The answer is arms race. An example is the cold war era nuclear arms race between the United States and the Soviet Union. Today's superpowers such as China, Russia and United States are also engaged in an arms race for the most technologically advanced weaponry.
Decreased surface-to-volume ratio. The dolphin's fusiform body shape and reduced limb size decrease the amount of surface area exposed to the external environment.
Increased insulation. Dolphins deposit most of their body fat into a thick layer of blubber.
