Why do puffer fish build sandcastles?

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1. A new discovery

A lot of good naturalists have been looking at a lot of animals for a very long time, so finding something completely new is sadly a rarity these days.

But in the seas off Japan a sculptured doughnut made of sand – an ephemeral ring of ridges and points made on the wave-washed sea floor – was one exciting, and very beautiful, example of an exception to that rule.

The master architect? A puffer fish. But why do they make such a delicate and intricate structure?

2. Why did it take so long to find?

Its fragility has no doubt played a role in this undiscovered secret. The structure has no permanence, or any need for permanence. Perhaps its simplicity has rendered previous witnesses confused or merely unimpressed.

Not me, I like its formalised patterns and the artist’s meticulous execution. The graphic nature and symbolic appearance is reminiscent of the wonderful Nazca Lines in Peru, or the designs of the Aztecs, or more recently of those patterns crafted into cornfields by miscreants bent on convincing the gullible that they had been made by visiting aliens. But who needs extra-terrestrials, when we have our own swimming over the sandy sea bottoms and making weird patterns?

Puffer fish are fantastic creatures in themselves. Scientists have discovered 120 species and their most famous attribute is to be able to ‘puff’ themselves up like a balloon when attacked, co-incidentally erecting sharp spines embedded in their skin. This has the effect of making them appear too large for the predator to eat and completely unpalatable given the covering of spines.

3. How to make the perfect love nest

A tiny Japanese puffer fish creates a grand sand sculpture on the featureless seabed by using his fins to dig furrows. He uses this to attract the attention of passing females.

Clip courtesy of Life Story (BBC One).

4. Which animal built these?

The natural world is full of amazing architects, but do you know which animals built these super structures?

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Although this may look like a children’s den, it is in fact a golden bowerbird nest.


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These are the mounds of termites in Australia. They can aid in controlling the temperature.

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This is the classic beaver dam. They're built to create ponds for protection and easy access to food.