Towers of Clay
Termites Play a Vital Role in African Ecosystems
Few creatures can claim to have such a massive impact on the environment in which they live as can the termites. The conspicuous mounds made by certain species are a dominant feature of African savannas and, though tiny and practically blind, these highly sociable insects play a major role in the functioning of ecosystems.
Impressive towers of clay built by some termite species provide a home for a variety of other creatures and are often colonised by plants to create new habitats such as thickets. On floodplains, the raised mounds can eventually become islands as silt is deposited on their margins and they grow outward.
Termites typically feed on dead plant material such as wood, bark and straw, being able to digest woody fibres with the help of bacteria that live in their stomachs. Acting as highly efficient decomposers, the termites return the plant nutrients to the soil through their faeces and saliva. Lacking pigment and a protective exoskeleton, termites operate mostly underground, but some species forage above ground after dark. In some parts of Africa, there may be as many as 10 000 termites to a square metre of soil surface, so it is not surprising that these insects also feature in the diet of numerous other species.
The gregarious and highly social termites are often incorrectly referred to as 'white ants' or 'flying ants' although they are not closely related to ants at all. But, like ants, they live in well-ordered colonies with soldiers, workers and reproductives. Over 2000 species of termite exist in seven families throughout the warmer parts of the world.
Mounds and Nests
Various species of the family Termitidae are responsible for the characteristic mounds (more primitive families do not construct mounds). Some species of Macrotermes are responsible for the often gigantic, pointed mounds while the species of Trinervitermes build smaller, conical domes. Most of these mound-building termites have a symbiotic relationship with various species of fungi, which serve to maintain a level of humidity in the mound and provide food for the reproductives and the young.
Harvester termites (of the family Hodotermitidae) are often the most abundant and conspicuous of termites, although the colony of these species create an underground nest, not a protruding mound. Dry-wood termites (of the family Kalotermitidae) make nests within dead or dying branches of trees and their conspicuous sand-excreted tunnels can often be seen on trunks and branches.
Predators of Termites
Termites consume prodigious amounts of plant matter, including dry grass, competing with large grazing mammals at certain times of the year. Termites themselves are filled with protein and relished as a food source by an enormous variety of creatures.
The Aardvark is a termite specialist, able to dig into mounds with its powerful claws, while the Aardwolf feasts mostly on harvester termites foraging above ground - both can consume tens of thousands of termites in a single night. Almost all kinds of birds will eat termites, particularly the winged alates, which leave the colonies after the heavy rains of spring and summer have softened the soil.
But it is those other highly sociable insects - the ants - which are the greatest predators of termites. Columns of ants frequently raid termite colonies, although many soldier termites possess chemical weapons which they use in defence. A range of substances, from toxins and irritants, to glues and anticoagulants are used to kill, immobilise or repel the ferocious ants. Other termite soldiers have armoured heads and large biting jaws with which to take on their adversaries.
Creating a New Colony
A new colony of termites begins when two of the winged alates, of opposite sexes, manage to avoid predation on their risky nuptial flight (birds, toads and bats consume most) and burrow into a suitable substrate. The offspring of this Royal Pair will then become the workers and soldiers required to build the often astonishing architecture of the mound.
The structure is built primarily with a combination of saliva and fine-grained soil particles (coarse sand is not appropriate). Partitions within the structure are made from carton - a combination of saliva and faecal pellets - and fungal gardens grow on this material (spores having been collected from the outside world). The large mounds of Macrotermes usually have tall columns which serve as air vents to regulate the inside temperature, while other families may excavate downwards to reach the water table. When the colony is active, the mounds are constantly being added to and repaired and, as such, their walls are sealed and devoid of vegetation.
Animals Live in Abandoned Colonies
Once a colony is abandoned - usually only after the fertile queen dies or is killed - it is often taken over by much larger burrowing animals which favour these raised sites, at least in part because they reduce the chance of flooding. Warthog, Porcupine, Spotted Hyena, Dwarf Mongoose, Pygmy Kingfisher, Rock Monitor, Black Mamba and Banded Rubber Frog are just a few of the animals which frequently occupy termite mounds.
The insulation of the mound is obviously of great appeal to other creatures which may usurp the architectural wonder, but animals are not the only ones to benefit from the industry of termites. Seeds germinate readily in the moist soil fertilised by the herbivorous termites and, once growing, the saplings are afforded protection from grass fires due to the elevation of the mound. The thickets which may ultimately form on the old mounds may, at some point, be occupied by large predators such as lion and leopard as ideal lairs for their cubs.
So, the next time you see a tiny termite struggling on its new wings after a thunderstorm, or you encounter a gang of workers repairing a damaged mound, think about the vital role they play in the intricate web of life.
Posted: Other by CC Africa, Date: 21 November 2006