Property may seem like a peculiarly human obsession, but securing a ‘des res’ is a pressing concern for many African animals, too. Mike Unwin investigates the intricate art of home building in the natural world.
Every species, at some point in its life cycle, needs a refuge in which to avoid predators or start a family. Often both. Many find convenient accommodation in natural retreats such as holes or hollow logs. Others embrace the DIY approach and knock up designer pads of their own.
Weaver of mass construction: the sociable weaver bird
In the avian world, weavers have taken the craft of nest building to elaborate extremes. But first prize for sheer scale goes to the sparrow-sized sociable weaver (Philetairus socius) of the Kalahari, whose monstrous constructions can measure over five metres across and weigh nearly a tonne.
Each sociable weaver nest is a thatched apartment complex that can house over 300 birds in up to 100 individual chambers. Construction starts with a platform of strong twigs built in a tree fork. Stiff grass stalks are then used to build up the nest mass. There is no actual weaving ‐ the birds simply push the stalks into the structure, which hangs together from sheer weight. Each nest chamber has a narrow tunnel that opens downwards, so that its occupants enter from below. Spiky grass stalks stuck into the tunnel walls help repel intruders such as marauding snakes.
Sociable weavers form tight-knit colonies that seldom venture more than a kilometre from their nest. They never stop building, and the nest remains home until they die (or, as sometimes happens, the supporting branch crashes to the ground). Its dense insulating thatch shields the birds from both the baking summer sun and the cold winter nights. The nest can also provide a home for other birds, including the diminutive pygmy falcon, a pair of which often take over an apartment, occasionally ‐ and ungratefully ‐ snatching the odd fledgling.
Insect architect: the termite
Termites are primitive social insects, more closely related to cockroaches than ants. However, like ants, they form huge organised colonies, with soldiers to protect the nest, workers to care for young and forage for food, and an egg-laying queen. In some species (the termitidae), all this activity takes place within a massive citadel of mud called a termitarium, whose design and construction is one of the true wonders of nature.
Most termites are nocturnal, so you will seldom see them above ground ‐ except when they emerge in swarms to mate and disperse. But you can’t fail to spot the impressive monuments of their industry: termitaria can tower four metres and last for decades. One mound alone may comprise several tons of soil, raised particle by particle by an army of minuscule, blind workers using just chemical signals to communicate. Inside, separate cells house brood galleries, food stores, fungus combs (where termites cultivate a fungus that breaks down plant cellulose for them) and the queen’s royal cell ‐ where she produces up to 30,000 eggs a day.
The whole structure is prevented from overheating by a miraculous air-conditioning system. Warm air from the nest chambers rises into thin-walled ventilation flues near the surface. Here it is cooled and replenished with oxygen, before circulating back down to the nest via special cooling vanes, kept damp by the termites. Thus termites create their own microclimate, with a constant temperature of 29-31°C and 100 per cent humidity: perfect for producing the eggs that will spawn the next generation of labourers.
Earth-moving equipment: the aardvark
The bizarre-looking aardvark is the JCB of African animals ‐ able, apparently, to dig a hole quicker than a team of men with shovels. Its powerful front limbs are equipped with spade-like nails for hacking through the soil in search of ants and termites, which it licks up with its 30-cm long tongue at a rate of up to 50,000 a day. This heavy-duty digging gear also enables it to excavate its breeding quarters, a labyrinth of underground passages with as many as twenty different entrances (or exits, depending on where you’re standing).
An aardvark will occupy one burrow for anything up to a month or so, before moving on. Flies around the entrance indicate when the owner is at home, as do its distinctive three-toed tracks nearby. Only a mother and her single offspring will share a burrow. The youngster first ventures outside after two weeks. By six months it can start digging for itself, but it stays with its mother until the next breeding season.
Farmers are not the aardvark’s greatest fans. Small wonder, when you see the damage it can do to dams and roads. Many other animals, however, have cause to be grateful. Abandoned aardvark burrows make perfect breeding dens for mammals such as hyenas, warthogs, porcupines and ground squirrels, as well as hidden nest sites for birds such as blue swallows and ant-eating chats. Shallower diggings scattered around an aardvark’s territory also offer temporary retreats to a wide range of animals, from leopards and scrub hares to crocodiles and pythons ‐ though not all at the same time.
Perfect parent: the crocodile
Reptiles are not generally known for their home-making prowess. Tortoises carry their accommodation around with them, while most snakes and lizards make do with a good flat stone or flaky piece of bark. And family responsibilities tend to end with egg laying.
Except for crocodiles, that is, whose domestic skills would shame many a mammal. Each breeding season, the female gives up six months of her life to maternal duties. First she digs her nest in a riverbank ‐ often some distance from the water. There’s nothing fancy about it, just an oblique burrow leading to a spacious egg chamber, but it does the job. Then she lays anything from 25 to 75 eggs inside, before finally scooping over a layer of sand to conceal them.
The eggs incubate for about three months. During this time, the female remains on guard day and night ‐ either lying directly over the nest or watching from nearby cover, ready to defend it from egg thieves such as baboons or monitor lizards. When the young crocodiles are ready to hatch, they squeak loudly inside the shell, summoning the mother to dig them out. Without her help they would never be able to break through the layer of sand that has become compacted above them.
Once out of the nest, the mother still doesn’t abandon her youngsters to their fate. Instead she uses her massive jaws with astonishing tenderness and dexterity to transport them to their nursery in a quiet, hidden backwater. Here they spend their precarious first few weeks in the world under her watchful and intimidating gaze.