now and then), he halfway expected the vessel to split in two “like a peapod” and dump the researchers into waters as brown and opaque as chocolate milk. But the craft, which the Wai Wai patched each night with sticky, resinous bark scrapings, was sound and sturdy in its ancient design. It never foundered.
After the researchers disembarked, they spent another day hiking into the forest to reach their first survey site.
It’s Marshall’s expertise as a coleopterist (beetle specialist) that made him vital to the expedition. That’s because beetles, particularly dung beetles, are important components of tropical rainforest systems. “Dung beetles are important decomposer organisms, involved in nutrient recycling, seed dispersal and the control of vertebrate parasites,” British researcher Andrew Davis and colleagues wrote in the Journal of Applied Ecology in 2001. “Consequently, dung beetles are a useful indicator group because they reflect structural differences between biotope types.”
The lowly dung beetle or scarab (family Scarabaeidae), largely ignored after its heyday as a deity in ancient Egyptian mythology, has recently reclaimed some of its lost stature, this time as an indicator organism. All over the planet, from Australia to Southeast Asia, ecologists and entomologists study scarabs as gauges of ecosystem well-being and harbingers of stress.
“There is a lot of interest in dung beetles globally because of their ability to reflect changes in ecosystem health and land usage,” says Marshall. “Each species has specific soil and forest ecological needs, and some of them are linked to very specific vertebrate fauna – mammals and birds. As mammal and bird diversity declines, so does the scarab beetle associated with that habitat.”
Collectors lure scarabs with baited traps. However, packing in buckets of hog manure, the usual bait, would be impractical in Guyana. And because scarabs are fast and efficient manure removers, finding it in the rainforest can be difficult. So Marshall and other dung beetle experts are sometimes forced to resort to human excrement.
“It’s not the ideal bait,” Marshall hastens to explain. “There is an ongoing effort to create a synthetic lure. But scarabs’ sense of smell is extremely sensitive, and designing an imitation for manure is actually more complex than it might at first appear.”
Distasteful as dung beetle baiting might be, the strategy brings speed and efficiency to ecological research. “With passive traps,” the entomologist explains, “you can do a survey of the dung beetle in 24 to 48 hours that can serve as a surrogate for the months of work necessary to survey birds or mammals.”
“…during the hot hours of the day only the full drone of insects, like the beat of a distant surf, filled the ear…”
When he wasn’t baiting traps and collecting captive scarabs, Marshall was chopping open rotting logs in search of his other Guyana get-list priority: patent-leather beetles. As shiny and black as Sunday-school shoes, these showy bugs have intrigued him since the 1990s when he was a Ph.D. student at Cornell, not so much for themselves but for their symbiotic bond with another species of bug, the mite (see sidebar, “Born To Love Bugs”).
One late afternoon near dusk, alone and far from camp, he was hurrying to collect his captive scarabs before the light failed. His excitement about finding a rare specimen in his trap dissolved instantly when he heard a sound in the brush. He froze, his senses on hyper-alert as the crunch-crunch-crunch of large feet on leaf litter got louder and louder. He weighed his options: Stick around and take pictures or back away slowly. Both hoping and fearing that the unseen creature was a jaguar, the researcher sucked in his breath and decided to stand his ground, focusing his video camera on the rustling shadows. When the beast emerged into the dappled light, it was standing just feet in front of him: a giant South American anteater, Myrmecophaga tridactyla, its funnel-like nose snuffling the earth in search of termites. The gangly, bushy-tailed animal stood up on its hind legs, looked curiously at the researcher and then lumbered away, snout to the ground.
Just another bug collector.
Sharing Guyana’s rainforests with the sloth and the anteater are arthropod species in the hundreds of thousands. Only a few thousand have been identified and cataloged. That ratio is reflected worldwide: Just 2 million of Earth’s total number of animal and insect species — estimated as high as 30 million — have been described, according to the World Conservation Union’s Species Survival Commission. Faster than scientists like Marshall can find and identify unknown life forms, others are disappearing forever. More than 15,000 species are at high risk for extinction, and the rate is speeding up as the Earth warms and habitats shrink.
For Marshall, knowing what’s at stake dwarfs the danger and discomfort of rainforest exploration.
“The knowledge gained far outweighs the risks,” he says. “It’s only through these types of expeditions that biologists discover new species and work toward our ultimate goal of documenting the Earth’s insect diversity.”
The global race to understand patterns of biodiversity and ecology is in full-tilt, Marshall says. “When a species goes extinct, we lose a piece of the puzzle forever,” he stresses. “To complete the whole picture, we need to do two things: halt or reverse the trends that are driving extinctions and share specimens with the world’s natural history museums.”
“We need to preserve as many pieces of the puzzle as possible. And we need to do it quickly.“