Animals that fall within the “sweet spot” of not being too big or too small in size are also equipped with the advantage of being faster than their predators or prey, according to a new study.

Myriam Hirt, a biologist at the German Centre for Integrative Biodiversity Research, and fellow researchers, determined that an animal’s weight and the environment it moves through – such as water, air or across land – is enough to calculate its maximum speed with 90 percent accuracy.

While working on a project that looked to estimate animals’ top speeds, Hirt found that traditional methods for calculating speed based on body size were severely inaccurate in some cases. For example, using the traditional method, elephants are estimated to reach speeds of 373 mph when in reality, they can only get up to about 21 mph.  This led Hirt and colleagues to create a new, more accurate, mathematical model.

The model includes a basic formula that determines how long it takes an animal to accelerate, which the team found depends on the animal’s body mass and locomotion mode (the method used to move – like swimming, flying or running). The formula is k=cMd-1 (where k—acceleration constant, M—body mass).

Larger animals, like elephants, tire out their muscles quickly and run out of anaerobic energy while attempting to accelerate, causing them to top out at speeds earlier than lighter, mid-sized animals. But animals that are too small in size do not have enough muscle mass to accelerate at top speeds, either.

Those that fall within the “sweet spot” between strength and energy bursts are the ones that tend to be the fastest, according to the study.

The researchers tested their method against data on 474 species, ranging in size from 1 gram to 10 tons. Some of the animals included molluscs, blue whales, whopper swans and even gnats.

In the bird category, falcons and hawks top the list as the fastest by reaching speeds of more than 87 mph. Not surprisingly, cheetahs are the fastest land animal, clocking in at about 62 mph. Some of the cheetah’s prey – antelope, springbok and blackbuck – can all run almost as fast.

The researchers were able calculate for extinct animals like dinosaurs, as well. They found that velociraptors could likely sprint at a speed of about 30 mph, while the much larger tyrannosaurus rex moved at half that pace.

"Species that gain the most selective advantage—predators and prey with few places to hide, for example—will approach the predicted maximum speeds," said Hirt.

But humans are the exception to this pattern. Instead of evolving to outrun prey or predators, homo sapiens evolved to outsmart them.

The findings have been published this week in the journal Nature Ecology & Evolution.