The saltwater crocodile is the largest living reptile
species
. It
can grow up to six metres
and is a serious
threat to humans. Saltwater crocodiles have evolved special characteristics that ma
ke them excellent
predators.
•
Large saltwater crocodiles can stay underwater for at least one hour because they can reduce
their heart rate to 2
-
3 beats per minute. This means that crocodiles can wait underwater until they
see prey, or if people are usin
g the same spot regularly, the crocodile can wait underwater until
someone approaches the water’s edge.
•
A crocodile can float with only eyes and nostrils exposed, enabling it to approach prey without
being detected.
•
When u
nder
water, a special transparent
eyelid
protects the crocodile’s
eye. This means that
crocodiles can still see when they are completely submerged.
•
The tail of a crocodile is solid muscle and a major source of power, making it a strong swimmer
and abl
e
to make sudden lunges out of the wa
ter to capture prey.
These strong muscles also
mean that for shorts bursts of time crocodiles can move faster than humans can on land.
•
Crocodiles have a thin layer of guanine crystals behind their retina. This intensifies images,
allowing crocodiles to se
e better at low light levels.
•
Crocodiles have a ‘minimum exposure’ posture in the water, which means that only their sensory
organs of eyes, cranial platform, ears and nostrils remain out of the water. This means that they
often go unseen by prey, but if
they are observed, the prey is often not able to
tell
how big the
crocodile is.
•
Crocodile eyes are located very closely together and they are oriented forward. This enables them
to
judge distance very accurately so they can
determine the exact location of
their prey prior to
attack
.
•
Crocodiles have excellent hearing, which
helps
them to locate prey
particularly in poor light
or low
visibility
conditions
.
•
While crocodiles may regularly lose teeth, they have a second tooth sitting
in reserve
underneath
the
external tooth, which
can
replace the lost tooth.
•
The jaws of crocodiles are designed to generate enormous power when the jaws are closing. This
enables them to
quickly
crush prey.
Why does the N
or
thern Territory have more crocodiles than Queensland
or
Western
Australia
?
A large proportion of the
coastal region of the Northern Territory
is
an
ideal habitat for saltwater
crocodiles
, particularly the big, productive “coastal” wetlands and rivers
. Much of the Queensland
coastline
is in the cooler, more
so
utherly latitudes
,
which is
less optimal
habitat for crocodiles.
Much of
the habitat
on the east coast
has also been
significantly
altered and fragmented by human settlement.
Western Australia has saltwater crocodile habitat around the Kimberley coastline
but this are
a
is not as
rich in mangroves
and wetlands
as the Territory coastline.
In the southern part of its range, winter temperatures reach a threshold below which crocodile eggs will
not hatch and the longer cold periods significantly lower crocodil
e growth rates. The effect of a cooler
climate on crocodiles can be seen in those animals kept in wildlife parks in southern Queensland. The
crocodiles do not feed over winter as they cannot absorb enough warmth to digest food.
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