As in human beings, many animals build different types of structures and tools to perform their daily tasks, such as sheltering themselves, feeding or communicating with individuals of their species. The effectiveness of the structures they build will determine whether the animals succeed in their tasks and may even determine their survival.
Animal architecture is therefore a key element in the life of many species, as being a good architect or builder will help them fulfill their vital functions. For example, having a well-built home (like a nest or a burrow) will allow for adequate food storage, the control of the physical environment (water, gas exchange, etc.) and will increase the likelihood of reproduction. The complexity and functions of these structures vary greatly. In this article, we will discover some of the functions of these structures and the fascinating architects who build them.
Structures to control temperature
In the animal kingdom, there are various structures that allow to control temperature, by capturing, conserving and dissipating heat. Such is the case of the termite nests of many termite species, which have walls that reduce heat loss and provide a pleasant amount of shade. These structures are generally oriented in north-south direction, so they enjoy more hours of sunshine. In addition, termite nests have a natural air-conditioning design that promotes ventilation and, consequently, oxygenation and breathing.
However, for these structures to be effective, a series of decisions need to be made: where to build, what type of structure to build, what materials to use, the orientation of the structure… In short, each environment is unique and requires a specific solution. For example, the spined micrathena spider (Michrathena gracilis) adapts its web to the environment; its orientation is north-south in shaded areas, and east-west in open areas. Orientation is closely related to thermoregulation, as we can see.
Structures to control water and humidity
A well-built structure can help effectively control water and humidity, which are vital to the survival of species. For example, there are several structures that can provide protection from rain (such as Cubitermes termites) and from desiccation (the cocoons that protect the pupae of many insects), or even that act as a natural water barrier, such as the dams that beavers build.
Fiddler crabs (Uca uruguensis) offer another fascinating example, as their shelters are full of air, offering greater protection and resistance to tides.
Defence structures against predators
When an animal builds its home, it is usually also a defensive structure, which prevents future residents from being captured by predators. There are two types of defence structures: those that prevent invasion (by avoiding detection) and those with mechanical defence.
There are many bird species that prevent invasion through crypsis; they camouflage the nests they build or live in by making them look like their environment, which prevents them from being detected. The Eurasian stone-curlew (Burhinus oedicnemus), for example, is a steppe bird that nests on bare ground, blending into the surrounding environment. Other birds, such as the red-faced spinetail (Cranioleuca erythrops), will cover nests with hanging vegetation, for them not to look edible.
As mentioned above, other structures use mechanical defence. A striking example is the Acanthaspis petax, an assassin bug that covers its body with dust, soil and the carcasses of ants it has hunted; this protects it from spiders and geckos. Other insects distract predators by camouflaging their body with droppings, for example.
Spiderwebs, a unique structure
Spiderwebs are a unique type of structure, as they present a conflict between visibility and strength; discreet webs can capture smaller prey, while stronger webs are more visible to predators. For example, the spiderwebs of the Theridiosoma globosum spider are of low density, and thus difficult to detect for predators and prey. However, they will only withstand minor impacts, like those of flies, which are unable to detect these spiderwebs, even under bright light.
Spiderwebs are amazing structures, with many fascinating particularities. For example, the threads of golden-silk orb-weavers have different shades, depending on the environmental conditions: in autumn (or in places with a lot of sunlight), they are yellowish; in dark areas, however, they are white. Another example is the silver argiope (Argiope argentata), whose threads turn blue and green, making them less detectable by insects. Lastly, there are spiders that decorate their threads (with patterns, amongst other methods) to attract prey.
How structures affect intraspecies and interspecies communication
Fiddler crabs (Uca genus) build their shelters based on two principles: territoriality and courtship. They place mud balls in the entrance of their den to protect it from predators and to attract females, promoting sexual selection. It has also been proved that these shelters attract females of non-building species, which means that a protected shelter is highly valued by females.
The role of structures during courtship
Effective sexual selection is necessary for species to reproduce, which is one of the vital functions of living things. In order to achieve it, a lot of species build structures that help them stand out during courtship.
For example, female Eurasian magpies (Pica pica) lay more eggs when the nest of their mate is large (they make a greater investment). Spotless starlings (Sturnus unicolor) do something similar: the males that build their nest with a lot of green plants achieve greater reproductive success. They build their nest and add green plants and flowers to attract females; when the female starts laying her eggs, the male stops adding green plants.
However, the most striking case may be that of bowerbirds, true masters of animal architecture. During courtship, they build a structure called “bower“, which helps attract females and enhances sexual selection. Females choose males based on the level of protection these bowers provide, as well as on the complexity of the ornaments and the appearance of the structure (firm, symmetrical and colourful bowers).
Translated by Carlos Heras