The Godzilla franchise consists of over 30 films that have elevated the famous kaiju to the status of a Japanese pop culture icon. An institution that has seen its main character evolve and grow over the years. Literally. At its beginnings in 1954, this peculiar dinosaur remained modest, standing at a height of (still) 50 meters.
More than sixty years later, in 2017, it was revealed in “Godzilla: Planet of the Monsters” and towered over the planet at 317 meters high, looking (almost) eye to eye with the Eiffel Tower. And, more recently, it has been battling alongside another giant of the big screen in “Godzilla vs. King Kong: The New Empire.” Two titans never seen in nature… but why? Is there a size limit for animals? The answer is yes, but it’s less obvious than it seems.
In the Grip of Physics and Math
One of the first factors to consider for all living beings is gravity. Without us realizing it, we – and all other land animals – constantly have to struggle against this force to move. And if we don’t notice it, well, it’s because we are not very large.
At over 300 meters high, our mass increases. It increases significantly. So much so that the efforts we would have to make to move would be far too great compared to our strength. Additionally, we would face a problem of pressure difference: the top of our body would be subjected to a different atmospheric pressure than the bottom of our body. Finally, our limbs would need to be strong enough to support the weight of the body without fracturing.
All of this leads us directly to our second factor: the mathematical law of the cube square. Stay with us, it’s not very complicated, we promise. This law formalizes the fact that when the linear size of an object (like the length of its side) increases, its volume increases much more rapidly than its surface.
A law that has important implications for living beings because it affects their ability to exchange gases with their environment and regulate their body temperature. For example, a larger animal will have a relatively smaller proportion of its surface in contact with the air, making gas exchange and temperature regulation more challenging.Some animals can grow to impressive sizes, but their maximum size is influenced by various factors such as metabolism, energy requirements, and environmental constraints. For example, mammals, being warm-blooded, need to spend a lot of energy to regulate their internal temperature, limiting their maximum size compared to cold-blooded reptiles. Dinosaurs, being reptiles, had the advantage of relying on their environment to regulate body temperature, allowing them to divert more energy towards growth.
Dinosaurs were able to reach colossal sizes due to their cold-blooded metabolism, which saved energy for growth, and their body structure, which provided support for their weight. Marine animals like whales also benefit from the buoyancy of water and lower gravity, enabling them to grow larger than their land counterparts like elephants. The availability of food resources also plays a crucial role in determining the size of animals, with herbivores needing vast areas to feed, limiting their potential size compared to carnivores.
As animals grow larger, their energy requirements increase, affecting their hunting efficiency. This is why even the largest known carnivore, the spinosaurus, was limited in size to about fifteen meters long and a few meters high. While impressive, these sizes are overshadowed by fictional giants like Godzilla or King Kong.