Animal Architects and the Structures They Build

A beaver dam is made from branches and material such as mud and stones. It slows the water and can flood a shallow area into a pond. Look for the difference between the dam, which changes the flow, and the lodge or bank den, which gives the beavers a place to live.

The tall earth mound is connected to the nest where the colony lives underground. Air moves through a network of channels in the mound. The aboveground structure helps exchange air with the outside while the termites keep most of their activity below it.

A colony layers dry plant material into a mass that can cover part of a tree. Look underneath for the separate entrances. The insulation differs across the structure, so a chamber deep inside and one near the edge can give the birds different protection from temperature swings.

A male pufferfish near Japan uses its fins to move sand into a broad circle. Deep grooves radiate through the outer ring. The center is worked into a much shallower pattern. Repeated passes by one fish produce a nest many times wider than its body.

Some caddisfly larvae bind sand grains, leaf pieces, or other debris with silk and carry the tube around as they move. Look at the open end to see how the animal can stick out far enough to walk. Different lineages have arrived at portable cases by different routes.

Workers pull living leaves together and hold larvae against the edges to apply silk. The leaves form the walls of a nest high in the canopy. The difference between a single leaf and several stitched together is a good clue to the amount of work a group can do.

The wasps scrape up plant fibers and mix them with saliva into pulp. A single comb of cells hangs from a narrow stalk, with the cells open to view from below. Its exposed construction makes it easier to see where new cells are added along the edge.

The spider builds a dense, nearly horizontal mesh with a tangle of silk held overhead. In a colony the individual webs can share support lines. Each spider still has its own web, so the whole structure can grow bigger without becoming one shared trap.

A female oriole weaves plant fibers into a pouch suspended near the end of a branch. She starts by looping long strands around the branch to support the nest. Those strands run down into the woven walls, and the opening stays at the top.

The soil piled around an entrance hints at a bigger structure below. Prairie dogs dig tunnels and chambers across the colony. The shape and height of different entrances can affect how air moves underground. On the surface the raised rim also gives a prairie dog a place to look out.

A hornero pair builds an oven-shaped shell out of mud and other material. Behind the visible opening, an internal partition makes the route to the breeding chamber turn. From the outside you can often see which side the entrance is on, while the chamber itself stays out of view.

One worm cements sand grains and shell fragments into a tube. Where many settle together, those tubes become a reef you can recognize by its honeycomb surface at low tide. The pattern is the ends of separate homes packed tightly alongside one another.

A female makes mud cells and stocks them with spiders for the young. The dried mud looks more like little pieces of pottery than a wasp’s paper comb. Look for the round holes adult wasps can leave after going through the sealed stage of their development.