The blue whale, ​Balaenoptera musculus, is the largest animal to have existed on earth.
Reaching a maximum length of 29.9 meters and 190 tons, which means it takes a lot of energy to
maintain such a large figure. Just the act of swimming can consume large amounts of energy,
which if not replaced, will lead to the death of this large mammal. Feeding is also important in
order to maintain the whale’s core body temperature since they are warm-blooded animals.
Living in such cold environments, it is important that the whale has the energy to maintain its
body temperature, or it will be at risk for hypothermia.
The blue whale lives in all the world's oceans, except the Arctic. Some challenges that
this vertebrate must overcome are challenges that are only faced with aquatic animals. For one,
water is more dense than air. This can pose as a challenge due to the great size of the whale. In
order to move through the water, the whale must overcome the drag that is produced when
swimming through water but, because it is so large the drag coefficient increases significantly
making it much harder to swim in this aquatic environment.
Another problem it has, is the pressure wave that is generated when it is trying to feed.
The whale, in its attempt to catcher its prey, will lunge at high speeds in order to collect as much
krill as possible in a single go. However, the water in front of the whale is pushed out, creating a
wave that would potentially push the prey out of the way.
Another challenge is maintaining certain depth in order to follow their prey’s migration
through the water column. In order to overcome the drag from the water it inhabits, the whale
has evolved over millions of years in order to become more streamline. Originally a four-legged
mammal living on land, the blue whale has developed stiff flippers, an elongated trunk, two large
flukes and got rid of its hind limbs. The flukes are an interesting adaptation since they move up
and down instead of side to side like most aquatic animals. The blue whale also has a solution to
the pressure wave it generates while lunge feeding. In order to overcome this, the blue whale has
developed a large mouth and a throat pouch. As the whale lunges at its prey, the water rushes
into the open mouth of the whale, expanding the throat pouch. The expanding of this throat
pouch is useful in maintaining a relatively neutral pressure in the mouth of the whale, allowing it
to take in more water without the water being pushed out. This allows the blue whale to take in
90 times more energy that it consumes. They then filter out the prey by forcing the water through
sieve-like baleen plates.
In order to follow the prey throughout the water column, the blue whale has developed an
interesting strategy. Before a dive, the whale will expel over 90% of the air in its lungs, then as
they are diving, they have reinforced airways which allow their lungs to collapse. This not only
allows the whale to become less buoyant and makes it easier for it to dive, but it also protects its
lungs from the immense pressure from these depths.
The saltwater crocodile, Crocodylus porosus, although definitely not as large as the blue
whale is the largest living reptile in crocodilian. These crocodiles tend to grow to a length of
about 20 feet and a weight of about 1000 to 1300 kilograms. Feeding is important for the growth
of the crocodile but because it is an ectothermic mammal it does not need to use energy in order
to maintain its body temperature, however, needs other ways of maintaining its temperature.
Because gravity has a larger effect on terrestrial animals the crocodile had to come up
with a strategy in order to be able to thrive in its environment. Also the saltwater crocodile
primarily lives in water that has a high salt content which for most mammals can be a problem
it's not managed. The saltwater crocodile has great eyesight, but when looking for food in murky
water it is hard for the crocodile to locate its prey. In order to maintain its body temperature the
saltwater crocodile must either bask in the sun or stay in warmer waters. Since most reptiles are
not very energy efficient this is considered an optimal strategy for these types of mammals.
Unlike the blue whale who uses buoyancy to their benefit, Crocodiles cannot. When a
crocodile bites on their prey, their jaws will bear the full weight of the prey. Because of this the
jaws of the crocodile have become stronger in order to manage the weight of larger prey. The
crocodile developed the jaw type called metautostylic. This allowed for better muscle attachment
and a larger and stronger jaw giving the saltwater crocodile one of the largest bite forces in the
world.
Living in saltwater environments can be hard for almost all mammals, however, the
saltwater crocodile has developed an organ to help regulate its own salinity. The salt gland helps
it excrete excess salt from its body and allows it to drink the salt water. The saltwater crocodile
has a very good site above water allowing it to see activity on or near the water's edge. However,
underwater their eyesight becomes severely hindered. One strategy that most crocodiles use
underwater involves the use of an integumentary sensory organ. These organs can detect surface
pressure waves allowing them to find prey quickly; they also play an important role in
thermoregulation since they are thermal sensitive. This particular system surprises most
researchers because it allows the crocodilians to evolve a highly armored yet very sensitive skin.