Africa's largest reptile and biggest aquatic predator, the Nile crocodile (Crocodylus niloticus) is a fearsome creature. Each year in Africa, hundreds of
people die from encounters with this reptile, but many more crocodiles die upon an encounter with humans, than the other way around. The Zambesi River, that runs
through central Africa, offers prime crocodile habitat, but due to excessive hunting, populations are lower than the carrying capacity. The pressure on wild
populations is relieved in some cases where crocodile farms raise the creatures to provide skin and meat at a low price and thereby reduce the incentive to poach
wild animals.
Crocodiles (Family: Crocodylidae) are the largest reptiles on earth. The African or Nile crocodile (Crocodylus niloticus) is one of the biggest, up to
18 feet (5.5 m) long. This is huge, but compare it with a Cretaceous monster crocodile that grew to a gigantic fifty feet (15.2 m) long. Such behemoths went the
way of the dinosaurs their smaller brethren live on.
Crocodiles differ from alligators which do not occur in Africa. There two easy-to-remember differences. First, a crocodile's lower jaw teeth protrude outside
the upper jaw but the alligator has a socket into which this tooth fits. Second, the crocodile's snout is longer and than the alligator's and tapers to a
narrow point.
The crocodile is known to us from our earliest childhood years. A huge primordial beast, skulking along tropical waterways amid the humid green jungle... its
scaly body slithers, dagger-toothed jaws gape wide and cold beady eyes stare blankly—images of a fearsome maneater. They are primordial. Crocodile fossils
date back to the Triassic, at least 206 million years ago. They were already an ancient group when dinosuars began to roam vast forests during the Jurassic.
As is well-known crocodiles are predators of humans. Numerous people have ended up this ghastly way. In his stories of India, Rudyard Kipling describes a
maneater, the mugger crocodile (C. palustris). This is an increasingly rare species as it has been hunted on the presumption of being a competitor for
fish.
From protection in certain areas, crocodilian populations have rebounded. While this is good news for the crocodile, it brings them into conflict with humans.
With knowledge of their habits we can avoid problems with crocodiles. If we face the facts, vastly more crocodiles have been killed, for skin and sport, by
humans than the reverse.
That explains why, like most wild animals, the tables are now turned and the crocodile has learned to fear humans and attacks only occur if they are hungry or
provoked. Normally, the crocodile is quite timid and will usually retreat back to water if someone approaches. Crocodiles can move quickly if the need arises,
but never chase prey onto land. Their jaws are extremely powerful, whereas at the other end, their tail serves as an effective battering device.
Crocodiles come close to shore and many people are attacked while bathing or even paddling in shallow water. There are numerous cases of people being eaten
because they ignored advice or warnings. Usually man-eaters are very old and large individuals. Humans, for their part are wise to heed signs of danger when
in croc country so not to put themselves at risk. As we learn more about these magnificent reptiles we can put aside our fears and learn to admire them.
It is, after all, a survivor. As tyrannosaurs ran after brontosaurs, crocodiles splashed in rivers and swamps among forests of giant ferns, horsetails and
palms. Yet the dinosaurs died out, seemingly in a geological instant, and the crocodile lived on.
All that time has taken its toll on crocodiles and many species went extinct. As a group they are ancient and old, yet with only 20 known species, the least
diverse of the three major reptile groups. Thus, crocodiles are slowly losing ground to more advanced homeothermic creatures (mammals). Somehow, they hang on
and even thrive where conditions have remained as they prefer and they are free from human interference.
The crocodile is successful partly because it switches feeding methods. They use four distinct techniques. First, they actively hunt fish. Second, when the
opportunity arises, a crocodile will swim underneath a floating water bird which it grabs at the surface. Third, it hides among water edge vegetation for a
gazelle or bush pig to amble by. When it sees the chance for an ambush, the crocodile lunges foward, knocks the animal down with its powerful tail and then
drags it to water where it quickly drowns.
Fourth, a crocodile waits utterly motionless, as still as the proverbial floating log, in watch for some unwary animal to come to the water's edge. In a
flash it is on the victim, which it grabs by the nose and pulls in the water where it is held to drown. Large antelope and other herbivores, even cattle are
taken by big, old crocodiles.
A hard-won carcass is usually dragged to some hiding place on a river bank until it is ripe enough for the crocodile taste. As well as their own food,
crocodiles will readily take carrion they happen upon by chance. One reason they leave their food to decompose is that they cannot tear it into small enough
pieces to swallow. Unable to chew they bite off chunks by holding the carcass in their jaws while violently twisting and turning. In a shark-like feeding
frenzy, a group of feeding crocodiles will thrash about taking turns at the prey.
Crocodiles have the famous log-like appearance when floating in water because their eyes, nostrils and ears are at the same level and positioned at the
top of the skull. Thus, they remain slightly above water while the rest of the body is submerged. When the animal dives, hinged valves shut water out of
the ears and nostrils.
The teeth of the crocodile wear out but they are replaced throughout the animals lifetime. Theoretically this should allow the animal to live to several
hundred years and crocodiles are supposed to live to great ages. Sadly, truth is far from fiction; the oldest recorded crocodilian reached 68 years of age
in captivity. Crocodiles would have more dental problems were it not for the services of the Egyptian plover which bravely pecks food particles from the
huge pointed teeth.
Reptiles rarely expend any effort by way of parental care for their young. Yet crocodiles build nests and actively tend their brood. Recent studies show
they are closely related to birds. Hence, alone among reptiles, crocodiles have nests and eggs much like those of primitive birds.
On a secluded, sandy river bank, the female uses her front limbs to dig the nest, an eighteen inch (46 cm) deep pit. In this she lays a large batch of between
thirty and sixty white eggs, each the size of a hen egg and like them covered with a hard calcareous shell. Once the laying is over she fills the nest with
sand and grass and lets the heat of the sun incubate the eggs.
The female watches over the nest to fend off potential egg-stealers. The most adept of these is the monitor lizard which quickly digs up an egg or two while
he mother is not watching and whisks them off to eat at its leisure.
If the eggs survive for about three months the nearby mother will soon hear the little hatchlings croak and chirp, whereupon she opens the nest. Most
tenderly she takes the babies in her mouth and goes to water, where she releases them. They stay around her, feeding on crustaceans and water insects,
until they are large enough to fend for themselves. Even with all her care, only two or three offspring at from a clutch survive to maturity. Baby crocodiles
are subject to numerous dangers, especially large wading birds, such as storks and herons, large lizards and adult crocodiles.
Amazingly, the sex of the embryonic reptile is not determined directly by the genes. It rather depends on the temperature to which the egg is exposed during
incubation. Cool temperatures near the bottom of the nest cause embryos to form into females, while warmer temperatures nearer the surface result in more males.
Several species of crocodile inhabit Africa, mostly confined to areas of warm riverine forest. The more interesting are the slender-nosed crocodile
(C. cataphractus), the West African dwarf crocodile (Osteolaema tetraspis) and the Osborn's dwarf crocodile (Osteolaema osborni). This last species is
the world's smallest crocodilian and rarely exceeds four feet (1.2 m) in length.
Crocodiles inhabit many freshwater lakes and rivers in Africa. Uncontrolled hunting ravaged crocodile populations and they are absent or scarce where
previously abundant. However, with vigilant protection some populations are on the increase. In Kenya, crocodiles can be regularly seen on the Galana River at Tsavo,
at Mzima Springs, at the hippo pools in National Park and on the Mara and Tana Rivers. Perhaps the best place is Lake Turkana, among the last great crocodile
sanctuaries. In Zambia, the Zambesi River harbors significant numbers, also found along the Luangwa Valley. In Malawi, the Shire River is home to the most abundant
populations, while Lake Malawi also supports several.
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