In the 19th century, the German zoologist Christian Bergmann pondered a simple question: why are some animals so small? His answer, that a warm-blooded animal’s size increases as its habitat cools, remains a rule in biology to this day.
“Bergmann pointed out that smaller species tend to live in warmer climes. This pattern is to do with surface area and volume: smaller animals lose heat faster and struggle to maintain their body temperature when it is very cold,” says Dr Simon Loader, the principal curator of vertebrates at the Natural History Museum. “Whatever the reasons, these small species are fascinating,” he says.
