The giant termite mounds that rise up from the sands of the African savanna are so distinctive it’s tempting to give them names, like “Art Deco Skyline” or “Trumpeting Elephant” or “Flagrantly Obvious Fertility Totem.”
Whatever the metaphor, the charismatic megaforms dominate their landscape, and not just visually. As scientists are just beginning to appreciate, termites and the often elaborate habitats they construct are crucial to the health and robustness of a broad array of ecosystems: deserts and semideserts; tropical and subtropical rain forests; warm, temperate woodlands; possibly your local park.
Researchers at Princeton University and their colleagues recently reported in the journal Science that termite mounds may serve as oases in the desert, allowing the plants that surround them to persist on a fraction of the annual rainfall otherwise required and to bounce back after a withering drought. The mounds could thus prove potential bulwarks against climate change, preventing fragile dryland from slipping into lifeless wasteland.
“Even when you see desertification start to happen between the mounds, the vegetation on or around the mounds is doing so well it will keep reseeding the environment,” said Corina Tarnita, an author on the new report and an assistant professor of ecology and evolutionary biology at Princeton.
And while the public may view termites as pale, blind, half-inch vermin that can genuinely eat you out of house and home, only a handful of the 3,000 or so known termite species are pests to people. Many of the rest, you can thank for the ground beneath your feet, which is where the majority of termites live and tirelessly work. The closer scientists look, the longer grows the list of subterranean tasks that termites take on.
“They’re the ultimate soil engineers,” said David Bignell, a termite expert and emeritus professor of zoology at Queen Mary University of London.
By poking holes, or macropores, as they dig through the ground, termites allow rain to soak deep into the soil rather than running off or evaporating. Termites artfully mix inorganic particles of sand, stone and clay with organic bits of leaf litter, discarded exoskeletons and the occasional squirrel tail, a blending that helps the soil retain nutrients and resist erosion.
The stickiness of a termite’s feces and other bodily excretions lend structure and coherence to the soil, which also prevents erosion. Bacteria in the termite’s gut are avid nitrogen fixaters, able to extract the vital element from the air and convert it into a usable sort of fertilizer, benefiting the termite host and the vast underground economy.
“Over all, termites are extremely good for the health of the soil” on which everything else depends, Dr. Bignell said.
Termites are also proving worthy as a so-called model system for understanding the origins of social life, the division of labor, and the sort of altruistic, self-abnegating behavior that we humans applaud in others but generally avoid engaging in ourselves.
In a new study of “panic escape” behavior among termites as they seek to flee from danger, researchers at Louisiana State University Agricultural Center determined that the one thing the termites do not do when experimentally disturbed is act panicky.
They don’t start running pell-mell, pushing and shoving, or clambering over the fallen. They don’t behave like people in a crowded theater when somebody yells fire, or like stampeding walruses, or, for that matter, like ants whose nest has been harrowed.
Instead, the researchers found that when they placed 110 termites on round plastic dishes and gave the plates a shake, the termites started running in an extremely orderly, rules-based fashion, depending on whether they were ordinary workers or soldiers dedicated to nest defense.
The workers fell into single-file formation. The ones in front decided whether to turn left or right, and the rest followed in a unidirectional flow at a uniform speed and spacing.
For their part, the soldiers migrated to either side of the flow, snapping their huge mandibles as though preparing to do battle. Round and round the dishbound termites trotted, fruitlessly but never frantically seeking an exit. If one termite stumbled or slowed down, those behind would stop and wait for it to right itself: No trampling allowed.
That unfailing etiquette distinguishes termites from their more famous counterparts among social insects, the ants. “Ants can be selfish,” said Gregg Henderson, an entomologist at the agricultural center and an author of the report, which appeared in the journal Insect Science. “Ants will crowd over each other and get trapped at exits or intersections. But I’ve seen no evidence of selfishness in termites.”
That may be because they have had a lot of practice. Termites, Dr. Henderson said, “were the first animals to form societies,” starting down the communal path about 200 million years ago, some 50 million years earlier than the ants and their hymenopteran cousins, the bees.
All eusocial insects share the same policy: a strict division of labor, and the assigning of colony breeding privileges to a single large, long-lived, perpetually egg-laying queen. Yet while the overwhelming majority of individuals in an ant nest or beehive are sterile, closely related females, a termite colony is pretty much 50-50 males and females, brothers and sisters.
Why termite society turned eusocial in the first place, an evolutionary leap that denied nearly all its citizenry the seemingly Darwinian right to personal reproduction, remains an active topic of research. By some calculations, the driving force was the sheer efficiency of scale. If the termites in a given colony are siblings, or at least close cousins, they can do a better job of fostering their genetic legacy by stoking their egg-laying queen mother than by bothering to mate on their own.
And termites have been enormously successful. Taxonomically, they’re considered “a superior kind of cockroach,” as Dr. Bignell puts it, but termites account for a far greater portion of the world’s insect biomass than do all the other cockroaches combined. In the tropics, where social insects rule, the termites outweigh the ants hundredfold.
With the help of symbiotic bacteria and protozoa packed into the termitic paunch at what might be the highest microbial densities in nature, termites thrive by eating what others can’t or won’t: wood, dung, lichen, even dirt.
The great termite artists of Africa, the mound builders, have also recruited an external symbiont, a fungus, which they cultivate in tunnels and galleries deep inside vast palaces built of sand, clay and termite excretions. The termites eat a small portion of the fungal spores and use the fungal enzymes to help break down their more fibrous food sources.
The termites in turn offer their fungal partners plenty of water, nourishment and a clean, safe, temperate and well-ventilated haven free of competing fungal strains. The mounds also protect their builders — against the sun that would desiccate them, the seasonal rain that would drown them, and the many predators that would happily devour them.
The largest African mounds can measure 30 feet high and 80 feet across, and house millions to tens of millions of termites. The mounds are refugia for plants, fungi and large herbivores, too. In Mozambique’s Gorongosa National Park, antelope like bushbuck and kudu often congregate around termite mounds, and not just for the grazing opportunities.
“The mounds are cooler in the heat of day and warmer at night,” said Robert Pringle, an ecologist at Princeton and an author of the report in Science. “They’re a very pleasant place to hang out.”
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