Crocodiles are carnivores, which mean they eat only meat. In the wild, they feast on fish, birds, frogs and crustaceans. At the zoo, they eat small animals that have already been killed for them, such as rats, fish or mice. They also eat live locusts.

1. By
Priyanka Rani Majumdar
Lecturer, FIMS, NSTU

2. Habitat
• Crocodiles live in various fresh water areas such
as lagoons, rivers, billabongs, and swamps.
• Some types of crocodiles can also live in salt
water.

3. Crocodiles
• Crocodiles or true crocodiles are large aquatic reptiles which
are included in the order Crocodilia, family Crocodylidae and
subfamily Crocodylinae
• The word "crocodile" comes from the Ancient Greek word
‘crocodilos’ means the lizard of the river.
• Crocodiles have elongated, armored, lizard-like bodies with
muscular flat tail.
• Live in water but also travel on land by sliding on their bellies,
stepping along with their legs extended or running
uncomfortably
• Its streamlined body enables it to swim swiftly, it also tucks its
feet to the side while swimming, which makes it faster by
decreasing water resistance.

4.  Crocodiles have smooth skin on their bellies and sides and their
dorsal surfaces are armored with large osteoderms i.e. embedded
bony plates or scales.
 The armoured skin has scales and is thick and rugged, providing
some protection.
 They are still able to absorb heat through this armour, as a network
of small capillaries allows blood through the scales to absorb heat.
 They have a long snout with nostrils at the end to allow breathing
while most of body is under water.
 When float in water they leave only their nostrils, eyes, and ears
above the surface. Eyes can be covered with semitransparent
membranes and the ears and eyes are closed over by folds of skin.

5.  Swim primarily by snakelike movements of their bodies and by
powerful strokes of their muscular tails which acts as a motor.
 Size greatly varies between species. Adult sizes range from
1.9m-7m and weight from 800-1000kg.
 The smallest crocodile is the dwarf crocodile which is about
1.7m in length and 6-7 kg in weight.
 The largest crocodile is the saltwater crocodile which is about
7m in length and 950 kg in weight.
 They have webbed feet which, though not used to propel the
animal through the water, allow them to make fast turns and
sudden moves in the water or initiate swimming.
 Webbed feet are an advantage in shallower water, where the
animal sometimes moves around by walking.

7.  Crocodiles are polyphyodonts.
 A polyphyodont is any animal whose teeth are continuously replaced.
New, permanent teeth grow in the jaws, usually under or just behind the
old tooth, from stem cells in the dental lamina. Young animals typically
have a full set of teeth when they hatch. Within days, tooth replacement
begins, usually in the back of the jaw continuing forward like a wave.
 They are able to replace each of their 80 teeth up to 50 times in their 35
to 75-year lifespan
 Next to each full grown tooth, there is a small replacement tooth and a
odontogenic stem cell in the dental lamina in standby that can be
activated if required.
 In crocodiles, the upper jaw and lower jaw are approximately the same
width, and so teeth in the lower jaw fit along the margin of the upper jaw
when the mouth is closed. Therefore, the upper teeth interlock with the
lower teeth when the mouth shuts.

8.  Their tongues are not free, but held in place by a membrane that
limits movement; as a result, crocodiles are unable to stick out their
tongues.
 Crocodilians have a flap of rigid tissue behind the tongue that covers
their throats when they submerge in water which is called palatal flap.
It is situated at the back of the mouth that blocks the entry of water.
 This flap prevents water from flowing into their throats and hence
prevents the crocodile from drowning when its mouth is open. This
allows the crocodiles to open its mouth under the water. Primarily
useful in capturing prey while submerged in water.

9.  Crocodiles are very fast swimmers, which helps them catch their
prey. They can swim up to 20 mph (32 kph) and can hold their
breath underwater for around one hour. On land, crocodiles aren't
nearly as fast. They can only run up to 11 mph (17.6 kph) for a
short distance.
 Crocodiles also have very keen hearing. It is so good, they can
hear their babies calling from inside their egg.
 Most crocodilians are social animals sharing basking spots and
food except saltwater crocodiles which are more territorial and are
less tolerant of their own kind; adult males will share territory with
females, but drive off rival males.

10. Jaw
 They have an extremely powerful bite for their extremely strong
jaw muscle.
 A crocodile's jaws can apply 5,000 pounds of pressure per square
inch where a human's jaw only produces 100 pounds of pressure
per square inch.
 The muscles responsible for opening the mouth are exceptionally
weak, allowing a man to easily hold them shut with a small amount
of force or to use duct-tape to adhere the jaws together even in
large crocodiles
 Their sharp conical teeth that sink into flesh allowing for a grip that
is almost impossible to loosen. They can apply high levels of force
for extended periods of time, a great advantage for holding down
large prey underwater to drown.

11. Vocalization
 Crocodiles are producing a wide variety of sounds during various
situations and conditions, depending on species, age, size and sex.
 Some species can communicate over 20 different messages through
vocalizations alone.
 Some of these vocalizations are made during social communication,
especially during territorial displays towards the same sex and courtship
with the opposite sex; the common concern being reproduction.
 Therefore most conspecific vocalization is made during the breeding
season, with the exception being year-round territorial behavior in some
species and quarrels during feeding.
 Crocodiles also produce different distress calls and in aggressive displays
to their own kind and other animals.

12.  Specific vocalisations include -
 Chirp: When about to hatch, the young make a “peeping” noise,
which encourages the female to excavate the nest. The female then
gathers the hatchlings in her mouth and transports them to the
water, where they remain in a group for several months, protected
by the female
 Distress call: A high-pitched call mostly used by younger animals
that alerts other crocodiles to imminent danger or an animal being
attacked.
 Threat call: A hissing sound that has also been described as a
coughing noise.
 Hatching call: Emitted by females when breeding to alert other
crocodiles that she has laid eggs in her nest.

13. Bellowing: Male crocodiles are especially vociferous. Bellowing
choruses occur most often in the spring when breeding groups
congregate, but can occur at any time of year. To bellow, males
noticeably inflate as they raise the tail and head out of water, slowly
waving the tail back and forth. They then puff out the throat and with
a closed mouth, begin to vibrate air. Just before bellowing, males
project an infrasonic signal at about 10 Hz through the water which
vibrates the ground and nearby objects. These low-frequency
vibrations travel great distances through both air and water to
advertise the male's presence and are so powerful they result in the
water appearing to 'dance’.

14. “Crying crocodile tears" refers to a person expressing
insincere remorse. Crocodiles DO produce tears. Their
lachrymal glands secrete a fluid behind their third eyelid,
called a nictitating membrane. The fluid helps clean the
eye, lubricate it and reduce bacteria. Crocodile tears aren't
usually noticeable unless the croc has been out of the
water for a while and the eyes begin to dry out.
“Crying crocodile tears"

15.  Crocodiles are indiscriminate carnivores. They will normally eat any
animal that comes near the water or that is near the banks.
 Nocturnal hunter.
 They will eat a variety of prey animals including fish, birds, snakes,
turtles, cattle, buffalo and virtually any other animal they are able
to take down and devour.
 They are ambush predators. They will wait really quiet until a prey
animal comes to the watering hole for a drink. Then when the
animal comes close to the river, they attack it.
 They are also called as Opportunistic killers because they also prey
young and dying elephants and hippos when they get the chance.
 The Nile crocodiles that live in Africa they will eat antelope, zebra,
domestic animals and they can also eat a human to.
Crocodile’s diet

17. • Human beings are not exempted from their diet, particularly in
Southeast Asia and Africa, where hundreds of people fall prey to
saltwater and Nile crocodiles annually.
• The diet of crocodiles varies greatly with species, size and age
• It is also greatly affected by the size and age of the individual within
the same species.
• All young crocodiles hunt mostly invertebrates and small fish,
gradually moving on to larger prey.
• Their sharp, peg-like teeth are well-suited to seize and tightly grip
prey, but not designed to cut off flesh.
• So they do not have the capability to chew or break off small pieces
of food like other animals.

18.  They will have to swallow the prey whole if the animal is small
enough to fit into the mouth. This means that they will have to
juggle their food into the small position that they wanted it to be.
Then after they are done with that then they will have to start
tossing their head back so that the food can fall into the crocodile’s
throat.
 Small prey are simply swallowed whole, while larger animals are
forcibly dragged into deep water and drowned or crushed.
 Large prey is then torn into manageable pieces by "death rolling"
(the spinning of the crocodile to twist off hunks of meat) or by
sudden jerks of the head.

19. “Death roll”
 The death roll is probably the most famous of behaviours. Once in a
death roll most creatures will not survive.
 When it grabs very large prey the crocodile has to drag it into the
water and drown it so the crocodile will use it's advantage in the
water and it's own body weight to roll over and over again to
drown it's prey.
 It will pause and if the animal moves again the death roll will once
again be applied by the crocodile.
 The death roll is also how a crocodile is going to separate limbs
from the body of big animals rotating and rotating until eventually
it will tear off the limb or simply chunks of it's prey right into
portions the crocodile can easily ingest.

21. Breeding Season
 The breeding season varies based on the type of crocodile and geographical location.
 Freshwater crocodiles breed during the dry season.
 Saltwater crocodiles breed during the opposite wet season.
 The male and female Saltwater crocodiles engage in courtship in September and
October, and the female lays eggs between November and March.
 Crocodile breeding in captivity does not follow the exact same cycle but it comes
close. Typically, captive crocodiles will breed within one month of their wild
counterparts.
 Crocodiles are sexually dimorphic, and adult males are larger than females.
 Crocodiles have a long lifespan and sexual maturity is determined by age and size.
Freshwater crocodiles are not as large and males reach maturity at 2 meters in length,
females at 1.5 meters.
 Sexual maturity of Nile crocodile is obtained from 12 to 16 years of age. Males become
sexual matured when they are about 3.3 m long and mass of 155 kg and females when
they reach 2.2 to 3 m in length.

22. Courtship
 Courtship takes place in a series of behavioral interactions that
include a variety of snout rubbing and submissive display that can
take a long time.
 Mating takes place in the water.
 Crocodiles signal each other using changes in body profile as well
as, touch, and vocalization.
 The breeding process begins with mature males staking out
territory. The males will posture and define their area. In rare
instances, they will actually fight over territory.
 After territory and dominance are settled, males will begin the
mating behaviour by bellowing above water, while producing low-
frequency infrasound, which humans cannot hear.

23.  Males may also slap their snouts on the water, blow water from
their noses or perform certain arched postures. At closer ranges,
they may release an oily musk, which floats on the surface of the
water, to further entice the female.
 Both the male and female are vocal. Though the male is leading the
dance, the female is participating with her own set of auditory,
visual and olfactory signals during this time.
 Males will approach females and gently rub head to head. The
female ultimately determines the appropriate mate after several
hours of courtship.
 After the introduction and rubbing, the female will either swim
away or raise her body to encourage copulation. The male then
mounts the female and proceeds with copulation to fertilize the
eggs.

25. Nesting
 After mating, females start to build or dig the nest to protect the
eggs.
 There are two main types of nesting known to be used by
crocodiles.
 Females can build or dig several trial nests which appear
incomplete and abandoned later.
 Some crocodiles dig the nest in the ground, place the eggs in, and
re-fill it with sand. e.g. Nile Crocodile, freshwater crocodile
 Others build a nest above the ground which is a mound of
vegetation and soil, deposit the eggs into the mound, and use the
suns heat and the decaying vegetation to help aid the development
of the embryo. e.g. Saltwater Crocodile
 The female Nile crocodile dig a nest into a sandy bank which is up
to 50cm deep and several meters from the water.
 The nest of Saltwater Crocodile is about 175 cm long and 53 cm
high, with an entrance averaging 160 cm (63 in) in diameter. The
raised nest is necessary to protect the eggs from high water during
the wet season.

26.  Nesting period ranges from a few weeks up to six months.
 Egg laying usually takes place at night and about 30–40 minutes.
 All crocodiles lay hard-shelled eggs, which may weigh 50–160
grams individually.
 A female lays 10 to 60 eggs at a time, depending upon her age, size,
and species.
 Females are highly protective of their nests and young.
 The average incubation period is around 80 days, and also is
dependent on temperature and species that usually ranges from 65
to 95 days
 The hatchlings stay in their eggs for 55 to 110 days. They are 7 to 10
inches (17.8 to 25.4 centimeters) long when they are born and
don't mature until they are 4 to 15 years. How long a crocodile lives
depends on its species. Some only live to around 30 years, while
others live up to 75 years.
 The females remain close to the nest until the eggs hatch.

28. Parental care of Crocodiles
 Among the all reptiles, crocodile exhibits a remarkable level of
parental care.
 The female crocodile is an attentive parent, and, after laying up to
around 60 eggs, will cover the nest with sand and guard it for the
entire incubation period, around 90 days.
 At the time of hatching, the young start calling within the eggs.
They have an egg-tooth at the tip of their snouts, which is
developed from the skin, helps them pierce out of the shell. The
female excavates the nest in response to "yelping" calls from the
hatchlings, and even gently rolls eggs in her mouth to assist
hatching. The female will then carry the hatchlings to water in her
mouth.

29.  She would then introduce her hatchlings to the water and even
feed them herself.
 The mother would then take care of her young for over a year
before the next mating season.
 In the absence of the mother crocodile, the father would substitute
itself to take care of the young.
 However even with a sophisticated parental nurturing, young crocs
have a very high mortality rate due to their vulnerability to
predation.

31.  Crocodile embryos do not have sex chromosomes, and unlike
humans, sex is not determined genetically.
 Sex is determined by inside temperature of the nest, where at 30 °C
(86 °F) or less most hatchlings are females and at 31 °C (88 °F),
offspring are of both sexes.
 If the nest temperature is 30ºC or less, females will hatch from all
the eggs
 If the temperature is above 34ºC, all will be males
 If the temperature is in between, there will be young of both sexes.
 But A temperature above 33 °C resulting in females in other species
, which are sometimes called as high-temperature females.
 Temperature also affects growth and survival rate of the young,
which may explain the sexual dimorphism in crocodiles.

32. Stage 1
Egg: lays in a nest on dry land
protected by the mother who sits
close by.
Stage 2 (1-3months)
Hatchling: an animal
that has just hatched
from an egg.

33. Stage 3-Adult Crocodile
Crocodiles become an adult between
8-10 years old. An adult male is a huge
creature and measures 6m long. It is
one of the largest reptiles in the
world. They are fierce predators.
Stage 2-Crocodile Youth (2-8 years)
Crocodiles grow and learn to hunt on
their own.

35. Predation by humans and large
animals such as hippos, lions,
tigers, elephant etc. - hatchlings,
juveniles and adults
Threats

36. Threats
 Loss of habitat
- by drainage and filling of wetlands
- by diversion of water for irrigation
- by growing cities and farms on the
shores of lakes and rivers.

37. Threats
 Illegal killing
- For safety of people and animals
i.e. grazing cattles
- For leather to make wallets, shoes,
handbags, and belts
- for their meat and other parts i.e.
fat or oil which is used for medicinal
purpose such as burns, skin ulcers,
cancer, asthma.

38. Threats
• Climate change such as saltwater
intrusion and inundation

39. Conservation
 Trading of Crocodile leather should be strongly prohibited.
 Wetlands conservation is key to crocodile survival and also will benefit other
wetland-dependent species.. This is the ideal way to manage all wildlife. For
crocodiles, mangrove cover should be monitored and laws banning mangrove
clearing enforced. Alternative fuels should be sought where mangroves are
used for firewood.
 Generate funds. To support conservation if crocodile farming could be
encouraged. Farming could be done by the Forest Department or tribal
cooperatives.
 Restock the wild population by rearing animals in captivity and releasing them
in suitable environments.
 Assess environmental impacts of development activity such as growing cities
and farms on the shores of lakes and rivers.
 Organize wildlife tourism.
 Promote traditional conservation. The tribal practice of crocodile worship could
be promoted as a way of creating public awareness and seeking compassion
for the animal on spiritual grounds.
 Generate public awareness through the mass media and signboards near the
crocodile habitat.
 Research and monitor wild and captive crocodile populations.

40. Saltwater crocodile
 The saltwater crocodile (Crocodylus porosus) is the largest of all living
reptiles, as well as the largest terrestrial and riparian predator in the world.
 this species of crocodile can live in salt water, but usually resides in
mangrove swamps, estuaries, deltas, lagoons, and lower stretches of rivers.
 It eats any animal that enters its territory, including fish, crustaceans, reptiles,
birds, mammals, including other predators such as sharks, and humans
 are the most dangerous extant crocodilian to humans
 has a wide snout compared to most crocodiles.
 Young saltwater crocodiles are pale yellow in colour with black stripes and
spots on their bodies and tails and adult is much darker greenish-drab, with a
few lighter tan or grey areas sometimes apparent.
 Generally very lethargic, a trait which helps it survive months at a time
without food, the saltwater crocodile will usually loiter in the water or bask in
the sun during much of the day, preferring to hunt at night.

41.  Among all crocodilians Saltwater crocodiles are the most active and
spending more time cruising and active, especially in water.
 They are much less terrestrial than most species of crocodiles, spending
less time on land except for basking.
 They can also swim at 15 to 18 mph (24 to 29 km/h) in short bursts, around
three times as fast as the fastest human swimmers, but when cruising, they
usually go at 2 to 3 mph (3.2 to 4.8 km/h).
 Like most crocodilians, saltwater crocodiles are not choosy in their choice of
food nor are they voracious, as they are able to survive on relatively little
food for a prolonged period.
 Most crocodilians are social animals sharing basking spots and food,
Saltwater crocodiles are more territorial and are less tolerant of their own
kind; adult males will share territory with females, but drive off rival males.
 Saltwater crocodiles mate in the wet season, laying eggs in a nest consisting
of a mound of mud and vegetation. The female guards the nest and
hatchlings from predators

42. Nile crocodile
 The Nile crocodile (Crocodylus niloticus) is an African crocodile and may be
considered the second largest extant reptile in the world, after the saltwater
crocodile (Crocodylus porosus).
 Lives in different types of aquatic environments such as lakes, rivers and
marshlands. Although capable of living in saline environments, this species is
rarely found in saltwater, but occasionally inhabits deltas and brackish lakes.
 The Nile crocodile is one of the most dangerous species of crocodile and is
responsible for hundreds of deaths of humans every year.
 Nile crocodiles are relatively social crocodiles. They share basking spots and
large food sources such as schools of fish and big carcasses.
 There is a strict hierarchy, that is determined by size.
 Large, old males are at the top of this hierarchy and have primary access to
food and the best basking spots. Crocodiles know their place in the
hierarchical order and rarely act against it, but when they do, the results are
very bloody and sometimes even fatal.

44. • How do crocodiles defend themselves
Crocodiles are apex predators, which means they
have no natural predators other than humans.
However, if it's attacked, a crocodile will use its tail
as a weapon. Of course, it could also bite its
attacker. Crocodiles have been known to bite down
with a force of more than 3,000 pounds per square
inch.

45. How do Humans defend from crocodile’s attack
Fight back if you're attacked.
If this occurs, just try to get away from the crocodile as quickly
as possible. In predatory attacks, however, as well as in some
defensive attacks, the crocodile doesn't let go and will often try
to drag a person into the water or underwater. Crocodilians can
stay underwater for much longer than humans can, so the only
hope of survival if you're attacked in this manner is to fight back
and get away. Simply struggling and trying to pull free is usually
futile and may induce the animal to go into an underwater death
roll, during which an arm or leg stuck in the crocodile's mouth
will likely be ripped off. A purposeful, deliberate attack on the
animal is therefore a better option.

46. • These are steps to fight back
• Go for the eyes. The most vulnerable part of a
crocodile's body is its eyes. Try to hit or poke the
eyes with whatever you have handy: an oar, a
stick, or a knife. Even your hands can be
effective weapons if you can hit the crocodile's
eyes. A Florida teenager recently escaped an
crocodile that had dragged him into the water by
jamming his thumb into the crocodile's eye.

47. • Go for the nostrils or ears. While not as sensitive as
the eyes, the nostrils and ears can be effectively
attacked. A hard blow or a cut to either of these areas
may cause the animal to release you. Many people have
been saved from a crocodile's jaws when other people
have hit the animal's snout with a pole or club.

48. Go for the palatal valve.
Crocodilians have a flap of tissue behind the tongue that
covers their throats when they submerge in water. This
flap prevents water from flowing into their throats and
hence prevents the crocodile from drowning when its
mouth is open. If your arm or leg is stuck in a crocodile's
mouth, you may be able to pry this valve down. Water will
then flow into the crocodile's throat, and crocodile will
most likely let you go. Hard strikes to this valve may also
cause the crocodile to release you.