Tallest animal-built structures

The tallest structures constructed by an animal (excluding humans) are the mounds of the eusocial insects termites (order Isoptera). These veritable skyscrapers of the animal kingdom are made from soil, plant matter and the saliva and faeces of the termites, forming a fortress-like structure that is impervious to most weather and predators. Some of the tallest documented examples are built by “cathedral termites" (Nasutitermes triodiae(), native to grasslands in Australia's Northern Territory. Their lofty chimneys can reach 8 metres (26 feet) off the ground. Scaling the length of a termite up to the height of a human, the mounds are equivalent to four Burj Khalifa towers (the tallest building in the world at 829.8 metres/2,722 feet) stacked on top of each other.

There are unconfirmed reports of a 12.8-m-tall (42-ft) mound in the Republic of Congo built by an African species known as the war-like termite (Macrotermes bellicosus) but this example remains unverified. Another particularly lofty example, noted in the Guinness World Records archives, is an 8.7-m-tall (28.5-ft) termite mound that was photographed by a W Page south of Horgesia in Somalia in 1968.

As well as the tallest animal-built structures, a South American species of termite (Syntermes dirus) is also the architect responsible for the largest underground city. A network of colonies in north-east Brazil, constructed over a period of 4,000 years and still partly occupied to this day, can be seen from space, spanning a vast surface area of 230,000 km2 (88,800 sq mi). It is comprised of around 200 million mounds made from an estimated 10 km3 (2.4 cu mi) of excavated soil.

Termite mounds are also among the first "air-conditioned" structures built by any animals - including humans. The mounds control temperature, humidity and respiratory gas concentrations in the nest using solar power. Recent studies of one species (Macrotermes michaelseni, which emerged c. 7.5 million years ago) indicate that the air conditioning works on convection currents driven by diurnal changes in outside temperature (solar-driven). In the day, air in thinner chimneys on outer edges of the mound heat up quickly; air in the large central chimney stays relatively cool. Hot air rises up the outer chimneys, while cool air in the central chimney sinks, circulating air continuously while injecting oxygen and flushing out carbon dioxide. At night, the flow reverses because the air in outer chimneys cools down quicker than the inner central chimney. Leafcutter ants' earthen nests also employ this technique to some extent, but termite mound air conditioning is on a far more sophisticated level.