The previously mentioned antarctic blue whale holds the title of the biggest animal on earth. It can weigh up to 400,000 pounds and reach a length of 98 feet. The giant’s heart is the size of a car.

One of the most fascinating facts about these animals is that they reach such mind-boggling size by almost exclusively consuming tiny shrimp like organisms called krill. During feeding season, they can eat 7936 pounds of them a day.

They consume them by gulping a big amount of water and pushing it through baleen (comb-like keratin plates attached to the upper jaw). The food is left behind in the mouth and then swallowed. 

In fact, their feeding type is the reason for their size.

Called lunge feeding, it allows blue whales to consume a large amount of food at a time, providing the nutrients and energy needed to reach such enormous size. And a sudden rise in ocean upwelling (when nutrient-rich water rises to the surface of the ocean) provided them with ample supply for prey—a perfect recipe for growing this big. 

The second runner-up is another aquatic animal—the colossal squid. It can grow as long as 46 feet and weigh as much as 1,650 lbs.

Since it inhabits cold and deep regions of the Southern Ocean ranging from 66 to 6,562 feet deep, scientists have never succeeded in observing the biggest invertebrates (organisms without a backbone) in their natural habitat. 

They only get a good look at them when fishermen accidentally catch them in the nets.

It’s not a coincidence that most of the biggest animals in the world live underwater. Scientists believe that it would be too cold for warm-blooded animals to survive without being an appropriate size. The amount of warmth a body can generate depends on how many cells it’s comprised of. Therefore, a smaller body means that it doesn’t generate enough heat and loses it relatively quicker than a bigger physique with a wider surface area.

Having a bigger body has other benefits for animals as well, like avoiding predators, catching prey, and enduring hardships. Having larger footsteps or swim strokes also allows them to cover greater distances to find food and reach mating places.

The reason animals on land can’t reach the size of some of the biggest aquatic animals is because they aren’t being supported by water. On the ground, they have to hold their weight against gravity. The bigger the animal, the thicker their legs have to be so they could support the weight without snapping. Meanwhile, a whale floats in water without the stress of gravity.

Even though being bigger in the animal kingdom has its perks, they are at greater risk of going extinct, mostly because of humans. The blue whale population was drastically reduced, almost driving it to the edge of extinction, after commercial whaling started seeking whale oil. Such hunting was made illegal in 1966. However, their recovery is minor, as larger animals take longer to reproduce.