According to Encarta dictionary (2009), a zoo is defined as a park displaying live animals in enclosures, a park where live wild animals from different parts of the world are kept in cages or enclosures for people to come and see, and where they are bred and studied by scientists. Wikipedia (2014) defined zoo (short for zoological park or zoological garden, and also called a menagerie) as a facility in which animals are confined within enclosures, displayed to the public, and in which they may also be bred.
The Nile crocodile (Crocodylus Nilotic-us Laurenti, 1768 ) is the largest of the four crocodilians found in the Africa continent and the second largest crocodilian after the saltwater crocodile in the world attaining a length of 6.2m from the head to the tip of the tail and usually weighs 225kg to 909 kg. The largest accurately measured male was shot near Mwanza, Tanzania and measured 6.45 m weighing approximately 1,090 kg. Like all crocodiles, they are sexually dimorphic, with the males up to 30% larger than the females.
Biologically the Nile crocodile is the best known of all the crocodilians, the snout is long, broad and ends in nostrils which can close under water, the eyes have a third eyelid (nictitating membranes) which protect them while under water. One distinguishing feature of crocodiles from alligators is that the teeth on the top jaw are in line with the lower jaw with the fourth tooth larger than the others and can be seen when the mouth is closed. They have a total number of 66 teeth are long and conical in shape.
TAXOMOMICAL CLASSIFICATION OF NILE CROCODILE
Scientific name: crocodilus niloticus
STANDARD OF MODERN ZOO PRACTICE
Zoos are charged with the responsibility of proving animals with a good animal welfare and standard zoo practice which are as follows;
Provision of food and water
Provision of animal health care
Provision of suitable housing and environment
Provision of freedom to express most normal behavior
Provision of freedom from fear and distress
MANAGEMENT OF CROCODILES
For one to manage crocodile (wild animal) effectively one need to know the animal general characteristics, behavior, basic needs. And try as much as possible to make the animal feel free in a more closely related natural environment.
The management includes bringing (transportation) the animal to its new home (zoo), providing housing, feed, mate, and other animal general requirements. The crocodile must be kept in an area that they can exhibit their normal behavior and free from fear and discomfort.
Zoological garden must take into consideration animal welfare and the five animal freedoms which are as follows according to Wensley (2009);
Freedom from thirst and hunger
Freedom from discomfort
Freedom from pain, injury, and disease
Freedom to express normal behavior
Freedom from fear and distress
CHARACTERISTICS OF CROCODILE
Cold blooded terrestrial craniates with two pairs of pentadactyle limbs.
Has four chamber hearts that behaves like three under water and breath is by the lungs.
Paired kidney and fertilization is internal, amniotic egg covered with calcerous leather shells.
Body Weight: 70 – 1000kg (adult)
Total Body Length: 2 – 5m
Sexual Matur1ty: 10-12 years
Dentition: 64-68 teeth, replaced throughout lifetime
Hearing: between 100 to 4,000 hertz (cycles per second)
Egg: 9×6 cm size, 30-80 per nest
Eyes: overall vision with 270° range
olfactory: Good sense of smell
Incubation: 2-3 months.
Territory Size: shoreline; 60 m, water; 50 m
Life span: 50-80 years
Sexual Dimorphism Males are larger than females.
HANDLING OF CROCODILES
Nile crocodiles are handled with care and high level of expertise and experience, a forked stick is one handy tool used in holding the head and tail in place.
HOW NILE CROCODILE CAN BE PROCURED
Purchase from fishermen, traders, farmers engaged in rearing
Direct capture from the pond, rivers (water bodies) by the aid of a strong fishing net, croc hook.
Gift: it could be donated by zoos or private owners
Confiscation from unauthorized persons or agency
TRANSPORTATION OF CROCODILES
Nile crocodiles are transported effectively in relation to their size and numbers.
Small size: They are placed in a wide basket dipped into large water filled the tank. The reason for this is to effectively remove the Nile crocodiles when the sun comes for them to the sun bask.
Bigger size Nile crocodiles are tied to stick, the two forelimbs are tied together and the two hind limbs tied together at the other end of the stick. The mouth is usually bound by a rope or cello tape.
HOUSING OF CROCODILES
A number of factors must be considered in putting up structures for crocodile and other wild animals.
(i) The original habitat
(ii) The level of aggressiveness and body size.
Crocodiles are highly aggressive animals and are dual in habitat demand they need the aquatic environment for feeding and swimming while the terrestrial enhance their basking in the sun, breathing and reproduction (egg laying and hatching) for these reasons the housing is constructed in a pattern that the animal has its pool and land area for sun bathing which is usually barricaded to keep the animal in and keep visitors out. The pool must be constructed in a way to allow constant water inlet and outlet.
FEEDING OF CROCODILES
Nile crocodiles in the zoological garden are fed with flesh involving meet (rats, mutton, beef), fishes and in some cases compound feed according to their body size. The feeding regime is usually once a week. The food and the manner in which it is presented are of importance in Nile crocodile and other wild animal feeding management. Nile crocodile under normal circumstance enjoys killing live meat on their own when zoological garden allows this it helps to even show the exciting feeding habit which sometimes involves the death row.
HEALTH CARE OF CROCODILES
Nile crocodiles are checked regularly for infections which may lead to diseases. Quarantines and vaccines are given to fight against infections. Some of the diseases that affect the Nile crocodile are; crocodile pox, coccidiosis, trichinellosis, adenoviral hepatitis, mycoplasmosis, chlamydiosis, salmonellosis, mycobacteriosis, dermatophytosis, and kyphoscoliosis. A crocodile that is diseased or sick display abnormal behavior or show symptoms of such illness and this should be immediately attended to enhance the survival of the crocodile.
The provision of hearth care centers in the zoological garden under the care of profession vet doctor is important to carry out the treatment and prevention of diseases among the crocodile.
BREEDING (REPRODUCTION) OF CROCODILES
Mature male Nile crocodiles are paired with a mature female for breeding sake since breeding is the paramount aim of zoo keeping (Nogge 1989). The female ratio to male is usually 3:1.
Female Nile crocodiles lay between 20-80 and sometimes 100 eggs. A clutch size of 60 is the commonest the eggs are laid in a nest in the sand and are covered up referred to as ditch. The young hatch 2-3 month later fully formed and equipped with sharp teeth.
Body temperature 25-300c, their eyes, and valvular nostrils are placed on top of the head and can be kept above the surface when the rest of the body is submerged. It can shut off the valvular flaps so that it can drown its prey without water going into its windpipe. They are partly nocturnal but spend much of the day basking gapping their jaws to cool themselves by evaporation of water through the lining of the mouth. They can replace their teeth throughout their life.
The males are highly territorial during the breeding period hence the paring at the ratio of 1:3 females. After the female might have laid her eggs both male and female Nile crocodiles also watch the ditch in the night. The timing of hatching of young Nile crocodiles from the egg is acknowledged by the female by hearing special sound emitted by the young crocodiles. On hearing such sound, the female takes out the young Nile crocodiles by removing sand off the ditch and breaks up unhatched eggs. After this, the female brings the young Nile crocodiles into the water keeping them on its back and looks after them till next breeding season. But even with so much care large numbers of young Nile crocodiles are eaten up by birds and other predators, very small numbers of young survives in nature.
BREEDING UNDER ZOO MANAGEMENT
Under proper zoo management, the loss of young ones can be minimized by watching the ditch after the female might have laid her eggs. Eggs are marked at the lower surfaces to avoid disturbing the orientation of the eggs. These eggs are placed in a sand filled cubicles of 1m* 1m*1m size at 30cm depth hatchery. The temperature and moisture of the hatchery sand are kept at par with the natural sand. Note that sex of Nile crocodiles is determined on the basis of temperature (male at 31.6oc while female slightly lower or higher temperature). After hatching they are kept in clean pool different from the parent’s pool. The young ones also do basking. They are fed with fishes 2-5% of their body weight. Being cold blooded animal (poikilothermic) they take less food during raining season and more food during the dry season. At the age of 3yrs, they attain a length of 2m and 20kg weight, at this stage they can then be introduced into their parent’s pool.