Creature Comforts: Amazing Animal Homes
They’re built with no hands — just beaks, paws, claws, and tails — yet animal homes are some of the most remarkable structures on Earth.
When we think of nests we think mostly of birds, but mammals, insects, amphibians, crustaceans, and even fish build them too.
Made from sticks and stones and whatever else is around, nests are generally either “sculpted” (like burrows) or assembled from parts. Those parts can be organic or inorganic and are either collected, like twigs and pebbles, or secreted. Saliva is a common material that’s often used as cement, making the nest solid and secure.
Apes build nests by lacing together high tree branches. It’s thought that getting a good night’s sleep may have helped spur human evolution.
But all the science doesn’t do them justice. The words “home” and “nest” have strong emotional meanings. They’re not mere structures, but touch something deep inside.
The homes that animals build are often beautiful in their own raw way, as ingenious as anything built by Man with his machines and opposable thumbs. Just as we decorate our homes to express our lifestyle and personality, animal homes express their own personalities and habitats.
The nesting instinct
The “nesting instinct” arises from animals’ need to raise their young, as well as to protect themselves from predators and extreme temperatures.
Some animals build more than mere nests, however. They construct vast complexes — veritable cities with gardens and climate control — that hundreds, thousands, or even millions of individuals call home. The complexity of a nest tends to be related to the level of parental care the adults provide, but some are just really impressive.
Birds weave wonders
Perhaps more than any other type of animal home, bird nests are where architecture becomes art.
Compared to mammals and other animal classes, birds exhibit the greatest degree of variation in their nests. They range from scrapes in the ground and basic bluebird nests to marvelously woven baskets and sculpted enclosures. The largest are complex treehouse condominiums like those of the sociable weaver bird of the Kalahari Desert and southern Africa.
“Nest” is too modest a term. They look like someone dropped a haystack on a tree. Social weaver complexes may hold more than a hundred bird couples and their young at a time. They’re insulated to be warmest inside and cooler in the outermost chambers. The hundreds of tiny entrances are outfitted with spiky straw to keep out predators. Weaver nests are built to last — the oldest known is about 100 years old. They’re so comfy and roomy that owls, lizards, and other creatures often move in anyway and are tolerated — as long as they don’t eat the residents.
Sticks and stones
Not all nests are made of twigs or in trees, however. The red ovenbird builds its kiln-like nests in stacks made out of mud and clay. The black swift of Colorado builds its nest only behind waterfalls, plastered to the side of the rock.
The cactus ferruginous pygmy owl of the American Southwest and northern Mexico nests in the side of tall cactus plants in holes usually pecked out by hungry woodpeckers. The sand martin lives in colonies burrowed into the soil or sand on the sides of embankments overlooking bodies of water, where the insects it feeds upon live.
But the Most Creative Nest Award, if there were one, would likely go to the bowerbird. The male builds a tent-like structure on the ground and decorates it with colorful artifacts, especially blue ones — feathers, beads, glass, berries, plastic, you name it — in order to attract a mate. The best bachelor pad wins, basically, and bowerbirds have been observed checking out their work to make sure it looks its best from any angle.
Beavers: Nature’s master builders
The image of beaver dams most of us have in our heads is a quaint, homey collection of logs and branches across a stream with beavers paddling busily to and fro.
In fact, beavers are the real architects of the animal world. But beavers are not just home builders; they’re landscape architects too.
Besides humans, they’re the only animal that changes the landscape to meet its living requirements — the only one that builds dams to block the flow of water. That raises the upstream water level, creating a pond as the stream overflows its banks.
They then build lodges to live in beside the pond, with the door underwater to ensure safety from predators. For greater security, they dig moats to surround the lodge with water. From the pond they excavate channels to reach trees for building that are deeper into the forest. From a logistical standpoint, it’s easier to transport tree trunks and large branches by floating them down the channels than dragging them across land.
Beaver dams don’t just make a place to live, however. They change landscapes.
By creating ponds, the dams conserve water in watersheds, prevent erosion, and promote plant growth in those areas. Wooded areas become wetlands, creating habitats for fish and birds. Decaying plants become peat, putting necessary carbon and other nutrients into the soil.
The world’s largest beaver dam can be seen from space. Beaver dams can be as long as 500 meters, but this one is an impressive 850 meters long (2,789 feet, just over half a mile).
It’s estimated to have taken 20 or more years to build and probably was created by the joining of several dams into a single one that has housed thousands of beavers spanning many generations.
On land, naked mole rats are practically blind but nonetheless dig extensive burrow systems. One of about 30 related species, naked mole rats look like fat sausages with teeth and legs. They’re not exactly hairless; fine hairs over their bodies are how they feel their way in the dark.
They’re rodents but live in societies like insects. A queen bears the young and workers dig complex burrow systems. They look for food using mostly their large front teeth and snouts.
Prairie dogs are native to the American Great Plains. They too live in complex tunnel systems, but so extensive they’re actually called towns and may cover half a square mile — underground.
Some are enormous, however. The largest recorded prairie dog town, in Texas, covered about 25,000 square miles and may have housed 400 million prairie dogs.
Towns include bedrooms, nurseries for their young, and multiple openings to create emergency exits. Some have listening posts for approaching predators. The many openings also create a sophisticated ventilation system. Building the upwind entrances on mounds (i.e. to make them higher) creates a pressure gradient that causes air to flow through the tunnels.
Snug as a bug in a rug
Spider webs are commonplace, but some like the trapdoor spider or leaf curling spider go the extra mile. They build tunnels or hinged doors to hide them until they spring out to catch approaching prey by surprise. Like the leaf curling spider, Australian weaver ants stitch up leaves into tubes using bodily secretions as glue.
Australia is also home to cathedral termites, named for the massive pillars they construct — of mud, chewed wood, dung, and saliva — which rise from the ground up to 15 feet or more. Each is a self-sustaining metropolis, but the tower is just the tip of the iceberg, so to speak.
Underground the colony can cover several acres, and supplies the termites with everything they need. Condensation collects in the cool interior of the tower, providing water. Some colonies maintain underground fungus gardens that the termites fertilize with plant matter to feed a population of millions. They’re even climate controlled, with tunnels serving as ducts to regulate air flow and temperature.
What’s the buzz
Finally, one of the most fascinating insect homes of all is perhaps the most common: the beehive. From the first observations in ancient Greek times, it took mathematicians 2,000 years and the invention of differential calculus to prove the sophisticated wonder of these deceptively simple structures.
You can read about the math here, here, and here, but the upshot is this: Beehives are precisely engineered to obtain the maximum possible volume using the least possible amount of material. In other words, their design is absolutely perfectly efficient, right down to the perfectly “chosen” angles of the closed back ends of the hexagonal tubes. The ends are not flat, which is less efficient. They’re rhomboids that interlock with the panel of honeycombs on the other side.
You can design a better mousetrap perhaps, but not a better beehive.
Homes & habitats
We hear much about habitat destruction these days. “Habitat” is such a clinical word though. Habitat doesn’t mean wetlands and forests in the abstract. We’re talking about the destruction of homes and families.
When natural disasters like flood or fire strike where people live, the news doesn’t report only how many acres were burned or flooded.
In my home state of California, where wildfires are common, we hear how many human homes were lost or threatened with destruction. Same in flood zones in other places, or after hurricanes or tornados.
But the number of animal homes lost doesn’t get reported on the news.