Termite mounds have networks of tunnels that function as ventilation systems. Credit: W. Bulach / Creative Commons.

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Three amazing structures from the animal world

The large nests of the sociable weaver, which house up to 500 individuals, are remarkable for their elaborate system of thermoregulation—while the central chambers retain heat, the outer chambers maintain lower temperatures. What lessons can the animal world teach us about techniques of sustainability?

ISABEL RUBIO ARROYO | Tungsteno

 

From giant, heat-retaining nests to termite mounds with sophisticated ventilation systems, the animal world has its own engineering marvels that can often be a source of inspiration for architects and builders. We take a look at the energy optimisation techniques used in some of nature's most unique structures.

 

Giant nests to keep the occupants warm

 

The communal nests of the sociable weaver (Philetairus socius) are probably the most spectacular structures built by any bird. Some are six metres wide, weigh a tonne and are home to up to 500 birds. Sociable weavers, which inhabit southern African countries such as Namibia and Botswana, take advantage of trees or other tall objects to construct their nesting colonies.

A study published in the journal PLOS ONE indicates that these birds behave aggressively towards individuals that don’t help to build the communal thatched roof of the nest and instead invest in interior chamber maintenance. The aim of this behaviour, according to the researchers, is to encourage cooperation for the good of the group.

These nests are the result of the work of several generations of birds and can be used for decades. In addition to their enormous size, they stand out because they are highly structured and provide the birds with a more advantageous temperature in relation to the outside. The central chambers of these nests retain heat and are normally used for night-time roosting, while the outer chambers have a lower temperature and are used during the day. Older birds occupy the chambers with the greatest thermoregulatory benefits, according to an article published in the Journal of Avian Biology. Breeding activity is also more common in these choice compartments.

 

Sociable weavers build nests that can measure six metres across and weigh a tonne. Credit: Harald Süpfle / Creative Commons.

 

Sun-seeking spider webs

 

To promote thermoregulation, many structures in the animal world are built with orientation in mind. One example is the web of the spined micrathena spider (Micrathena gracilis). Specimens in shaded microhabitats tend to face their webs north or south, while those in well-lit environments orient them east or west. The orientation of the web influences the amount of solar radiation to which a spider is exposed, and thus affect its body temperature. Both too low and too high a body temperature can affect the spider's activity, according to research published in the journal Ecology.

Spiders are one of the oldest and most diverse groups of species on earth, and approximately 45,000 different species have been identified. They are usually generalist predators, that is, they do not specialise in a particular type of prey. Known for weaving the most sophisticated webs, the diversification of spider webs is impelled by the need to better adapt to challenging new habitats.

In fact, over millions of years they have also devised different strategies for catching prey. For example, pirate spiders (Mimetidae) devour other spiders in their own webs by posing as prey. Some species resort to decorative patterns on their webs to obtain a larger haul. In some cases, these patterns also reflect ultraviolet light, which can be used to deceive and attract more insects. This is precisely the strategy followed by wasp spiders, which use zigzag patterns starting from the centre of the web. "The effects of these patterns on the quantity of insects seem to be due to their impact on pollinating insects sensitive to ultraviolet light," says Kil Won Kim, a scientist at Incheon University in South Korea.

 

Some spiders build their webs with the best solar orientation in mind. Credit: Pixabay.

 

Termite mounds with a sophisticated ventilation system

 

A massive network of 200 million termite mounds in northeastern Brazil covers an area the size of Great Britain and required the excavation of over 10 km3 of earth—equivalent to the volume of 4,000 pyramids of Giza—according to a paper published in the scientific journal Current BiologyThese mounds were raised by generations of millimetre-sized termites (Syntermes dirusover the centuries as they excavated a vast network of interconnected tunnels to gain access to dead leaves in the forest.

There are over 3,000 described species of termite. Many are builders, seeking to protect their queens and ensure the survival of their colonies. To construct their mounds, termites use their saliva, excrement and the surrounding soil. These mounds usually have a main underground chamber and a porous upper structure that allows outside air to enter unhindered. Some mounds house millions of individuals, reaching a height of 8 metres and a diameter of about 30 metres.

Their networks of tunnels allow carbon dioxide to escape from the mounds and oxygen to enter. In addition to being used as a ventilation system, the tunnels regulate the heat and humidity in the mounds. The warm air circulates through the tunnels and is driven by currents from the lower galleries outwards. This is important to prevent the nest from overheating. The termites are responsible for maintaining the tunnels, opening new ones or blocking existing ones to optimise this thermoregulation system.

 

Termites use saliva, excrement and the surrounding soil to build these mounds. Credit: Cell Press.

 

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Tungsteno is a journalism laboratory to scan the essence of innovation. Devised by Materia Publicaciones Científicas for Sacyr’s blog.

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