CBD
Belly Crawl
General Biology / Moving around: Crocodiles need to move around in order to survive.

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GENERAL BIOLOGY Locomotion - Belly Crawl
high walk
Fore limb being raised (left), rapid belly crawl (below)
C. porosus belly crawl to water
TYPE:Behaviour
FUNCTION:Moving the body from one place to another to satisfy requirements (e.g. thermoregulation, finding food, social interactions, nesting, escape from threats). Used on land and very shallow water. Normally slow except when used for escape.
INVOLVING:Front and hind limbs. The whole body and tail undulates rapidly from side to side when escaping

GENERAL | BELLY CRAWL | HIGH WALK | GALLOP | SWIMMING | JUMPING

The belly crawl is probably the most commonly-used way in which crocodiles move around on land. It is usually slow, although it can be modified so that the crocodile reaches speeds of 5 to 10kph when required. Although the term "belly crawl" implies a certain style of locomotion, in reality there are several variations on this gait suited to different situations, and only at very slow speeds does the crocodile actually crawl as the name suggests.

crocodile belly crawl on sand At slow speeds, the classic belly crawl sees the chest, stomach and tail flat on the ground. The legs are only raised a short distance above the surface - enough to clear the ground and move them forwards. Like a lizard, the legs move in an alternating diagonal pattern - the front left leg and the rear right leg move forward simultaneously (clear of the ground), while the front right and rear left legs push backwards to provide the force needed to slide the body along.
hind foot showing clawsventral tail scales The blunt claws on each foot (far left) help to provide traction as the retreating legs grip the substrate and push backwards. The scales on the crocodile's belly and tail (left) are smooth and flat, and this helps to reduce friction on the neck, chest, belly and tail as they slide along, particularly on mud or sand. In a modification to this gait, the crocodile positions its legs on either side of its body and pushes vertically upwards before pushing forwards. Hence, the majority of the body trunk is elevated off the ground - this reduces friction, and is often used when "crawling" over rougher surfaces such as soil, grass or rock.


At these slow speeds, the body trunk hardly moves, with only the shoulders and hips swaying slightly from side to side, with the tail falling alternately left and right. As the crocodile starts to accelerate, the trunk starts to move in a more exaggerated, horizontal s-shaped (or sinusoidal) manner more like a lizard. This flexion of the body trunk enhances positioning of the fore and hind limbs when they contact the ground ready for the powerful back stroke. Flexion of the trunk in the opposite direction, in conjuction with the back stroke of the leg, provides greater kinetic force. The legs are raised further off the ground at higher speeds as they cycle and propel the body forwards (see photograph below).

high speed belly crawl As the crocodile accelerates, the name "belly run" becomes more appropriate as the crocodile can move at considerable speed using this gait. At these higher speed (approaching 10 kph), the legs tend to push downwards as well as backwards. This causes the body to lift off the ground somewhat, which also helps to reduce friction in most cases. The body's sinusoidal movements become exaggerated and the tail whips from side to side quickly. Not only does this provide additional propulsive force on land as mentioned above, but it also aids the crocodile once it begins to enter water, as the tail provides thrust for swimming.


Escaping into the water Crocodiles nearly always use this higher speed belly crawl to escape from potential threats, usually into the nearest body of water. The slower gait, however, can be used for a variety of purposes involved in getting the crocodile from one place to another at a more leisurely pace.



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