Danger Dust

The fastest animal on land is the cheetah, capable of reaching top speeds of 104 kilometres per hour. In the water, the fastest animals are yellowfin tuna and wahoo, which can reach speeds of 75 and 77 km per hour respectively. In the air, the title of the fastest level flight (excluding diving) goes to the white-throated needletail swift, at more than 112 km per hour.

What do all of these speedy creatures have in common? None of them are particularly big, nor particularly small for the group of animals they represent. In fact, they are all intermediately sized.

The reason for this is a bit of a mystery. As animals increase in mass, several biological features change as well. For example, in general leg length steadily increases. But clearly long legs are not the answer, since the largest land animals, like elephants, are not the fastest.