B. The first crocodile-like ancestors came into existence approximately 230
million years ago, and
they had many of the features which make crocodiles
natural and perfect stealth hunters: streamlined body,
long tail, protective
armour and long jaws. They are born with four short, webbed legs, but this
does not
mean that their capacity to move on the ground shall ever be
underestimated. When they move, they are so
fast that you won’t even have
any chance to try making the same mistake again by getting too
close,
especially when they’re hunting.
C. Like other reptiles, crocodiles are poikilothermal animals (commonly known as coldblooded,
whose body temperature changes with that of the surroundings) and consequently, require exposure to
sunlight regularly to raise body temperature. When it is too hot, they would rather stay in water or shade.
Compared with mammals and birds, crocodiles have a slower metabolism, which makes them less
vulnerable to food shortage. In the most extreme case, a crocodile can slow its metabolism down even
further, to the point that it would survive without food for a whole year, enabling them to outlive mammals
in relatively volatile environments.
D. Crocodiles have a highly efficient way to prey catching. The prey rarely realises there might be a
crocodile under the water because the crocodile makes a move without any noise or great vibration when
spotting its prey. It only keeps its eyes above the water level. As soon as it feels close enough to the victim,
it jerks out of the water with its wide open jaws. Crocodiles are successful because they are capable of
switching feeding methods. It chases after fish and snatches birds at the water surface, hides in the waterside
bushes in anticipation of a gazelle, and when the chance to ambush presents itself, the crocodile dashes
forward, knocks the animal out with its powerful tail and then drags the prey into the water to drown.
E. In many crocodilian habitats, the hot season brings drought that dries up their hunting grounds,
leaving it harder for them to regulate body temperatures. This actually allowed reptiles to rule. For instance,
many crocodiles can protect themselves by digging holes and covering themselves in mud, waiting for
months without consuming any food or water until the rains finally return. They transform into a quiescent
state called aestivation.
F. The majority of crocodilian is considered to go. into aestivation during the dry season. In a six-year
study by Kennett and Christian, the King Crocodiles, a species of Australian freshwater crocodiles, spent
nearly four months a year underground without access to water resources. Doubly labelled water was
applied to detect field metabolic rates and water flux, and during some years, plasma fluid samples were
taken once a month to keep track of the effects of aestivation regarding the accumulation of nitrogenous
wastes and electrolyte concentrations.