Animals come in a wide range of shapes and sizes, from spindly stick insects to blubbery whales. Round animals are harder to come by, but they're more common in the ocean than on land. So what is the roundest animal, and why are round animals uncommon?
At a glance, round animals might not seem that out of place on land. After all, small mammals like rabbits and pikas often look a bit spherical when their fur is puffed out and they're sitting. But Chris Law, an evolutionary biologist at the University of Washington in Seattle, said this shape is mostly an illusion.
"They're physically not as round as they appear to be," he told Live Science.
A sphere has the lowest surface-area-to-volume ratio of any shape, which is ideal for heat conservation. Law said the ability to curl or scrunch into a sphere can be essential to the survival of small animals, which lose heat more quickly than larger animals do.
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