Termites at Rifa

Introduction

Termites play an immense role in the ecosystems of Africa. The large termite mounds at Rifa, each with up to two million inhabitants, point to the importance of termites in the environment. The part they play in maintaining “the balance of nature” is finely tuned. They remove litter such as wood fragments and dead grass and so tone down the hot fires which are so destructive to woodlands.

On the other hand, if their numbers go unchecked their feeding activities destroy too much of the grasslands, thus depriving game of grazing. But the numbers are held in check by the many animals that feed on them, including man. In National Parks areas most termite predators are present, but in agricultural areas many of the efficient termite exterminators – the aardwolf, aardvark and pangolin – have been persecuted and often killed or their habitat reduced, and their numbers have declined, leading to a rise in termite populations.

I have provided some guidelines for the identification of termite species. There are thought to be over 4000 species of termite but only about 2600 are properly scientifically classified and termite classification has many gaps with some species mis-identified and others not even named. The British Museum had undertaken much of this classification work, but now funding has been withdrawn despite world interest in biodiversity.

Much is still to be discovered about termites according to Mr M. Mitchell, an expert on termites, who has given of his time to read through this material (which contains some of his current research work) and has made useful suggestions.

I have included a number of suggestions for activities and short-term investigation projects that you can carry out during a Rifa visit or in relation to termite mounds in your area. Maybe this will stimulate a few of you to keep up a special interest in termites or to become entomologists.

Leslee Maasdorp

Rifa Conservation Camp, May 1996

Ants vs. Termites

Termites are incorrectly called “white ants” because they tend to be pale coloured, but they are actually more closely related to cockroaches than to ants, and slightly more distantly related to mantises.

Termite Species in Southern Africa

As mentioned in the Introduction there are over 4000 species of termite in the world. Some 165 species in 52 genera of termites are described from Southern Africa. The table below shows the relationship of the species we will be discussing (highlighted in yellow) to the taxonomy of termites in general.

At Rifa Macrotermes michaelsmi, Macrotermes subhyalinus and Macrotermes falciger, and the Odontotermes species are important mound-builders. Macrotermes falciger termites are larger than those of Macrotermes michaelseni and are much more widely distributed in Zimbabwe. (They can be found in Harare gardens.) Macrotermes species are noted for having two sizes of workers and two sizes of soldiers (major and minor workers and soldiers). This is called caste dimorphism. The Odontotermes genus is recognised by having only one type of soldier (monomorphism).

Activity: By collecting and examining several soldiers from each mound studied, you can distinguish between different common mound building genrea.

The larger harvester termite, Hodotermes mossambicus, is common at Rifa and is often seen eating the lawn grass in the dry season. The casual visitor to the camp attributes the bareness of the ground to lack of watering, but in fact on closer examination, the harvester termite can be found eating off both green and dry grass leaves. This termite is pigmented and active during the day. The workers and soldiers have eyes.

Termite Mounds

The big termite mounds, such a feature at Rifa, can reach three to five metres in height. There are about two million termites per nest. Large termites, Macrotermes, build these impressive earthen structures, chiefly out of clay soil bonded together with saliva and water.

Activity – Test the outer layer of a termite mound for hardness.

Apart from termites themselves, many termite mounds harbour various other invertebrates as guests (e.g., beetles, flies, bugs, caterpillars, millipedes).

Mound shape

Can you see the differences in mound shape?

Mounds of Macrotermes michaelseni are tidy. Those of Macrotermes falciger tend to be untidy, often with several “knobs” on top. The mounds of Odontotermes have chimneys, each with an opening on top.

Mound asymmetry

Most people notice that a termite mound is asymmetrical in shape with the biggest surface area on the East side while the West side slopes more or less steeply to the ground.

How would this shape benefit the colony?

The tip of the mound faces NNW towards the sun at the hottest time of day and year. The orientation of the mound tip is arranged to face the sun in the afternoon on the 1st of November, the hottest day temperature in the year at Chirundu (M. Mitchell, personal communication).

Termites may wet the tip of the mound in very hot weather. How does this help cool the nest?

Activity: Are the nest shapes and orientation the same in mounds exposed to the sun as constructed in the shade? Make sketches to illustrate your observations.

Interior of a mound

The huge mounds of Macrotermes termites (technically called “termitaria”) are complex structures with their own ventilation, air ducts, heating and cooling systems, and chambers containing fungus gardens which the termites cultivate. The fungus decomposes the plant-substrate and forms asexual fruiting bodies, which are eaten by the younger termites for nutrition and re-inoculation of the fungus garden.

The unique thing about Macrotermes termites is this fungus cultivation habit. They maintain a constant temperature range in their nests in the range of 29-32 degrees Celsius, in order to simulate the right conditions for their fungus gardens to grow. (This is despite anything that is happening with the outside temperatures of the savannah.) The fungus grows from the chewed-up pieces of plant matter which the workers bring back from foraging. This fungus is a specialized wood rot fungus of the genus Termitomyces, which is edible for humans as well as termites and is considered a prized delicacy in tropical regions of the world when the fruiting bodies of the fungus grow out from mounds, sprouting out from within the termite nests.

Once every 40 or so years fungus is cleared out of the nest in what seems to be a spring-cleaning endeavour and the scattered fungus briefly grows on the ground outside the nest, sometimes called “African snow”.

The queen cell is housed deep surrounded by Termitomyces fungus-combs. And the brood cells housing the eggs she lays are in chambers below the royal cell.

Temperature and Water Regulation in a Mound

As mentioned above, the outer layer of the mound is hard and impervious, made of clay the workers obtain from the subsoil mixed with saliva. The mound has some openings to the outside, many channels and deep channels plunging deep into the earth.

Air exchange through the mound keeps the interior cool in hot weather. Up to 500 litres of air may circulate through the mound. A more or less consistent temperature is maintained within 2 – 3 degrees of 28 “C to support fungal growth.

Activity:  On a cool morning place your hand over an opening in a mound and feel the warmer-than-ambient temperature coming out of the vent.

Termites also collect water from as deep as 100 metres in the dry season, for use in cooling the nest (Some water engineers believe that termite mounds are indicative of underground water nearby.) Much metabolic water is produced by the myriads of termites and by the fungal colonies. The water is conserved or dissipated as needed for humidity control, which is maintained at around 95%, providing for optimum fungal growth.

Flooding can destroy a colony. The number of termite mounds in the channels of the Zambezi River was formerly controlled by flooding in pre-Kariba Dam days.

The Social System of Termites

These social insects evolved some 180 million years ago and belong to one of the oldest order of insects (Isoptera).

Population in a Termite Colony

There are different groups or “casts” in a termite colony.

1. Queen (and king)

The engine room of the community contains the breeding royal pair. The queen termite lays up to 80 000 eggs per day. The king is much smaller and fertilises the eggs.

2. Winged Reproductives (Alates)

• Develop two pairs of wings equal in size.
• They are darker in colour, often appearing brown or black.
• Produced in mature colonies ready to expand their territory.

3. Worker Termites:

• Wingless and constitute the majority of the colony population.
• In most colonies they are two types of worker: “major workers”, who are sterile males, and “minor workers” who are sterile females
• Responsible for foraging, feeding the colony, and caring for young termites.

3. Soldier termites

• Wingless with specialized adaptations for defending the colony.
• Have larger jaws or glands that can spray defensive chemicals.
• In most colonies they are of two types of soldier, major and minor. Both are sterile females

The Reign of a Queen

• Nuptial flight

During their lifetime, alates will only fly once when conditions are right, swarming from the nest en masse, a survival strategy to increase the likelihood that some will evade predators and successfully mate. A nuptial flight of a winged female is a prerequisite for her becoming a successful queen. Only after flying can she lay fertile eggs.

• Wing Shedding: After landing, the individuals who were swarming shed their wings. The flight was a single event, signalling that the termite is ready to mate and seek a new location for colonization.
• Mate Search: The alates, now known as deflates, search for suitable mates, usually looking for partners from different colonies to maintain genetic diversity.
• New Colony Foundation: Once paired, the termite couple finds a hospitable environment to start their new colony. This can be underground, in wood, or in other cellulose-rich materials.
• Queen and King Roles: The wingless female and male assume the roles of queen and king of the newfound colony. The queen’s abdomen enlarges massively as she becomes an egg-laying machine. The king remains by her side, continuing to mate with her and fertilise her eggs throughout his life.
• First Generation: Initially, the queen lays a relatively small number of eggs. When these hatch, she and the king care for the young termites who will become the first generation of workers and soldiers.
• Colony Expansion: As the colony matures, the workers care for the young, foraging for food, and expanding the nest. The king and queen’s role becomes almost exclusively reproductive.

Workers stack the eggs laid by the queen and other workers collect them and store them in brood chambers that fill much of each nest. The eggs produce larvae or nymphs that moult four or five times before maturing. (Their cast-off skins provide another food source for the waste-nothing colony.)

• End of a reign If there is a decline in egg production, the reigning queen is killed and eaten (as food is at a premium in the nest).

Communication

The blind workers and soldiers keep in touch mainly by the exchange of chemical products among themselves and with the queen. The workers attending the queen obtain a chemical product which is a fatty secretion (pheromone) and pass it through saliva exchange. Thus the colony is kept under control by chemical means.

If the queen’s secretion drops to a low level or if she is killed, the workers respond by replacing her.

Termite Feeding Affecting the Earth’s Climate

Termites feed on wood and dead grass. To digest the cellulose of this plant material, primitive termite workers enlist the services of over 100 species of bacteria and protozoa in the hindgut, a mutually beneficial arrangement. One of the breakdown products of cellulose is methane. The methane acts as a greenhouse gas. In this way, termites contribute to climatic change.

As tropical forests are cleared, termite numbers increase by 3 to 5 times and methane emissions increase, adding to the warming effects of deforestation.

Ant Raiders

Certain ants attack termite nests. One common species is a shiny black ponerine ant. Its scientific name is Megaponera foetans but it is commonly called the Matabele ant or suuswe mukange or samukange because of its raiding habits. A column of these ants will attack termites that are feeding away from the nest. The termite soldiers counterattack.

Activity: Watch out for ant attackers on tracks in the bush, when columns can be seen after a raid, with each ant carrying a termite worker in its jaws. Disturb a section of the column with a stick (Why not your finger?) and hear the rustling noise made by the ants. Is there any scent given off by them? Note the specific name “foetans”, which means “stinking” in Latin.)

Another species of ant attacks the termites in the nest. This ant is a Dorylus species. (The male might be known to you as the sausage ant or bomber or “camel worm”. This is the harmless, bumbling flying male of the species and is very much larger than the female.)

Mammal Raiders

Aardwolf

 Aardwolves are shy nocturnal animals that are seldom seen. At dusk, aardwolves emerge from the protection of their den and begin their nocturnal feeding excursions in search of surface foraging termites, though it also has effective claws for some digging into nests.

Termites are easy prey, particular as the aardwolf can tolerate a great deal of their chemical defence secretions. It has a broad tongue has adapted to be tough enough to withstand the strong bite of termites., large salivary glands and a specialized digestive system which assists with the consumption of large quantities of termites, roughly 200 000 to 300 000 a night.

The aardwolf feeds almost entirely on the Nasute harvester termite Trinervitermes or snouted termites. This termite has pigment in its skin and can feed in daylight and is therefore a surface feeder on grass. When the aardwolf is feeding on the snouted termites it comes up against the persistent soldier termites determined to protect their colony. As the aardwolf feeds on the termites the soldiers gather in increasing numbers squirting a sticky irritant at the invader until it is overwhelmed and moves away to another nest.

Hodotermes mossambicus also provide food for the aardwolf especially in winter months, when nights are too cold for Trinervitermes to forage on the surface at night. Macrotermes form a small part of the aardwolf diet.

Aardvark

Aardvarks are medium-sized, nocturnal, burrowing, mammals belong to the same group of mammals as the African elephant. They are solitary foragers and walk between 2 and 15km per night in search of their insect prey, moving slowly with their long snout-like noses close to the ground, using their exceptional sense of smell to locate their prey.

Once they locate an ant or termite nest they dig it open with their thick claws on powerful forefeet that are well adapted for digging. The aardvark then sticks its snout deep into the nest tunnels, and, using a long, sticky tongues (up to 30 cm long) slurps up and swallows tens of thousands of insects. Although the aardvark has teeth, the mastication of termites is performed in a muscular region of the stomach.

Pangolin

Pangolins are also solitary and active mostly at night. Their diet consists mainly of 15 kinds of ants and 5 kinds of termites without an obvious preference (though they also eat insect larvae, bees pupae, flies, earthworms and crickets).

Like the aardvark they excavate mounds with their powerful forelimbs and hard claws modified for digging and they have long snouts and even longer tongues, which they use to lap up ants and termites. They are not, however, as well adapted for digging deep into hard soil as the aardvark.

Several common termite species, especially of the genus Macrotermes, are not often available to pangolins because their nests are either too deep or they are constructed with a particularly hard outer crust of compacted soil whereas various ant species have their tunnels closer to the surface and are therefore more accessible.

The harvester termite H. mossambicus nests are approx. 1.5 m below the soil surface which is also inaccessible to pangolins, and they are only preyed on when they were active around the entrances to mounds at the soil surface. In summer, it is easier for pangolins to find ants on the ground, while termites hide in underground tunnels, so ants are the main food source for pangolins. In winter, however, when ants move into underground nests because of low temperature, pangolins prefer termite nests because their biomass is larger than that of ants.

Farmers need to protect these three! Farmers need to recognize the value of these mammals in the control of termites. Poisons need to be used with great discretion, if at all. Poisoned termites and other insects can kill all three.

As explained in the introduction, termites have many important environmental benefits but if the termite population rises unchecked their feeding activities destroy too much of the grasslands, thus depriving game and livestock of grazing. Normally (for example in National Parks) their numbers are held in check by the many animals that feed on them. In agricultural areas, however, many of the efficient termite exterminators – such as the aardwolf, aardvark and pangolin – have been persecuted and often killed or their habitat reduced, and their numbers have declined, leading to a massive rise in termite populations and consequent decline in the quality and carrying capacity of grasslands.

Termites as Landscapers

Termitaria are often situated just above the drainage lines or depressions. Elephant drive their tusks into these mounds to break them up, especially those that are disused, and consume the soil in search of the minerals present. These elephant and other large mammals, e.g. buffalo, kudu and impala, also puddle the surrounding area during wet weather, removing the mud on their hooves and hides. Trampling produces a hardpan floor allowing the hollow to hold water. After a time a pan forms, providing waterholes for the animals, and enabling them to use these woodlands well into the dry season.

An example of the process can be seen at Mopane Pan just behind Rifa Camp (east and across the road). The large termitarium on the east side has been worn down sharply on the pan side over the last six years to half its original size. This pan has been formed by ungulates and elephants seeking mineral licks and for mud baths. Small pans are forming nearby in a similar way.

Other waterholes have been formed in the same way in dry mopane woods and one can say that mound building termites have played a role in landscaping the Rifa area.

The food taken into the nest is a valuable store that may well become available for re-cycling in years to come. Grass left over by the grazers is removed by the termites and often the surface becomes quite bare. The reduction of inflammable grass protects trees from hot bush fires. Some ecologists believe that were it not for the termites’ removal of the grass, much of the country’s woodlands would have been destroyed by fire. So it appears that the termites’ greatest role in the bush has been the conservation of our woodland.

What Grows on Termite Mounds?

Mounds provide a habitat for plant growth which differs from the surrounding habitat. The type of plants associated with mounds depends on the rainfall regime. In the plateau (highveld) region of Zimbabwe where rainfall is higher than in the lowveld, grass may be the dominant plant type especially in open parts and around dambos (vleis).

At Rifa and in most woodland areas, trees are invariably associated with mounds. Factors that promote tree growth are:

• The termites produce upper horizons of finer material making an impervious outer layer which is drought stressed.
• This layer suppresses grass production and enhances tree production mainly because the water that remains in the deeper horizons can be reached by tree roots.
• There is a slow release of nutrients from mound soils which favours tree growth.
• Trees produce shade which restricts grass growth. This enhances availability of water for trees.

Tree leaf and wood litter production increase and feed more termites. These systems are stabilised in a woodland.

What effect do termites have on dead and living vegetation?

Crops: In certain areas, termites may damage crops e.g. tobacco, which is, of course, an alien plant.

In some lands, farmers may unwittingly increase the numbers of termites of the smaller species by ploughing in the soil from the termite mounds, thus mixing clay into sandy soils. Ancistrotermes cannot nest in sandy soil but when the clay content is increased, they will thrive. At the same time this farming practice reduces the number of species, resulting in reduced competition for food. (M. Mitchell, pers. com.)

Grass: The harvester termites, including the genera Hodotermes and Trineruitermes, gather both dead and living grass material and store much of it as food in the dry season.

Dung: Though dung beetles play an important role in the removal of dung from the surface of the land, termites account for more dung disposal than any other insect group.

Trees:

(a)Termites do not attack the live material of indigenous trees, but they do feed on the bark. This stripping may make the tree more vulnerable to fire. An exception is the harvester, Hodotermes, which sometimes consumes the leaves of Faidherbia albida.

(b) Some of the alien trees e.g. gums (Eucalyptus spp.) are attacked and killed by fungus-growing termites such as Macrotermes. The lack of resistance to these African termites is due to the fact that Eucalyptus evolved in Australasia where there are no fungus-growing termites so there is no ecological benefit in the trees being resistant to them.

Timber: All fungus-growing termites attack dead wood and timber in the bush and in buildings. Ancistrotermes latinotus is considered the most serious termite pest of trees, timber and crops such as maize, cotton and wheat. It does not build mounds but lives underground in a nest made of a series of chambers, from which it emerges through holes in the ground.

Importance of Termites

N.B. Termites exist throughout the savanna biome whereas earthworms are not found in areas with below 800mm of annual rainfall.

1. By removing grass and dead tree materials, the termites reduce the intensity of fires and conserve woodlands.

2. By storing food and developing fungal gardens and bringing up mineral and clay rich soil for their mounds, the termites increase the fertility of the soil which encourages plant growth. (However, the impervious outer layer and steep slope makes for good run-off of rain and the mound becomes drier than its surroundings.  The removal of litter by termites, furthermore, reduces the soil fertility in certain areas and may increase compactness at the surface. The stores within the mound may not be released for many decades.)

4. The flying reproductives (alates) provide a seasonal feast for a vast array of invertebrates and vertebrates.

5. The large termite mounds provide structural features which may last hundreds of years. Many pans or waterholes were initially mounds that were destroyed by big game (see above). This change in the landscape is a valuable one, as water is conserved into the dry season and the pan also supports a variety of big trees on its fringes. Many of them are fruit-bearing, providing food for birds, browsers and primates.

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Conclusion

In conclusion, termites have a significant impact of termites on ecosystems in southern Africa. Through their complex social structures and sophisticated nesting behaviours, termites play a crucial role in shaping soil composition, facilitating nutrient cycling, and influencing vegetation patterns and are ecosystem engineers and key ecological actors in the region. Furthermore, termite presence has implications for conservation and management strategies in southern Africa, suggesting that termite populations may serve as indicators of ecosystem health and resilience.

Suggestions for the study of termites and their mounds

• Distribution of termite mounds

If you have access to aerial photos of the hills around you can you pick up any features that look like termite mounds? Otherwise find some higher ground and look carefully at the hill slopes. Can you identify the mounds?  If you come across any of the mounds on the hills, find out if they are occupied or deserted.

• Direction and aspect of mounds

(a) Check on the direction in which the Macrotermes mound faces. Use a compass. When presenting your result give the location of the mound.

(b) Given that almost the entire above-ground mound structure is designed for temperature regulation, suggest why it is that the mound height varies in different parts of the country, for example, mounds at Rifa tend to be far taller than mounds in the Karoi area.

(c) Examine a number of Macrotermes mounds in (i) full sunlight (ii) in the shade. Do the shapes of the mounds vary in these two situations?

Present your results in table form and include the location for the mounds.

(d) If you are lucky or foolhardy enough to be at Rifa on the first of November, check out the explanation for the orientation of the Macrotermes mound given under the heading “Mound shape” above.

• Temperature regulation

(a) The study of the way in which termite nests are air conditioned is fraught with difficulties. The nest is built just above or below ground level and with careful manipulation, a thermometer could be lowered through the air tunnel to the nest and the temperature recorded.

(b) What is the average temperature of the hottest month of the year? (See meteorological records)

 Wet mud patches are sometimes noticed on the chimney of the mound. What factors would cause termites to put wet mud on to the mound? Think of two reasons.

• Tunnelling

To keep the huge numbers fed in the big termite mounds, foraging termites work day and night. Their lack of pigment prevents them feeding in the open sunlight and they build tunnels to their food source. How else do these dark tunnels help the workers? Have you seen the muddy tunnels up trees?

• Damage repair

Study the way in which termites repair damage, after the breaking off a small section of the nest.

• Vegetation on or around a mound

Look for differences between the soil of the mound and the surrounding soil. Look for differences in vegetation between that growing on the mounds and that of the surrounding area.

• Construct a food web radiating out from a termite nest.

List any animals you may see eating termites. You may see Matabele ants carrying off termites, or birds pecking at the covered runways that foraging termites use. Include animals that feed on winged termites.

• Others making use of mounds

 Other animals may use the mound. Is anything else living in the mound? Make a note of any of these e.g. spiders, insects or reptiles or mammals. Have you seen animals using a mound as a look-out point or perch?

• Termite Species comparison

To collect soldiers and workers, place cardboard pieces around the mound or runways. Look underneath a few days later. Compare the soldiers and workers of different species.

• Mound changes over time

If you are in a position to observe the same mound over a series of years keep a record of the changes and developments that take place.

World’s oldest termite mounds discovered in South Africa – and they’ve been storing precious carbon for thousands of years

https://tinyurl.com/Oldest-Termite

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Leslee Maasdorp’s References

Batra, S.W.T., Batra, L.R. 1967. “The fungus gardens of insects”. Scientific

American, Offprint no. 1086.

Lusher, M. 1961 “Air-conditioned termite mounds”. Scientific American. Vol. 205.

Mitchell, B.L. “Report on a survey of termites of Zimbabwe”. National Museums and Monuments. Vol. 6 Part 5. 1980

Mitchell, M. of Kutsaga Research Station, Tobacco Research Board. Personal communications.

Further reading.

Marais, Eugene, The Soul of the White Ant.

Skaife, S.H. African Insect Life. 1979.