DIET:
Although the juveniles are generally restricted to eating small aquatic
invertebrates and insects, they soon move onto larger vertebrates (fish, amphibians and reptiles). Adults, however, can potentially
take a wide range of large vertebrates, including antelope, buffalo, young hippos, and large cats. Fish and smaller vertebrates
often form the greatest part of their diet, however. As with C. porosus, they have a reputation as being man-eaters,
although probably kill more people than all other crocodilian species combined. Along with hippos and lions, crocodiles account
for perhaps a few hundred deaths and disappearances each year, although exact figures are very hard to verify. Nile crocodiles
will also often scavenge from carcasses, together with a number of other animals, all of which seem to tolerate each others'
presence. They have a rather well-known relationship with several species of birds (e.g. spur-wing plover, called "trochilus"
by Herodotus) which are reputed to pick pieces of meat from between the teeth of the crocodiles as they gape - the birds gain
a meal, the crocodiles have their teeth cleaned of scraps they could not eat themselves. Whether such a mutual relationship
actually exists is hard to determine from the literature and anecdotal reports, but seems more likely to be opportunistic
rather than symbiotic.
Several prey animals have been found wedged under submerged branches and stones, leading to reports that the crocodiles
store unwanted prey here until a later date. Some claim that it is necessary for the prey to decompose before the crocodiles
are able to tear portions of flesh off, but this is unlikely to be true. The flesh may become softer if the prey remains in
water after death, but crocodiles will certainly avoid rotting meat. When feeding, a number of individuals will hold onto
a carcass with their powerful jaws whilst twisting their bodies. The anchorage provided by the other individuals allows large
chunks to be torn off for easier swallowing. A few lone individuals have been reported to wedge prey between branches in order
to provide the anchorage necessary for such actions to be effective, which could even be claimed to be a form of primitive
tool use.
Other cooperative feeding behaviour has been reported, such as the action of many animals to cordon off an area
of water to concentrate fish within. A hierarchy of feeding order is often observed in such situations, with more dominant
animals feeding first. Groups of crocodiles will often move onto land to scavenge from kills made up to several hundred metres
from the water. Adults have also been observed fishing using their bodies and tails to corral the fish towards the bank where
they are concentrated and picked up with a sideways snatch of the jaws. Social behaviour in Nile crocodiles is often underestimated,
although there are many aspects still poorly understood.
It has been observed that social status may influence an individual's feeding success, with less dominant animals tending
to eat less in situations where they come into frequent social contact with other, more dominant individuals.
BREEDING:
This species digs hole nests up to 50cm deep in sandy
banks, several metres from the water. These may be in close proximity to other nests. Timing of nesting behaviour varies with
geographic location - it takes place during the dry season in the north, but at the start of the rainy season further south,
usually from November through to the end of December. Females reach sexual maturity around 2.6 m, males at around 3.1 m. Females
lay around 40 to 60 eggs in the nest, although this number is quite variable between different populations. Females remain
near the nest at all times. Incubation time averages 80 to 90 days (ranges from 70 to 100 days), after which females open
the nest and carry the juveniles to the water. Both males and females have been reported to assist hatching by gently cracking
open eggs between their tongue and upper palate. Hatchlings remain close to the juveniles for up to two years after hatching,
often forming a creche with other females. As with many crocodilians, older juveniles tend to stay away from older, more territorial
animals.
Despite the vigilance of the female during the incubation period, a high percentage of nests are raided by a variety of
animals, from hyaenas and monitor lizards to humans. This predation usually occurs when the female is forced to leave the
nest temporarily in order to thermoregulate by cooling off in the water.
