Crocodiles are ambush hunters,
waiting for fish or land animals to come close, and then rushing out to attack.
As cold-blooded predators, they have a very slow metabolism, so they can
survive long periods without food. Despite their appearance of being slow,
crocodiles are top predators in their environment, and various species have bee-n
observed attacking and killing sharks.
Nile crocodiles had a symbiotic
relationship with certain birds which enter the crocodile's mouth and pick
leeches feeding on the crocodile's blood; with no evidence of this interaction
actually occurring in any crocodile species, it is most likely mythical or
allegorical fiction. Many large crocodilians swallow stones (called gastroliths
or stomach stones) which may act as ballast to balance their bodies or assist
in crushing food, similar to grit in birds. Salt glands are present in the
tongues of most crocodiles and they have a pore opening on the surface of the
tongue. They appear to be similar to those in marine turtles. Crocodilians can
produce sounds during distress and in aggressive displays. They can also hear well,
but their tympanic membranes are concealed by flat flaps that may be raised or
lowered by muscles.
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| The Nile Crocodile |
Crocodiles eat fish, birds, mammals
and occasionally smaller crocodiles. Crocodiles are protected in many parts of
the world, but they also are farmed commercially. Their hides are tanned and
used to make leather goods such as shoes and handbags; crocodile meat is also
considered a delicacy. The most commonly farmed species are the saltwater and
Nile crocodiles, while a hybrid of the saltwater and the rare Siamese crocodile
is also bred in farms. Farming has resulted in an increase in the saltwater
crocodile population, as eggs are usually harvested from the wild, so
landowners have an incentive to conserve their habitat. Crocodiles are more
closely related to birds and dinosaurs than to most animals classified as
reptiles, the three being included in the group Archosauria ('ruling
reptiles').
Crocodile embryos do not have sex
chromosomes, and unlike humans, sex is not determined genetically. Sex is
determined by temperature, with males produced at around 31.6 °C, and females
produced at slightly lower and higher temperatures. The average incubation
period is around 80 days, and also is dependent on temperature.
Size greatly varies between species,
from the dwarf crocodile to the saltwater crocodile. Species of Palaeosuchus
and Osteolaemus grow to an adult size of just 1 meter to 1.5 meters. Larger
species can reach over 4.85 meters long and weigh well over 1,200 kilograms.
Crocodilians show pronounced sexual dimorphism, with males growing much larger
and more rapidly than females. Despite their large adult sizes, crocodiles
start their lives at around 20 centimetres long. The largest species of
crocodile is the saltwater crocodile. Measuring crocodile age is unreliable,
although several techniques are used to derive a reasonable guess. The most
common method is to measure lamellar growth rings in bones and teeth—each ring
corresponds to a change in growth rate which typically occurs once a year
between dry and wet seasons. Bearing these inaccuracies in mind, the oldest
crocodilians appear to be the largest species.
Human-Crocodile
conflict
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| Crocodile killed on dual carridge-way in Kitwe, Zambia |
Crocodiles have been considered to be
a problem to communities that live in close proximity with them and rely on the
same water source for livelihood. The problem of people living in close
proximity to wild animals and the associated conflict is well documented but is
not an easy problem to find a solution for where all parties benefit. Human-Crocodile conflicts have been recorded in areas such as Chiawa and in
Kitwe along the Zambezi and Kafue River respectively. There are various ways in
which mitigation of attack can be undertaken. That is:
- Constructing more boreholes at the villages to reduce the reliance of local people on the river. This appeared to be the most popular mitigation measure.
- Constructing crocodile-proof barriers at water collection locations which are well used by the local populace. This is a cheap, quick and easily implemented measure. Further studies are required to determine their actual effectiveness.
- Building suitable foot bridges across tributaries to allow safe access to agricultural fields. Although there are some of these in the area improved initial construction and continued maintenance could ensure that these are safer to traverse.
- Education, simply by varying the locations and times when visiting the river can reduce the chance of crocodile attack. Education could also help in a more fundamental way, by realizing the potential economic and ecosystem gains from having wildlife could increase the tolerance of people to animals. This has been proven to have a beneficial effect on people’s attitude to wildlife and the success of conservation ideals.
- An improved system of reporting crocodile (and other animal) attacks so that potential danger zones can be identified and monitored. Quite often, attacks were not reported especially when the person escaped unharmed. It is important these areas are identified to prevent future problems. This also includes cross-border co-operation between Zambia and Zimbabwe so that the true extent of human crocodile conflict is realised.
- Increased communication between the local community the wildlife department and involving crocodile farms/ranches to relocate or remove “problem” crocodiles. The follow-up of reported incidents and feedback is important for involving the local communities who are responsible for the initial reports.
Continued monitoring of the crocodile
population, this is essential and a common concept in crocodilian management
plans. Realising potential crocodile attack “hot-spots”
and areas with high densities of crocodiles, nesting areas, etc. are important
for both the mitigation of human crocodile conflict as well as the continued
conservation of crocodiles.
One the activities that our society
(The Wildlife Biology & Management Society) plans on undertaking this year
will be the sensitisation of the community living near the Kafue River in Kitwe
on Human-Crocodile conflicts and how they can be avoided and mitigated.
Share
with us your experiences, comments and recommendations. Send emails to wildlifemgtsociety@gmail.com
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