What makes some birds spend years perfecting their nests, why do spiders spin webs, and who has the blueprint for the queen bee's palace? Karen Gold gets the answers from the UK's only professor of animal architecture, Mike Hansell

What goes on inside the brain of a caterpillar while it constructs a cocoon? Does a badger seek privacy, mod cons or social status by extending its 50-room ancestral pile? Do 100,000 termites follow a blueprint for their underground air-conditioning system? Does the long-tailed tit calculate how much feather lining per square inch will create a perfect nesting environment?

The temptation to anthropomorphise animals' domestic arrangements must run deep in the human psyche, or children's novels would not be so full of carpeted, curtained and book-lined dens, holes and burrows: think Mole and Ratty, Peter Rabbit, Mr and Mrs Beaver... If animals make homes like us, how can they not think like us?

Mike Hansell, the UK's first and only professor of animal architecture, now retired from Glasgow University, has been pondering answers to that question throughout his 40-year career.

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Even an amoeba builds itself a one-cell home, he observes. A coral reef, however exquisite, is an agglomeration of domestic pods. Yet the amoeba and the polyp have no brain to speak of. The spider and the ant are not much better endowed. So how can it be, when human beings invest such vast intellectual and economic capital in their homes, that animals build so much, with so much less?

Hansell's boyhood obsessions were architecture and nature: he collected birds' nests and butterflies; on Sunday afternoons he visited Norfolk churches, Pevsner's architectural guide in hand. During his final undergraduate year at Trinity College, Dublin, his tutor suggested that he study "case"-building among caddis fly larvae.

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He stayed with the caddis cases for his PhD; as a new lecturer in animal behaviour at Glasgow he was offered a non-curriculum three-lecture slot and filled it with a more broad-ranging inquiry - "three whole lectures on the caddis seemed a bit much" - into how, and why, insects and animals build.

Since then he has travelled across India, Malaysia and New Guinea to examine social wasps' candelabras of golf-ball-sized nests and studied bird's nest collections in Europe and America - "Paris is abysmal; dusty and dirty... the best in the US is the Smithsonian" - before launching a Scottish nest collection in Glasgow's Hunterian Museum at the end of the 1990s.

Hansell appeals to amateur ornithologists to collect verifiably abandoned nests and send them in. "We have over 1,000 now, from over 100 species. It's a big, significant collection," he says.

His interest in animal builders ranges across beavers, shrimps (they bore into rocks), rats (a rat burrow can have 500 entrances), woodlice, dinosaurs (they just dug holes in the ground) and male bowerbirds, which practise for two years to perfect the "avenue" and "maypole"-shaped courtship bowers into which they summon their mates.

Entomologists, arachnologists and primatologists will study the building habits of their chosen species. What makes Hansell so rare is his determination to ask common questions across all species. Why do animals build, he asks? For security against excessive heat or cold, and against predators; for food storage and protection, for waste disposal, for traps and displays. Are they specially equipped to build? Generally not, he concludes: they use feeding and grooming tools, beaks and claws that they possess anyway. How do their building habits affect their environment and ours? Quite substantially: lugworm burrows form microhabitats for other organisms; fossilised termite mounds have shaped landscapes for 180 million years.

Above all, what are animals thinking when they build? Surely young spiders must have to watch and learn all that embroidery before achieving it? No: put newly hatched spiders in isolation and they make perfect webs. Surely bees and wasps cannot build a complex dwelling around their queen without the plumbers, the brickies, the plasterers talking to each other? Not to mention the foreman giving orders? No, again: the queen emits pheromones that enable her subjects to measure the space around her; beyond that, they seem to build with no direct communication between themselves.

Animals build, says Hansell, using simple, stereotyped, repeated actions. They interact with the built object, not with each other. Although their architectural sum may be hugely impressive, often its parts are simple cells, linked or piled together.

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Some species do appear to practise construction skills - birds in particular - and to require some mental flexibility in starting the process. (Birds again: is this branch preferable to the next one? How can I get round that protruding twig?) Animals build the way they do because they are genetically programmed to do so, Hansell concludes. Evolution has determined their architectural style. If their environment changes, they adapt to it, or they do not survive. They don't think about what they are doing; they just do it.

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This has some advantages for the behaviourist researcher: Hansell's next research project involves observing building-style variations among African weaver birds: "I expect we'll find it's like tying shoelaces: the outcome is the same, but people do it lots of different ways."

In the project, he and his researchers will destroy their chosen bird's work every evening, so that the next day it has to start all over again. And it will. No wonder one of his favourite phrases is: "You don't need brains to be a builder."

But if animals don't build like us, could we build more like them? Professional human architects, hearing of Hansell's work, have approached him asking for ideas, particularly on greener building processes, drawn from the animal kingdom. They were, he says, largely disappointed. We just don't build the same way. "The only thing it might work for is building a space station, using robots. You could do it like a termite mound: program them with very simple instructions - they don't need to communicate with each other, they just need to avoid bumping into each other. I'm sure Nasa's already thought of it."

He holds the human obsession with inter-species resemblance partly to blame for our lack of interest in the variety of animal architecture. Instead, he says, we study primates, those most boring of builders who just pull a few branches together for night-time shelter and then move on, just because what they do in using tools looks more human, even though actually it is not.

So where does that leave our human wonderment at the delicate nest, the massive structure, the intricate web? (It was Hansell's idea, as BBC consultant, to put David Attenborough inside a termite mound in the Trials of Life series.) Until his retirement last year, Hansell had written only research monographs and academic books; the reception of his first popular science book, soon to be published by Oxford University Press, will give some indication of whether the public is prepared to grapple with a species perspective different from its own.

Hansell has no doubt where the answers lie: "All questions in biology end up at evolution... I'm allowed to think something is wonderful. But there must be something in my biological ancestry that makes me feel that. It's not haphazard; my wonderment has evolved as a result of some selection process.

"If you look at the caddis case, it's beautiful. There's design to it; it's the product of an elegant building routine. It's what the caddis is meant to build. There's a French artist, Hubert Duprat, who puts caddis larvae in pearl and gold sand so they build cases that come out as jewellery. I think that's absolutely awful. Of course the caddis will build with gold and pearls if that's what you give them, because they are so desperate to cover themselves with something. But I like to see what they're designed to produce, because that fulfils a purpose in their world, not ours."

Mike Hansell's Built by Animals: The Natural History of Animal Architecture is published by Oxford University Press on October 11, ?16.99.

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