Across the southern hemisphere, there’s one type of insect that seems to dominate the landscape. In the heart of Africa's wild landscapes, beneath the golden grasslands and towering baobabs, a hidden world of meticulous architects exists. These tireless workers, known as termites, are perhaps one of the most underappreciated yet crucial creatures in the ecosystem.
Termites belong to the infra order Isoptera which includes over 2,600 species worldwide. They are often referred to as ants which they are not. A colony of termites will include different castes, all with specific roles. They feed on dead and decaying plant material such as leaf litter, soil and wood.
Here in North America, termites are known as destructive pests that invade our homes, slowly devouring and weakening the wooden framework. In Australia, South America and parts of Asia, termites are seen differently.
At least 165 termite species, from 54 genera, are found in southern Africa. Although there are large differences between genera they are all characterised by a high degree of social organisation, with each species containing several distinct “castes”. Depending on their caste - reproductive (king and queen), soldier or worker - termites of the same species can look and behave completely differently.
Termite Mounds: Architectural Marvels
The large towers of mud that termites live in, known as termite mounds, can stand over three metres in height above ground, while their "living space" beneath the ground can cover up to approximately 50 square metres! What may appear at first as a huge lump of dirt is in fact a complex architectural masterpiece designed to house termites and help them break down the cellulose components of wood, decaying plants, and fungi.
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The mounds sometimes have a diameter of 30 metres (98 ft). Most of the mounds are in well-drained areas. Termite mounds usually outlive the colonies themselves. If the inner tunnels of the nest are exposed it is usually dead.
Termite mounds are wonders of engineering and probably don’t function exactly as you think they might. For example, a common misconception is that the termites live inside the mounds, which they don’t.
The structure of the mounds can be very complicated. Inside the mound is an extensive system of tunnels and conduits that serves as a ventilation system for the underground nest. In order to get good ventilation, the termites will construct several shafts leading down to the cellar located beneath the nest. The mound is built above the subterranean nest. The nest itself is a spheroidal structure consisting of numerous gallery chambers.
They come in a wide variety of shapes and sizes. Some, like Odontotermes termites build open chimneys or vent holes into their mounds, while others build completely enclosed mounds like Macrotermes.
The extensive system of tunnels and conduits have long been considered to help control climate inside the mound. The termite mound is able to regulate temperature, humidity and respiratory gas distribution.
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How Termites Evolved to Build Massive Mounds
The Mounds as Ventilation Systems
A termite mound is a complicated system of tunnels and conduits providing ventilation to the underground nest. The mound is built above ground with the nest below. Shafts provide ventilation to the cellar located below the nest.
Termitaria are also known as termite mounds. Communicating entirely through pheromones, millions of blind worker termites can raise several tonnes of soil, particle by particle, into an enormous structure over three metres high. Below the mound lies the nest, where separate chambers house brood galleries, food stores, fungus combs (where termites cultivate a fungus that can break down plant cellulose) and the queen's royal cell.
Warm air rises from the nest chambers, up a central chimney, into thin-walled ventilation flues near the surface. In this way, termites maintain the 100% humidity and constant temperature of 29-31 degrees Celsius required for the successful production of eggs and young. These conditions are exploited by other animals, including monitor lizards, which seal their eggs inside the mounds for safe incubation.
The tall chimneys are exposed to higher wind velocities compared to openings at ground level due to surface boundary condition. Therefore, a Venturi flow draws fresh air into the mound through the openings at ground level which flows through the nest and finally out of the mound through the chimney.
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Recent studies on the Macrotermes michaelseni mound with a better built custom sensor to measure airflow suggests that the air in the mound largely moves due to the convective flows induced by the diurnal oscillation of the external temperature. A secondary thermal gradient is generated due to partial exposure of east side of the mound to the sun before and west side of the mound after noon. Improved reliability of the sensor suggests that wind plays a secondary role relative to the dominant thermal mechanism in ventilation.
Not all mounds feature a sky-high chimney, though. The Macrotermes bellicosus species of termites have two mound styles - the first is the standard chimney and the second, used in cooler forests, is more dome-like and is built to retain heat rather than flush it away. Another species, found in Australia, builds its mounds in a wedge shape, and orients it to the magnetic poles. This position allows them to warm in the morning and shed heat in the afternoon.
What accounts for a mound’s decades-long durability? They may look like they’re just made from mud, but it’s actually a hard, cement-like mix of dirt, clay, plant materials and the glue that sticks it all together - termite saliva.
Termite mounds formed from the old wooden poles of the Cape York telegraph line. Mound-building termites are a group of termite species that live in mounds which are made of a combination of soil, termite saliva and dung. These termites live in Africa, Australia and South America.
Termitaria is the name given to the large mounds which are built by termites. In Africa the termites build mounds which are 2 to 3 metres high. But in some countries mounds can be 9m high and others 30m wide. These mounds maybe 4,000 years old and are up to 10m high.
Fungus-growing termite mounds, or termitaria as they are also know are made with a mixture of soil, saliva and faeces which dry as hard as concrete.
Key Facts About Termites:
- A termite queen may live up to 45 years old, at the end of her life she may be licked to death by the workers.
- Unlike ants that mate only once, the female stores the male’s sperm for future use, the termite king and queen mate daily.
- If the colony is in danger, say from an ant attack, the soldier termites will tap on the walls of the tunnels to alert the rest of the colony.
- The large termite mounds, termitaria, are created by fungus-growing termites (Macrotermes natalensis).
- A queen termite runs the colony via chemical signals (pheromones), these are exchanged across the colony by the sharing of food and saliva. Such signals may prompt her to produce termites of a certain caste, e.g.
- A colony of termites will include different castes, all with specific roles. Kings and queens are responsible for reproduction, soldiers for defence, workers for general tasks and alates establish new colonies. They cannot tolerate sunlight; some of them are even blind.
Typical termite mound in northern Australia. Source: Wikimedia Commons
The Castes of a Termite Colony
Termites are known for their highly organised, social structure. Each colony operates like a well-oiled machine, with castes that include workers, soldiers, and reproductive individuals, all with clearly defined roles.
Workers, smallest in size, are the most numerous of the castes. They are all completely blind, wingless, and sexually immature. Their job is to feed and groom all of the dependent castes.
The soldiers' job is to defend the colony from any unwanted animals. When the large soldiers attack, they emit a drop of brown, corrosive salivary liquid, which spreads between the open mandibles. When they bite, the liquid spreads over the opponent.
Finally, there are the reproductives, which include the king and the queen, responsible for reproducing.
Termites as Ecosystem Engineers
Either way, research by Clarke and Francis shines a light on the role these misunderstood insects play as ecosystem engineers. Termites play a role similar to gardeners in these ecosystems, aerating the soil as they build, which helps with water infiltration and nutrient cycling.
Termites break down dead plant material like wood and grass, turning it into fertile soil. These conditions are exploited by other animals, including monitor lizards, which seal their eggs inside the mounds for safe incubation.
The termites' activities allow water to penetrate into the ground, holding on to critical nutrients and retaining water. In combination with nutrients being deposited by wildlife, the islands become reservoirs of life, even during the harshest droughts.
The southern harvester termite has a broad distribution range, but heuweltjies - which are the result of a buildup of fine soil material, carbon and salts over centuries - only form in semi-desert regions. The southern harvester termite is also common in and around Stellenbosch (the picturesque Winelands university town, about 50km east of Cape Town, where Clarke is based), but the heavy winter rains and dense vegetation prevent mound formation. Here the presence of the termites is highlighted by large bush clumps in the scrubby fynbos (native vegetation) and in nutrient-rich patches in vineyards and fruit orchards.
Vegetation on termite mounds usually differs highly from vegetation in the surrounding. In African savannas, Macrotermes mounds form 'islands' with high tree densities. This is usually attributed to the fact that the mound soils are generally more fertile than other soil due to the digging of termites and their decomposition of plant material.
In the Okavango Delta, it is the fungus-growing termites Macrotermes michaelseni that create the large, characteristic mounds that you see on your game drive or from the air. Together with elephant, hippo, and fire, termites are ecosystem engineers that maintain and build systems like the Delta.
The humble termite has been credited with helping discover the world's richest diamond mine, Jwaneng, in Botswana. In the dry Kalahari soil, termites will burrow as deep as 70 m below ground in search of moisture. At Jwaneng, their activity brought indicators of mineral wealth to the surface, and the subsequent discovery of these led to the opening of the world's richest diamond mine.
After the rains, when conditions are right, the queen produces a reproductive caste of winged males and females - known as imagoes - which leave the colonies in huge swarms to mate, disperse and establish new nests. As the first rains hit the parched Kalahari ground, millions of these winged alates emerge for their nuptial flight. A female from one colony meets a male from another, and they shed their wings and establish a new colony. She becomes the queen, and he the king of their new domain, giving rise to a dynasty that will shape the landscape for decades to come.
An accidental discovery occurred in Buffelsrivier, a desolate corner of Namaqualand some 530km (329 miles) north of Cape Town, Stellenbosch University soil scientists Cathy Clarke and Michele Francis watch as a giant Volvo excavator tears into the dry ochre earth. Over the next five hours the excavator works hard to dig a trench, 60m (197 feet) long and 3m (10 feet) deep, through the heart of a giant, low-slung mound known locally as a heuweltjie or “little hill”. It’s all part of a university project to understand why the groundwater in the area is so salty.
Once the digger has returned to the nearby town of Springbok, population 12,790, Clarke, Francis, and a bevvy of grad students begin to explore the trench. They start at its extremities, what Francis describes as the “boring bits”, feeling the soil and looking for signs of life. As they move inwards, they start to notice small conglomerations of bewildered southern harvester termites (Microhodotermes viator) furiously trying to repair the damage done to their home.
At the centre of the trench, two metres (6.6 feet) below ground level, they encounter “this huge nest that looks like a giant alien”, Francis tells Al Jazeera. Clarke nods in agreement: “The moment I saw it I knew we were witnessing something special. It was just so obviously ancient … And alive.”
Once they’d taken some time to simply marvel at the work achieved by these 1cm (0.4 inch)-long creatures, they moved on to the business at hand: taking soil samples. “I delegated the task to a young male student with a pickaxe,” laughs Clarke. “But he couldn’t get the steel blade to penetrate the sides of the trench.” The ground was so hard, according to John Midgley - an entomologist at the KwaZulu-Natal Museum who was not involved in the project - because it was part of an “ancient mound” created by termites over thousands of years. Eventually, after lots of huffing and puffing, the grad student was able to obtain a sample the size of a soccer ball, which was sent for testing.
This kind of challenge is all in a day’s work for soil scientists, says Clarke, who describes her discipline as “a fun mix of everything from bucket science to high precision X-ray techniques”.
Francis tells me that when they got back to their hotel in Springbok at the end of the day, the cleaner reported them to the manager: “She thought we were zama zamas [South African slang for illegal miners] because our rooms were coated in orange dust,” she says, adding, “I guess she [the cleaner] had a point.”
Pick-axe stuck in the side of the giant termite mound. The ground is extremely hard because the mound is so old, built by termites over thousands of years. Courtesy of Teneille Nel.
How Old is Old? Dating the Mounds
The soil scientists knew instinctively that they had dug up a very old termite nest. But neither of them was prepared for quite how old it would be. They submitted samples for radiocarbon dating from the nests and soils from locations across the giant mound.
These tests analysed the soil organic carbon (decomposed organic matter dragged into the nests by termites) and the soil mineral calcite (inorganic carbon in the form of calcium carbonate) to give a complete picture of the mound’s age.
The tests showed that the organic matter dragged into the nest by the termites had been there for at least 19,000 years. The mineral calcite in the nests, also a result of termite activity, was even older: It had been around for 34,000 years, since before the last Ice Age.
Francis is quick to point out that “this doesn’t mean the termites were living in ice”. As she explains, in arid parts of the world, the Ice Ages were actually a time of plenty: “The Namaqualand received abundant rainfall and was a magnet for animals of all types.”
While the entomologist Midgley has no doubt that termites have been active in the area for at least 30,000 years (fossilised nests were first found in the area in the 1930s), he says there is no way of proving that the nest has been continually inhabited for all of that time. “There is a high density of nests in the area. Recolonization seems inevitable, if not necessarily intentional,” explains Midgley.
Southern harvester termites - known as stokkiesdraers (stick carriers) or houtkappers (woodchoppers) in Afrikaans - mainly feed on sticks and twigs, which they carry down into their nests. Nick Dall/Al Jazeera.
