A healthy full-term hatchling will have a scar-line on the belly where the body wall
has almost closed over the mass of yolk. The abdomen will be rounded and firm but there
should be no obvious lump of yolk. Crocodiles may hatch prematurely with a bloated abdomen
and yolk still visible through the open slit.
All hatchlings are likely to have wet membranes (and possibly bits of eggshell) hanging
from them.
There is general agreement that hatchlings should be kept out of water for at least 24
hours after hatching so that the membranes can dry, shrivel and break away. There should
be no attempt to wash the hatchlings or pick them clean by hand. Premature hatchlings
should be kept out of water until the yolk has been absorbed and the abdomen has closed.
Drinking water should be provided in a small container. Keeping the animals dry lessens
the risk of the yolk becoming infected. Mesh-covered incubation boxes would be suitable
containers in which to leave premature hatchlings (still inside the incubation room) for
the first few days. If possible the temperature should be maintained at 34°C to speed up
absorption of the yolk and strengthen the hatchlings as quickly as possible.
Flies, ants and other insects can be troublesome if the containers are not screened with a
fine mesh.
1/ 65 days for American alligator and about the same for mugger (C. palustris) 84 days for
Nile crocodile and about the same for C. novaeguineae. About 90 days for C. porosus and gharial.
Because of their remaining yolk supply young crocodiles do not require food for a few
days after hatching. Their immediate need is for warmth and, behaviourally, for seclusion.
Warmth, even for strong, healthy hatchlings is extremely important. It has been found
(Lang 1981) that New Guinea freshwater crocodiles, less that two weeks old, prefer a
temperature of 33.4-33.9°C. This is 3-4°C higher than the preferred temperature of
juveniles and older animals. In general, rapid growth in young crocodiles depends on a
high body temperature, a high food intake and a management routine that minimizes disease
and stress.
It is most probable that low temperatures are the indirect cause of many, perhaps most,
early deaths. Certainly, crocodiles in captivity are far more delicate during their first
year or so than they are later. In New Guinea it is generally found that both saltwater
and freshwater crocodiles are much easier to keep after they reach about 45cm in length.
They hatch at about 28-30 cm.
The need for seclusion appears to be an instinctive urge which in captivity can prevent
hatchlings from feeding or even keeping warm. In badly designed enclosures or under
careless management it can result in young crocodiles remaining hidden in a cold place
because they are not willing to be exposed in a warmer place where they could also feed.
It is probably also responsible for the tendency of baby crocodiles to burrow under one
another until all the animals in a pen are lying in a heap. Thus the natural fears of baby
crocodiles (which must help them to survive in the wild) can work against them in
captivity.
Enclosures must obviously meet the needs of the hatchlings as well as being
escapeproof, convenient for feeding and other management operations. The size of
enclosures will depend mainly on the length of time the hatchlings are to remain there.
It is usually found that within a few weeks some hatchlings have grown to be much bigger
and stronger than others. The dominant ones can then suppress the growth of the weaker
individuals by affecting their feeding and other behaviour. For this reason crocodiles
should be sorted periodically and those of a similar size kept together. Three size
categories will be enough. This need to segregate the sizes means that more enclosures
have to be used or, to save space and expense, enclosures have to be divided by
partitions.
Crocodiles have been reared successfully under very crowded conditions. In Florida up to
20 alligators of 25-35 cm long were kept in fibreglass tanks of only 60 x 60 cm floor
space of approximately 60% was water (Smith & CArdeilhac, 1981). In Thailand
hatchlings of C. porosus and C. siamensis are kept in groups of 8-15 in tiny enclosures of
30 x 50 x 40 cm - a density of 40-75 per square metre of floor space. Mortality during the
first year was 20-30% (Yangprapakorn and others, 1971). Most authorities would consider
this density (and mortality) much too high. Ten or twelve hatchlings per square metre is
more widely accepted as a maximum density for the first few months. In a most successful
programme for captive rearing of the gharial only 10 hatchlings were stocked in pools of 2
x 2 m each with a 1 m surround (Bustard, 1980).
It is certainly wise to keep not more than about 50-60 very young crocodiles in a single
enclosure, regardless of space, in order to limit losses in the event of disease. Sixty
hatchlings at 10-12 per m² would occupy a minimum floor space of 5 square metres but if
crocodiles are to remain in the same enclosure for more than a few months then the pens
will have to be bigger than this minimum. The needs of juvenile crocodiles are discussed
in section 8.
The enclosures used for alligator research in Louisiana have proved extremely
successful and have been described in detail by the designers, Joanen and McNease (1976,
1979). These environmental chambers, as they have been called, measure approximately 5 x 3
x 1 m high and have floors and walls of concrete. There are hinged plywood doors on top,
lined with styrofoam for insulation. The walls are clad externally with Styrofoam covered
with plywood and there is styrofoam beneath the concrete floor. The floors are stepped so
that half the width holds 15 cm of water. The dry side is sloped concrete. The chambers
are divided by partitions. Electrical heating is by thermostatically controlled thermal
conductors embedded in the floor. Each chamber is separate and independent but a number of
them are situated beneath a single large sheet metal roof. Within the chambers maximum
stock density is limited to one alligator per 0.1 square metre until the animals are one
year old. The temperature is maintained at 30°C. Within these chambers alligator survival
from hatching to the age of three years, has averaged 95%.
Although the chambers are highly successful it should be borne in mind that they are
primarily intended for research. They make it possible to rear hatchlings ( and incubate
eggs) under precisely controlled but different conditions. For commercial purposes, where
all stock is to receive the same treatment, such duplication would be un necessarily
expensive.
At the other extreme Smith and Cardeilhac (1981) have described how a heated building of
10 x 46 cm can accommodate 1750 alligators comprising 350 individuals in each of 5 size
classes from hatchlings to 1.8 metres.
To get maximum value from the heated space alligators are crowded and tanks are stacked.
Fibreglass hatchling tanks of 60 x 60 cm and 91 x 91 cm are set in tiers, one row above
another. For bigger animals fibreglass tanks of 2.4 x 1.2 x 1.2 m are set in pairs above
concrete tanks of 4.3 x 3 m. Servicing aisles 1.2 m wide separate the rows of tanks.
Within the tanks water slopes to a depth of 30 cm below dry deck with a ratio of about 60%
water to 40% deck.
The building is well insulated and admits no sunlight. The most economical heating method
was found to be a system of circulating hot water (71ºC) beneath the concrete floor of
the building. In N. Florida this was necessary for more than half the year.
Only in exceptional circumstances would a system such as this be likely to show a profit
but when hatchlings are reared without any extra heat they usually suffer high mortality
and grow more slowly even in locations well within the tropics. One reason for this is
that small pools of water do not retain beat through the night and the air and water
temperatures commonly fall towards 20°C even at sea level quite close to the equator. In
Zimbabwe farmers on the shore of Lake Kariba tried pumping lake water continually through
the hatchling pools at night (Blake, 1982).
Complete environmental control will obviously permit highly efficient management but in a
commercial situation a compromise between unheated pens and controlled environmental
chambers might be the most cost-effective arrangement.
In sunny climates crocodiles can maintain their body temperature by basking as necessary
and if they are kept in pens within an enclosure which provides a limited greenhouse
effect they will benefit even on dull, rainy days. At night ai r temperatures can be
allowed to fall while shallow pools of water are heated to 30°C (or 32ºC for the first
two weeks). In this way heating costs are kept to a minimum and crocodiles can choose
cooler water/warmer air during the day and cooler air/warmer water at night. They need
never be colder than about 30°C and, with good ventilation and the provision of some
shade in each pen they need never be overheated. An afternoon air temperature of 35°C is
not excessive and hotter periods will do no harm provided that the crocodiles always have
access to shade and cooler water.
With such a system it is essential that crocodiles are allowed to regulate their own body
temperature and are not forced to lie in one situation because of stress or disturbance. A
great advantage of a totally controlled environment is that a crocodile's temperature
stays within safe limits irrespective of his behaviour.
The best combination of roof shade and ventilation for the main shed or enclosure will
vary according to climate and season. It can be found by trial and error if the shed has
enough opening/closing windows. In this regard colourless (translucent) fibre glass
roofing sheets are very useful and easy to work with. If the shed becomes too hot, despite
maximum ventilation, some panels can be painted white or shaded. In the very hottest
climates an enclosure with open, netted sides may be adequate. Shade and seclusion within
the pens is provided by raised boards placed across parts of the land and water.
A suggested layout for an enclosure with four blocks of five pens is shown in Fig. 3. Five
to six hundred hatchlings could be accommodated in two blocks and by successive spacing
and size segregation they would come to occupy three or four blocks depending on the
length of time they were kept in the enclosure. The blocks should have independent heating
so that cost of heating as well as maintenance, will be minimized.
Various methods of heating could be used depending on available resources and technology
but details must be planned at the outset so that any hot water pipes can be laid during
pool construction. If liquid or solid fuels are used there must be no risk of smoke or
fumes within the hatchling enclosure.
In the design shown the pens are 2.5 m long and 2 m wide. Each pen has two water pools of
60 cm wide and 15 cm deep running the length of the pen, along each side. This leaves a
strip of dry land (80 cm wide) between them. The entire floor area is concreted and the
pen walls, which should be 60 cm high, must be plastered smooth to prevent escapes.
With two pools in each pen disturbance to the hatchlings can be reduced and sudden
temperature changes to the entire water supply can be avoided. The daily management
routine would be as follows:
- at the end of the working day food is laid in the pens on clean feeding boards about 1 m
long. Water heating is switched on before water temperatures fall below 30°C.
- at the start of the next working day heating is switched off and all pools on one side
of a block are drained and washed clean. Any uneated food is removed and feeding boards
are taken out for cleaning. During this disturbance the hatchlings will usually enter the
other (full) pool.
- empty pools are refilled with clean water. A small diameter hose from a standpipe is
adequate for washing and filling such small pools.
- For the rest of the working day the crocodiles are disturbed as little as possible.
A disadvantage of this system is that pools are only cleaned on alternate days. With
juvenile crocodiles, even at high density this has proved to be satisfactory but hygeine
is very important for hatchlings so an extra effort must be made to keep uneaten food out
of the water. A raised edge to the feeding boards may help. If single pools are used or
all pools are cleaned daily it will be an advantage to refill with water from a storage
tank or reservoir rather then water from underground which may be several degrees colder.
During cleaning operations the hatchlings must have seclusion under raised boards so that
they are not stressed more than necessary.
Where hatchling pens have been built with no provision for heating, there are various
possibilities for improving the situation. Brooders in the form of boxes or reflectors
fitted with electric light bulbs, have been used with some possible benefit but any
arrangement which requires crocodiles to spend the night huddled beneath a lamp is not
likely to produce the best results. If bulb, (infra red or not) are used to heat the
entire floor space then it will probably be no more expensive, but more effective, to use
aquarium heaters in the water.
Finally, if hatchlings must be reared without extra heat the comments on site location
(8.1) are relevant. In general, large pools should be used so that more heat will be
retained through the night. Hatchlings must then be kept at low densities so that frequent
water changing (for cleaning) is not necessary.
Nor will it be necessary to concrete the land area. Concrete is a heat sink and no
young crocodiles should be forced to lie on cold concrete if it can be avoided.
Hatchling enclosures must be surrounded by a predator-proof fence of wire netting. A
netted roof, high enough for workers to be able to stand, will protect hatchlings from
birds and also provide support for shade Cloth or other light material. See also section
8.
Occasionally it may be possible to divert water from a stream or spring to supply a
crocodile farm but such water is often colder than local static water. A reservoir, or
even a large water tank for a hatchling complex, is an asset even if water has to be
pumped. It is uneconomical and mechanically inefficient to keep starting and stopping a
powered pump every time water is needed. Where possible water should be pumped to a higher
reservoir and then piped off by gravity. This also ensures a water supply if the pump is
temporarily out of action. In addition it serves as a settling tank for muddy water,
although it is easy enough to install a filter in the main line.
Portable sand medium filters, sold for irrigation purposes, are very effective. Small
models, weighing less than 50 kg with sand, will filter about 6m³ /hr. They will operate
at low pressure and are easy to clean by back-flushing.
A cheaper filtration method for larger volumes of water can sometimes be devised by
sinking a filter box in a specially prepared cavity of a natural water body such as lake
or river. One firm (S.W.S Filtration Ltd., of Northumberland England) has specialised in
this type of filtration.
In some circumstances it could be an advantage to chlorinate the water supply for
hatchlings in order to destroy bacteria. This is best done by using an automatic control
system which injects chlorine, at a selected rate (e.g. 1 part per million) into the
supply pipe. Known as proportional chlorination plants, these units are electrically
operated and sold for domestic water supplies. Small models are available for flow rates
of less than 5 m³/hr.
Water can be throughly disinfected by using an ultra violet water sterilizer. These
incorporate a light bulb which kills bacteria and viruses by passing ultra violet light
through the water supply pipe. The method has been used in fish hatcheries and public
aquaria where very pure water was required. Small units are available for flow rates down
to about 2.5 m³/hr.
Water pumps are available in great variety and the best one for the job can only be
selected when the precise requirements are known. Manufacturers will recommend a model if
they are supplied with details to include the height to which water must be raised and the
required rate of discharge. In general, low pressure, high volume pumps are preferred and,
if water must be drawn from a deep well or bore, an electrical submersible pump will
probably be best.
For low lift applications electrical or diesel pumps of the centrifugal type are generally
suitable and trouble free. Petrol pumps are not recommended for prolonged use.
Where it can be arranged a hydraulic ram could be a cheap way of keeping a reservoir
filled. The ram depends on flowing water which falls down an inlet pipe. A pair of check
valves causes about 15% of the water to rise in the outlet pipe. The maximum rise is about
five times the vertical fall in the inlet pipe.
Manual pumps are adequate for only the very smallest applications or for emergency use in
hatchling pools. Hand pumps of the semi-rotary type are simple and long lasting. They are
operated by moving a handle from side to side and with a 40 mm outlet they deliver about
70-90 litres per minute. A foot valve should be fitted to the bottom of the intake pipe so
that water is held in the system when pumping stops. Otherwise the pump will probably need
priming with water before every operation. A foot valve with a grid or coarse filter is
worth fitting to the intake of all pumps.
For water distribution plastic pipes and fittings are much better than metal ones . Black
polythene pipe is now used extensively for irrigation systems in agriculture and
horticulture and is ideal for use in crocodile farms. The pipe is usually sold in rolls of
150 to 300 m with various diameters ranging from 10 to 50 mm. Pipe of 50 mm is suitable
for a mainline which brings water from the source to a block of hatchling pens. Submains
of about 30 mm may then be run between the rows of pens and, finally, laterals or about 15
mm, each fitted with a plastic gate valve can be passed to each small pool.
The pipe is flexible, durable and easily cut to length. A variety of plastic fittings are
also available such as joiners, reducers, elbows, tees, crosses and gate valves. These are
fitted to the cut end of the pipe without the need for a threaded (i.e. screwed) end. If
pipe and fittings are ordered from the same supplier all should be well but if different
suppliers are used it is important to make sure that stated diameters correspond. The
stated diameter of pipe made under the metric system usually refers to the outside
diameter (e.g. 50 mm OD). In some counties however pipe is manufactured to Imperial
measure (inches) and may be given a nominal metric size which refers to the internal
diameter. For example, inch and a quarter pipe is sold as 32 mm ID.
The smaller diameters in low density polythene (maximum about 25 mm) can be connected by
plastic fittings that simply push into the end of the pipe. It may be necessary to soften
the end first by heating it, briefly, with a flame or in hot water. These push-in fittings
are the cheapest. Heavier pipe and systems where there is high pressure must be connected
by more expensive plastic fittings which grip the outside of the pipe and incorporate a
rubber seal. The larger gate valves are normally in brass which is much more expensive
than plastic.
While a screened pipe of 30-40 mm will be adequate for draining very small hatchling pools
the submains into which they flow must be much larger to avoid troublesome blockages. PVC
drainpipes (100 mm) are suitable but joining the smaller pipes to it can be a nuisance. An
alternative is to have open drain channels, concreted so that they can be hosed and
scrubbed clean. Earth drainage ditches may become foul and must only be used at a distance
from the hatchling units.
Routine care consists mainly of feeding, cleaning and keeping the crocodiles segregated
according to size. The animals should not be handled or disturbed more than necessary.
Sudden shock, such as accidentally dropping a bucket or brooder near a hatchling, can
cause it to go into convulsions and die.
In general, hatchling crocodiles in the wild feed on small invertebrates such as water
beetles, insect larvae and shrimps. This is a difficult diet to provide for captive stock
but it can sometimes be done. In certain parts of Papua New Guinea, for example, villagers
are able to catch small freshwater prawns (probably Macrobrachium species) in basket
traps. Chopped fish (Tilapia) is mixed with them and hatchling crocodiles thrive and make
rapid growth on the diet. A similar mixed feed, with a large proportion of shrimps or
prawns, is obtained in Burma from tidal reaches of the Rangoon River. Hatchlings of
Crocodylus porosus do extremely well on that diet. Freshwater prawns can be bred in ponds
or tanks.
It is not necessary to offer live food to hatchlings but live food does appear to be more
attractive to them. Presumably the movement of prey is an extra stimulus to feeding. Some
hatchlings will start to feed very soon after hatching, others will not begin for a few
days. All should be feeding within 10 days. The sight of crocodiles eating seems to
stimulate others to feed.
A danger in giving food which is not live is that it may not be fresh either. The
importance of fresh food must be impressed upon those responsible for food preparation.
Fish should be gutted before freezing and made up into parcels in plastic bags so that
just enough can be taken out each day. Surplus must not be re-frozen after thawing.
Food should be prepared in an enclosure screened against flies and, for hatchlings, the
food can be put through a very coarse mincing machine. The aim Must be to produce tiny
pieces that can be picked up and swallowed easily. Obviously the pieces must not be too
big but neither should the food be reduced to a slimy, mushy consistency for this seems to
be unpalatable to young crocodiles. The food can, of course, be chopped by hand.
Variety in the diet is beneficial and because of the tiny amount needed for hatchlings it
is usually possible to vary the diet more than adequately. Fish, butcher's meat and
poultry offal can usually be found, at least in small quantities, and livers and hearts
can be fed with priority to the hatchlings.
Very fatty meat should not be given; it may be eaten but then regurgitated. Bone must not
be given to hatchlings except when crushed. If no bone is given then another form of
calcium, such as powdered cuttlefish shell, should be sprinkled over the food. With a
varied diet including red meat, liver, fish and perhaps some invertebrate food there will
be no need for feed supplements. If it is suspected that the diet is not rich enough then
a proprietary vitamin and mineral mix, as sold for the poultry industry, could be tried or
a special mixture can be made up (see Appendix).
Another possibility for enriching the diet of hatchlings is that of attracting insects to
the pens. Mercury vapour lamps, or even ordinary electric light bulbs, suspended over the
pools at night will attract insects. The trouble is that they may attract large beetles
and other insects which are not eaten and become a nuisance. It is probably better to
attract the insects into a trap. Unless they are needed as live food they can then be
killed in the freezer and fed selectively.
Hatchlings weigh about 40-70 grams (depending on species) and may at first eat only 5 to
10% of their body weight in a week. But for the next few months they should eat, on
average, about 25-30% of their body weight a week. Food should be offered to hatchlings
every day, though a weekend break does no harm.
Small crocodiles can quickly be weighed (on a spring balance fitted with a box) at times
when they have to be handled for size segregation. It is also good policy to weigh the
food placed in each pen and to weigh any uneaten food when it is removed. This will
provide a useful record for comparing progress under different conditions or diets. The
only way to be sure that crocodiles are being given as much food as they want is to adjust
the amount each day until it is found that a very little remains uneaten.
Food should be sprinkled along boards so that it presents a long row of food rather than a
pile which crocodiles have to squabble over. Squabbling can prevent the weaker or more
nervous individuals from feeding. Some will only eat after dark and for this reason it is
necessary to leave food overnight and remove uneaten food first thing next morning.
The boards must be scrubbed clean but disinfectant which might taint the food, or leave a
smell, should not be used in the course of routine feeding.
If a young crocodile simply will not feed, it can be kept alive by force feeding. The
animal's mouth is held open (by thumb and forefinger in the case of hatchlings) and a
morsel of food, such as a tadpole or small fish, is gently pushed down its throat. It
should be pushed with a smooth rod, rounded at the end. The jaws are then held shut and
the food is massaged down the gullet with a fingertip. Force feeding may keep a young
crocodile alive until it begins to feed normally but it is a last resort. The process of
force feeding can make matters worse for crocodiles which are not feeding because of
stress or fright. Before force feeding is tried the crocodiles should be left with similar
sized companions in warm pens of maximum seclusion with a variety of live food.
