Earthy abodes built by nature’s architects

By Shweta Mukundan

Indigenous people worldwide have learnt to build dwellings from mud. The mud fabric of these houses modulates climatic parameters to create comfortable living conditions within, however harsh, the outdoor weather. But long before humans, many animals constructed their homes with mud. What makes mud such a good building material? And how do animals transform this building material into sturdy, protective structures?

Wasps are a group of insects with diverse biology. Those that belong to the subfamily Eumeninae are commonly called potter wasps, which refer to the nests they build for their young using mud. A female potter wasp builds her nest singlehandedly, beginning with choosing an appropriate nesting site and cleaning it with water droplets carried in her mouth. She goes on to mix water with dry soil to make tiny balls of soil called boluses, which are then carried to the construction site.

Using her mouth parts, antennae and forelegs, she lays out the design of her mud nest, in which she will later lay an egg into a single chamber and provision with paralyzed caterpillars— food for her egg, which will hatch and feed upon the rich source of protein in the form of the paralyzed caterpillar. These wasps select the right kind of soil, constructing nests with the ideal shape and size for the offspring to develop. 

While potter wasps are solitary, termites work in groups to make their mound. Termite colonies have a caste system where individuals are assigned specific roles— workers, soldiers or reproducers— each with a set job that helps the colony survive. The blind, wingless and most numerous workers participate in the nest-building process. Research has shown how termites make nests that are stable and energy-efficient structures.

Swallows, a group of small, agile birds, build nests with various materials. But the Red-rumped swallow, common in Bengaluru and nearby places, builds an inverted retort-shaped nest made of mud. These swallows gather beakfuls of mud from riverbanks and carry it to a sheltered surface. The breeding pair take turns to layer and shape the mud with their beaks. A study investigating the mineralogical and textural characteristics of the materials used in nest construction has revealed that these swallows prefer large-grain-sized particles and a high quartz content in their nesting material. 

These remarkable examples show how animals instinctively harness the unique properties of mud to build strong and functional homes. Observing them gives us insights into natural construction strategies and inspiration for creating sustainable buildings.