The blue whale can grow to be 80 – 100 feet long (60 – 80 ft. on average) and weigh more than 150 tons when it is fully matured.
Although blue whales can grow to be massive marine animals they have slender, streamlined bodies which allow them to easily move through the ocean with very little water resistance.
Blue whales also have an aerodynamically flat, U-shaped head which helps them reach relatively high speeds of up to 30 miles per hour for short periods of time when they feel threatened or alarmed, however most blue whales generally keep a speed of between 3 – 12 miles per hour depending on their activities such as foraging for food, resting or traveling to different locations.
At birth a baby blue whale can measure in at around 25 feet and will grow very quickly over the next few years.
During the first year of birth a baby blue whale can gain as much as 200 pounds per day and consume up to 100 gallons of milk every 24 hours.
In addition to being the largest living animal in existence blue whales are also known to have some of the largest organs of any known animal.
A blue whales tongue for instance can weigh as much as 3 tons and its heart can grow to weigh more than 1,300 pounds!
However despite being the largest living animal in the world a blue whales diet consists largely of krill (a small aquatic life-form that measures between 1 centimeter & 6 inches in size depending on the krill’s species), however in some cases blue whales may consume fish and other small aquatic sea life while in the process of consuming krill.
Another amazing fact about blue whales is that in additional to having a relatively small diet these whales will also forgo eating for as long as 4 months during migration periods by living off of the stored fat they’ve acquired during feeding season.
Even with their diet and long food-less migration periods blue whales still manage to be impressively large.
In regards to why some of the largest living animals are whales it make perfect sense that the largest living animals would inhibit the sea because factors such as body size and food supply play a big role in an animals ability to survive.
Land animals have to be able to maneuver on land so their physical size is very important in order for them to be able move around without worrying about getting stuck or bumping into objects such as trees, rocks and other animals.
Food scarcity would also prevent land animals from growing beyond a certain size.
The amount of food a large whale consumes on a daily basis would be nearly impossible to find in most environments on earth, with of course the exception of the ocean.
If an animal as large as a whale lived on this earth it would require a tremendous amount of food and energy to support the muscles needed to move around on land.
In fact land animals would need additional muscles to support gravity, which is not necessary in the ocean, so they would likely consume even more food than a blue whale would need in order to survive.
On an even smaller and lighter scale flying species such as birds need to lift their bodies off the ground for extended periods of time and maintain flight so most flying species have relatively light bodies and wings which are required in order to maintain flight.
For whales and other marine mammals water provides buoyancy which allows them to grow very large without the need for strong muscular limbs or a skeletal system that would be needed to support the additional weight and protect their organs which would be required if they lived on land.
In addition to buoyancy water also provides whales with an abundant food supply which would be nearly impossible to find on land.